Organic Geochemistry: trends for the 21st Century 26th IMOG
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EVALUATING MIGRATION EFFICIENCY AND ITS KEY CONTROLLING FACTORS Gary P.A. MUSCIO1*, Andrea A. MICELI ROMERO2 and Kalin T. McDANNELL3 1. Chevron, 1500 Louisiana, Houston, TX 77002, USA 2. University of Oklahoma, ConocoPhillips School of Geology and Geophysics, 100 East Boyd St., Suite 710, Norman, OK 73019, USA 3. Lehigh University, Dept. of Earth and Environmental Sciences, 1 W. Packer Ave., Bethlehem, PA 18015, USA . *) Corresponding author:
[email protected] The assessment of migration efficiency in general and the quantification of losses associated with petroleum migration are crucial parameters required to accurately predict volumes of hydrocarbon charge. However, migration efficiency is one of the least understood components of hydrocarbon charge. While numerical tools (e.g. full-physics forward modeling tools or stochastic modeling tools) are based on a detailed description of the geologic parameters and are specific to the prospect or petroleum system being evaluated, migration efficiency is considered to be relatively low and is typically applied using analog data from a variety of different petroleum systems (Lewan et al., 2002; Katz & Kahle, 1998). The objective of the present study is to evaluate migration efficiency and improve our understanding of the key factors that control the loss of hydrocarbons during migration. For the purpose of this study, migration losses are considered as the difference between in-place discovered volumes, which can be obtained from available production data, and expelled volumes, which are calculated from a numerical model created for the area of interest. Multiple field-scale petroleum systems from a variety of structural and depositional settings were selected that are generally well documented. Additionally, the following requirements were deemed essential: Well documented source rock properties through direct evidence (well data such as TOC, HI, kerogen type, maturity and effective thickness) with proven source rock to oil correlations, an established subsurface geological framework including structural maps for fetch area calculations, a single liquids-dominant source system and well constrained in-place volumetrics. As the cumulative effects of alteration and degradation (e.g. biodegradation, water washing, secondary cracking) on petroleum volumes are hard to quantify, emphasis was placed on selecting petroleum systems where such effects are negligible. For each petroleum system, initial (i.e. prior to generation) source rock properties were established, and used as input for the mass balance calculations.
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Organic Geochemistry: trends for the 21st Century 26th IMOG
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The results obtained after considering different sensitivities and establishing base case scenarios suggest that migration efficiencies can cover a broad range, and can be significantly higher than previously thought. In addition to source rock specific parameters such as TOC and HI, factors controlling overall migration pathway effectiveness, such as the distance between source rock kitchen and reservoir (lateral and vertical), the complexity of carrier system and potential for migration loss (faulting, tortuosity, thief zones, fill and spill, remigration) as well as timing relationships between the critical petroleum systems elements appear to play an important role in determining the efficiency of migration.
REFERENCES Lewan, M.D., Henry, M.E., Higley, D.K., Pitman, J.K., 2002. Material-balance assessment of the New Albany-Chesterian petroleum system of the Illinois Basin. AAPG Bulletin, v. 86, no. 5, pp. 745-777 Katz, B.J. and Kahle, G.M. (1988) Basin evaluation: A supply-side approach to resource assessment. Proceedings of the Seventh Annual Convention, Volume I, Indonesian Petroleum Association, pp. 135-168.
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