Geologic characteristics, controlling factors and hydrocarbon accumulation mechanisms of China’s Large Gas Provinces of low porosity and permeability

Based on the analysis of the geological characteristics and controlling factors, we analyzed the formation mechanism of different types of gas reservoirs. The main characteristics of gas provinces with low porosity and permeability are mainly as follows: large area, low abundance, small gas pools and large gas provinces; widely distributed excellent hydrocarbon source rocks with closely contacted source-reservoir-cap association; development mainly in large continental depressions or in paralic shallow-river delta systems; many kinds of traps coexisting in large areas, dominantly para-layered lithologic, digenetic and capillary pressure traps; double fluid flow mechanisms of Darcy flow and non-Darcy flow; complicated gas and water relations; and having the resource distribution of highly productive “sweet spots”, banding concentration, and macroscopically large areas integrated. The main controlling factors of large sandstone gas provinces with low porosity and permeability are stable dynamic backgrounds and gentle structural frameworks which control the extensive distribution of alternate (interbedded) sandstones and mudstones; weak hydropower of large gentle lake basins controlling the formation of discontinuous, low porosity and permeability reservoirs in shallow-water deltas; regionally differential diagenesis and no homogeneous digenetic facies controlling the development of favorable reservoirs and digenetic traps; and weak and dispersive reservoir-forming dynamic forces leading to the widely distributed small traps with low abundance. Low porosity and permeability gas provinces with different trap types have different formation mechanisms which include fluid diversion pressure difference interactive mechanism of lithologic-trap gas accumulations, separated differential collection mechanism of digenetic-trap gas accumulations, and the Non-Darcy flow mechanism of capillary-pressure gas accumulations.

[1]  Tao Shizhen.  Connotation,classification,formation and distribution of giant oil and gas province , 2007 .

[2]  J. Masters.  Deep Basin Gas Trap, Western Canada , 1979 .

[3]  R. H. Lander,et al.  Predicting Porosity through Simulating Sandstone Compaction and Quartz Cementation , 1999 .

[4]  J. Heiland,et al.  Experimental investigation of the influence of differential stress on permeability of a lower permian (rotliegend) sandstone deformed in the brittle deformation field , 2001 .

[5]  K. Shanley,et al.  Factors controlling prolific gas production from low-permeability sandstone reservoirs: Implications for resource assessment, prospect development, and risk analysis , 2004 .

[6]  P. G. Berkenpas.  The Milk River Shallow Gas Pool: Role of the Updip Water Trap and Connate Water in Gas Production From the Pool , 1991 .

[7]  Kewen Li,et al.  New formula for acid fracturing in low permeability gas reservoirs: Experimental study and field application , 2007 .

[8]  R. Mast,et al.  Geology of Tight Gas Reservoirs , 1987 .

[9]  A. Cerepi,et al.  Pore microgeometry analysis in low-resistivity sandstone reservoirs , 2002 .

[10]  E. D. Sloan,et al.  Gas production potential of disperse low-saturation hydrate accumulations in oceanic sediments , 2006 .

[11]  K. Mohanty,et al.  Effect of surfactants on wettability of near-wellbore regions of gas reservoirs , 2006 .

[12]  P. Dobson,et al.  Porosity, permeability, and fluid flow in the Yellowstone geothermal system, Wyoming , 2003 .

[13]  E. Pittman,et al.  Compaction of lithic sands; experimental results and applications , 1991 .

[14]  Guo Zhidong.  Formation Conditions and Distribution Rules of Large Lithologic Oil-Gas Fields with Low Abundance in China , 2006 .

[15]  R. R. Berg,et al.  Capillary Pressures in Stratigraphic Traps , 1975 .

[16]  J. Gerald,et al.  Feedbacks between deformation, hydrothermal reaction and permeability evolution in the crust: Experimental insights , 2006 .

[17]  Wettability of reservoir rock and fluid systems from complex resistivity measurements , 2002 .

[18]  Robert M. Gies,et al.  Case History for a Major Alberta Deep Basin Gas Trap: The Cadomin Formation , 1984 .

[19]  M. L. Sweet,et al.  Modeling Heterogeneity in a Low-Permeability Gas Reservoir Using Geostatistical Techniques, Hyde Field, Southern North Sea , 1996 .

[20]  Kristine Haug,et al.  Hydrodynamic trapping of injected acid gas in the Alberta Basin, Western Canada , 2005 .

[21]  J. Baas,et al.  Directional petrological characterisation of deep-marine sandstones using grain fabric and permeability anisotropy: methodologies, theory, application and suggestions for integration. , 2007 .

[22]  M. N. Islam,et al.  Foam flow in low-permeability Berea Sandstone cores: a laboratory investigation , 2002 .

[23]  Zeng Lian-bo,et al.  The Relationship between Fractures and Tectonic Stress Field in the Extra Low-Permeability Sandstone Reservoir at the South of Western Sichuan Depression , 2007 .

[24]  Dongbo He,et al.  Diagenesis and genesis of effective sandstone reservoirs in the Sulige Gas Field , 2004 .

[25]  A. MacDonald,et al.  Geophysical methods for locating groundwater in low permeability sedimentary rocks: examples from southeast Nigeria , 2001 .

[26]  Torsten Friedel,et al.  Investigation of non-Darcy flow in tight-gas reservoirs with fractured wells , 2006 .