Biological and Geochemical Factors influencing aaccumulation of Petroleum

8/9/2019 Biological and Geochemical Factors influencing aaccumulation of Petroleum

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BIOLOGICAL AND GEOCHEMICALFACTORS INFLUENCING THE

ACCUMULATION OF PETROLEUM

Presentation on


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BASIC COMPONENTS OF ORGANIC

MATTER IN SEDIMENTS

PROTEINSPROTEINS CARBOHYDRATESCARBOHYDRATES LIGNINLIGNIN

All of these + Time + Temperature +All of these + Time + Temperature +Pressure =Pressure = KEROGENKEROGEN


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Organic MatterOrganic Matter WhenWhenWhenWhen anananan organismorganismorganismorganism (plant(plant(plant(plant orororor animal)animal)animal)animal) dies,dies,dies,dies, itititit isisisis normallynormallynormallynormally

oxidizedoxidizedoxidizedoxidized

UnderUnderUnderUnder exceptionalexceptionalexceptionalexceptional conditionsconditionsconditionsconditions:::: organicorganicorganicorganic mattermattermattermatter isisisis buriedburiedburiedburied andandandand

TheTheTheThe compositioncompositioncompositioncomposition of ofofof thethethethe organicorganicorganicorganic mattermattermattermatter stronglystronglystrongly strongly influencesinfluencesinfluencesinfluenceswhetherwhetherwhetherwhether thethethethe organicorganicorganicorganic mattermattermattermatter cancancancan produceproduceproduceproduce coal,coal,coal,coal, oiloiloiloil orororor gasgasgasgas....

TheTheTheThe bacteriabacteriabacteriabacteria playplayplayplay somesomesomesome partpartpartpart inininin thethethethe formationformationformation formation of ofofof petroleum,petroleum,petroleum,petroleum, butbutbutbuttheirtheirtheirtheir rolerolerolerole probablyprobablyprobablyprobably doesdoesdoesdoes notnotnotnot extendextendextendextend beyondbeyondbeyondbeyond modifyingmodifyingmodifyingmodifying thethethethe OMOMOMOM....


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phytoplanktons


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Where the organic matter can become mature, not all of it becomespetroleum.In a typical case a normal marine shale with only 1% original organic matterwill have less than a third of it converted to the hydrocarbon molecules thatmake up oil and natural gas

The rest remains behind as an insoluble organic residue


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Formation and Preservation of Organic

Matter

suggested that the original source material of petroleum isorganic matter formed at the earth's surface.The process begins with photosynthesis, in which plants, in

the presence of sunlight, convert water and CO2 intoglucose, water &O2:

(6CO2 + 12H2O = C6H6O6 + 6H2O + 6O2).Glucose is the starting material for the synthesis of more

complex polysaccharides and other organic compounds,

either in plants or the animals that eat them.

This can occur through plant and animalrespiration, or through oxidation and bacterial decay

when organisms die.


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In the open ocean, zones of high productivity occur at highlatitudes of about

60north and south and along the equator.

These are regions in which cold, vertically movingocean currents bring nutrients and dissolved oxygen

from the deep ocean back up to the surface.Productivity is very high in the shallow waters over the

continental shelves, particularly where large rivers enter the.

Also productivity is high in quiet water or low energy

environments.

These low energy environments are usually found in oceans

& lakes

Consequently, organic matter is found mostly in fine-grained

rocks (shale & lime mud).


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Preservation and Organic Productivity

The main producers are phytoplankton(diatoms, dinoflagellates & blue-green

algae) & Bottom-dwelling algae.

food chain. Their distribution controlsthe animal forms such as themicroscopic zooplankton and higher

animal life, all of these contribute to thebiomass.


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amount of organic matter, about 1 part in 1000,

escapes recycling and is buried. Over geologictime, this small influx has produced vast quantities

of fossil organic material

However most of this material is widel

dispersed within the sedimentary column.

Only about one CO2 molecule out of every millioninitially taken up by photosynthesis is eventually

converted into economically exploitable oil, natural

gas or coal.


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major groups of organic compounds or biopolymers that are

biologically synthesized by plants & animals ------

Carbohydrates occur in both animals & plants & include simple

sugars such as glucose & their complex polymers like cellulose &

starch.

Proteins are found largely in animals & to a lesser extent plants.

Lignin is built up of high molecular weight aromatic carbon rings &occurs only in the higher land plants.

Lipids occur in both plants & animals. They are insoluble

compounds that include the fats, oils & waxes & are the major

source materials for the formation of liquid hydrocarbons.


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Figure shows how during early diagenesis, the complex biopolymersare broken down into smaller, simpler molecules, called

geomonomers.


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The end product of the diagenesisof organic matter is kerogen.

erogen s e ne as t e organ cmaterial in sedimentary rocks that isinsoluble in organic solvents.


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Kerogen Type

Origin OrganicConstituents

I Algal Algae of marine, lacustrine, Mostly algal components: of exinite

II MixedMarine

Decomposition in reducingenvironments, mostlymarine

Amorphous particles derived mostly fromphytoplankton & zooplankton

III Coaly Debris of continentalvegetation ( wood, spores,leaf cuticle, wax, resin, planttissue )

Mostly vitrinite & some exinite ( not algal )

IV

Inert oxidized material Mostly inertinite

Table: Kerogen types, their origin,& organic particle constituents


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How geochemical factors are

associated with oilaccumulation ?


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Relationship?

1. The geochemical characteristics of

petroleum.

2. The geochemical characteristics of water.

3. T e Associate su stances in petroleumdeposits.

4. Through geochemical reactions.

5. Through geochemical environment.

6. Through geochemical mobility.


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The geochemical characteristics of petroleum


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Tables !!Phase Source C H S N N+O OCrude oils Humboldt, Kans. 85.6 12.4 0.37 - - -

Healdton, Okla 85.0 12.9 0.76 - - -

Beaumont, Tex 85.7 11.0 0.7 - 2.61 -

Wax, Natural

Asphalt

Athabaska Tar 84.4 11.2 2.73` 0.04 - -

Asphalt from Utah 89.9 9 0 - - -

SOURCE OF OIL TRACE ELEMENTS IDENTIFIED

Canada Fe, Al, Ca, Mg, Au and Ag

Ohio Fe, Al, Ca, Mg, Au, Ag, Cu

Mexico Si, Fe, Al, Ti, Mg, Na, V, N, Sn, Pb, Co, Au

Japan Si, Fe, Ca

Limestone

Asphalt Gilsonite 85-86 8.5-10 0.3 2 - -

Glance Pitch 80-85 7-12 2-8 - 0-2 -

Asphalt

Pyrobitumens Albertite

83.4-

87.2

8.9-13-

2

1.2 0.4 - 2.0

ELEMENTAL COMPOSITION OF SOME CRUDE OILS, MINERAL WAX AND ASPHALTIC

SUBSTANCES

Egypt Fe, Ca, Ni, VIraq Fe, Ni, Y

Texas Si, Fe, Al, Ti, Ca, Mg, V, Ni, Ba, Sr, Mn, Pb,

Cu, Cr, Ag


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The geochemical characteristics of water

Brine interstitial water and salinity. Bottom water or edge water.

rre uc e m n mum sa ura on an u ywater saturation.

Salinity gradient and diffusion or

displacement.

Common ions of Na, Mg, Cl, Ca, Al, Fe, Mn, Zn,

Ba, Cu, Ag, Rb, F, B, Ni and SiO2.


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Brine water also contains organic substances like naphthenates,

salts of aliphatic acids, phenols, phenols and benzene etc. It is proposed that a lateral increase in the benzene content of the

brine in a given statum may point towards an oil accumulation in

that stratum. (after W.M.Zerella, R.J. Mousseau, N.D. Coggeshall et

al 1967)

In sea water, Mg is more abundant than Ca, whereas in oilfield it isreverse. The formation of chlorite rather than dolomite, or to its

slow incorporation in fine grained mixed layer micas in thesediments suggest relative decrease in Mg.

High salinity in water found in coarse-pored rocks such as reservoir

rocks underlying clays or shales, the cap rocks of oilfields.

Filtration mechanism Ca++ is less mobile than Na+, and Cl- is lessthan water molecule, Mg++ is slightly less mobile than Cl-, which is

more mobile than Ca++ and SO4--


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OTHER ASSOCIATES

Geochemical characteristics of


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CO2 Many N/gas contains small amount of carbon dioxide As much as 92% CO2 has been found in a gas from Upper

Cretaceous sandstones in the Walden Field in Colorado

Sufficient CO2 was at one time produced from the Santa Mariaoilfield in California to Justify the operation of a local dry iceplant on a commercial scale

,

Much CO2 is clearly of magmatic origin, and is related to areas ofrecent volcanism

May also be a product of metamorphism

Produce from breakdown or oxidation of many organicsubstances


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Microorganisms can fix the CO2 in following ways:

Reverse Krebs cycle (also known as the reverse

tricarboxylic acid cycle, the reverse TCA cycle, or the

reverse citric acid cycle). The reaction is basically the Citricacid cycle run in reverse and is used by photolitho-

autotrophic eubacteria of the Chlorobiales and some

- - .

Reductive acetyl CoA Pathway is found in methanogenicarchaebacteria and in acetogenic and some sulfate-

reducing eubacteria as a way of fixing carbon.

3-Hydroxypropionate Pathway is found in photolitho-autotrophically grown eubacteria of the genus Chloroflexus

and in modified form in some chemolitho-autotrophically

grown archaebacteria as a way of fixing carbon.


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Hydrogen sulphide H2S

Mainly magmatic action 3,00,000 tons per year produce fromone fumarole area in Alaska alone !!

Non-volcanic origin swamps, peat bogs, stagnant water etc.

It is formed at the present time as a result of bacterial reductionof sea water sulphates due to lack of circulation of oxygenated

water.

Usually associated with N/Gas due to bacterial breakdown. e.g.

Spindletop field of US.

Association with Anhydrites, gypsum, suggest there is a reducing

action of liquid bitumens on gypsum.

When it contains appreciable amount of H2S, it is called as sourand free of this is called sweet.

It is actively corrosive, and so is generally removed by a chemical

desulphurisation process (along with dehydration).


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GEOCHEMICAL REACTIONS

Role played by different


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The role of diagenesis in hydrocarbon generation

Organic matter (lipids, proteins, carbohydrates and

lignin-humic compounds) > sedimentation > organicmolecules break down due to the increase in

temperature and pressure > creation of two primary

products: kerogens and bitumens. Thermal alteration > kerogens > break down to form

hydrocarbons through a chemical process known as

cracking, or catagenesis. Kinetic model > dissolution-precipitation mechanism.


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COMPOSITION OF OIL- AND GAS-

BEARING ROCKS


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Solutional behaviour ion strength

PH and Eh Dissolved CO2 and CH4 content

water

Presence of dissolved phases like halite, sylvite and

anhydrite.


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pH control

Carbon dioxide can be used as a mean of controlling the pH of swimming pools, by

continuously adding gas to the water, thuskeeping the pH level from rising. Among the

handling (more hazardous) acids.


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where Z = the free energy of reactions; n= the number of

electrons taking part in the reaction; F = the Faraday constant(96,520C/g-eq.); and y = the constant for a given reaction.

As alkalinity of the environment declines, a less reducingenvironment is needed for the reduction of the same

components.

It appears that a strongly alkaline environment is not

necessary and may even be detrimental for the

transformation of organic matter into hydrocarbons.


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Minerals participating in the processes have significantly different pH and Eh stability

limits. A stage of syngenesis and early diagenesis (p


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GEOCHEMICAL ENVIRONMENT

Role of different


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Factors which affects the post

depositional settings Temperature and Pressure

Permeability appearance and redistribution of the cement,

changes in the structural (textural) orientationof rock-forming minerals, and

dissolution of minerals unstable in a given

environment.


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South Louisiana, USA.

unconsolidated Tertiary sandswith admixture of clay

(after P. A. Allen and J. E.

Allen, 1990). < Depth distribution of areas of

(1) reservoir rocks (OR) and (2) oil

accumulations (OA)(afterMaksimov and Minskiy, 1972)

POROSITY AND PERMEABILITYPOROSITY AND PERMEABILITYPOROSITY AND PERMEABILITYPOROSITY AND PERMEABILITY


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POROSITY AND PERMEABILITYPOROSITY AND PERMEABILITYPOROSITY AND PERMEABILITYPOROSITY AND PERMEABILITY

DEF R ATI F R KS I


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DEFORMATION OF ROCKS IN

DEPTHAccording to Eremenko et al. (1986), the

following vertical zones may be identified forthe platforms:

.

Zone II. Calcite cementation zone

Zone III. Decompaction zone

Zone IV. Gravitational compaction andsilica/silicate generation/regeneration zone.


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ZoneZone IIIIII

montmorillonite-to-illite transformation is accompanied bythe release of water and shale loosening, after which shales

compact further.

Released water (that had been previously chemically bonded)is chemically aggressive and dissolves various salts as well as

hydrocarbons in the surrounding rocks.

ZoneZone VIVI Reservoir pressure exceeds the pore pressure in shales.

Silicified reservoir rocks become fluid barriers, whereas

compacted argillaceous rocks experience fracturing andbecome reservoir rocks.

Factors: elevated subsurface pressures and temperatures; tectonic stresses, seismic

activity, changes in the energy and magnetic fields, and exothermal reactions of

mechanochemical nature.


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PETROLEUM

The mobility of


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mobility


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mobility

primary

May be in situ accumulation

Movement and segregation

SR RSVR rock P/T and Solulilization -

colloidal electrolytes

secondary

capillary pressure,displacement pressure or

diffusion Hydrodynamic gradient

Buoyancy

Aromatics >> nephthenes>> paraffins

Compaction effects

Pore pressure and direction

of water flow

Differential entrapment Movement in structural and

stratigraphic traps.

Mobility of associated phases and


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Mobility of associated phases and

buoyancy


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TheTheTheThe chemicalchemicalchemicalchemical compositioncompositioncompositioncomposition ofofofof formationformationformationformation waterswaterswaterswaters cancancancan


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TheTheTheThe chemicalchemicalchemicalchemical compositioncompositioncompositioncomposition ofofofof formationformationformationformation waterswaterswaterswaters cancancancan

bebebebe usedusedusedused asasasas anananan indicatorindicatorindicatorindicator forforforfor thethethethe presencepresencepresencepresence ofofofof

petroleumpetroleumpetroleumpetroleum (V(V(V(V.... AAAA.... Sulin,Sulin,Sulin,Sulin, inininin:::: Vassoyevich,Vassoyevich,Vassoyevich,Vassoyevich, 1954195419541954))))::::


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The specific hydrochemical indicators for the presence of oil

include:


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Presented by:

Manash Pratim Gogoi

M.Sc. 4th semester

Department of Applied Geology

Dibrugarh University

[email protected]

[email protected]

Biological and Geochemical Factors influencing aaccumulation of Petroleum

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