Petgeo1 6

PETROLEUM GEOLOGY

"Petroleum prospecting is an art."E. DeGolyer

Assoc. Prof. Dr. Volkan . Ediger

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Volkan . Ediger, Petroleum Geology'2005

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A STORY OF AN OILMAN

"By the time Mark 'took a package' in early 1999, we had become good friends. For 17years Mark and his wife traipsed around the world in the employ of Schlumberger, with stops inEgypt, Pakistan, and Venezuela (twice). As natives of North Dakota, they welcomed their firstdomestic assignment, a transfer to Houston, in early 1998. If nothing else, it would be a goodthing for their three young daughters. Being laid off was a twist they hadn't expected.

A highly competent and highquality character in his early 40s, Mark was completelyunphased by the event (after all, oil had dropped to $ 10 a barrel), and even welcomed thechange of pace. As it turned out, he decided on a whole new careerin the funeral business.

In just three months with a major funeralhome chain, Mark moved from an entrylevelsales position to midmanagement. This is not surprising if you know Mark, but consider some ofthe details. Early in his new job and just getting his feet on the ground, Mark pulled togetherand charted some local sales and growth figures in Excel. He presented them to his workgroupin PowerPoint using a computer projector. On the basis of his presentation, he was dubbed theresident 'computer techie.'

I know Mark pretty well, and frankly, I'd rate him at the lower end of the techieladder. The whole event struck Mark as weird, as it did me. The thought flashed to my brain.I'd spent the past six years developing research programs at Texas A&M University and theUniversity of Houston, all the while sounding the alarm that the oil industry is underresearchedand not nearly as hightech as it claims. How did I reconcile my claims with this story?

Then it occurred to me. The strength of the oil industry is not research or technologydevelopment, per se; it is that we innovaterelentlesslyon the basis of technological advances, nomatter where the advances come from. If Bill Gates can make a better computer program, mythinking goes, we in the oil business probably can put it in use faster and better than any otherindustry.

Mark relays another interesting story. It seems the funeral home's tracking system hasa small breakdown, with the result that one of their (deceased) clients was misplaced. This upsetthe relatives tremendously.

Mark had only overheard the incident (the shouting of an angry relative, I think), butnonetheless took the initiative to raise the issue at the next staff meeting. His question wasobvious and simple: What are we doing to ensure this does not happen again?

The response? Blank stares. No one had any intention of doing anything. A smallchange in the standard work flow did the trick. For people in the oil industry, isolating andsolving problems competently is so natural, like drinking water, that we don't even realize weare doing it."

From; Economides, M.J. and Oligney, R.E., 1999, The color of oilPart V: Primary Colors:Hart's E&P, October 1999, p 156162.

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SYLLABUS

I. INTRODUCTIONLogistics, Energy Resources, Petroleum Industry, Upstream Business (Exploration &Production), Megatrends, Synergistic Teams.

II. HISTORY AND GLOBAL PETROLEUM SYSTEMPetroleum History of Turkey, Global Oil System, Reserves & Resources, Hubbert'sCurve, World Reserves, Productions & Consumptions.Exercise: Past, Present, and Future of Oil.

III. COMPOSITION OF HYDROCARBONS AND SEDIMENTARYORGANIC MATTERMain Compounds in Crude Oils, Plant Kingdom, Main Contributors of Organic Matterin Sediments, Color of Sedimentary Rocks, Sedimentary Organic Matter,Transportation & Deposition of Kerogen, Physicochemical Conditions, DepositionalEnvironments.Exercise: Palynofacies Analysis.

IV. SOURCE ROCKS & PETROLEUM GENERATIONSource Rocks of the World, World Petroleum Realms, Source Rock Analysis, VanKrevelen Diagram, Oil Generative Capacity, Diagenesis, Catagenesis & Metagenesis ofOrganic Matter, Petroleum Generation & ExpulsionExercise: Source Rock Evaluation.

V. RESERVOIR ROCKS AND MIGRATION & ENTRAPMENTGiant Fields, Migration and Entrapment, Reservoir Rocks, Cap Rocks, TrapFormation, Geological Framework of Migration & Accumulation, Oil Halflife Model,OilOil and OilSource Rock Correlations, PreservationDegradationDestruction ofTrapped Oil.Exercise: OilSource Rock CorrelationExercise: Oil Halflife Model

VI. PETROLEUM SYSTEMPetroleum System (Classification, Subsystems, Factors, Styles) Sedimentary Basins,Plays & Prospects, Petroleum System Name, Characteristics & Limits.Exercise: DeerBoar (.) Petroleum System.Exercise: Partial or Complete Petroleum Systems.

MIDTERM EXAMINATION

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(Midsemester Assignment: Literature Survey on Petroleum Geology)

VII. GEOLOGICAL INVESTIGATIONPetroleum Investigation, Petroleum System Logic, Petroleum Geology, Laws ofGeology, Topographic & Geologic Maps.Exercise: Surface Geologic Mapping

VIII. STRATIGRAPHYStratigraphic Classification, Lithostratigraphy, Biostratigraphy, Chronostratigraphy.Exercise: Age InterpretationExercise: Biozonation of a well.

IX. WELL LOGGING & GEOPHYSICAL METHODSDipmeter and Gammaray Logs, Spontaneous Potential (SP) and Resistivity Curves.Exercise: Gamma Ray and Dipmeter Logs.

X. CORRELATIONSCorrelation, Lithostratigraphic Correlation, Correlation of Electric Logs.Exercise: Correlation of Intertonguing Deposits.Exercise: Regional Correlation of Electric Logs.Exercise: Local Detail Correlation of Electric Logs.

XI. SUBSURFACE GEOLOGYSubsurface Maps, Lithofacies Mapping, Structural Contour Maps, Isopach Maps,Paleogeologic Maps, Facies Maps, Block (Panel, Fence) Diagrams.Exercise: Regional Lithofacies Mapping.Exercise X: Structure, Isopach, and Lithofacies Mapping.Exercise XI: Preparation of Block Diagram.

XII. PETROLEUM GEOLOGY OF TURKEYExercise: Petroleum Geology of Thrace Basin.Exercise: Petroleum Geology of Southeastern Anatolia.

XIII. PETROLEUM ECONOMICSEconomic Evaluation of International Petroleum Projects.

TERM PROJECT & PRESENTATIONS“Teamwork on Petroleum Geology of Turkey”

FINAL EXAMINATION

Schedule

Time: Wednesday 8:409:30, 9:4010:30, 10:4011:30, 11:4012:30Place: Prof. Dr. Ayhan Erler Room (Deceased October 13, 1998).

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Major Text Books (In chronological order)

Levorsen, A. I., 1969, Geology of Petroleum: W.H. Freeman & Company.LeRoy, L.W., LeRoy, D.O., and Raese, J.W., 1977, Subsurface Geology: Colorado School of Mines.Brooks, J., 1981, Organic Maturation Studies and Fossil Fuel Exploration: Academic Press.Waples, D., 1981, Organic Geochemistry for Exploration Geologists: Burgess Publishing Company.Tissot, B.P. and Welte, D.H., 1984, Petroleum Formation and Occurrences: Springer and Verlag,

Second Edition.Tearpock, D.J. and Bischke, R.E., 1991, Applied Subsurface Geological Mapping: Prentice Hall.Lerche, I., 1992, Oil Exploration: Basin Analysis and Economics: Academic Press.Magoon, L.B. and Dow, W.G., 1994, The Petroleum System: AAPG Memoir No. 60.Hunt, J., 1995, Petroleum Geochemistry and Geology: W. H. Freeman, Second Edition.Tyson, R.V., 1995, Sedimentary Organic Matter: Chapman and Hall, London.Selley, R.C., 1997, Elements of Petroleum Geology: Academic Press, Second Edition.Kearey, P., Brooks, and M., Hill, I., 2002, An Introduction to geophysical Exploration: Blackwell

Publishing, United Kingdom, Third Edition.Gluyas J. and Swarbrick, R., 2004, Petroleum Geosciences: Blackwell Publishing, United Kingdom.

Major Periodicals (In alphabetical order)

American Association of Petroleum Geologists BulletinJournal of Petroleum GeologyJournal of Petroleum TechnologyOil and Gas JournalOPEC ReviewPetroleum EngineerPetroleum GeologyPetroleum GeoscienceWorld OilWorld Petroleum Congress Proceedings

Grading

Attendance and Participation 10 %Midsemester Assignment 10 %Midterm 25 %Term Paper and Presentation 25 %Final 30 %

Required Course Material

Lecture NotesColored Pencils (At least six colors), Ruler and Protractor.

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MIDSEMESTER ASSIGNMENT

"Literature Survey on Petroleum Geology"

Procedure

1) Search for an article written on one of the subjects that will be discussed during this course (see the syllabus). METU, TPAO, MTA, and ULAKBIM libraries are the best places to look for such articles.2) The article should be published in one of the recent journals dated between 20002003.3) Write only a halfpage summary of the article and return it together with the xerox copy of the article. (Please summarize it with your own words, do not copy! ).4) The reference of the article should be given on top of the page, following AAPG’s standard format, of which the examples are given below:

A) A published book written by one or more authors:Flavin, C. and N. Lenssen, 1994, Power surge: Guide to the coming energy revolution: New York,

Mc Graw Hill, 382 p.B) A published book written by a company or an organization:Worl Energy Council, 1993, Energy for tomorrow’s world: World Energy Council, London, Nichols

Publishing, 320 p.World Energy Outlook, 1994, International Energy Agency: Paris, France, Organization forEconomic

Cooperation and development, 305 p.C) An Article (or paper) written by one or more authors in a periodical (or journal):Weeks, L. G., 1958, Fuel reserves of the future: AAPG Bulletin, v. 42, no. 4, p. 2431.Ivanhoe, L. F., 1995, Future world oil supplies: there is a finite limit: World Oil, October 1995, v.216,

p. 7788.D) An anonymous article (or a paper) published in a periodical (or a journal):The Economist, 1994, A survey of energy: The Economist, v. 331, p. 6077.E) An article (or a paper) written by one or more authors in a published proceeding:Masters, C. D., 1985, Distribution and quantitative assessment of world crude oil reserves:Proceedings

of the 11th World Petroleum Congress, v. 2, p. 229237.F) An article (or a paper) written by one or more authors as a chapter (or a section) in a book (orin any kind of publication) edited by one or more authors:Roodman, K. N., 1997, A cas history of oilshortage scares, in L. Starke and B. Supple, eds., Our oil

resource: New York, McGrawHill, p. 306406.Dolton, G., D. L. Gautier, and H. Root, 1993, Natural gas resources, in D. G. Howell, ed., The futureof

energy in U.S.: U.S. Geological Survey Professional Paper 1570, p. 495576.G) An unpublished report by a company, a survey, or an organization etc.:Lewin and Associates, 1976, The potential and economics of enhanced oil recovery: Final report

proposed for the Federal Energy Administration under contract No. 60445874998.Merritt, D. R., 1986, Map of Alaska’s coal resources: Alaska Division of geological and Geophysical

Survey Openfile Report 8424, 64 p.Meyer, F. L., 1995, Geology of Pennsylvanian rocks in the southeast New Mexico: New Mexico

Institute of Mining and Technology Memoir 17, 123 p.H) An article (or paper) written in a different language:

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Muslimov, R. K. and G. Akhmedzova, 1975, Outlining and preparation of small petroleum fields forproduction: Geologiya Neft i Gaza, no. 1, p. 2334. (In Russian).

TERM PROJECT AND PRESENTATION

"Teamwork on Petroleum Geology of Turkey”

Term project is designed to improve students’ ability to apply the principles ofgeology to the petroleum industry of Turkey. Students are expected to design anddevelop new exploration strategies to improve exploitation of the domestic petroleumresources in Turkey. For this, the already known petroleum systems and the presentexploration activities should be evaluated thoroughly to be able to propose possibleapplications of modern information, theory, technique, and process. Examination of themodern international literature will enable students to investigate the most recentimprovements in the world’s petroleum industry.

Building a Synergistic Teams

Synergy simply means the action of discreet agencies so that the total effect isgreater than the sum of the effects taken independently. In petroleum exploration andproduction business synergistic teams mean that geologists, geophysicists, petroleumengineers, and others work together on a project more effectively and efficiently as ateam than working as individuals. It has almost been proven that the old style lineorganization cannot compete with the new teams. Therefore, you should either choosenot to play or you integrate into a team system so that you can play.

A team consists of a project manager (team leader) and team members (in ourcase, datagathering, dataevaluation, reportwriting, presentation etc.). Eachindividual of the team should always keep in mind that he or she will be rewarded if theteam is successful.

The critical individual in the team is the project manager who plans, organizes,reviews project performance, and communicates results. He also identifies andeliminates barriers between individuals and between other teams. Team members doindependent thinking but share their experience and talents with the other members byfeeling responsible for all the results.

Term Paper and Presentations

Each team is expected to return a term paper, which is written in standardAAPG article format. The articles should include an introduction (statement, purpose,and scope), a main section (presentation and evaluation of data and discussion), and aconclusion. The reference list, which includes the cited literature, is to be given at theend of the article. The team members may write and also present the term paper

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together or one member may be assigned for each of these purposes. The presentationswill last only 15 minutes sharp! and overhead projector transparencies should be usedduring presentations.

I. INTRODUCTION

References

Cavoulacos, P. and Deffarges, E., 1997, Achieving profitable growth in E &P: Newstrategies, business model: Oil and Gas Journal, May 26, 1997, p. 4248.

Hart's Petroleum Engineer International, 1997, Megatrends of 1997An industryperspective, v. 70, no. 1, p. 2537.

Ivanhoe, F.F., 1995, Future world oil supplies: There is a finite limit: World Oil,v. 216, no. 10, p. 7790.

Masters, J.A., 1990, Teamwork: p. 336340.Oil and Gas Journal, 1996,, Stateowned companies top reserves ranking outside

U.S.: Oil and Gas Journal, v. 94, no. 36, p. 6874.Sneider, R.M., 1993, The economic values of a synergistic organization, p. 328331.

Megatrends

Hart's Petroleum EngineerInternational reviewed the opinions ofH. Carlsen, M. Mes, L. Robinson, M.Simmons, J. Thorogood on themegatrends in the petroleum industry in1997. The experts commonly believedthat the megatrends in the industrytowards the 21th century will be; 1)from status quo to flexibility, 2) fromvogue to value added, 3) from nationstate to business state, 4) fromvulnerability to self preservation,5) from nationalism to globalism, 6)from passivity to interactivity, 7)from competition to cooperation, 8)from human power to automation, 9)from homogeneity to diversity, 10)from mass marketing to micromarketing.

World E & P Business

A variety of activities isinvolved in the course of oil and gasindustry, from upstream (exploration,development, and production) todownstream (refining and marketing).Transportation with pipelines andtankers is usually considered as at themiddle.

Stateowned oil companiescontinued to dominate the OGJ100 listof the world's biggest oil and gascompanies outside the US for manyyears. For instance, Saudi Arabian OilCompany and National Iranian OilCompany were listed in both reservesand production list of the top five stateowned companies outside the US in1996 (Table I. 1).

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Table I. 1. Reserve and production leaders (Oil and Gas Journal, 1996).

RANK

COMPANY PRODUCTIONmillion bbl

RANK

COMPANY RESERVEmillion bbl

1 Saudi Arabian Oil Co. 2,944.5 1 Saudi Arabian Oil Co. 258,703.0

2 National Iranian Oil Co. 1,318.4 2 Iraq National Oil Co. 100,000.03 Petroleos Maxicanos 1,119.0 3 Kuwait Petroleum Corp. 94,000.04 China National Petroleum Co. 1,097.6 4 Abu Dhabi National Oil Co. 92,200.05 Petroleos de Venezuela SA 962.3 5 National Iranian Oil Co. 88,200.0

The leading nongovernmental company in both reserves and production isRoyal Dutch/Shell: No. 6 in liquids production and No. 12 in liquids reserves. BritishPetroleum is the next largest nongovernmental company, ranking 12th in liquidsproduction and 17th in liquids reserves. Elf Aquitaine of France ranked 14th in liquidsproduction, Total of France 19th in the same category. Several major oil companiessuch as Exxon, Chevron, Mobile, and Texaco would rank in the OGJ100 top 20.However, the lists have changed after the merging of the major oil companies allaround the world.

Major changes in the oil and gas industry during the last decade and a half havenecessitated significant changes in upstream business strategies (Cavoulacos andDeffarges, 1997). Successful upstream players have changed their strategiesfromfrontier exploration to development/production new ventures and on to gas and powerplaysand built the capabilities necessary to achieve profitable growth. Moreover, thesecompanies have adopted a new business model, an organisation paradigm based onprocessdriven networks of business units, accountability and payforperformance,empowered multidisciplinary teams, and best practice sharing.

Synergistic Teams

The synergistic team approach (Figure I. 1) has been tried by several largeand small oil companies in the late 1970's and 1980's in order to compete moreeffectively and profitably with fewer staff and managers (Sneider, 1993). Synergy isdefined as the action of discreet agencies so that the total effect is greater than thesum of the effects taken independently. Within the context of the petroleumexploration and production business, synergy means that geologists, geophysicists,petroleum engineers and others work together on a project more effectively andefficiently as a team than working as a group of individuals.

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Masters (1990) who considered team building a social activity, tribal, andattitude reviewed what is needed:

1) Recognition that many complex problems require the integrated brain power ofnumerous specialists (team),2) Commitment and support from the top for the team concept (receptiveenvironment),3) Consistently highquality people,4) Trust, from the management and amongst themselves,5) Friendship,6) Freedom to contribute,7) Freedom to communicate,8) Job satisfaction by achievement rather than title,9) Supportive, enabling management style,10) Flexible, fluid organisation. No planners,11) Once committed, anyone who doesn't participate is out,12) The incontrovertible ethic (We pull together!),13) The guts to stand behind this and make it work. This is not a system for pussycats.

Exploration Milestones

Ivanhoe (1995) has noted that petroleum exploration is an efficient technicalprocedure. However, he also noted that the largest oil and gas fields in any basin or oilprovince were also the biggest targets and the easiest to find with any given technologyand thus they were normally found in any exploration phase. There are today virtuallyno areas where petroleum exploration cannot be successfully carried out if preliminarygeological studies indicate a good chance of finding major oil fields.

The exploration and drilling techniques routinely used by large oil companiesand the dates of first applications are as follows:

1) Surface geology (1900),2) Rotary drilling (1920),3) Refraction seismic (1925),4) Electric well logs (1930),5) Analog reflection seismic (1935),6) Mud logging (1940),7) Offshore drilling barges (1950),8) Deepwater drill ship (1956),9) Semisubmersible rigs (1964),10) Digital reflection seismic (1965),11) 3D digital reflection seismic (1978),12) Horizontal drilling (1985).

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Energy ResourcesThe simplest definition of energy is the capacity to do work (to do things or to

get things done). Since work is done when a force is used to move an object somedistance, it can easily be calculated by using the formula; Work=ForcexDistance.

It is a hard work to push an automobile but hard studying does not fit into themechanical work concept. When we work we get hungry, then we eat and gainenergy. If we don't eat enough, we loose weight.

Energy is found in different forms, such as; work, heat, electrical, chemical,nuclear, kinetic, potential, light, magnetic, sun, mass etc. Some forms of energy arenonspontaneous which takes place only as a result of an external stimulus; others arespontaneous which has a natural tendency to occur of its own accord.

Energy is obtained from energy resources of which some are renewable andothers are nonrenewable. The use of renewable resources is limited by the rate ofrenewal, the use of nonrenewable resources is limited by the reserves. Fossil fuels,including oil, natural gas, hard coal, and lignite and radioactive minerals arenonrenewables whereas the renewable are sun, wind, hydrothermal, tides, hydrogenetc.

According to the first and second laws of thermodynamics although theuniverse never loses any energy, less and less of that energy can be converted intowork as times go on. This is mainly because every spontaneous change is accompaniedby an increase in entropy, which is a measure of randomness, disorder, or chaos.

Shortage of energy and environmental problems are the major causes ofenergy crises or energy dilemma. Shortage of energy is the result of some naturalcauses such as limited reserves, increasing population and thus consumption. Artificialcauses, on the other hand, result from some political and economical reasons.

The ultimate goal is the efficient use of clean energy but we are going up thedown escalator on energy.

Figure I. 1. Synergistic organization in a small company which has from four tosix teams of exploration and production technical staff.

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II. HISTORY AND GLOBAL PETROLEUM SYSTEM

References

BP Amoco, Statistical Review of World Energy, 2002.Hubbert, M.K., 1956, Nuclear energy and the fossil fuels: American Petroleum

Institute Drilling and Production Practices, p. 725.Ivanhoe, L.F., 1984, World crude output, reserves by region: Oil & Gas Journal

Dec. 24, 1984.Ivanhoe, L.F., 1995, Future world oil supplies: there is a finite limit: World Oil,

v. 216, no. 10,p. 7790.PIGM (Petroleum Directorate of Turkey), Petroleum Activities in 1998.Turkish Petroleum Company, Annual Report, 1998.World Energy Yearbook, 1996.

Petroleum History of Turkey

1859 COLONEL EDWIN L. DRAKE ’S WELL IN OIL CREEK, PA, USA.1860 PRODUCTION IN USA REACHED TO 650,000 BBL.

PRICES DROPPED FROM 20 $ TO 2$.1876 34YEARSOLD SULTAN ABDULHAMID ASCENDED THE THRONE

ON 31 AUGUST. HE RULED THE EMPIRE FOR 33 YEARS BETWEEN18761908.

1887 CHEMICAL ANALYSES OF THE SKENDERUN OIL SAMPLEBY CHEMIST MOREAU IN STANBUL ON 17 JULY.

1888 MOUSUL & SURROUNDINGS WERE INCLUDED IN THE SULTAN’SHAZ NE HASSA (PRIVATE ASSET) ON 13 JANUARY.

1889 FIRST LICENCE TO AHMED NECAT EFEND ON 23 JUNE.FOR THE ÇENGEN OIL & GAS IN SKENDERUN.

1897 MÜREFTE LICENCES GRANTED TO HAL L R FAT PA A1898 OPENNING A SQUARE WELL (108 M) BY THE ROMANIAN

WORKERS IN GANOS. SOME OIL AND GAS SHOWS.18901900 GREAT BRITAN'S ARCHEOLOGICAL STUDIES. GERMANY'S

BAGDAT RAILROAD PROJECT.1901 FOLLOWING THE ESTABLISHMENT OF THE OTTOMAN BANK,

EUROPEAN PETROLEUM CO. DRILLED THE HORADERE1 WELLTURKEY’S FIRST PRODUCTION: 47 TONS OF OIL.

1901 D’ARCY CONCESSION: ANTOINE KITABJI KHAN MARKETTEDIRAN TO WILLIAM KNOX D’ARCY.

1908 FOCFIRST OIL COMPANY (CHANGED TO APOC IN 1909, LATER TOBP) DRILLED IN MESC D SÜLEYMAN IN IRAN. DISCOVERY OFOIL IN THE MIDDLE EAST.

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1912 MÜ R FUAT PA A GRANTED A LICENCE IN KÜRZOT, VAN.1912 KALTUZ GULBENKIAN ESTABLISHED THE TURKISH

PETROLEUM COMPANY WITH BRITISH, GERMAN, AND DUTCHINVESTORS.

19141918 WORLD WAR I (GREAT WAR!). CHANGE FROM BRITISH+GERMANTO BRITISH+FRENCH ALLIANCES.

1918 MONDROS CEASE FIRE AGREEMENT ON 30 OCTOBER.1920 TURKISH GRAND NATIONAL ASSEMBLY MEETING ON 23 APRIL.

OIL PANIC IN USA1925 REVISION OF LAW NO. 608: MAAD N N ZAMNAMES ON 12

APRIL.1926 ACCEPTANCE OF LAW NO. 792: PETROLEUM LAW ON 12 MARCH.1922 NEGOTIATIONS IN LAUSANNE. CURZON NÖNÜ (HASAN BEY VE

RIZA NUR BEY)1923 DISCUSSIONS ENDED ON 23 JANUARY. APPLICATION TO

COUNCIL OF THE LEAUGE OF NATIONS.1925 TBMM’S CONTRACT WITH M. LUCIUS FROM LUXEMBURG1925 TBMM ACCEPTED THE COUNCIL’S REPORT ON 16 DECEMBER.

MUSUL AND KERKÜK IN IRAQ.1927 IRAQ PETROLEUM COMPANY DISCOVERED BABA GURGUR OIL

FIELD IN IRAQ ON 15 OCTOBER. 95,000 BBL/DAY !...19291932 WORLD ECONOMIC DEPRESSION.1929 LUCIUS’S FIELD TRIPS WITH KEMAL LOKMAN WHO EDUCATED

IN FRANCE, CEVAT EYUP WHO EDUCATED IN USA, AND GERMANKURT SCHMIDT.

1930 SHIRLEY L. MASON’S PAPER AT AAPG NEW ORLEANS MEETING:“NOT ENOUGH OIL IN TURKEY”

1931 LOKMAN’ ANSWER. CEVAT EYUP’S PAPER AT AAPG SANANTONIO MEETING:“PLENTY OF OIL IN TURKEY”

1933 ACCEPTANCE OF LAW NO. 2189 (PIGM: PETROLEUMDIRECTORATE OF TURKEY; MINISTRY OF ECONOMY) ON 20 MAY.CEVAT EYÜP: GENERAL DIRECTOR.

1934 BASBIRIN1 STARTED BEFORE THE MINISTER OF ECONOMYCELAL BAYAR ON 13 OCTOBER.

1935 LAW NO. 2804: MTAE (MINERAL RESEARCH AND EXPLORATIONINSTITUTE OF TURKEY) ON 22 JUNE.

193738 HERM S1, KERBENT1, HERM S2 WELLS19381945 WORLD WAR II.1940 DISCOVERY OF OIL IN RAMANDA 1 ON 24 APRIL. FIRST FALSE

OIL DISCOVERY IN TURKEY.1940 PRIME MINISTER REFIK SAYDAM, MINISTER OF ECONOMY

HÜSNÜ ÇAKIR VISITED RAMANDA 1 ON 24 APRIL.

1940 KEMAL LOKMAN:LK TÜRK PETROLÜNÜN BULUNU TAR N, BÜYÜK M LLET

MECL N KÜ AD LE TÜRKÜN M LL VE S YASHAK YET EL NE ALDI I GÜNÜN AR FES NE TESADÜFETMES B R FAL HAYRA ALAMETT R. BUGÜN, AYNI ZAMANDAPETROL ARA TIRMA VE BULMA TAR ZDE BÜYÜK B RBA LANGIÇ, B R DÖNÜM GÜNÜ OLUP KALACAKTIR”

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1946 MULTIPARTY ELECTIONS: DEMOCRATIC PARTY (DP) ANDREPUBLICAN POEOPLE’S PARTY (CHP)

1948 DECLERATION OF RAMANDA AS ECONOMICAL FIELD ANDPRESIDENT NÖNÜ & PRIME MINISTER GÜNALTAY VISITED THEAREA IN MARCH.

1951 DISCOVERY OF THE GARZAN OIL FIELD.1954 ACCENTANCE OF LAW NO. 6326 (PETROLEUM LAW) AND LAW

NO. 6327 (TPAO'S ESTABLISHMENT LAW) ON 7 MARCH.ESTABLISHMENT OF THE GENERAL DIRECTORATE OFPETROLEUM AFFAIRS.

1983 ACCEPTANCE OF LAW NO 2929 ON 20 MAY. TPAO CHANGEDINTO TPA . REFINARY (TO TÜPRA CHANGED FROM PRA ),PIPELINES (TO BOTA ), MARKETTING (ATA CHANGED TOPOA ), SHARES IN GSA AND PETK M TO TÜRK YE K MYASANAY KURUMU, POA , D TA , AND PETKUR.

1984 ON 18 JUNE, AGAIN TPAO (SUBSIDIARIES: TÜPRA , POA ,BOTA ,D TA ; ASSOCITED COMPANIES: PRAGAZ, TÜMA ,

BYATÜRK)1986 PRAGAZ’S (D TA IN 1993) SHARES TO TOPLU KONUT ON 28

MAY. KAMU DARES BA KANLI I. PRIVITIZATION PROGRAM.1988 88/13180 GOVERNMENTAL DECISION SIGNED BY THE COUNCIL

OF MINISTERS ON 21 AUGUST. TPAO'S AUTHORIZATION FORPETROLEUM ACTIVITIES ABROAD.

1988 TPIC ESTABLISHED IN JERSEY CHANNEL ISLANDS (ENGLAND)ON 7 DECEMBER. OIL ACTIVITIES IN EGYPT.

1993 TPAO’S AUTHORIZATION FOR ACTIVITIES IN KAZAKHSTAN ON20 JUNE. 4 FEBRUARY KAZAKTURKMUNAY LTD ESTABLISHED

1993 AIOC (AZERBAIJAN INTERNATIONAL OPERATING COMPANY).TURKISH SHARES INREASED TO 6.75 %

1995 COUNCIL OF MINISTER’S DECISION NO: 95/6526 ON 8 FEBRUARY.BOTA REORGANIZED. BOTINT, TURKGAS IN 1997.

1998 700 PRODUCTION WELLS IN ABOUT 100 OIL FIELDS. AROUND3,2 M TONS DOMESTIC (TPAO: 2,4 M TONS, SHELL: 598,5 M TONS,MOBIL AND DORCHESTER: 85,1 M TONS, ERSAN: 3,7 M TONS,OTHERS: 76,9 M TONS). DOMESTIC PRODUCTION IS AROUND 12%.53 WELLS A YEAR (TPAO: 38 WELLS, OTHERS: 15 WELLS).

The Global Oil System

The most widely accepteddefinitions of the oil and gasaccumulations in the pools are asfollows:

Global expelled oil system(=Global oil resources) includes all theexpelled oil that existed before humanintervention. Resources are defined asthe reserves and currently uneconomicdeposits.

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The term "reserve" includesthe amount of proven petroleum, whichexists in identifiable fields. Therefore,reservoired oil system can be definedas the total original oilinplace in allfields, known and yettobefound oilwhich would be included in global oilreserves using current economiccriteria. Oilinplace is the totalamount of oil in situ and yettobefound oil is the quantity ofeconomically extractable oil, whichremains to be discovered.

Reserves can not be extractedtotally and some will remain in placedepending on the available technology.The amount that can be extracted fromthe reservoirs is called recoverablereserve. Ultimate global recoverableoil reserves, therefore, depend upon aglobal recovery factor for thereservoired oil system.

R/P ratio is the recoverablereserves (bbl or tons of oil) divided bypresentday yearly production (bbl/yearor tons/year). It gives an idea abouthow many years will your reserves lastif you continue producing them withthe presentday rate.

Reserves and Resources

Ivanhoe (1995) considers thatoil reserves are by definition economic,or profitable while resources,conversely, are less tangible. Reservesare engineers' (conservative) opinionsof how much oil is known to beproducible, within a known time, withknown techniques, at known costsand in known fields. Conservativebankers will loan money on reserves.Resources are geologists' (optimistic)opinions of all oil theoretically

present in an area. Conservativebankers will not loan money onresources. Explorationists must firstfind and then petroleum engineersconverttheoretical resources intoproducible reserves. An example ofresources that will never become areserve is gold in seawater.

Ivanhoe (1995) has emphasizedthat oil companies are in business tomake money not to find oil per se.He proposed the terms active andinactive reserves. Active reserves arethose producible within the foreseeablefuture (20 years or less), whereasinactive reserves are existence knownbut not considered producible within20 years, ie. inaccessible or producibleonly with asyet noncommercialmethods like enhanced oil recovery,etc. Conservative bankers will not loanmoney on inactive reserves and someinactive reserves are called inferredreserves.

Some reserves are calledpolitical reserves. Governmentpetroleum ministries have an inherentinterest in announcing the "good news"of large national hydrocarbon reservesinasmuch as large political reserves areuseful for national prestige and innegotiations for OPEC productionquotas, World Bank loans and grants,etc. Sudden unsubstantiated reserveincreases announced by anygovernment should, therefore, beviewed with considerable scepticism.

Hubbert's Curve

M. King Hubbert was amongthe first scientists who noticed thatpetroleum industry shows aunidirectional evolution, including aperiod of beginning, period of ascent, a

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period of decline, and an end (FigureII. 1).

He made the only scientificallyvalid projection of future oil productionin 1956. He correctly forecasted onthe basis of statistical projections ofpast U.S. (onshore and offshore lower48 states without Alaska) that oilproduction would peak in 1969. Sincethen, the US oil production hasdeclined within 5% of Hubbert's 1956prediction. Ivanhoe (1995) concluded

that there is strong evidence that therestricted Hubbert curve for the world'stotal EUR (estimated ultimate reserve)of oil may first peak about the year2000. It may then fluctuate along ahorizontal production line (restricted bySaudi Arabia/OPEC) before inevitabledecline towards a low baseline afteryear 2050. At an annual globalproduction of 20 billion bbl/year, anultimate difference of global EUR of300 billion bbl will defer the inevitabledoomsday by only 15 years, ie. 300/20.

Figure II. 1. Hubbert's curve (Ivanhoe, 1984)Exercise: Past, Present, andFuture of Oil

1) Try to determine the most possiblereasons for the collapse of the OttomanEmpire during First World War bystudying the history of the world's

petroleum industry and the history ofpetroleum in Turkey.

2) Try to establish the common pointsamong the collapses of the OttomanEmpire and the Soviet Union withrespect to their petroleum resources.

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3) Study the world's oil (Tables II. 12)and gas (Tables II. 34) reserves,productions, and R/P ratios.

4) Study the world oil productionhistory and future production curvebased on future reserve life by area(Figure II).

5) Write a scenario for the future of theTurkish petroleum industry byexamining Figure II.

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Figure II. 2. World oil production history and future production curve based on future reserve life by area (Ivanhoe, 1995).

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Table II. 1. Distribution of world oil reserves in 2004 (Bp Amoco, 2005)

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Table II. 2. World oil production (Bp Amoco, 2005)

Table II. 3. Distribution of world natural gas reserves in 2004 (Bp Amoco, 2005)

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Table II. 4. World natural gas production (Bp Amoco, 2002)

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III. COMPOSITION OF HYDROCARBONS ANDSEDIMENTARY ORGANIC MATTER

References

Braiser, M.D., 1980, Microfossils: George Allen & Unwin Ltd., London, 193 p.Burgess, J.D., 1974, Microscopic examination of kerogen (dispersed organic matter)

in petroleum exploration: Geological Society of America Special Paper, No.153, p. 1930.

Duran, B., 1980, Sedimentary organic matter and kerogen. Definition andquantitative importance of kerogen, in: B. Durand (Ed.), Kerogen: Organicmatter from sedimentary rocks: Editions Technip, Paris, p. 1334.

Hunt, J.M., 1979, Petroleum geochemistry and geology: Freeman, San Francisco,617 p.

Krumbein, W.C. and Garrels, R.M., 1952, Origin and classification of chemicalsediments in terms of pH and oxidationreduction potential: Journal ofGeology, v. 60, no. 1, p. 133.

Potter, Maynard, and Pryor, 1980, Sedimentology of shales: SpringerVerlag, NewYorkHeidelbergBerlin.

Staplin, F.L. et al., 1982, How to assess maturation and paleotemperatures: Societyof Economic Paleontologists and Mineralogists, Short course No. 7, 289 p.

Tschudy, R.H. and Scott, R.A., 1969, Aspects of palynology: John Wiley and Sons,Inc., New York, 510 p.

Tissot, B.P. and Welte, D.H., 1984, Petroleum formations and occurrences: Springerand Verlag, Berlin, Second Edition, 699 p.

Traverse, A. (Ed.), 1994, Sedimentation of organic particles: Cambridge UniversityPress, Cambridge, 544 p.

Tyson, R.V. 1995, Sedimentary organic matter: Chapman and Hall, U.K., 615 p.Whittaker, R.H., 1969, New concepts of kingdoms of organisms: Science, vol. 163,

p. 150160.

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Main Compounds in CrudeOils

Crude oil is basically composedof hydrocarbons and heteroatomsTissot and Welte (1984). Some of thehydrocarbons are saturated (paraffins,alkanes) and others are unsaturated.Saturated hydrocarbons are in theform of straight chains (normalalkenes), branched, or cyclic(naptehenes: cycloalkanes or cycloparaffins). Unsaturated hydrocarbonsare alkenes (olefine), alkynes(acetylene), and arenes (aromatics).

The gross composition of acrude oil can be defined by the contentsof saturated hydrocarbons, aramotichydrocarbons, and resins andasphaltenes (Table III. 1). Theseparameters are not independent, as allcrude oils consist of these three groupsof components. If one of these groupsis missing, the other two groupsamount to 100 %, as saturates plusaromatics plus resins and asphaltenesare unity.

This fact automaticallyintroduces a certain degree ofcorrelation between these groups and

their further subdivisions. Furthermore,the concentration of severalhydrocarbon types or N, S, Ocompounds show a high degree ofcovariance, as a result of a commonorigin, or common chemical affinities.

Saturated hydrocarbonscomprise normal and branched alkanes(paraffins). Aromatic hydrocarbonsinclude pure aromatics,cycloalkanoaromatics (naphthenoaromatics) molecules, and usuallycyclic sulfur compounds, which aremost frequently benzothiophenederivatives and their total abundance ofaromatic hydrocarbons, can be roughlyevaluated through the sulfur content ofthe aromatic fraction.

Resins and asphaltenes aremade of the higher molecular weightpolycyclic fraction of crude oilscomprising N, S, and O atoms.Aspaltenes are insoluble in light alkanesand thus precipitate with nhexane.Resins are more soluble, but arelikewise very polar and are retained onalumina when performing liquidchoromatography.

Table III. 1. Gross composition of crude oils (Wt. % of the fraction boiling above210 0 C) (Tissot and Welte, 1978).

NORMALPRODUCIBLE OIL

(AVER. OF 517)

ALL CRUDE OILSINCLUDING TARS

(AVER. OF 636)

DISSEMINATEDBITUMEN

(AVER. OF 1057)

SATURATED HC 57.2 53.3 29.2

AROMATIC HC 28.6 28.2 19.7

RESIN+ASPHALTS 14.2 18.5 51.1

AROMATIC SULFUR 2.07 (230 samples) 1.85 (88 samples)

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Plant Kingdom

In the nineteen century it wasusual to recognise only the twokingdoms: Plantae and Animalae(Braiser, 1980). Plants were consideredto be nonmotile and photosyntheticwhereas animals were considered to bemotile and feeding by ingestion of preformed organic matter. Although thesedistinctions are evident amongstmacroscopic organisms living on land,the largely aqueous world ofmicroscopic life abounds withorganisms that appear to straddle theplant/animal boundary.

Whittaker (1969) overcamethese anomalies by recognising fivekingdoms: the Monera, Protista,Plantae, Fungi, and Animalia (Figure

III. 1). The main precursor ofhydrocarbons is Protista which aremotile unicellular organisms with rathervaried morphology. Some have whiplike flagella for locomotion(dinoflagellates of DivisionPyrrhophyta) and photosynteheticpigments. Some engulf their food withthe aid of mobile pseudopodia(foraminifers and radiolarians ofPhylum Sarcodina), whilst some othershave a coat of bristlelike cilia andingest their food through a mountsurrounded by 'tentacles' (tintinnids ofPhylum Ciliophora). Therefore, someresemble the true Plantae and areprobably close to the ancestral line ofthat group, others are more akin toanimals than plants.

Figure III. 1. The kingdoms of life (Braiser, 1980).

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Main Contributors of OrganicMatter in Sediments

Bacteria, phytoplankton,zooplankton, and higher plants are themain contributors of organic matter insediments (Tissot and Welte, 1984).Lipids and lipidlike fractions oforganisms play a dominant role in theformation of petroleum.

Lipids encompass fatsubstances such as animal fat, vegetableoil, and waxes. Fats are used as energystorage in plants and animals since theyhave high energy content. Waxes aredesigned for protective function (bee'swax, leaf coating etc.). Seeds, spores,fruits especially of higher plants are richin lipids. Algae growing undernitrogendeficient conditions and incold water have high lipid. Forinstance, diatoms have up to 70 % on adry weight basis lipid. Oilsolublepigments, terpenoids, steroids, andcomplex waxes (suberin and cutin) arecalled lipidlike compounds.

Proteins are highly orderedpolymers, made from individual aminoacids. They account for most of thenitrogen compounds in organisms.They catalyse biochemical reactions inthe form of enzymes.

Carbohydrate is collectivename used for individual sugars andtheir polymers. They include mono, di, tri, and polysaccharides.Carbohydrates are among the mostabundant constitutes of plants andanimals. They are sources of energyand form the supporting tissues ofplants and certain animals. Celluloseand chitin are among the mostprominent palysaccharides occurring innature. Wood tissue in higher plants

consists of cellulose and lignin. Mostalgae are usually devoid of cellulose.

Lignin and tannin arearomatic (phenolic) structures whichare not synthesized by animals but verycommon in plant tissues. Lignin occursas a threedimensional network locatedbetween the cellulose miscelles ofsupporting tissues of plants. Tannins,although widespread, are quantitativelyless important than lignins. They areintermediate between cellulose andlignin in composition and in behaviour.Lignin and tannin are typically found inhigher plants but also in fungi andalgae.

PhysicoChemicoBiologicalConditions

Physicochemicobiologicalconditions of both transportation mediaand depositional environments aresignificant for the organic matterpreservation. The major agenciescausing decomposition of plant tissuesare oxidation, aerobic and anaerobicbacteria, fungi, hydrolysis, enzymes,and insect attack. While protoplasm,chlorophyll, oil and starch disappearquickly, cuticle, sporepollen exine,waxes, and resins are very resistant.

EhpH conditions of the mediaplay an important role in organic matterpreservation (Figure III. 2). Theoxidationreduction potential (Eh) ofsediments is intimately related to andperhaps more important thanhydrogenion concentration (pH) forthe preservation of organic matter insediments (Tschudy and Scott, 1969).Acidic (pH is less than 7) and reducing(Eh is negative) environments are the

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best for the organic matter preservation.

Figure III. 2. Sedimentary chemical endmember association in their relations to

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environmental limitations imposed by selected Eh and pH values. Associations in bracketsrefer to hypersaline solutions (Krumbein and Garrels, 1952)

Color of Sedimentary Rocks

Potter et al. (1980) showed thatcolor is by far the most importantfeature of a shale and is controlled bytwo rock variables that are directlymeasurable, Fe3+ and organic carbon(Figure III. 3). It is valuable forstratigraphic correlation and seems tohave possible environmentalsignificance.

The color of mudrocks isindependent of the total amount of ironpresent but strongly controlled by the

Fe3+/Fe2+ ratio. High ratios areassociated with red colors, low withgreens. However, the removal of iron isnot necessary to develop green colors,only reduction of the Fe3+ to Fe2+.

The amount of organic carbonpresent is another important, and partlyindependent, control of color.Therefore, the darkcoloured and finegrained sedimentary rocks usuallyconsist of enough organic matter forpetroleum generation.

Figure III. 3. Suggested relationship of shale color to carbon content andoxidation state of iron. The mole fraction is used to indicate theproportion of the total iron that is in the +2 state and m represents thenumber of moles of iron per gram of rock. Finer subdivisions of colorare possible, but are difficult to reproduce. Colors determined on wetsamples in natural light (Potter et al., 1980).

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Basically three environmentalvariables are important in controllingthe amount of organic matter:

1) The rate of production of organicmatter in surface waters of the basin, orin some cases its introduction by rivers.

2) The rate of sedimentation of othercomponents, such as terrigenousparticles or the shells of pelagicorganisms, which serve to "dilute" theorganic matter.

3) The rate of decomposition of theorganic matter in the upper fewcentimeters of sediments.

Sedimentary Organic Matter

Sedimentary rocks commonlycontain minerals and organic matterwith the pore spaces filled withprimarily by water, bitumen, oil and/orgas.

The most common term used todescribe the fossil organic matter insedimentary rocks is kerogen and Inthe absence of migrant hydrocarbons,kerogen is usually 95% or more of thetotal organic matter in sedimentaryrocks (Tyson, 1995). Kerogen is amixture of macerals and otherdegraded plant and/or animalremains. Bitumen is that fraction oforganic matter that is soluble in organicsolvents

The most comprehensivediscussion on sedimentary organicmatter and kerogen can be found inTyson (1995). He noted that there isno absolute and precise correspondencebetween the organic matter recognizedby geochemists, palynologists, andorganic petrologists, because each uses

different preparation and observationtechniques.

Durand (1980) uses thedefinition sedimentary organic matterinsoluble in the usual organic solvents.Tissot and Welte (1984) prefer todefine kerogen as the organicconstituents of sedimentary rocks thatare insoluble in both aqueous alkalineand common organic solvents. Burgess(1974) defines kerogen in a specificallyoptical way as finely disseminatedorganic material freed from asedimentary rock after acid treatment.Hunt (1979) broadened this definitionto disseminated organic matter ofsedimentary rocks in nonoxidizingacids, bases, and organic solvents.

Kerogen is not a single variablesubstance but nearly always a complexand heterogeneous mixture whosecomposition reflects widely varyingproportions of a large number ofdiffering precursor materials (Tyson,1995). These materials may also havevaried widely in their preservation state(and thus composition) at the time theybecame fossilized in the host sediment.The original organic matter istransformed into kerogen by a varietyof geochemical reactions that takesplace during diagenesis and burial.However, some workers have refusedto accept any redefinition of the termkerogen (Tyson, 1995).

Sedimentary organic matter,dispersed organic debris, organicdebris, palynodebris, organoclaste,palynoclast, clast, palynologicalorganic matter, particulate organicmatterPOM, dispersed organicmatterDOM are some of thesynonyms proposed by various authors.The kerogen classification, which iscommonly used in oil industry, is givenin Table III.

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Table III. 2. The commonly used kerogen classification

MACERAL (FOR COAL) KEROGEN (FOR OIL) ORIGIN

Alginite AlgalType IHighlyOil Prone

PROTISTA(Algae, includingdinoflagellates,Botryococcus etc.)

LIPTINITEGROUP Sporinite

CutiniteResinite(?Type I)

Herbaceous(?Amorphous)

Type IIOil Prone

PLANTA(Spores, Pollen,Resin, Leaf, Barketc.)

VITRINITEGROUP

Vitrinite Woody Type IIIGas Prone

PLANTA(Wood Tissue,Cortex Tisuue)

INERTINITEGROUP

FusiniteSclerotinite(Microforamlinings)

Coaly Type IVInert

PLANTAFUNGIPROTISTA

Exercise: Palynofacies Analysis

1) Prepare a kerogen distribution chart(xaxis: 0100 %, yaxis: depth) inFigure III. 4 to illustrate variation ofpalynofacies percentages with depth(time) by using data given in Table III.

2. Draw type I kerogen first, then typeII, type III, and type IV kerogens. Use

Table II. 2 for kerogen classification.

3) Try to interpret the paleoenvironment where deposition tookplace.

4) Discuss the source rock potential ofsedimentary organic matter recordedthroughout the well.

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Table III. 3. Palynofacies data for the Ankara1 well.

DepthM

WoodTissues

%Dinoflagellate

%

SporesPollen

%Fusinite

%

VariousAlgae

%

LeafTissue

%Resins

%TOTAL

%

1000 19.0 36.1 4.2 5.4 28.0 6.2 1.1 100.0

1200 18.1 54.0 1.3 2.1 18.3 4.1 2.1 100.0

1500 16.2 50.1 6.2 4.3 21.0 1.0 1.2 100.0

1750 14.1 42.3 2.2 10.1 23.1 5.0 3.2 100.0

2000 14.4 48.1 1.0 6.2 26.2 2.1 2.0 100.0

2300 10.5 64.0 3.3 19.1 3.1 100.0

2700 9.2 47.1 8.2 6.1 28.3 1.1 100.0

3000 18.4 46.1 3.4 7.1 22.0 2.0 1.0 100.0

3500 23.2 41.1 4.1 7.4 21.1 1.0 2.1 100.0

3600 39.6 21.2 1.0 11.1 27.1 100.0

3800 42.1 18.2 13.1 24.4 1.1 1.1 100.0

4000 28.3 18.3 2.1 12.2 34.1 2.0 3.0 100.0

4500 41.3 13.1 1.1 13.4 31.1

100.0

4600 45.0 9.2 1.5 14.1 28.2 1.0 1.0 100.0

4800 100.0 100.0

5000 100.0 100.0

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Figure III. 4. Palynofacies distribution chart of the Ankara1 well.

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IV. SOURCE ROCKS &PETROLEUM GENERATION

References

Klemme, H.D. and Ulmishek, G.F., 1991, Effective petroleum source rocks of theWorld: stratigraphic distribution and controlling depositional factors: AAPGBulletin, v. 75, No. 12, p. 18091851.

Peters, K.E. and Cassa, M.R., 1994, Applied source rock geochemistry, in: L.B.Magoon and W.G. Dows (Eds.), The petroleum systemfrom source to trap:AAPG Memoir No. 60, p. 93120.

Tissot, B.P., Durand, B., Espitalie, J., and Combaz, A., 1974, Influence of thenature and diagenesis of organic matter in formation of petroleum: AAPGBulletin, v. 58, p. 499506.

Ulmishek, G.F. and Klemme, H.D., 1992, Areal and spatial distribution andeffectiveness of the world's petroleum source rocks: Proceedings of theThirteenth World Petroleum Congress, v. 2, John Wiley and Sons, U.K., p.121136.

Waples, D., 1980, Organic geochemistry for exploration geologists: BurgessPublishing Co., USA, 151 p.

Welte, D.H., 1965. Relation between petroleum and source rock: AAPG Bull., 49:22492267.

Source Rocks of the World

The uneven distribution ofworld's oil and gas reserves is widelybelieved to have resulted fromvariations in conditions of generation,maturation, entrapment, andpreservation of petroleum. However,Ulmishek and Klemme (1992) (alsoKlemme and Ulmishek, 1991) havenoted that one of the most importantfactors is the uneven areal andstratigraphic distribution ofhydrocarbon source rocks and otherimportant factors are the availability

and quality of reservoir rocks and seals,their juxtaposition with source rocks,and maturation and migration history.

They have also noted thatseveral primary factors controlled theareal distribution of source rocks, theirgeochemical type, and theireffectiveness which means the amountsof discovered original conventionallyrecoverable reserves of oil and gasgenerated by these rocks. These factorsare;

1) geologic age,

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2) paleolatitude of the depositionalareas,3) structural forms in which thedeposition of source rocks occurred,4) the evolution of biota.

Geologic Age: Six stratigraphicintervals, representing onethird ofPhanerozoic time, contain petroleumsource rocks that have provided morethan 90 % of the world's discoveredoriginal reserves of oil and gas (inbarrels of oil equivalent).

The maturation time of thesesource rocks demonstrates that themajority of discovered oil and gas isvery young. Almost 70% of the world'soriginal reserves of oil and gas has beengenerated since the Coniacian, andnearly 50% of the world's petroleumhas been generated and trapped sincethe Oligocene (Figure IV. 1). They are:

1) Silurian (generated 9% of world'sreserves),2) Upper DevonianTournaisian (8% ofreserves),3) PennsylvanianLower Permian (8%of reserves),4) Upper Jurassic (25 % of reserves),5) middle Cretaceous (AptianTuronian) (29 % of reserves),6) OligoceneMiocene (12.5 % ofreserves).Paleolatitude: A warm and moistclimate, characteristic of low to middlepaleolatitudes is believed to be

favourable for source rock deposition.Twothird of the source rocks of thesix principal stratigraphic intervals weredeposited between the paleoequatorand 450 paleolatitudes.

Structural Forms: Structural formsreflecting tectonic stages in basindevelopment significantly affectedsource rock deposition. Source rocksdeposited in platforms, circular sags,and linear sags provided more thanthreequarters of original reservesgenerated from the six principalintervals.

Biologic Evolution: The significanceof biologic evolution for oil and gasgenesis is poorly understood. Theeffect of biologic evolution of sourcerock deposition during the Phanerozoicwas principally expressed as twoopposing developmental trends:

1) Diversification and expansion ofproducers increased the areas ofbioproduction and widened the rangeof organic matter types,

2) the evolution of consumers anddecomposers was directed to morecomplete use of organic matter.

These developments resulted ina change of environments suitable fordeposition and preservation of organicmatter in sediments.

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Figure IV. 1. Petroleum source rocks of the World (Klemme and Ulmishek, 1991)

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World Petroleum Realms

The distribution of oil and gasreserves in the world, relation of thereserves to specific source rocks, andmaturation history of the source rocksas related to the plate tectonicevolution, suggest that the world maybe divided into four main petroleumregions (petroleum realms) which arecharacterised by different richness inhydrocarbon reserves and variation inthe formation and occurrences ofpetroleum basins (Klemme and

Ulmishek, 1991; Ulmishek andKlemme, 1992; Figure IV.2).

In the Tethyan Realm (17% ofthe total area; 68 % of the petroleumreserves), favourable tectonic andpalegeographic development resulted inrich hydrocarbon reserves. The realmoccupies only onesixth of thecontinental (including shelves) area ofthe globe; yet, it contains twothirds oforiginal discovered hydrocarbonreserves of the world.

Figure IV. 2. Petroleum realms of the world (Klemme and Ulmishek, 1991).

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Boreal Realm (28% of the totalarea; 23 % of the petroleum reserves)is the second in petroleum richness. Itoccupies Precambrian cratonic blocksof the Laurasian continents andaccreted terranes formed in the courseof their collisions. During thePaleozoic, the continents were locatedin low paleolatitudes and moved to thenorth in the Mesozoic.

Pacific Realm (17 % of thetotal area; 5 % of the petroleumreserves) is areally equal to the Tethyanrealm; however, it contains only 5% ofthe world's oil and gas reserves. Therealm includes the late Mesozoic andTertiary basins of the Pacific rim andbackarc and foredeep basins of Northand South America which aregenetically related to the Pacifictectonics.

South Gondwana Realm (38% of the total area; 4% of thepetroleum reserves) is the largest inarea and poorest in hydrocarbonsreserves. The realm includes theGondwana continents outside the areaof the Tethyan and Pacificdiastrophism.

Source Rock Analysis

The application of organicgeochemical techniques to petroleumexploration has only recently achievedwidespread acceptance amongexploration geologists. Sourcerockevaluations, oiloil correlations, and oilsource rock correlations are the organicgeochemists’ common applications oforganic geochemistry in petroleumindustry.

Thermal maturity is theconversion of sedimentary organic

matter to oil, wet gas, and finally to drygas and pyrobitumen as a result oftemperaturetime driven reactions.Thermal alteration of organic matteroccurs in three stages, namelydiagenesis (immature), catagenesis(early, peak, late mature), andmetagenesis (postmature orovermature) (Figure IV. 3).

Diagenesis refers to allchemical, biological, and physicalchanges to organic matter during andafter deposition of sediments but priorto the reaching burial temperaturesgreater than about 60o80o C.

Catagenesis can be divided intothe oil zone (or oil window), whereliquid oil generation is accompanied bygas formation, and the wet gas zone,where light hydrocarbons are generatedthrough cracking.

Metagenesis corresponds to thedry gas zone where dry gas isgenerated. Dry gas consists of 98% ormore of methane.

Thermally immature sourcerocks have been affected by diagenesiswithout a pronounced effect oftemperature and microbial gas isproduced in this stage. Thermallymature source rock is in the oil windowand has affected by thermal processes.Thermally overmature (or postmature)source rock is in the wet and dry gaszones (gas window).

Sourcerock evaluations involvereasonably good semiquantitativepredictions of the probability ofsedimentary rocks containing oil. It haslong been known that sedimentaryorganic matter in the source rocksshould satisfy four independentconditions for petroleum generationand expulsion.

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These are the amount oforganic matter in the rock (Quantity),the oilgenerating capability of thatorganic matter (Quality), the maturityof the kerogen (Maturity), and theexpulsion efficiency of the bitumenfrom the rock. If any one of theseconditions is not met, no migratable oilcan be generated and if one condition is

met only partially, oil generation will beseverely reduced.

Welte (1965) has noted that aminimum organic carbon content (0.5%) in a source bed is necessary beforebitumen expulsion can occur, eventhough small amounts of bitumen isadsorbed on kerogen and clay surfaces,and no bitumen can be expelled fromthe source rock until these adsorptionsites are filled.

Figure IV. 3. Evolution of hydrocarbons from Kerogen (Brooks, 1981 afterDurand,1980).

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Van Krevelen Diagram

Peters and Cassa (1994) listedall of the geochemical parametersrelated to the quantity, quality, andmaturation for any sedimentary rock tobe a good source rock (Table IV.1).

Kerogen types are distinguishedusing the atomic H/C versus O/C orVan Krevelen diagram, originally

developed to characterize coals by VanKrevelen (1961). Tissot et al. (1974)extended the use of the Van Krevelendiagram from coals to include kerogendispersed in sedimentary rocks.Modified Van Krevelen diagram(Figure IV. 4) consists of hydrogenindex (HI) versus oxygen index (OI)plots generated from RockEvalpyrolysis and TOC analysis of Wholerock (Peters and Cassa, 1994).

Table IV.1. Geochemical parameters describing quantity, quality, andmaturation of sedimentary organic matter (Peters and Cassa, 1994).

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Figure IV. 4. Combined use of organic petrography, elemental analysis, andRockEval pyrolysis and TOC improves confidence in assessment of thequality and maturity of kerogen in rock samples. A sample anaylzed byRockEval pyrolysis was characterized as being marginally mature (Tmax=435 oC) and gas prone (HI=150 mg HC/g TOC). Organic petrographyshows a TAI of 2.5, and Ro of 0.5 % (supporting the maturity assessmentfrom pyrolysis), and the following maceral composition: type II 20 %,type III 60 %, and type IV 20 %. The calculated atomic H/C (0.90)corresponds with that determined by elemental analysis, supporting adominantly gasprone character (Peter and Cassa, 1994).

Oil Generative Capacity

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Following the determination ofa source rock rock in an explorationarea, geochemists are interested in totaloil that is the amount of oil whichcould be generated from a givenvolume of source bed if generationwent to completion.

Oil already generated is the oilwhich has already been generated froma given volume of source bed. Bothaspects are important but in a givengeologic setting one may be much morerelevant than the other.

There are basically twomethods of calculating total oil and oilalready generated. In the directapproach, the rock is actually subjectedto catagenetic conditions in order tomeasure directly how much bitumen isproduced. The RockEval and otherpyrolysis techniques are among suchmethods.

The indirect approaches involvemeasuring quantity, quality, andmaturity of the organic matterindependently, and then combiningthese data to predict what the oilgenerative capacity should be. Thesemethods rely on the assumption that itis possible to predict bitumengenerative capacity from the chemicaland physical properties of a kerogen.The following formulas can be used forcalculations in indirect methods:

Total Oil= Q1 Q2

Oil Already Generated= Q1 Q2 M

Oil Expelled= Q1 Q2 M E

Where;Q1, Scaled for quantity. If TOC= 1.0%, Q1 = 1.0

Q2, Scaled for quality (If Type I+IIKerogen is 100 %, Q2=2.0, if it is 50% Q2=1)

M, Percentage generation factorcorresponding to the thermal maturityof the kerogen (Ro %)

E, The expulsion efficiency of thesource sequences. E is not quantifiableat the present time, so it is preferable toomit it.

Because the quantity andquality factors of an average rock arenormalised to 1.0, a Total Oil of 1.0represents an average shale. Anaverage shale generates 80 millionbarrels of oil (or bitumen) per cubicmile of rock.

Exercises: Source RockEvaluation

1) Perform a typical source rockanalysis by using data on quantity,quality, and maturity of organic matterin the rock samples taken from theAnkara1 well (Table IV.2) in FigureIV. 5. Use the parameter ranges givenin Table IV.1 to determine the sourcerock capacity of the samples (TOC >0.5 %, HI > 1, Type I+II > 50 %, TAI:2.63.3).

2) To use the atomic H/C data, youmust first convert the measured,presentday H/C ratios to the ones thatthe kerogens had when they werethermally immature. This can easily bedone by plotting atomic H/C versusTAI for each sample on Van Krevelendiagram (Figure IV. 6) and then tracingthe H/C ratios back to its immaturevalue to find the calculated immatureH/C ratios. The immature values aregiven in Table IV. 3.

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3) The immature H/C ratios data needto be scaled by converting atomic H/Cratios of immature kerogen to qualityfactor (Q2 from H/C data) in FigureIV. 7. Quality factors are given inTable IV. 3.

4) Maceral analysis data also need to bescaled (Q2 from maceral analysis)Quality factor is equal to 1 ifalginite+exinite is 50% and the qualityfactor is equal to 2 if alginite+exinite is100%. Complete the empty column inTable IV. 3.

5) Calculate M values by convertingTAI to Ro using the conversion factorsin Table IV. 4.

6) Calculate total oil for H/C ratio andfor maceral analysis, and also oilalready generated for H/C ration andfor maceral analysis and complete thecolumns in Table IV.5. Note that Q1 isequal to Corg.

7) Draw the total oil and oil alreadygenerated profiles for the Ankara1well in Figure IV. 8. The amount of oilgenerated can be calculated, assumingthat total oil of 1.0 corresponds 80million bbls of oil per cubic mile ofrock (Note that the volume of reservoirshould be known for this calculation).

8) Discuss the possible causes of thediscrepancies between the H/C andmaceral analysis results for severalsamples (Samples 1000, 1500, 1750,2000, 2300, 4000, 4500). Should thesediscrepancies be taken seriously by theinterpreter or just be overlooked orswept under the rug?

9) Discuss also the reason for thediscrepancies in total oil profiles.

10) Discuss the reason why no maceralanalysis was possible in the lowermosttwo samples?

Table IV.2. Source rock data for the Ankara1 well.

Depthm

Type ofSample

C org%

AtomicH/C

TAI Type I+II %

1000 Sidewall Cores 0.6 1.07 2.02.5 751200 " 0.8 1.22 2.02.5 801500 " 0.5 1.05 2.02.5 801750 " 0.3 0.65 2.02.5 752000 " 1.3 0.77 2.2 802300 " 0.7 0.81 2.6 902700 " 1.6 1.33 2.5 853000 Core 2.5 1.27 2.5 753500 Cuttings 0.5 1.15 2.6 703600 " 1.2 0.98 2.7 503800 " 1.0 0.86 2.9 454000 " 0.7 0.75 3.0 604500 " 1.5 0.72 3.1 454600 " 1.7 0.66 3.2 404800 " 2.1 0.41 3.7 ?5000 " 2.2 0.38 3.8 ?

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Figure IV. 5. Source rock evaluation of the Ankara1 well.

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Figure IV. 6. H/C versus TAI for the Ankara1 well samples (An example is given for the sample taken from 4000 m).

Figure IV. 7. Kerogen quality factor as a function of H/C ratio of the immature kerogen (An example is given for the sample taken from 4000 m).

Table IV. 3. Quality factors from H/C and maceralsDepth

mMeasured

H/CImmature

H/CQuality Factor

(From H/C)Quality Factor

(From macerals)1000 1.07 1.07 1.051200 1.22 1.22 1.501500 1.05 1.05 1.001750 0.65 0.65 0.17

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2000 0.77 0.77 0.352300 0.81 0.81 0.432700 1.33 1.35 1.853000 1.27 1.30 1.703500 1.15 1.20 1.353600 0.98 1.05 0.903800 0.86 1.05 0.904000 0.75 0.90 0.604500 0.72 0.90 0.604600 0.66 0.90 0.604800 0.41 ? ?5000 0.38 ? ?

Table IV. 4. Conversion between Thermal Alteration Index (TAI) and Vitrinite Reflectance Index (Ro).

Ro TAI Ro TAI0.30 2.0 1.26 3.150.34 2.1 1.30 3.20.38 2.2 1.33 3.250.40 2.25 1.36 3.30.42 2.3 1.39 3.350.44 2.35 1.42 3.40.46 2.4 1.46 3.450.48 2.45 1.50 3.50.50 2.5 1.62 3.550.55 2.55 1.75 3.60.60 2.6 1.87 3.650.65 2.65 2.0 3.70.70 2.7 2.25 3.750.77 2.75 2.5 3.80.85 2.8 2.75 3.850.93 2.85 3.0 3.91.00 2.9 3.25 3.951.07 2.95 3.5 4.01.15 3.0 4.0 4.01.19 3.05 4.5 4.01.22 3.1 5.0 4.0

Table IV. 5. Calculation of total oil and oil already generated.

DepthM

Q1 Q2 (H/C)

Q2(Mac.)

M Total Oil(H/C)

Total Oil(Mac.)

OilAl. Gen.

(H/C)

OilAl.Gen.(Mac.)

1000 0.61200 0.81500 0.51750 0.3

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2000 1.32300 0.72700 1.63000 2.53500 0.53600 1.23800 1.04000 0.74500 1.54600 1.74800 2.15000 2.2

Figure IV. 8. Total oil and oil already generated profiles for the Ankara1 well.

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V. RESERVOIR ROCKS ANDMIGRATION & ENTRAPMENT

References

Biddle, K.T. and Wielchowsky, C.C., 1994, Hydrocarbon traps, in: L.B.Magoon and W.G. Dows (Eds.), The petroleum systemfrom source totrap: AAPG Memoir No. 60, p. 219235.

Carmalt, S.W. and St. John, B., 1986, Giant oil and Gas fields, in: Halbouty, M.T. (Ed.), Future petroleum provinces of the world: Proceedings of the Wallace E.Pratt Memorial Conference, Phoenix, December 1984: AAPG Memoir No. 40,p. 1153.

Demaison, G. and Huizinga, B.J., 1991, Genetic classification of petroleum systems:AAPG Bulletin, v. 75, no. 10, p. 16261643.

Levorsen, A.I., 1969, Geology of petroleum: W.H. Freeman and Company,p.538550.

Waples, D., 1980, Organic geochemistry for exploration geologists: BurgessPublishing Co., USA, 151 p.

Magoon, L.B. and Dow, W.G., 1994, The petroleum system, in: L.B.Magoon and W.G. Dows (Eds.), The petroleum systemfrom source totrap: AAPG Memoir No. 60, p. 324.

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Giant Fields

Carmalt and St. John (1986)defined giant field as the one which theestimate of ultimate recoverable oil is500 million bbl of oil or gasequivalent. Although the giant fieldsare few in numbers, they contain abouttwothirds of the discoveredrecoverable reserves (Table V.1). The509 giant fields contain a total of868,115 million bbl of oil and 3,193 tcfof natural gas. Converting gas to oilequivalent (6,000 cu ft/bbl) results inthe giants containing 1,400,343 millionbbl of oil equivalent (boe).

Geologically, giants are foundmost commonly in provinces that canbe classified as having formed incontinental crust and having beenassociated with a plate collision. Basins

in these provinces are found across awide range of geographic area, many ofwhich remain only moderately or lightlyexplored. The basins offer, therefore,significant geologic scope for futureexploration.

In more than 350 basins whichcontain a giant field, anticlines are themain trap type. Reefs, faults, saltrelated, and stratigraphic traps are lessthan 50 each Majority of the giantfield's reservoir rocks are ofCretaceousTertiary age. The Jurassicand Permian reservoir rocks are in thesecond the Triassic, Carboniferous andDevonian reservoir rocks are in thethird place. Around 300 of thereservoir rocks are sandstones and thenumber of carbonates (limestone anddolomite) reservoirs are close to 200.

Table V.1. Ten biggest Giant Oil and Gas Fields (Carmalt and St. John, 1986)

Field Name(Discovery Date)

Country RecoverableEquival. Oil

ReservesBillion bbl

Depthm

Trap Type GeologicAge

Lithology

1. Ghawer (1948)

SaudiArabia

87.500 2,200 Anticline Jurassic Carbonate

2. Burgan (1938)

Kuwait 87.083 1,400 Anticline Cretaceous Sandstone

3. Urengoy (1966)

RussianFederation

47.602 1,200 Anticline Cretaceous Sandstone

4. Safaniya (1951)

SaudiArabia


5. Bolivar Coastal (1917)

Venezuela 30.100 900 Stratigraphic Miocene Sandstone

6. Yamburg (1969)

RussianFederation

27.983 1,000 Broad Arch Cretaceous Sandstone

7. Bovanenkovo (1971)

RussianFederattion


8.Cantarell Complex (1976)

Mexico 20.000 1,500 Anticline Cretaceous Carbonate

9. Zakum Abu Dhabi 18.400 2,700 Anticline Jurassic Carbonate

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(1964)10. Manifa (1957)

SaudiArabia


Migration and Entrapment

Petroleum System consists oftwo subsystem: 1) GenerativeSubsystem and 2) Migration andEntrapment Subsystem (Demaison andHuizinga, 1991). The generativesubsystem includes the

biochemical transformationfrom organic matter to kerogen andthermochemical kinetics from kerogento petroleum, while the migration andentrapment subsystem includes onlythe physical processes leading to theentrapment of petroleum into the traps.

By the time diagenesis wascomplete at the end of the oil window,most of the oilprone organic matterwere in the form of petroleum. Duringand after diagenesis, water wassqueezed out of the source rock intothe reservoir rock and a fraction ofpetroleum and some kerogen wasentrained in the water (expulsion).Expulsion may continue afterdiagenesis. Petroleum expelled from anactive source rock can migrate along afault plane or a permeable carrier bedto porous reservoir rocks (primarymigration) and further migrates into atrap which is the part of the reservoirrock capped or surrounded by acomparatively impermeable seal or caprock (secondary migration).

Once petroleum has reached thereservoir rock, it must be concentratedinto pools if it is to be commerciallyavailable. Petroleum was also depositedin the nonreservoir shales or carbonatesas disseminated hydrocarbon particles(bitumen) associated with thenonsoluble organic matter (kerogen).

Trap Formation

Trap identification is the firststep in prospect evaluation and animportant part of any exploration orassessment program (Biddle andWielchowsky, 1994). Future success inexploration will depend increasingly onan improved understanding of howtraps are formed and an appreciaiton ofthe numerous varieties of trap typesthat exist.

Investigations of plays describea series of presentday traps, and ofprospects, an individual trap, anddetermine whether they have economicvalue and are exploitable with availabletechnology and tools (Magoon andDow, 1994). A series of relatedprospects is a play. A play is defined asa continuous portion of sedimentaryvolume which contains pools (or manytraps). Plays should have; 1) sameproductive sequence, 2) similarchemical composition of petroleum,and 3) coeval traps.

A trap is a subsurface lociwhere petroleum can no longercontinue its migration towards thesurfaces because its buoyant movementhas been arrested (Magoon and Dow,1994). To be a viable trap, subsurfacefeature must be capable of recevinghydrocarbons and storing them forsome significant length of time (Biddleand Wielchowsky, 1994). This requirestwo fundamental components: areservoir rock in which to store thehydrocarbons, and a seal (or set ofseals) to keep the hydrocarbo ns frommigrating out of the trap.

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Traps are either structural,stratigraphic, or a combination of both.(Figures V. 13) Structural traps arecreated by the syn to postdepositionaldeformation of strata into a geometry(a structure) that permits theaccumulation of hydrocarbons in thesubsurface. In 1936, Levorsenproposed th term stratigraphic traps forfeatures "in which a variaiton instratigraphy is the chief confiningelement in the reservoir which traps theoil." Today, we would define a

stratigraphic trap as one in which therequisite geometry and reservoirseal(s)combination were formed by anyvariaiton in the stratigraphy that isindependent of stratucturaldeformation, except for regional tiltingtime (Biddle and Wielchowsky, 1994).Combination trap is any trap that hasboth structural and stratigraphicelements, regardless of whether bothare required for the trap to be viable(Biddle and Wielchowsky, 1994).

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Figure V. 1. Major catagories of structural traps: (A) fold, (B) fault, (C)piercement, (D) combination faoldfault, (E) and (F) subunconformities.The situation in (E) is commonly excluded from the structural category(Biddle and Wielchowsky, 1994).

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Figure V. 2. Primary or depositional stratigraphic traps. (A) Traps created bylateral changes in sedimentary rock type during deposition. Top:juxtaposition of reservoir and seal caused by lateral facies changes.Bottom: reservoir termination due to the depositional pinchout of porousand permeable rock units. (B) Traps formed by buried depositional relief.In each example, sedimentary processes form a potential trappinggeometry, but require burial by younger impermeable section to createthe required top seal (Biddle and Wielchowsky, 1994).

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Figure V. 3. Combination traps. (A) Intersection of a fault with an updipdepositional edge of porous and permeable section. (B) Folding of anupdip depositional pinchout of reservoir section. In these examples, boththe structural and stratigraphic elements are required to form a viabletrap (Biddle and Wielchowsky, 1994).

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Geological Framework ofMigration and Accumulation(Levorsen, 1969)

1) Nearly all petroleum pools existwithin an environment of waterfree,interstitial (in fractures or cracks), edgeand bottom water. This means thatmigration is intimately related tohydrology, fluid pressure, and watermovement (hydrodynamic).

2) The gas and oil are chieflyimmiscible in the water and both are oflower density then the surroundingwater.

3) Reservoir rocks that containpetroleum differ from one another invarious ways; in geological age (fromPrecambrian to Pliocene), incomposition (from siliciclastics tocarbonates), in origin (fromsedimentary to igneous), in pororsity(from 1 to 40 %), and in permeability(from 1 md to many md).

4) There is a wide variation in thecharacter of the trap or barrier thatretains the pool. The traps may bestratigraphical, structural orcombination of these.

5) Size and shape of pores (porosity),paths between the pores (permeability)and the chemical character of thereservoir rocks may vary widely.

6) The minimum time for oil and gas togenerate, migrate and accumulate intopools is probably less than 1 my.

7) The temperatures of the reservoirrock may flactuate, generally between50100 0 C (122212 0 F). Themaximum temperature observed is 1630 C (325 0 F).

8) The fluid pressure within thereservoir rock may flactuate between 11,000 atm. They may very many timesduring the geological history of theregion.

9) The geological history of the trapsmay vary widely from a singlegeological episode to a combination ofseveral phenomena.

Reservoir Rocks

Reservoir rocks are any rockthat contains connected pores(Levorsen, 1969). Nearly all reservoirrocks are unmetamorphosedsedimentary rocks. Reservoir rocks areclassified as silisiclastics (clastic,fragmental, or detrital) or chemicalbiochemicals (carbonates, precipitatedsedimentary rocks).

Pore spaces may either beprimary (original or interconnectedporosity) or secondary (intermediate,induced, or limestone porosity). Theprimary porosity is mainly determinedby:

1) arrangement and form of pores(packing, uniformity of grain size, andshape of grains).

2) degree to which they areinterconnected.

3) their distribution in the sedimentaryrocks. While some diagenetic processessuch as solutions, recrystallization anddolomitization, and fractures andjoints contribute others such ascementation and compaction reducesthe secondary porosity. Clays usuallycreate significant problems bydecreasing the porosity andpermeability and by negatively

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influencing the drilling and productionactivities.

Sedimentary rocks consist ofgrains of solid matter with varyingshapes which are more or lesscemented, and between which there areempty spaces called porosity. It is thesepores which are able to contain fluidssuch as water or liquid or gaseoushydrocarbons and to allow them tocirculate (porous and permeable).

Porosity is the ratio of porevolume to total volume. The effectiveporosity is the ratio of the volume ofinterconnected pores to the totalvolume of the sample. Porosity isclassified as negligible (05 %), poor(510 %), fair (1015 %), good (1520%), and very good (2025 %).

Permeability characterizes theability of rocks to allow the circulationof fluids contained in their pores. It isthe coeeficient k in Darcy's formula andis measured in md (milidarcy).Permeability depends upon poredimensions and configuration.Permeability is classified as fair (110md), good (10100 md, and very good(1001000 md).

Oil Half life Model

Miller (1992) who proposed theoil halflife model made three majorgeological assumptions. One of them isthat the global rate of oil generationand expulsion equals the are of naturalloss. This means oil is continually beinggenerated in which an equilibriumsituation will balance the loss. Thesecond assumption that the oil loss canbe described by a natural decay law. Ona global basis, oil is destroyedexponentially with time in analogy with

radioactive decay. The thirdassumption processes are uniform andfilling rates are constant. Althoughindividual oil fields do not have auniform halflife, the global populationdoes. Reservoired conventional oil hasa welldefined halflife of 29 millionyears derived from the distribution ofoil generation.

Oiloil and Oilsource rockCorrelations

Shows of petroleum are proofof a petroleum system and whenencountered during drilling are usefulexploration clues, particularly whenthey can be quantified and regionallymapped. Cutting or cores that bubbleor bleed oil and gas during removalfrom the well are called live shows, incontrast to the asphaltic staining ofdead shows. The quality of shows canbe evaluated by their fluorescenceunder ultraviolet light, by colour oforganic solvent extracts, or bygeochemical screening methods.

Oiloil and oilsource rockcorrelations are of great importance toexploration. Oiloil correlations aresimpler, because one is comparing thesame kind of organic material. Two oilsamples having common origin maydiffer substantially in chemicalcomposition because of changes whichhave occurred during migration orstorage in the reservoir rocks. Thesechanges can include loss of heavy,light, or polar components;biodegradation and water washing; andthermal disproportination. In order toattempt oiloil correlations, it isnecessary to know how each of theabove transformations will affect anoil's chemical properties.

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Table V.2 shows the effects offive types of alteration processes oncrude oil composition. Duringmigration, the heavier and more polarcomponents are left behind, much asthe polar compounds and asphaltenesare left behind during column

choromatography. Most of themigrationally induced changes in oilcomposition probably occur as thebitumen makes its way out of the finegrained source rock (primarymigration). Secondary migrationgenerally causes smaller changes.

Table V. 2. Effects of alteration processes on crude oil composition (Waples, 1981).

Migration WaterWashing

Biodegradation

GasDeasphalting

ThermalMaturation

API Gravity INCREASES DECREASES DECREASES INCREASES INCREASES

% Sulfur DECREASES INCREASES INCREASES DECREASES DECREASES

C15 + Fraction(% of crude) DECREASES INCREASES INCREASES DECREASES DECREASES

Asphaltenes(% of crude)

DECREASES INCREASES INCREASES DECREASESINCREASES

UNLESSDEASPHALTING

OCCURSGasoline (C4C7)Fraction(% of crude)

INCREASES DECREASES DECREASES INCREASES INCREASES

Paraffinicity INCREASES INCREASES DECREASES INCREASES INCREASES

Porphyrin content DECREASES ? INCREASES INCREASES DECREASES

nparaffins(% of crude) INCREASES GENERALLY

INCREASESDECREASES INCREASES INCREASES

nparaffinsMaximumin distribution curve

SLIGHTLYDECREASES

INCREASESINCREASING

ORNO EFFECT

NO EFFECT DECREASES

nparaffinsCPI

NOSIGNIFICANT

EFFECTNO EFFECT

DECREASESOR

NO EFFECTNO EFFECT DECREASES

δ13C DECREASES DEPENDS ONCOMPOSITION

INCREASES DECREASES INCREASES IFGAS IS NOT LOST

Water washing andbiodegradation often go together.Water washing can occur withoutbiodegradation, but biodegradation willalways be accompanies by at least some

degree of water washing. During waterwashing, the more soluble componentsof petroleum are simply removed insolution. Light hydrocarbons,

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particularly aromatics, and the smallerpolar molecules become depleted.

Microorganisms are veryselective in which compounds theymetabolize. Anaeorobic bacteria arenot thought to be important inbiodegradation of hydrocarbons.Compounds containing heteroatomsare often consumed relatively rapidly,and nalkanes are generally severelydepleted or totally in extensivelydegraded oils. Occasionally, theisoprenoid hydrocarbons are alsonoticeably depleted.

Oil inherit biomarkerdistributions similar to those in thebitumen from the source rock, thusallowing oiloil and oilsource rockcorrelation or fingerprinting and paleoreconstruction of source rockdepositional conditions. An advantageof biomarkers is their resistance tobiodegradation by aerobic bacteria inthe reservoir. For heavily biodegradedoils where biomarkers have beenpartially altered, correlation sometimesrequires sealed tube pyrolysis ofasphaltenes, followed by biomarkeranalysis of the generated bitumen.Biomarker and other correlationtechniques, such as stable carbonisotope analysis and pyrolysisgaschromatography are among the mostpowerful tools for mapping petroleumsystems to reduce exploration risks.

Exercise: Oilsource rockcorrelation

1) The following exercise involves oilsource rock correlation in the stanbul1 well. Source rock data for which aregiven in Table V.3. Apparent oil showwas detected in a sandstone core takenat 7927 feet in this well.

2) Evaluate the oilsource history of thewell by performing a typical sourcerock evaluation in Figure V. 4. Sincethe TAI data show some scatter,particularly in the oilgenerative zone(TAI= 2.63.3), it would be wise toobtain the best fit of the maturity curveto the all the data. For this plot the TAIdata against depth and then obtain thebest fit curve.

3) Compare your interpretation withthe total oil and oil already generatedcurves for the complete section whichis given in Figure V. 5.

4) Discuss the nature and origin of theoil show of which the analytical data isgiven in Table V. 4. Is it possiblethat upward migration could haveoccurred ? Note that the geochemicaldata of 9,000 ft, 9,500 ft, 10000 ft, and10,500 ft samples are also given in thesame table.

Table V.3. SourceRock Data for the stanbul1 Well

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Depth(ft)

TOC%

Alginite+ Exinite

%

TAI

1,000 1.2 60 1.521,500 1.5 70 2.02,000 1.8 60 2.02,500 0.9 50 2.23,000 1.3 70 2.33,500 2.6 80 2.24,000 2.1 80 2.54,500 1.5 75 2.55,000 1.2 50 2.55,500 1.3 35 2.66,000 1.9 50 2.56,500 1.0 25 2.67,000 0.5 10 2.77,500 0.8 10 2.77,9278,000

Core1.3

(Oil show)60 2.9

8,500 1.4 80 2.89,000 1.1 70 3.09,500 3.7 90 2.7

10,000 3.2 80 3.010,500 1.3 60 33.511,000 0.1 100 3.511,500 0.2 95 3.512,000 0.1 95 3.512,500 0.4 90 3.5

Table V. 4. Analytical Data for Oil Stain and Bitumens from PostulatedSourceRock Intervals, stanbul1 Well.

Depth (ft) PorphyrinsNi V

δ13C (‰ PDB)Kerogen Bitumen

Pristanea

Phytane CPIa2331

maximumnparafin

7,927 1.21 0.55 26.0 0.57 1.09 C25

9,000 0.88 0.15 30.2 30.7 0.92 1.02 C17

9,500 1.52 0.59 26.1 27.2 0.48 1.18 C27

10,000 1.37 0.65 25.3 25.7 0.66 1.29 C27

10,500 1.91 1.02 28.3 25.5 0.51 1.28 C27

aobtained from gas chromatograms.

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Figure V. 4. Source rock evaluation of the stanbul1 well.

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Figure V. 5. Total oil and oil already generated for the stanbul1 well.

Exercise: Oil halflife Model 1) Assuming there is only one sourcerock of 250 Ma in age, oil is generated145 million years ago and migrated

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immediately after generation, theaccumulation of oil in the system withconstant generation and exponentialdecay as it is progressively created anddestroyed,

2) Draw a typical "degree of systemfilling" (yaxis) versus "time in halflives" (xaxis) diagram in Figure V. 6.

3) Calculate the total amount of oil thatexisted in the reservoir rock 100 millionyears ago, assuming 500,000 bbl of oilexist today in the present reservoir.

Figure V. 6. Degree of system filling versus time in halflives diagram.

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VI. PETROLEUM SYSTEM

Reference

Magoon, L.B. and Dow, W.G., 1994, The petroleum system, in: Magoon, L.B. andDow, W.G. (Eds.), The Petroleum SystemFrom Source to Trap: AAPGMemoir 60, p. 324.

Definition

A petroleum system is definedas a natural system that encompasses apod of active source rock and allrelated oil and gas and which includesall the geological elements andprocesses that are essential if ahydrocarbon accumulation is to exist .

Petroleum includes highconcentrations of; 1) thermal orbiogenic gas found in conventionalreservoirs or in gas hydrate, tightreservoirs, fractured shale, and coal; or2) condensates, crude oils, and asphaltsfound in nature.

The terms petroleum,hydrocarbon, and oil and gas aresynonyms. The term conventional oilis used for the petroleum other than gasand unconventional oil which areheavy oil, tar sand, and oil shale.Petroleum originally referred to crudeoil, but its definition was broadenedlater to include all naturally occurringhydrocarbons, whether gaseous, liquid,or solid. Condensate is in a gas phasein the accumulation and in a liquid

phase at the surface, but either way it isconsidered petroleum, as are solidpetroleum materials such as naturalbitumen and asphalt, and bituminoussands (=unconventional oil).

System describes theinterdependent elements and processesthat form the functional unit thatcreates hydrocarbon accumulations.

A pod of active source rockindicates that a contiguous volume oforganic matter is creating petroleum,either through biological activity(biologically) or temperature(thermally), at a specified time. Thevolume or pod of active source rock isdetermined by mapping the organicfacies (quantity, quality, and thermalmaturation) considered to be thepresently active, inactive, or spentsource rock using organic geochemicaldata displayed as geochemical logs. Asource rock is active when it isgenerating this petroleum, whereas aninactive or spent (depleted) source wasat some time in the past an activesource rock. From the time a petroleumphase is created a petroleum system

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exists and a petroleum system existswherever the essential elements andprocesses occur. The active time can bepresent day or any time in the past.

The essential elements includea petroleum source rock, reservoirrock, seal rock, and overburden rock,whereas the processes are trapformation and generationmigrationaccumulation of petroleum. Theseessential elements and processes mustoccur in time and space so that organicmatter included in a source rock can beconverted to a petroleum accumulation.

The essential elements are apetroleum source rock, reservoir rock,seal rock, and overburden rock at thecritical moment. The functions of thefirst three rock units are obvious.However, the function of theoverburden rock is more subtlebecause, in addition to providing theoverburden necessary to thermallymature the source rock, it can also haveconsiderable impact on the geometry ofthe underlying migration path and trap.

The generationmigrationaccumulation of hydrocarbons, or ageof the petroleum system, is based onstratigraphic and petroleumgeochemical studies and on the burialhistory chart. These processes arefollowed by the preservation time,which takes place after the generationmigrationaccumulation ofhydrocarbons occur, and is time whenhydrocarbons within the petroleumsystem are preserved, modified, ordestroyed.

When the generationmigrationaccumulation of the petroleum systemextends to the present day, there is nopreservation time, and it would beexpected that most of the petroleum ispreserved and that comparatively littlehas been biodegraded or destroyed.

Petroleum System Name

The name of a petroleumsystem includes the source rock,followed by the name of the majorreservoir rock, and then the symbolexpressing the level of certainty. Apetroleum system can be identified atthree levels of certainty: known,hypothetical, or speculative. The levelof certainty indicates the confidence forwhich a particular pod of active sourcerock has generated the hydrocarbons inan accumulation. In a known (!)petroleum system, a good geochemicalmatch exists between the active sourcerock and the oil or gas accumulations.In a hypothetical (.) petroleum system,geochemical information identifies asource rock, but no geochemical matchexists between the source rock and thepetroleum accumulation. In aspeculative (?) petroleum system, theexistence of either a source rock orpetroleum is postulated entirely on thebasis of geologic or geophysicalevidence

For example, the DeerBoar (.)is a hypothetical petroleum systemconsisting of the Devonian Deer Shaleas the oil source rock and the BoarSandstone as the major reservoir rock.

Characteristics and Limits

The geographic, stratigraphic,and temporal extent of the petroleumsystem is specific and is best depictedusing a table which includes fieldname, discovery date, reservoir rock,API gravity (0API), cumulative oilproduction (million bbl), and

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remaining reserves (million bbl) andfollowing four figures:

1) A burial history chartdepicting the critical moment, age, andessential elements at a specifiedlocation;

2) A map and 3) A crosssection drawn at the critical momentdepicting the spatial relationship of theessential elements; and

4) A petroleum system eventschart showing the temporalrelationship of the essential elementsand processes and the preservation timeand critical moment for the system.

The critical moment is thatpoint in time selected by theinvestigator that best depicts thegenerationmigrationaccumulation ofmost hydrocarbons in a petroleumsystem. Geologically, generation,migration, and accumulation ofpetroleum at one location usually occurover a short time span.

A map or cross section drawnat the critical moment best shows thegeographic and stratigraphic extent ofthe system. The geographic extent ofthe petroleum system at the criticalmoment is define by a line thatcircumscribes the pod of active sourcerock and includes all the discoveredpetroleum shows, seeps, andaccumulations that originated form thatpool. The cross section shows thegeometry of the essential elements atthe time of hydrocarbon accumulationand best depicts the stratigraphicextend of the system. A plan map,drawn at the critical time, includes aline that circumscribes the pod of activesource rock and all related discoveredhydrocarbons. This map depicts the

geographic extent or known extent ofthe petroleum system.

The burial history chart showsthat time when most of the petroleumin the system is generated andaccumulating in its primary trap.

The petroleum system eventchart shows eight different events. Thetop dour events record the time ofdeposition from stratigraphic studies ofthe essential elements, and the next twoevents record the time the petroleumsystem processes took place. Theformation of traps is investigated usinggeophysical data and structuralgeologic analysis.

Exercise: DeerBoar (.)Petroleum System

1) Examine the plan map showing thegeographic extent of the fictitiousDeerBoar (.) petroleum system at thecritical moment (250 Ma) which isgiven in Figure VI. 1. Thermallyimmature source rock is outside the oilwindow. The pod of active source rocklies within the oil and gas windows.

2) Examine the geologic cross sectionshowing the stratigraphic extent of thesame petroleum system at the criticalpoint which is given in Figure VI. 2.Thermally mature source rock liesupdip of the oil window. The pod ofactive source rock is downdip of the oilwindow.

3) Examine the burial history chartshowing the critical moment (250 Ma)and the time of oil generation (260240Ma) for the same petroleum system,which is given in Figure VI. 3.Neogene (N) includes the Quaternary(Q) here.

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4) Prepare the events chart (Figure VI.4) showing the relationship between theessential elements and processes as wellas the preservation time and criticalmoment for the fictitious Deer

Boar (.) petroleum system. Neogene(N) also includes the Quaternary (Q).5) Describe briefly the geologicalhistory of the region.

6) Write a brief report about thepetroleum geology of the area.

Figure VI. 1. Plan map showing the geographic extent of the fictitiousDeerBoar (.) petroleum system at the critical moment (250 Ma) (Magoonand Dow, 1994).

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Figure VI. 2. Geologic cross section showing the stratigraphic extent of thefictitious DeerBoar (.) petroleum system at the critical point (Magoonand Dow, 1994)

Figure VI. 3. Burial history chart showing the critical moment (250 Ma) and thetime of oil generation (260240 Ma) for the fictitious DeerBoar (.)petroleum system (magoon and Dow, 1992).

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Figure VI. 4. The events chart showing the relationship between the essentialelements and processes as well as the preservation time and criticalmoment for the fictitious DeerBoar (.) petroleum system (Magoon andDow, 1994)

Exercise: Partial or CompletePetroleum Systems

1) Three examples of partial orcomplete petroleum systems at thecritical moment are given in Figure VI.5. Complete the cross sections in B andC. Note that petroleum accumulation ischarged by a single pod of activesource rock (one petroleum system).

2) The number of petroleum systems isdetermined by the number of pods ofactive source, as shown by the threeexamples in Figure VI.6. Complete thecross sections in A and C. Note thatpetroleum accumulation is charged by asingle pod of active source rock (A andC) and by two pods of active sourcerock (B).

3) Discuss the differences between onepetroleum system and two petroleumsystems.

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Figure VI. 5. Three examples of partial or complete petroleum systems at thecritical moment are given in Figure II.5. (A) The essential elements arepresent, but the system is incomplete (thus no petroleum system); (B) onepetroleum system; and (C) two petroleum systems. Notice that theoverburden rocks creates the geometry of the most recent sedimentarybasin and that the source rock was deposited in a larger, oldersedimentary basin (Magoon and Dow, 1994).

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Figure VI. 6. Petroleum accumulation is charged by (A) a single pod of activesource rock, or one petroleum system; (B) two pods, or two petroleumsystems; and (C) one pod, or one petroleum system (Magoon and Dow,1994).

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Petgeo1 6

Education

Transcript of Petgeo1 6