Conventional natural gas is being exploited rapidly to achieve energy security and to satisfy the demand. However, due to the high demand for oil and gas it is becoming more difficult to find sufficient conventional reserves. To anticipate the predicted shortage of gas, we need to explore new, unconventional resources, such as shale gas. Shale gas is shale lithology that has high TOC, is brittle, and is located in the dry gas window zone. This study describes the early exploration of shale gas potential in one block in South Sumatra basin area.
In this study, the integration of geochemical data, rock physics and seismic inversion for characterizing and searching for shale gas potential will be described. The preliminary exploration stage of gas shale play covers sweet spot analysis using the Passey method to create a pseudo TOC in the target formation. Secondly, the overpressure area is mapped to avoid any potential pitfalls. Thirdly, seismic inversion is performed to map the distribution of shale based on the parameters Vp / Vs and map its TOC through conversion from Vp parameter.
As a result, log analysis shows one target zone of potential shale gas with TOC above 1% with a thickness of 100 feet. Integration of pore pressure data, shale distribution and TOC distribution of the target zone shows two potential areas in west, north-south trending, and in the east relatively of the well-X. Both locations can be recommended for the next pilot holes in order to acquire a complete set of new data and to be able to evaluate more intensively.
Fossil fuel is finite energy. The common conventional oil and gas that we use every day are fossil fuels, which are located in the subsurface reservoir having good porosity and permeability. But, because of high demand and the limited amount of available conventional oil and gas, reserves are getting low. It is essential to find other resources as additional fossil fuel stock for the near future. One solution is to expand oil and gas exploration to include unconventional resources, such as shale gas, shale oil, basement fracture, heavy oil, tight gas and CBM.
Shale gas resource is located in the gas-rich shale zone. Horizontal drilling is common in shale gas exploration and exploitation because the shale has to be fractured in several stages due to low permeability.
This is the chart from American century investment
Shale gas play rapidly develop in USA since 1990 (Summer, 2008). In 2008, production of shale gas reach 5000 MMCFD (Navigant, 2008)
Integration of Seismic Inversion, Pore Pressure Prediction, and TOC Prediction in Preliminary Study of Shale Gas Exploration
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Integration of Seismic Inversion, Pore
Pressure Prediction, and TOC Prediction in
Preliminary Study of Shale Gas Exploration
Andika Perbawa (1), Bayu Kusuma (1), Sonny Winardhi (2)
PIT HAGI 2012 - 216
(1) Medco E&P Indonesia
(2) Institute of Technology Bandung
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• Basic theory
• Data Availability and Method
• Conclusions and Recommendations
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“Natural gas that cannot be produced at economic flow rates or in
economic volumes of natural gas unless the well is stimulated by a
large hydraulic fracture treatment, a horizontal wellbore, or by using
multilateral wellbores or some other technique to expose more of the
reservoir to the wellbore”
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What is Shale Gas ?
Source: US Energy Information Administration
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Organic rich shale : TOC > 1.0%, HI > 100
Gas type : Free gas and absorb gas
Permeability : Low need fracture job
Maturation : Mature to over-mature zone window (> 1.3 %Ro)
Thickness : > 75 ft
Kerogen type : Type I and II generates more gas than type III.
Mineralogy : More quartz / less clay, brittle shale / more fracture.
Storage : Fractures and pores
Low recovery efficiency : 8-15%
Performance of production : Depend on natural fractures and artificial fracture
• Rock type, lithology, mineralogy and V-clay estimation
• Kerogen estimation and distribution
• Fracture orientation
• Maturation distribution
• Shale distribution
• TOC distribution
• Reservoir pressure distribution
• Brittleness and ductile distribution
• Porosity distribution
• Permeability distribution
• Depositional setting, direction and isopach of shale distribution
• Gas saturation and composition estimation
• Fluid sensitivity
• Volume calculation
Key Parameter in Shale Gas Exploration
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Delineate potential shale gas play using available
data, then recommend a drilling location to acquire a
complete set of new data and to be able to evaluate
shale gas resources more intensively
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• Total Organic Carbon: TOC
• Maturation : %Ro , Tmax, LOM
• Kerogen type : HI, S2/S3
Data needed to evaluate the potential of shale gas in exploration:
2. Petrophysics and Petrography
• Mineralogy: XRD, SEM
• Fracture evaluation
• Gas content and capacity (absorbed and free)
3. Well Data
• GR, spectral GR, Vp, Vs, Density, Neutron, Resistivity,
Image log, dip meter, PE, ect.
• Core Data
4. Seismic Data
• 3D pre-stack seismic data
*Red indicates data available for this study
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(GR, ILD, Sonic, RHOB,
Sweetspot identification and
Probable Shale Gas
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Method – Application (2)
Velocity actual (ms)
Method test in the other well that has Vs
Check relationship between prediction and actual data
Method – Application (2)
TELISA MARKER 3
26 m.a. LOWER TAF
-base inversion window-
21 m.a. UPPER TAF
-top inversion window-
Simultaneous Seismic Inversion Result: Vp
Method – Application (2)
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Pore Pressure Prediction
Method – Application (3)
Pore Pressure Prediction
using velocity data from:
1. DT log/Sonic (purple).
2. Pseudo DT derived from
resistivity (red) using
Faust (1953) equation.
3. Calibrated velocity
After all of velocity data are
aligned, apply Eaton’s
equation to calibrated
velocity stack cube
Potential Shale Gas Area
• Passey’s method shows a sweet spot interval in Upper Talang Akar Fm.
• The potential shale gas is about 100 feet thick and has more than 1% of TOC
in Upper Talang Akar Fm.
• The Lower Talang Akar Fm. has less potential shale gas.
• The shale distribution covers a whole objective area (Upper Talang Akar Fm.)
• There are several spotty areas that have a medium pressure regime in the
north, west and south-east relative to well- X. Drilling needs to be aware.
• The two interesting potential shale gas areas (TOC ≥ 1%) are located in the
west, trending north-south, and in the east relative to well-X.
• Both locations can be recommended for the next pilot holes in order to
acquire a complete set of new data and to be able to evaluate more
• Use actual shear wave data to reduce uncertainty.
• Use TOC data from Core or SWC for accurate depth location.
• Drill a pilot hole in order to acquire a complete set of new data and to be able
to evaluate more intensively.
• Core Data
• Geochemist analysis (TOC, Ro, HI, Rock eval, etc.)
• Complete well log data (include shear wave data)
• Conduct a 3D data with small bin and narrow inline/xline interval. Perform
anisotropic processing and analysis to determine young modulus and bulk
modulus cube for brittleness identification.
• Conduct coherence, variance, dip-azimuth attribute to determine fracture
• Argakoesoemah R.M.I., Raharja M., Winardhi S., Tarigan R., Maksum T.F., Aimar A., 2005, Telisa Shallow
Marine sandstone As An Emerging Exploration Target In Palembang High, South Sumatra
Basin, Proceedings Indonesian Petroleum Association, 30th Annual Convention, Jakarta.
• Bishop, Michele. G., 2001, South Sumatra Basin Province, Indonesia: The Lahat/Talang Akar-Cenozoic
Total Petroleum System. USGS 99-50-S. USA.
• Dutta, N.C., ed, 1987, Geopressure: Society of Exploration Geophysicists Reprint Series 7, 365 p.
• Eaton, Ben A., 1975. The Equation For Geopressure Prediction From Well Logs. SPE 50th Annual Fall
Meeting, Dallas, TX, September 28 – October 1, 1975. SPE paper # 5544, 11 pp.
• Fatti, J. L., P. J. Vail, G. C. Smith, P. J. Strauss, and P. R. Levitt, 1994. Detection of gas in sandstone
reservoirs using AVO analysis: A 3D seismik case history using the Geostack technique. Geophysics, 59,
• Faust, L. Y., 1953, A velocity function including lithologic variation, Geophysics, 18, 271-288.
• Finnegan, J., 2011, Is Shale Gas a Game Changer in the Global Energy Supply Outlook?, American
Century Investment, In-Fly-72552 1107.
• Ginger, D., K. Fielding, 2005, The Petroleum Systems and Future Potential of the South Sumatra Basin.
• Holditch, S.A., 2007, Unconventional Gas. NPC Global Oil and Gas Study, Texas.
• Lee. M.W., 2005, A simple method of predicting S-wave velocity. Geophysics 71, 161-164.
• Passey. Q. R., 1990, A Practical Model For Organic Richness from Porosity and Resistivity Logs, AAPG
Bulletin V.74, No.12.