Published on March 16, 2014
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.
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 Anticli ne Syncline Rawalpindi Group Oil fields N Dhulian Oil Field Kazmi and Abbasi, 2008 GEOLOGICAL MAP
PETROLEUM PLAY PLAY ELEMENTS FORMATONS AGE TRAP Structural Trap SEAL Murree Formation Nammal Formation Miocene Paleocene RESERVOIR Chorgali Formation Sakesar Limestone Lockhart Formation Wargal Formation Eocene Eocene Paleocene Permian 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, 22-03-1963 Formations 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-113 WELLDATA 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
T-D CHART 0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000 0 200 400 600 800 1000 1200 1400 1600 1800 2000 T-D Graph T-D Graph Lockhart Formation Wargal Formation Chorgali Formation Depth 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 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 ft S.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 Formation Starting depth (m) Ending depth (m) Total thickness (m) Chorgali Fm 2494m 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
8200 8250 8300 8350 8400 8450 0 10 20 30 40 50 60 70 Depth Vs Shale Volume Depth Vs Shale Volume Depth(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)
8200 8250 8300 8350 8400 8450 0 5 10 15 20 Depth Vs Average Porosity Depth Vs Average Porosity Depth(ft)
8200 8250 8300 8350 8400 8450 0 2 4 6 8 10 12 14 Depth Vs Effective Porosity Depth Vs Effective Porosity Depth(ft)
RESISTIVITY LOG Use for determination of resistivity of formation.
8200 8250 8300 8350 8400 8450 0 5 10 15 20 25 30 35 40 Depth Vs Saturation of Water Depth Vs Saturation of Water Depth(ft)
8200 8250 8300 8350 8400 8450 0 20 40 60 80 100 120 Depth Vs Saturation of Hydrocarbons Depth Vs Saturation of Hydrocarbons
COMPOSITE DIAGRAM 8200 8250 8300 8350 8400 8450 0 20 40 60 80 100 120 Volume of Shale Average Porosity Effective Porosity Saturation of Water Saturation of Hydrocarbons Depth(ft)
9120 9140 9160 9180 9200 9220 9240 9260 9280 9300 9320 0 20 40 60 80 100 120 Depth Vs Volume of Shale Depth Vs Volume of Shale Depth(ft)
Depth(ft) 9120 9140 9160 9180 9200 9220 9240 9260 9280 9300 9320 0 5 10 15 20 Depth Vs Average Porosity Depth Vs Average Porosity
9120 9140 9160 9180 9200 9220 9240 9260 9280 9300 9320 0 2 4 6 8 10 12 14 Depth Vs Effective Porosity Depth Vs Effective Porosity Depth(ft)
9120 9140 9160 9180 9200 9220 9240 9260 9280 9300 9320 0 10 20 30 40 50 Depth Vs Saturation Of Water Depth Vs Saturation Of Water Depth(ft)
9120 9140 9160 9180 9200 9220 9240 9260 9280 9300 9320 0 10 20 30 40 50 60 70 80 Depth Vs Saturation of Hydrocarbons Depth Vs Saturation of Hydrocarbons Depth(ft)
COMPOSITE DIAGRAM 9120 9140 9160 9180 9200 9220 9240 9260 9280 9300 9320 0 10 20 30 40 50 60 70 80 Volume of Shale Average Porosity Effective Porosity Saturation of Water Saturation of Hydrocarbons Depth(ft)
Formation Name Lithology Volume Of Shale (%) Average Porosity (%) Effective Porosity (%) Avg. Water Saturation (%) Avg, Hydro carbon 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 ft S.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 Contour Area (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
Annexure Structural Model of Dhulian
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