Jan 03, 2016
GEOLOGICAL MAPPING AND OIL RESERVE ESTIMATION
IN MEHSANA OIL FIELDSTATE OF GUJARAT, INDIA.
Report on the Project work submittedin partial fulfilment for the requirement
of the Degree of
Master of Technologyby
SUBU.SUDEESABABUReg. No. 56040001
SCHOOL OF MARINE SCIENCESCOCHIN UNIVERSITY OF SCIENCE AND
TECHNOLOGYCOCHIN - 682016
JUNE 2006
INTRODUCTION
Oil and natural gas are an important source
of Energy. It is an important source from
which organic material, plastics, life-saving
medications, clothing, cosmetics, pesticides,
and many other items you may use daily.
The petroleum geologist is the center pier in
the foundation of the petroleum industry. The
industry is completely dependent upon a
continuing discovery of new pools, or
extension of old pools, for maintenance of its
supply crude oil and thereby of itself; and
most certainly “the discovery and production
of oil is a geologic enterprise.”
About ONGC- Institute of Reservoir Studies The Institute of Reservoir Studies (IRS) was
founded in 1978 as a single- source and multi-
service reservoir engineering agency with the
objectives to:
• Maximize hydrocarbon recovery at minimum cost• Provide holistic reservoir description through integration of all data• Maximize the value of proven reserves with conventional and improved recovery techniques• Enhance the skills and knowledge for better reservoir management
Fig: ONGC-Institute of Reservoir Studies, Ahmedabad
This project here at IRS was about sub-surface
Geological Mapping and Estimation of reserves OIIP
(Oil Initial Inplace). The study area is located within
the Cambay Basin near the Mehsana town, State of
Gujarat, India. The structure in this area was
delineated in early sixties. The earlier well drilled in
the study area did not yield encouraging results but
latter wells drilled proved to be hydrocarbon
bearing. The well encountered about 11m of oil
column in sandstone reservoir of Kalol Formation.
The study area mainly comprises of sandstones,
shales, and claystones with shales generally
forming the non-reservoir part of the oil field. Most
of these Formations belong to Middle-Eocene, age.
At the very beginning of the training program, I
introduced to the basic concepts of Petroleum
Geology, Logging and Enhanced Oil Recovery
Techniques. Following that we were given a
basic demonstration of the software used in log
correlation. As part of the introduction that can
be summarized-as-follows.
Our study was confined only to the peak an
individual of the sand unit which we refer to as
sand unit-1. Various parameters like porosity, oil
saturation etc. were determined in this area
through various logs taken from One Hundred
and Thirty-six (136 Nos.) wells drilled in the
study area which were then used for
determining various aspects-of-the-field.
OBJECTIVE OF THE STUDY
Although the study area had good permeability,
but due to high viscosity of the oil the primary
recovery was quite low. In order to enhance the
recovery of the field a Geocellular model was
prepared and various Enhance Oil Recovery
schemes were carried out one of them being In-
Situ Combustion method. This study was
basically to determine, volumetric reserves of
hydrocarbon in the sand unit-1 of the study
area.
GENERAL GEOLOGY OF THE STUDY AREA
The study area lies in the northern part of
Ahmedabad-Mehsana tectonic block of Cambay
Basin. The Cambay basin is a N-S trending intra-
cratonic rift bounded on eastern and western
margins by N-S Boundary faults. Major transfer
faults divide the basin into eight tectonic blocks
and Mehsana is one of them. The Deccan Traps
forms the technical basement in the basin and is
overlained by thick pile of Tertiary sediments.
FIG: Study Area ( Ahmedabad Mehsana Block)
Stratigraphy of Cambay Basin
GEOLOGICAL MAPPING & OIL RESERVE
ESTIMATIONS Subsurface mapping is practiced chiefly in working
out the geology of petroleum deposits .The
information from well data, however, makes geologic
mapping in three dimensions possible over wide
areas in which there are no outcrops and whose
underground geology could not be deciphered by the
earlier methods. Geologic maps of many kinds are
prepared from these data to show various conditions
underground, and these maps are interpreted to
show the geologic history of the region and to predict
the location of petroleum pools yet undiscovered.
Subsurface structure may be mapped on any
formation boundary, unconformity, or producing
formation that can be identified and correlated by
well data. Structure may be shown by contour
elevation maps or by cross-sections. Since most
formations in the oil regions are below sea level, the
contoured elevations are generally minus figures,
meaning bellow sea level datum, and subsurface
structural maps are sometimes called sub-sea maps.
PROCEDURE
The process early involves log correlation which is
done using a software known as LANDMARK. This data
is then used for preparation of base maps which are
produced using LANDMARK which itself has a subsidy
known as Z-Map plus which is used for obtaining base
maps. Various contour maps are prepared on this
base maps from which latter volumetric estimation
are done.
CORRELATION The sand unit of the study area is about 10m - 11m
broad with horizons bearing shale. Sandstones are
coarse to fine grained, grey colored, medium to well
sorted and at places limonitic.
The unit-1 can also be subdivided locally into sub-units
on the basis of the development of intervening shale
layers. However development of these shale layers are
very localized and are restricted mostly along the
crestal part of the structure, hence making sand unit-1
as a single hydro dynamic unit. The unit-1 also shows
development of thin layers of coal / carbonaceous
streaks in some part of the field.
RESERVOIR PARAMETERS
The provided data which include the reservoir
parameters like NPHI (Neutron Porosity), RHOB (Bulk
Density), CALI (Caliper Logging), GR (Gamma ray
Logging), ILM (Medium Resistivity), VCL (Volume of
Clay type Material relative to total volume), SP
(Spontaneous Potential), DT (Distance Travel, Sonic),
RT (True Resistivity)
Using the following equations we can find out the
various reservoir parameters such as water
saturation (Sw), oil saturation (So), porosity (Phi)
have been computed at log sampling rate for entire
study area and are used for preparing Geocellular
model and volumetric estimation. Average layer
wise parameters have been computed and the
values can be listed in underneath table.
I. VCLRT (Volume of Clay calculated from True Resistivity):
VCLRT = Rclay X RLim – RT
RT RLim – Rclay
Rclay = 2.5
RLim = 1000
2. VCLGR (Volume of Clay calculated from Gamma Ray Log):
VCLGR = GR – GR min
– GR max GR min
3. VCLmin (Volume of Clay Minimum): VCLmin = Min (VCLRT, VCLGR) 4. PHIS (Porosity Calculated from Sonic Log):
PHIS = Δt - Δtma + Vclay (Δtma – Δtclay)
Δtf - Δtma Δtf - Δtma
Δt = DT, Δtma = 55.5 (sst), Δtf = 189, Δtf – Δtma = 133.5
Vclay = Volume of Clay minimum
Δtclay = DT. max value
5. PHID (Porosity calculated from Density Log):
PHID = (RHOB – RHOma) + Vclay (RHOma – RHOclay)
(RHOf – RHOma) (RHOf – RHOma)
RHOB = Bulk Density
RHOf = Average Fluid Density
RHOclay = High GR corresponding RHO value
Vclay min = Volume of Clay minimum
RHOf = 1.0, RHOma = 2.65
6. PHINC (Neutron Porosity Corrected):
PHINC = PHIN – (Vclay min X PHIN Clay)
PHIN = Neutron Porosity
Vclay min = Volume of Clay minimum
PHIN Clay = 0.54
7. PHIE (Effective Porosity):
PHIE = (7 X PHID) + (2 X PHINC)
9
PHID = Porosity calculated from Density Log
PHINC = Neutron Porosity corrected.
8. SW (Water Saturation):
SW = 1/SW -1
SW-1
= [(Vcl
(1-Vcl) ) + (
m/2 ) ] x RT
SW = Saturation of Water
Vcl = Volume of Clay minimum
Rclay = High VCL minimum corresponding RT value
a = 0.62
m = 2.15
RW = 0.25
= Effective Porosity
RT = True Resistivity
a X Rw
2 Rclay
9. SO (Oil Saturation):
SO = (1 – SW)
SW = Water Saturation
10. F (Formation Resistivity Factor)
F = a / m
m = Cementation Factor
a = Constant, 0.81 for sand, 1.0 for compact formation
= Effective Porosity
11. RW (Resistivity of Saturated Formation):
RW = RT / F
RT = True Resistivity
F = Formation Resistivity Factor
AVERAGE RESERVOIR PARAMETERS OF SAND UNIT-1
Well No TOP BOT
KB (mt)
TOP msl
BOT msl
Gross thic
Net thic hp PHI
wat sat Sw
OIL sat So Hp*So*Phi IHM
2 922.00 932.51 61.99 860.01 870.52 10.51 3.38 0.25 0.58 0.42 0.3549 0.355 4 916.97 927.82 61.90 855.07 865.92 10.85 3.13 0.16 0.54 0.46 0.230368 0.230 5 931.61 944.23 62.38 869.23 881.85 12.62 7.00 0.26 0.53 0.47 0.8554 0.855 6 923.20 934.29 60.71 862.49 873.58 11.09 3.05 0.26 0.53 0.47 0.37271 0.373 7 914.20 924.24 60.67 853.53 863.57 10.04 4.88 0.24 0.50 0.50 0.5856 0.586 8 920.50 930.03 62.04 858.46 867.99 9.53 3.00 0.28 0.58 0.42 0.3528 0.353 9 918.90 929.70 61.87 857.03 867.83 10.80 6.86 0.23 0.57 0.43 0.678454 0.678
10 917.87 928.49 61.27 856.60 867.22 10.62 4.60 0.19 0.55 0.45 0.3933 0.393 11 947.23 955.55 63.59 883.64 891.96 8.32 0.00 0 0.000 12 927.43 936.14 61.76 865.67 874.38 8.71 3.96 0.26 0.58 0.42 0.432432 0.432 13 939.60 947.72 63.06 876.54 884.66 8.12 2.90 0.30 0.51 0.49 0.4263 0.426 14 926.38 935.79 60.38 866.00 875.41 9.41 4.59 0.23 0.50 0.50 0.52785 0.528 16 937.84 951.74 61.38 876.46 890.36 13.90 7.93 0.27 0.41 0.59 1.263249 1.263 18 928.73 938.63 61.00 867.73 877.63 9.90 7.61 0.29 0.45 0.55 1.213795 1.214 19 920.90 928.64 61.91 858.99 866.73 7.74 5.13 0.26 0.47 0.53 0.706914 0.707 20 955.03 963.17 63.01 892.02 900.16 8.14 0.00 0 0.000 23 939.12 948.65 62.12 877.00 886.53 9.53 0.38 0.31 0.78 0.22 0.025916 0.026 24 942.71 952.29 60.70 882.01 891.59 9.58 0.00 0 0.000 25 926.90 937.36 52.02 874.88 885.34 10.46 5.21 0.20 0.54 0.46 0.47932 0.479 27 922.86 932.41 61.10 861.76 871.31 9.55 2.44 0.20 0.55 0.45 0.2196 0.220 28 915.80 925.85 60.39 855.41 865.46 10.05 4.23 0.24 0.44 0.56 0.568512 0.569 29 993.02 1005.02 138.02 855.00 867.00 12.00 5.05 0.21 0.44 0.56 0.59388 0.594 30 985.54 993.61 123.54 862.00 870.07 8.07 4.42 0.23 0.59 0.41 0.416806 0.417 31 923.44 934.53 61.28 862.16 873.25 11.09 4.66 0.23 0.50 0.50 0.5359 0.536 33 920.23 927.25 61.93 858.30 865.32 7.02 2.56 0.23 0.52 0.48 0.282624 0.283 34 924.18 931.54 62.34 861.84 869.20 7.36 0.00 0.00 0.00 1.00 0 0.000 35 934.50 947.90 61.93 872.57 885.97 13.40 5.64 0.21 0.54 0.46 0.544824 0.545 36 958.14 967.70 105.14 853.00 862.00 9.00 5.21 0.21 0.66 0.34 0.371994 0.372 37 920.50 930.47 62.35 858.15 868.12 9.97 6.79 0.21 0.55 0.45 0.641655 0.642 38 923.44 931.28 62.51 860.93 868.77 7.84 2.44 0.26 0.62 0.38 0.241072 0.241 39 982.78 992.58 132.01 850.77 860.57 9.80 6.79 0.22 0.59 0.41 0.612458 0.612 42 920.45 931.54 60.02 860.43 871.52 11.09 8.84 0.26 0.44 0.56 1.287104 1.287 43 916.63 924.58 62.13 854.50 862.45 7.95 1.52 0.19 0.67 0.33 0.095304 0.095 44 1005.03 1016.37 147.03 858.00 869.34 11.34 6.10 0.19 0.58 0.42 0.48678 0.487 45 977.48 986.70 129.51 847.97 857.19 9.22 7.93 0.25 0.64 0.36 0.7137 0.714 46 923.92 935.58 60.26 863.66 875.32 11.66 6.87 0.22 0.56 0.44 0.665016 0.665 48 919.32 931.61 60.18 859.14 871.43 12.29 6.62 0.23 0.48 0.52 0.791752 0.792 49 937.84 946.09 62.33 875.51 883.76 8.25 4.63 0.26 0.68 0.32 0.385216 0.385 50 928.74 937.96 60.30 868.44 877.66 9.22 4.72 0.28 0.44 0.56 0.740096 0.740 52 981.05 992.12 127.13 853.92 864.99 11.07 6.73 0.23 0.45 0.55 0.851345 0.851 53 920.50 931.80 61.06 859.44 870.74 11.30 2.13 0.22 0.46 0.54 0.253044 0.253 54 922.17 931.85 59.99 862.18 871.86 9.68 5.18 0.23 0.42 0.58 0.691012 0.691 55 919.34 929.72 61.80 857.54 867.92 10.38 3.18 0.29 0.46 0.54 0.497988 0.498 56 981.86 993.74 127.80 854.06 865.94 11.88 10.52 0.32 0.31 0.69 2.322816 2.323 57 921.64 930.86 61.13 860.51 869.73 9.22 2.90 0.18 0.61 0.39 0.20358 0.204
Well No TOP BOT
KB (mt)
TOP msl
BOT msl
Gross thic
Net thic hp PHI
wat sat Sw
OIL sat So Hp*So*Phi IHM
60 943.20 954.97 62.00 881.20 892.97 11.77 0.00 61 994.55 1004.78 129.80 864.75 874.98 10.23 4.07 0.28 0.72 0.28 0.319088 0.319 62 978.86 990.16 124.06 854.80 866.10 11.30 8.01 0.21 0.44 0.56 0.941976 0.942 64 976.56 985.88 127.83 848.73 858.05 9.32 5.18 0.25 0.46 0.54 0.6993 0.699 65 921.48 929.94 62.36 859.12 867.58 8.46 7.49 0.29 0.33 0.67 1.455307 1.455 66 917.02 928.48 61.70 855.32 866.78 11.46 6.69 0.27 0.51 0.49 0.885087 0.885 70 914.79 925.04 62.12 852.67 862.92 10.25 4.03 0.22 0.48 0.52 0.461032 0.461 71 923.30 933.00 62.58 860.72 870.42 9.70 5.12 0.24 0.52 0.48 0.589824 0.590 72 920.60 927.97 62.69 857.91 865.28 7.37 1.98 0.31 0.54 0.46 0.282348 0.282 73 927.51 938.99 62.96 864.55 876.03 11.48 6.48 0.30 0.52 0.48 0.93312 0.933 74 926.38 936.65 61.61 864.77 875.04 10.27 1.22 0.25 0.49 0.51 0.15555 0.156 75 924.63 933.70 60.21 864.42 873.49 9.07 5.18 0.22 0.45 0.55 0.62678 0.627 76 932.43 940.17 59.60 872.83 880.57 7.74 4.92 0.26 0.53 0.47 0.601224 0.601 77 927.00 937.71 62.00 865.00 875.71 10.71 4.64 0.27 0.44 0.56 0.701568 0.702 78 917.08 925.93 60.08 857.00 865.85 8.85 6.10 0.23 0.52 0.48 0.67344 0.673 79 927.58 935.14 59.88 867.70 875.26 7.56 6.41 0.30 0.29 0.71 1.36533 1.365 80 917.48 926.70 61.12 856.36 865.58 9.22 2.59 0.26 0.40 0.60 0.40404 0.404 81 940.70 950.86 59.68 881.02 891.18 10.16 4.72 0.29 0.60 0.40 0.54752 0.548 83 918.45 930.92 62.46 855.99 868.46 12.47 8.22 0.24 0.44 0.56 1.104768 1.105 84 931.30 940.47 61.54 869.76 878.93 9.17 3.75 0.26 0.42 0.58 0.5655 0.566 85 929.14 947.65 60.63 868.51 887.02 18.51 7.47 0.26 0.30 0.70 1.35954 1.360 86 922.95 937.83 60.45 862.50 877.38 14.88 6.71 0.33 0.45 0.55 1.217865 1.218 87 932.65 938.70 63.20 869.45 875.50 6.05 4.42 0.30 0.45 0.55 0.7293 0.729 91 939.66 950.33 61.34 878.32 888.99 10.67 4.75 0.32 0.57 0.43 0.6536 0.654 92 923.91 934.80 60.07 863.84 874.73 10.89 0.88 0.25 0.45 0.55 0.121 0.121 93 924.92 935.10 59.63 865.29 875.47 10.18 9.54 0.33 0.33 0.67 2.109294 2.109 94 929.42 936.86 62.30 867.12 874.56 7.44 4.38 0.28 0.47 0.53 0.649992 0.650 96 923.12 931.93 60.38 862.74 871.55 8.81 3.50 0.32 0.59 0.41 0.4592 0.459 97 929.14 937.79 63.05 866.09 874.74 8.65 7.03 0.31 0.51 0.49 1.067857 1.068 98 927.95 938.23 61.48 866.47 876.75 10.28 4.71 0.24 0.53 0.47 0.531288 0.531 99 920.49 931.51 60.00 860.49 871.51 11.02 8.57 0.30 0.42 0.58 1.49118 1.491
100 926.73 935.72 61.45 865.28 874.27 8.99 5.00 0.28 0.72 0.28 0.392 0.392 102 931.00 939.47 63.50 867.50 875.97 8.47 5.38 0.32 0.54 0.46 0.791936 0.792 103 915.55 923.35 61.56 853.99 861.79 7.80 3.64 0.25 0.50 0.50 0.455 0.455 104 934.12 950.35 63.75 870.37 886.60 16.23 5.33 0.25 0.46 0.54 0.71955 0.720 105 933.16 1003.75 61.16 872.00 880.00 8.00 4.24 0.22 0.47 0.53 0.494384 0.494 107 930.42 940.72 62.70 867.72 878.02 10.30 4.45 0.27 0.42 0.58 0.69687 0.697 108 933.98 946.21 60.13 873.85 886.08 12.23 1.50 0.39 0.62 0.38 0.2223 0.222 109 926.94 933.64 63.20 863.74 870.44 6.70 3.83 0.29 0.48 0.52 0.577564 0.578 111 926.98 933.92 61.74 865.24 872.18 6.94 2.88 0.15 0.61 0.39 0.16848 0.168 114 926.85 932.83 62.09 864.76 870.74 5.98 3.13 0.24 0.52 0.48 0.360576 0.361 115 922.99 931.91 61.49 861.50 870.42 8.92 4.88 0.23 0.48 0.52 0.583648 0.584 116 927.98 931.93 62.83 865.15 869.10 3.95 7.57 0.28 0.48 0.52 1.102192 1.102 117 921.04 929.37 61.55 859.49 867.82 8.33 3.38 0.21 0.62 0.38 0.269724 0.270 118 926.31 934.63 62.34 863.97 872.29 8.32 3.31 0.27 0.38 0.62 0.554094 0.554 119 928.56 939.56 61.00 867.56 878.56 11.00 6.00 0.32 0.60 0.40 0.768 0.768
Well No TOP BOT
KB (mt)
TOP msl
BOT msl
Gross thic
Net thic hp PHI
wat sat Sw
OIL sat So Hp*So*Phi IHM
60 943.20 954.97 62.00 881.20 892.97 11.77 0.00 61 994.55 1004.78 129.80 864.75 874.98 10.23 4.07 0.28 0.72 0.28 0.319088 0.319 62 978.86 990.16 124.06 854.80 866.10 11.30 8.01 0.21 0.44 0.56 0.941976 0.942 64 976.56 985.88 127.83 848.73 858.05 9.32 5.18 0.25 0.46 0.54 0.6993 0.699 65 921.48 929.94 62.36 859.12 867.58 8.46 7.49 0.29 0.33 0.67 1.455307 1.455 66 917.02 928.48 61.70 855.32 866.78 11.46 6.69 0.27 0.51 0.49 0.885087 0.885 70 914.79 925.04 62.12 852.67 862.92 10.25 4.03 0.22 0.48 0.52 0.461032 0.461 71 923.30 933.00 62.58 860.72 870.42 9.70 5.12 0.24 0.52 0.48 0.589824 0.590 72 920.60 927.97 62.69 857.91 865.28 7.37 1.98 0.31 0.54 0.46 0.282348 0.282 73 927.51 938.99 62.96 864.55 876.03 11.48 6.48 0.30 0.52 0.48 0.93312 0.933 74 926.38 936.65 61.61 864.77 875.04 10.27 1.22 0.25 0.49 0.51 0.15555 0.156 75 924.63 933.70 60.21 864.42 873.49 9.07 5.18 0.22 0.45 0.55 0.62678 0.627 76 932.43 940.17 59.60 872.83 880.57 7.74 4.92 0.26 0.53 0.47 0.601224 0.601 77 927.00 937.71 62.00 865.00 875.71 10.71 4.64 0.27 0.44 0.56 0.701568 0.702 78 917.08 925.93 60.08 857.00 865.85 8.85 6.10 0.23 0.52 0.48 0.67344 0.673 79 927.58 935.14 59.88 867.70 875.26 7.56 6.41 0.30 0.29 0.71 1.36533 1.365 80 917.48 926.70 61.12 856.36 865.58 9.22 2.59 0.26 0.40 0.60 0.40404 0.404 81 940.70 950.86 59.68 881.02 891.18 10.16 4.72 0.29 0.60 0.40 0.54752 0.548 83 918.45 930.92 62.46 855.99 868.46 12.47 8.22 0.24 0.44 0.56 1.104768 1.105 84 931.30 940.47 61.54 869.76 878.93 9.17 3.75 0.26 0.42 0.58 0.5655 0.566 85 929.14 947.65 60.63 868.51 887.02 18.51 7.47 0.26 0.30 0.70 1.35954 1.360 86 922.95 937.83 60.45 862.50 877.38 14.88 6.71 0.33 0.45 0.55 1.217865 1.218 87 932.65 938.70 63.20 869.45 875.50 6.05 4.42 0.30 0.45 0.55 0.7293 0.729 91 939.66 950.33 61.34 878.32 888.99 10.67 4.75 0.32 0.57 0.43 0.6536 0.654 92 923.91 934.80 60.07 863.84 874.73 10.89 0.88 0.25 0.45 0.55 0.121 0.121 93 924.92 935.10 59.63 865.29 875.47 10.18 9.54 0.33 0.33 0.67 2.109294 2.109 94 929.42 936.86 62.30 867.12 874.56 7.44 4.38 0.28 0.47 0.53 0.649992 0.650 96 923.12 931.93 60.38 862.74 871.55 8.81 3.50 0.32 0.59 0.41 0.4592 0.459 97 929.14 937.79 63.05 866.09 874.74 8.65 7.03 0.31 0.51 0.49 1.067857 1.068 98 927.95 938.23 61.48 866.47 876.75 10.28 4.71 0.24 0.53 0.47 0.531288 0.531 99 920.49 931.51 60.00 860.49 871.51 11.02 8.57 0.30 0.42 0.58 1.49118 1.491
100 926.73 935.72 61.45 865.28 874.27 8.99 5.00 0.28 0.72 0.28 0.392 0.392 102 931.00 939.47 63.50 867.50 875.97 8.47 5.38 0.32 0.54 0.46 0.791936 0.792 103 915.55 923.35 61.56 853.99 861.79 7.80 3.64 0.25 0.50 0.50 0.455 0.455 104 934.12 950.35 63.75 870.37 886.60 16.23 5.33 0.25 0.46 0.54 0.71955 0.720 105 933.16 1003.75 61.16 872.00 880.00 8.00 4.24 0.22 0.47 0.53 0.494384 0.494 107 930.42 940.72 62.70 867.72 878.02 10.30 4.45 0.27 0.42 0.58 0.69687 0.697 108 933.98 946.21 60.13 873.85 886.08 12.23 1.50 0.39 0.62 0.38 0.2223 0.222 109 926.94 933.64 63.20 863.74 870.44 6.70 3.83 0.29 0.48 0.52 0.577564 0.578 111 926.98 933.92 61.74 865.24 872.18 6.94 2.88 0.15 0.61 0.39 0.16848 0.168 114 926.85 932.83 62.09 864.76 870.74 5.98 3.13 0.24 0.52 0.48 0.360576 0.361 115 922.99 931.91 61.49 861.50 870.42 8.92 4.88 0.23 0.48 0.52 0.583648 0.584 116 927.98 931.93 62.83 865.15 869.10 3.95 7.57 0.28 0.48 0.52 1.102192 1.102 117 921.04 929.37 61.55 859.49 867.82 8.33 3.38 0.21 0.62 0.38 0.269724 0.270 118 926.31 934.63 62.34 863.97 872.29 8.32 3.31 0.27 0.38 0.62 0.554094 0.554 119 928.56 939.56 61.00 867.56 878.56 11.00 6.00 0.32 0.60 0.40 0.768 0.768
CORRELATION-1
WELL NO. 35 WELL NO. 152 WELL NO. 27 WELL NO. 29
WELL NO. 29 WELL NO. 37 WELL NO. 30 WELL NO. 76
CORRELATION-2WELL NO. 153 WELL NO. 125 WELL NO. 86 WELL NO. 155
CORRELATION-3WELL NO. 76 WELL NO. 64 WELL NO. 36 WELL NO. 6
STRUCTURE CONTOUR MAP OF TOP
STRUCTURE CONTOUR MAP OF BOTTOM
CONTOUR MAP OF GROSS THICKNESS
CONTOUR MAP OF NET THICKNESS
CONTOUR MAP OF PHIE
CONTOUR MAP OF SO (Oil Saturation)
METHODOLOGY
The method involves preparation of different contour
maps of the study area and then preparing cross-sections
along the different wells to delineate an overall structure
of the basin. These contour maps were also used in
Volumetric estimation of the Oil Field.
Structure Contour Map was first prepared, using the top
and bottom values of the log data from different wells.
The top and bottom values were corrected using a
parameter known as KB. This map was further used in
preparation of different cross-section along different
wells.
Various cross-sections were prepared vertically,
horizontally and across the study area. Some of them
are;
1. Section through wells 35-152-27-29-37-66-30-76:- It is
an N-S section representing a constant thickness of the
sand unit which towards southern end gets a bit
tapered. The section shows a doming towards the
center which may itself indicate doming of the
basement.
2. Section through wells 153-125-86-130-155:- It is an E-
W section representing sand unit-1. It represents an
anticline which has a steeper western flank and gentler
eastern flank. The thickness almost remains constant.
3. Section Through wells 76-64-36-2-6-73:- It is an SW-NE
trending section which represents again an anticlinal
structure of the study area with western side steeper
and eastern gentler.
Net Thickness (Hp) contour map, Porosity
(Phi) contour map, Oil Saturation (So) maps
were also prepared which were used for
volumetric estimation. The product of
above three parameters gives another
parameter known as Integrated
Hydrocarbon Measures (IHM). A contour
map for IHM is also plotted, which is
generally useful in determining locations
which may show high prospects of oil
accumulation and will act as a guide to
which location are economically ideal for
exploration.
VOLUMETRIC ESTIMATION
Volumetric calculations involve determination of:-
1. First the area of the whole sand unit-1. It
was calculated (by using planimeter) to be
as 35.78 sq km.
2. Secondly areas between successive
contours were calculated (by using
planimeter) for porosity map, oil saturation
map and net thickness map.
DIGITAL PLANIMETER The planimeter is a drafting instrument
used to measure the area of a graphically
represented planar region. The region
being measured may have any irregular
shape, making this instrument remarkably
versatile
Fig: Digital Planimeter
Further calculations can be represented below:-
1) To calculate Average Net Thickness (Hp):-
Contour Interval Midpoint
(a)
Area (sq km)
(b)
Z=(a)x(b)
0-9 4.5 15.812 71.154
9-7 8 5.360 42.880
7-5 6 6.712 40.272
5-3 4 7.896 31.568
Total 35.78 185.874
Average Net Thickness (Hp) = ΣZ ÷ Σ b
Hence Average Net Thickness = 5.1945M
2) To Calculate Average Oil saturation (So):-
Contour Interval Midpoint
(a)
Area(sq km)
(b)
Z=(a)x(b)
0-0.7 0.35 14.78 5.173
0.7-0.6 0.65 6.56 4.264
0.6-0.5 0.55 9.17 5.044
0.5-0.4 0.45 5.27 2.372
Total 35.78 16.853
Average Oil Saturation (So) = ΣZ ÷ Σ b
Hence Average Oil Saturation = 0.471
3) To calculate Average porosity:-
Contour
Interval
Midpoint
(a)
Area(sq km)
(b)
Z=(a)x(b)
0-0.3 0.15 18.184 2.728
0.3-0.25 0.275 7.388 2.032
0.25-0.2 0.225 10.208 2.297
Total 35.78 7.057
Average Porosity (Phi) = ΣZ ÷ Σ b
Hence Average Porosity = 0.1972
Volume of Hydrocarbon (surface)
= Area x Avg. Hp x Avg.Phi x Avg. So x Bo
Where Bo Oil Expansion Factor (1.1) and
depends on a particular oil field.
= 35780000 x 5.1945 x 0.1972 x 0.471 x 1.1
= 18.98 MMm3
Original Oil In place (OIIP)
= Volume of hydrocarbon (Surface) x Density of Oil
= 18.98 x 0.96
= 18.22 MMt
CONCLUSION
• The sand unit makes the reservoir and the shale
body forms the non reservoir part of the study area.
• The sand unit-1 has estimated an OIIP of 18.22 MMt
and volume on surface as 18.98 MMm3
• From the IHM contour map produced one can
conclude other than the northern section of study
area in area around well no. 56 and area around
well no. 93 are good prospecting options which
show IHM values ranging from 1.2 to 2.0.
• The study area is a heterogeneous reservoir and
the oil bearing sand units which were earlier not
perforated may be perforated for additional
production.