Characteristics and accumulation mechanism of tight sandstone gas reservoirs in the Upper Paleozoic, northern Ordos Basin, China
Tóm tắt
The Ordos Basin is a significant petroliferous basin in the central part of China. The Carboniferous and Permian deposits of transitional and continental facies are the main gas-bearing layers in the north part of the basin. The Carboniferous and Permian natural gas reservoirs in the northern Ordos Basin are mainly tight sandstone reservoirs with low porosity and low permeability, developing lots of “sweet spots” with comparatively high porosity and permeability. The tight sandstones in the study area are gas-bearing, and the sweet spots are rich in gas. Sweet spots and tight sandstones are connected rather than being separated by an interface seal. Sweet spot sand bodies are vertically and horizontally overlapped, forming a large gas reservoir group. In fact, a reservoir formed by a single sweet spot sand body is an open gas accumulation. In the gentle dipping geological setting and with the source rocks directly beneath the tight reservoirs over a large area, the balance between gas charging into tight reservoirs from source rocks and gas loss from tight reservoirs through caprock is the key of gas accumulation in tight sandstones. Both the non-Darcy flow charging driven by source-reservoir excess pressure difference and the diffusion flow charging driven by source-reservoir gas concentration difference play an important role in gas accumulation. The results of mathematical modeling indicate that the gas accumulation cannot be formed by just one of the above mechanisms. The diffusion of gas from source rocks to reservoirs is a significant mechanism of tight sandstone gas accumulation.
Tài liệu tham khảo
Berkenpas P G. The Milk River shallow gas pool: Role of the updip water trap and connate water in gas production from the pool. SPE Annual Technical Conference and Exhibition. USA. 1991
Berry F A F. Hydrodynamics and geochemistry of the Jurassic and Cretaceous systems in the San Juan Basin, northwestern New Mexico and southwestern Colorado. Dissertation. Stanford California: Stanford University 1959
Brown A, Crafton J W and Golson J G. The Niobrara gas play: Exploration and development of a low-pressure, low-permeability gas reservoir. Journal of Petroleum Technology. 1982. 34(12): 2863–2870
Brown C A, Smagala T M and Haefele G R. Southern Piceance Basin model—Cozzette, Corcoran, and Rollins Sandstones. Geology of Tight Gas Reservoirs. AAPG Studies in Geology. 1986. 24: 207–220
Fang D Q, Song Y and Xia X Y. Natural gas diffusion model and diffusion computation in well Cai25 Bashan Group oil and gas reservoir. Science in China Series D: Earth Sciences. 2001. 44(3): 213–220
Fu G and Su Y P. Geological factors controlling gas diffusion loss in strata section. Natural Gas Geoscience. 2004. 15(1): 58–61 (in Chinese)
Gies R M. Lateral trapping mechanism in the deep basin gas trap, western Canada. AAPG Bulletin. 1981. 65(5): 930
Gies R M. Basic physical principles of conventional and deep basin gas entrapment. AAPG Bulletin. 1982. 66: 572
Gies R M. Case history for a major Alberta deep basin gas trap: The Cadomin Formation. Tulsa: AAPG. 1984
Hao S S, Huang Z L and Gao Y. A study of the diffusion of light hydrocarbon and the dynamic equilibrium principle in the migration and accumulation of natural gas. Acta Petrolei Sinica. 1991. 12(3): 17–24 (in Chinese)
He Z X. Basin Development and Hydrocarbon Exploration in the Ordos Basin. Beijing: Petroleum Industry Press. 2003. 1–44 (in Chinese)
Huang Z L and Hao S S. Study on sealing of gas concentration and diffusion in overlying gas reservoirs. Acta Petrolei Sinica. 1996. 17(4): 36–41 (in Chinese)
Jones R M P. Basinal isostatic adjustment faults and their petroleum significance. Bulletin of Canadian Petroleum Geology. 1980. 28(2): 211–251
Krooss M and Leythaeuser D. Diffusion of methane and ethane through the reservoir cap rock: Implications for the timing and duration of catagenesis: Discussion. AAPG Bulletin. 1997. 81(1): 155–161
Krooss M and Leythaeuser D. Experimental measurements of the diffusion parameters of light hydrocarbons in water-saturated sedimentary rocks—II. Results and geochemical significance. Organic Geochemistry. 1988. 12(2): 91–108
Krooss M, Leythaeuser D and Schaefer R G. The quantification of diffusive hydrocarbon losses through cap rocks of natural gas reservoirs—a reevaluation. AAPG Bulletin. 1992. 76(3): 403–406
Law E and Dickinson W W. Conceptual model for origin of abnormally pressured gas accumulations in low-permeability reservoirs. AAPG Bulletin. 1985. 69(8): 1295–1304
Leythaeuser D, Schaefer R G and Yukler A. Role of diffusion in primary migration of hydrocarbons. AAPG Bulletin. 1982. 66(4): 408–429
Liu G D, Li J, Li J M, et al. The controls and the assessment method for the effectiveness of natural gas migration and accumulation process. Natural Gas Geoscience. 2005. 16(1): 1–6 (in Chinese)
Liu G D, Sun M L, Lu Y F, et al. The effectiveness assessment of gas accumulation processes in Kuqa Depression, Tarim Basin, Northwest China. Science in China Series D: Earth Sciences. 2008. 51(s2): 117–125
Liu G D, Zhao Z Y, Sun M L, et al. New insights into natural gas diffusion coefficient in rocks. Petroleum Exploration and Development. 2012. 39(5): 559–565 (in Chinese)
Masters J A. Deep basin gas trap, western Canada. AAPG Bulletin. 1979. 63(2): 152–181
Masters J A. Lower Cretaceous oil and gas in western Canada. Tulsa: AAPG. 1984
McPeek L A. Eastern Green River basin: A developing giant gas supply from deep, overpressured Upper Cretaceous sandstones. AAPG Bulletin. 1981. 65(6): 1078–1098
Nelson J S and Simmons E C. Diffusion of methane and ethane through the reservoir cap rock: implications for the timing and duration of catagenesis. AAPG Bulletin. 1995.79(1): 1064–1074
Prinzhofer A and Pernaton E. Isotopically light methane in natural gas: Bacterial imprint or diffusive fractionation? Chemical Geology. 1997. 142(3–4): 193–200
Rahmani R A. Facies control of gas trapping, Lower Cretaceous Falher A cycle, Elmworth area, northwestern Alberta. Tulsa: AAPG. 1984
Shanley W, Cluff R M and Robinson J W. Factors controlling prolific gas production from low-permeability sandstone reservoirs: Implications for resource assessment, prospect development, and risk analysis. AAPG Bulletin. 2004. 88(8): 1083–1121
Wang W G and Gao N. Estimation of loss of gas diffusion from source rock in Binbei region. Journal of Daqing Petroleum Institute. 2005. 29(4): 1–3 (in Chinese)
Welte D H, Schaefer R G, Stoessinger W, et al. Gas generation and migration in the deep basin of western Canada. In: Elmworth (ed.), Case Study of a Deep Basin Gas Field. AAPG. 1984. 35–47
Wilson H H. Diffusion of methane and ethane through the reservoir cap rock: Implications for the timing and duration of catagenesis: Discussion. AAPG Bulletin. 1996. 80(9): 1483–1485
Yang H, H, Li Z H, et al. Characteristics of underpressured gas pool in Upper Paleozoic Shiqianfeng Formation of eastern Ordos Basin. Earth Science—Journal of China University of Geosciences. 2004. 29(4): 413–419 (in Chinese)
Yang J J. Basin Structure Development and Distribution of Hydrocarbon in Ordos Basin. Beijing: Petroleum Industry Press. 2002. 8–22 (in Chinese)
Yuan J H and Liu G D. Distribution characteristics and formation process of Upper Paleozoic abnormally low pressure zones in Ordos Basin. Oil & Gas Geology. 2005. 26(6): 792–799 (in Chinese)
Zhang T W and Krooss B M. Experimental investigation on the carbon isotope fractionation of methane during gas migration by diffusion through sedimentary rocks at elevated temperature and pressure. Geochimica et Cosmochimica Acta. 2001. 65(16): 2723–2742
Zhao Z Y Natural gas accumulation mechanism in low porosity and permeability sandstones: A case study of the Sulige gas field. Ph.D. Thesis. Beijing: China University of Petroleum. 2012. 77–84 (in Chinese)