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March Technical Luncheon
Devon Energy
333 West Sheridan Ave
Oklahoma City , Oklahoma 73102
Wednesday, March 22, 2023, 11:30 AM - 1:00 PM CDT
Category: Events

March 22nd, 2023 11:30 AM - 1:00 PM


Speaker: Wahid Rahman, Ph.D. - Director of Geoscience and Laboratories, Impac Exploration Services, Inc

Title: Geochemistry and Petroleum Systems Analysis for understanding of Unconventional Petroleum Resources: A Case study from Anadarko Basin, Oklahoma, USA

Location: Devon Energy

Dates: March 22, 2023

Cost: $30 Members $35 Non-members (lunch included)

11:30 AM - 1:00 PM


Presentation Abstract:  It is hypothesized that oil and gas migrate in an up-dip direction, but the extent of hydrocarbon migration has not been very well documented in many petroleum basins around the world. This study provides some new insights and an overview from US unconventional perspectives through produced oil geochemistry to forecast the extent of self-sourced petroleum, its migration, areal extent, hydrocarbon phase behavior and key reservoir engineering properties evaluations for reservoir geochemistry-based exploration, which leads to proper field development and economic production of oil and gas. Source rock maturity produced oil and gas molecular chemistry, biomarker ratios, and carbon isotopes were analyzed and compared to better understand migration and self-sourcing in the study area (e.g., Anadarko Basin). In this paper, major emphasis is given to the Woodford Shale, Anadarko Basin, Oklahoma, USA, which is one of the most prolific unconventional petroleum source rocks/reservoirs in the United States. Within the study area, the petroleum produced from this reservoir is self-sourced with a significant component having migrated in from deeper in the basin.

This geochemical work was performed on well cuttings, cores and oils extracted from source rocks, as well as produced oils and gases from the targeted reservoirs. Sampled Woodford organic-rich shales contain very little vitrinite; however, they contain abundant solid bitumen. Thermal maturity data from solid bitumen were converted to a vitrinite reflectance equivalent (Jacob, 1989) and compared with pyrolysis data (e.g., Tmax and Hydrogen Index (HI)). Both methods were found to be in excellent agreement. Source rock maturities vary across the area of study from early oil (~0.70 % Ro) to gas windows (~>1.35 % Ro) and approximately follow the present-day structural depth of the Woodford source rock.

Produced oil and gas geochemistry data (molecular fingerprints, isoprenoid distributions, saturate and aromatic carbon isotopes, biomarker ratios and gas carbon isotopes) from several wells suggest a common Woodford source; however, the oil maturities (e.g., Ro equivalent from biomarkers) are significantly higher than the Woodford source rock in many locations. Furthermore, the predicted GOR (gas-to-oil ratio) values from the same oil chemistry data are well matched with the produced GOR and estimated GOR from the recombined fluid samples. These findings support the interpretation (Rahman, 2021, Rahman, 2019; Peryum et al., 2018; Peryum et al., 2017; Rahman et al., 2017a; 2017b) that production from several Woodford wells includes migrated hydrocarbons from a deeper source. This study highlights many important ways in which geochemistry can be used to better evaluate unconventional reservoirs: 1) by identifying the existence and extent of hydrocarbon migration, 2) by predicting and understanding the quality and type of petroleum fluids stored in tight, unconventional source rocks, and 3) by explaining high GOR anomalies as the result of multiple charging episodes in certain areas in tight reservoirs (e.g., Meramec). The approaches described in this paper can be utilized to predict, understand, and more accurately classify unconventional reservoirs all over the world.


Author BIO: Dr. Wahid Rahman is currently working as the Director of Geoscience and Laboratories at Impac Exploration Services, Houston Texas. Dr. Rahman has previously worked as Sr. Staff Scientist/Program Coordinator for CWQMN (Continuous Water Quality Monitoring Network) at Texas Commission on Environmental Quality (TCEQ), Austin, Texas; as Director of Geoscience at Geoscience and Petroleum Research (GPR) Inc., Houston, Texas; as Chief Geochemist at Paladin Geological Services, Edmond, OK; as Geological Adviser at Ossidiana Energy, Denver, CO; Staff Geochemist at Pioneer Natural Resources, Irving, Texas; and as Sr. Geochemist at Devon Energy, Oklahoma City, OK. Dr. Rahman has 20+ years of industry, academic, and research experience in the field of geochemistry, petroleum systems analysis, basin modeling, hydrogeology, environmental geochemistry, and geology. He worked on most of the North American onshore unconventional and conventional petroleum plays/basins. Dr. Rahman’s research interest include organic geochemistry, basin modeling, environmental geochemistry, isotope geochemistry, surface geochemistry, conventional and unconventional resource play evaluation, HC migration pathway analysis, thermal maturity of organic matter (OM) and hydrocarbons (oil and gas), relationship between OM maturity versus Gas Oil Ratio (GOR), pressure gradient, kerogen/OM density, formation water geochemistry to understand reservoir continuity, production allocation, reservoir geochemistry, and water resistivity (Rw), oil (So), gas (Sg) and water saturation (Sw). Wahid has over 50 conference presentations, papers, and peer reviewed journals (with more than 750 citations) in the field of geochemistry, environmental geochemistry, and geology. He received his Ph.D. in Organic Geochemistry from Southern Illinois University, Carbondale, IL; M.S. in Geology from Auburn University, Auburn, AL; M.S. and B.S. in Geology from University of Dhaka, Dhaka, Bangladesh.

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