2-D SEISMIC DATA INTERPRETATION AND VOLUMETRIC ANALYSIS OF DHULIAN AREA

UPPER INDUS BASIN, PAKISTAN.

FASIH AKHTAR

WASEEM ABBAS

HASNAIN ZAHOOR AWAN

SUPERVISOR: M. FAHAD MAHMOOD

EXTERNAL SUPERVISOR: Mr. SARMAD HASSAN SHARIF

2010-2014

OUTLINE OF PRESENTATION

Introduction Of the Area Objectives Methodology Adopted Overview of Potwar Sub Basin Petroleum System Seismic Interpretation Petrophysical Analysis Conclusions

OBJECTIVES

To carry out the seismic data interpretation and mapping of the area in order to understand the subsurface structural geometry of Dhulian anticline.

Preparation of Time and Depth Sections

Petrophysical Analysis of Dhulian-43 well to understand the reservoir potential of the structure.

Volumetric Analysis of the area to calculate remaining potential of the structure.

AREA OF INVESTIGATION

The Study area of Dhulian is located in the Eastern Potwar basin.

The Dhulian Area is bounded by Latitude 33°12'41“N and Longitude 72°12'00“E.

The Nearest city to the Dhulian study area is Pindi Gheb.

Oil was also discovered for the first time in Indo-Pakistan from Paleocene reservoirs, during further appraisal of Dhulian structure.

LOCATION MAP

A total of 49 wells were drilled in Dhulian oil field

Three wells have been drilled by Attock Oil Company (A.O.C.)

46 wells have been drilled by Pakistan Oilfields Limited (P.O.L)

Seven wells did not reach objective reservoirs and three wells could not be put on production due to various technical reasons.

ACCESSIBILITY MAP

Courtesy: P.O.L. Geologic Bulletin 2004

Dhulian Oil Field

Alluvium, Sandstone, siltstone etc

Siwaliks Group

Thrust Fault

Anticline

SynclineRawalpindi

GroupOil fields

N

Dhulian Oil Field

Kazmi and Abbasi, 2008

GEOLOGICAL MAP

PETROLEUM PLAY

PLAY ELEMENTS

FORMATONS AGE

TRAP Structural Trap

SEAL Murree FormationNammal Formation

MiocenePaleocene

RESERVOIR Chorgali FormationSakesar LimestoneLockhart FormationWargal Formation

Eocene EocenePaleocenePermian

SOURCE Patala Formation Paleocene

TECTONIC MAP OF POTWAR SUB-BASIN

(Kadri, 1995)

GENERAL STRATIGRAPHY OF DHULIAN AREA

(Kazmi and Jan, 1997)

BOREHOLE STRATIGRAPHY

Total Depth 3788m , A.O.C, 22-03-1963Formations Depth (m)

CHINJI 0

RAWALPINDI GROUP 886

MAMI KHEL 2498

CHORGALI 2524

SAKESAR 2590

NAMMAL 2683

PATALA 2741

LOCKHART 2813

HANGU 2869

MIANWALI 2886

CHIDDRU 2932

WARGAL 2987

AMB 3136

SARDHAI 3214

WARCHA 3291

DANDOT 3444

TOBRA 3508

SALT RANGE 3632

STRUCTURE Dhulian fold is flanked by the Soan Syncline to the south and by the

tight Pindi Gheb syncline to the north

The Dhulian structure was originally thought to be a conventional anticline with a fold axis trending northeast southwest.

Based on this new seismic evidence, Dhulian structure was proved to be a thrust-bounded salt-cored anticline,

It is cut across by a major wrench fault that splits Dhulian into two major fault blocks

As a result, the Dhulian structure may be compartmentalized.

3-D VIEW OF DHULIAN STRUCTURE

Courtesy: P.O.L Geologic Bulletin 2004

SEISMIC DATA INTERPRETATION

Depth Contour Maps

Time to Depth Conversion

Velocity Analysis

Time Contour Maps

Time Picking

Marking of Faults

Marking of Prominent Reflectors

T-D Chart

METHODOLOGY

DATA USED

Line

Name

PDK-102 PDK-103 PDK-104 PDK-113WELLDATA

Line Dip line Dip line Dip line Strike line

DHULIAN-43(Gamma ray log, Neutron Log and Resistivity logs)

Line

Direction

North-South North-South North-South East-West

SP Range 108-188 108-218 108-298 108-340

Date

Recorded

1981 1981 1981 1981

BASE MAP

T-D CHART

0 200 400 600 800 1000 1200 1400 1600 1800 20000

250

500

750

1000

1250

1500

1750

2000

2250

2500

2750

3000

3250

3500

3750

4000

T-D Graph

T-D Graph

Lockhart Formation

Wargal Formation

Chorgali Formation

Dep

th

Time

SEISMIC SEQUENCES & REFLECTION FEATURES

In the study area four sets of seismic sequence are encountered on the basis of seismic reflection features.

Sequence 1: Continuous and Dark reflectors at the bottom of Seismic Section

stands for the basement of Pre-Cambrian age.

Sequence 2: Strong to medium continuous reflections, great change in thickness, it is Infra Cambrian aged Salt Ranges Formation composed of salt and evaporates. A great decollement plane is development.

Sequence 3: Parallel and continuous reflections high amplitude and frequency. It stands for Paleocene –Eocene ages formation. The traditional reservoirs in Potwar were developed in this sequence.

Sequence 4: Parallel and weak to continuous reflections. It stands for Miocene aged Mollasse architecture.

REFLECTORS MARKING

In total three horizons have been mapped throughout the study

1. Chorgali Formation (Eocene)2. Lockhart Formation (Paleocene)3. Wargal Formation (Permian)

These three horizons comprise the target horizons for hydrocarbon exploration in the study area.

Chorgali Formation was picked as it is a very strong reflector beneath the Kohat Formation i.e. Eocene

 

Lockhart Formation (Paleocene) was picked in the base of decreasing acoustic impedance from Nammal Formation to Patala Formation and then increasing peak of Lockhart Formation.

Wargal Formation was picked below to Lockhart Formation. The reflection continuity is fair to good.

PDK-102

PDK-103

PDK-104

PDK-113

PDK-102

Time Section

PDK-103

Time Section

PDK-104

Time Section

PDK-113

Time Section

TIME CONTOUR MAPS

Contouring the time structure maps and finding structural traps are one of the basic goals of Seismic data interpretation.

In this respect three time contour maps have been prepared on three different horizons in the whole area at the scale of 1:50, 000.

1.    Time Contour Map of Chorgali Formation (Eocene) 2.    Time Contour Map of Lockhart Formation (Paleocene) 3.    Time Contour Map of Wargal Formation (Permian)

TWT Map on Top Chorgali of Dhulian D & P Lease

TIME CONTOUR MAP OF CHORGALI FORMATION

TWT Map on Top Lockhart of Dhulian D & P Lease

TIME CONTOUR MAP OF LOCKHART FORMATION

TWT Map on Top Wargal of Dhulian D & P Lease

TIME CONTOUR MAP OF WARGAL FORMATION

DEPTH CONTOUR MAPS

The following depth maps have been prepared at the scale of

1:50,000 with respect to mean sea level.

1. Depth Structure Map of Chorgali Formation

2. Depth Structure Map of Lockhart Formation

3. Depth Structure Map of Wargal Formation

These maps have been prepared mainly using the drilling well tops available on different wells in Dhulian area.

DEPTH CONTOUR MAP OF CHORGALI FORMATION

C.I. 20 ftS.R.D 400 m

DEPTH CONTOUR MAP OF LOCKHART FORMATION

DEPTH CONTOUR MAP OF WARGAL FORMATION

PETROPHYSICAL ANALYSIS

Well Dhulian-43.

Located on:

Lattitude 33°12'41“N

Longitude 72°12'00“E.

Total Depth:

3788 meters

Interpretation is done on Chorgali and Lockhart Formation.

WORK FLOW

Marking of Zone of Interest

Lithology Identification

Volume of Shale

Effective Porosity

Total Porosity

Saturation of Water Saturation of

Hydrocarbon

Summation

MARKING ZONE OF INTEREST

Formatio

n

Starting

depth

(m)

Ending depth

(m)

Total thickness

(m)

Chorgali

Fm2494m 2560m 66m

Lockhart

Fm 2783m 2839m 56m

PETROPHYSICAL ANALYSIS

Logs used

• Gamma Ray Log

• Neutron Log

• Density Log

• Resistivity Log

GAMMA RAY LOG

Amount of radioactivity.

Differentiate between shale and sand content.

To calculate shale volume

Volume of Shale (Vsh) = GRlog – GRmax / GRmax – GRmin

0 10 20 30 40 50 60 70 808100

8150

8200

8250

8300

8350

8400

8450

Depth Vs Shale Volume

Depth Vs Shale Volume

Dep

th (

ft)

DENSITY & NEUTRON LOG

Delineation of porous formation and their porosity.

Density Porosity = Densitymatrix – Densitylog / Densitymatrix – Densityfluid

Neutron Porosity = Value of Neutron Log

Average Porosity = (Density Porosity + Neutron Porosity) / 2

Effective Porosity = Porosityavg *

(1- Vsh)

4 6 8 10 12 14 16 188100

8150

8200

8250

8300

8350

8400

8450

Depth Vs Average Porosity

Depth Vs Average Porosity

Dep

th (

ft)

0 2 4 6 8 10 12 148100

8150

8200

8250

8300

8350

8400

8450

Depth Vs Effective Porosity

Depth Vs Effective Porosity

Dep

th (

ft)

RESISTIVITY LOG

Use for determination of resistivity of

formation.

18 20 22 24 26 28 30 32 34 36 388100

8150

8200

8250

8300

8350

8400

8450

Depth Vs Saturation of Water

Depth Vs Saturation of Water

Dep

th (

ft)

60 80 100 1208100

8150

8200

8250

8300

8350

8400

8450

Depth Vs Saturation of Hydrocarbons

Depth Vs Saturation of Hydro-carbons

COMPOSITE DIAGRAM0 20 40 60 80 100 120

8100

8150

8200

8250

8300

8350

8400

8450

Volume of ShaleAverage PorosityEffective PorositySaturation of WaterSaturation of Hydrocarbons

Dep

th (

ft)

Lockhart Formation

0 20 40 60 80 100 1209000

9050

9100

9150

9200

9250

9300

9350

Depth Vs Volume of Shale

Depth Vs Volume of Shale

Dep

th (

ft)

Dep

th (

ft)

4 6 8 10 12 14 16 189000

9050

9100

9150

9200

9250

9300

9350

Depth Vs Average Porosity

Depth Vs Average Porosity

0 2 4 6 8 10 12 149000

9050

9100

9150

9200

9250

9300

9350

Depth Vs Effective Porosity

Depth Vs Effective Porosity

Dep

th (

ft)

24 26 28 30 32 34 36 38 40 429000

9050

9100

9150

9200

9250

9300

9350

Depth Vs Saturation Of Water

Depth Vs Saturation Of Water

Dep

th (

ft)

58 60 62 64 66 68 70 72 74 769000

9050

9100

9150

9200

9250

9300

9350

Depth Vs Saturation of Hydrocarbons

Depth Vs Saturation of Hy-drocarbons

Dep

th (

ft)

COMPOSITE DIAGRAM

0 10 20 30 40 50 60 70 809000

9050

9100

9150

9200

9250

9300

9350

Volume of ShaleAverage PorosityEffective PorositySaturation of WaterSaturation of HydrocarbonsD

ep

th (

ft)

Formation

Name

Lithology Volume Of

Shale

(%)

Average

Porosity

(%)

Effective

Porosity

(%)

Avg. Water

Saturation

(%)

Avg,

Hydrocarb

on

Saturation

(%)

Chorgali

Formation

Limestone,

Shale

33.80

%

10.81

%

7.34

%

26.33

%

73.66

%

Lockhart

Formation

Limestone,

Marl

32.55

%

9.84

%

7.56

%

42.6

%

57.4

%

RESERVOIR ESTIMATION

The total estimated amount of oil in a reservoir, including both

producible and non-producible oil, is called oil in place.

C.I. 20 ftS.R.D 400 m

N = 7758 * GRV * N/G * Φ * So * 1/Bo

Where

7785 = Conversion factor (acre-ft*7758 =barrels)

GRV = Gross Rock Volume (acre-ft)

N/G = Net to Gross Ratio (decimal)

Φ = Porosity of this net reservoir rock (decimal)

So = Oil Saturation (decimal)

Bo = Formation Volume factor.

VOLUMETRIC RESERVE ESTIMATION

RESULT OF VOLUMETRIC RESERVES

Reserve Calculation

(7758*Area(acre)*Net Pay(ft)*Avg. Porosity(phi)*Sw)/Bg

Formation Case ContourArea

(Acre)Net Pay

(ft)Phi avg.

(fraction)Sw avg.

(fraction)Bo

OIIP (MMBL)

Recovery Factor

Recoverable Reserves

(MMBL)

GOR (scf/stb)

Gas Recovery

(BCF)

Chorgali

P90 2470 3706 130 0.05 0.28 2.047 65 30 19.5 1975 38512.5

P50 2600 6177 130 0.05 0.28 2.047 109 30 32.7 1975 64582.5

P10 2700 9884 130 0.05 0.28 2.047 175 30 52.5 1975 103687.5

CONCLUSIONS

The multifold seismic acquired by OXY and POL demonstrated that Dhulian subsurface structure is more complicated than what was originally thought.

The structure is a three way dip closure bounded by thrust fault.

Based on this new seismic evidence, Dhulian structure was proved to be a thrust-bounded salt-cored anticline.

It is cut across by a major wrench fault that splits Dhulian into two major fault blocks.

RECOMMENDATIONS

For more detailed study and to define potential sites in the area, more

seismic lines are required.

High resolution seismic data and wire line logs should be acquire in future

operations.

3D seismic survey should acquire in future to obtain the maximum

information of subsurface.

REFERENCES

Dolan P., (1990) Pakistan: a history of petroleum exploration and future potential; in Classic Petroleum province edited by Brooks J. Special Publication of The Geological Society London

Iqbal B. Kadri, (1995), Petroleum Geology of Pakistan

Khan M. A. Ahmed R., Raza H. A., and Kemal A., (1986), Geology of Petroleum in Kohat-Potwar depression, Pakistan, AAPG Bulletin, Vol 70, No. 4

Iqbal, M.W.S, and Shah, S.M.I, 1980. A guide to the Stratigraphy of Pakistan.V.53

Thank You

AnnexureStructural Model of Dhulian