Evaluation of highly thermally mature shale-gas reservoirs in complex structural parts of the Sichuan Basin

Abstract

Successful exploration and development of shale-gas in the United States and Canada suggest a new solution to the energy problem in China. The Longmaxi (龙马溪) Formation in the Sichuan (四川) Basin is regarded as a strong potential play for shale-gas with the following significant features: (1) complex structural types caused by multiphase tectonic superposition and reconstruction; (2) varied slippage processes that enhance porosity and permeability; (3) high thermal maturation of organic matter (Ro>2.5%); (4) high brittle mineral contents; (5) high and constant thicknesses of shale horizons within the formation. Evaluation of shale-gas prospects in this area should consider not only hydrocarbon parameters, but also preservation conditions and structural stability. Data from several new exploration wells in the Sichuan Basin indicate that tectonically induced net-shaped fractures effectively enhance shale reservoir properties. Structural types providing favorable storage conditions for shale-gas are described and evaluated. The high-yielding shale gas reservoir shares the same characteristics of conventional gas reservoirs except for its consubstantial source rock and reservoir in South China.

Keywords

Sichuan Basin / Longmaxi Formation / high thermal maturity / shale-gas

References

[1] Chalmers G R, Bustin M, Power I M. Characterization of Gas Shale Pore Systems by Porosimetry, Pycnometry, Surface Area, and Field Mission Scanning Electron Microscopy/Transmission Electron Microscopy Image Analyses: Examples from the Barnett, Woodford, Haynesville, Marcellus, and Doig Units. AAPG Bulletin, 2012, 96(6): 1099-1119.

[2] Chen H D, Guo T L. The Sedimentary Filling Process and Material Distribution of the Upper Superimposed Yangtze basin, 2012 Beijing: Science Press, 113-118.

[3] Chen S B, Zhu Y M, Wang H Y, . Characteristics and Significance of Mineral Compositions of Lower Silurian Longmaxi Formation Shale Gas Reservoir in the Southern Margin of Sichuan Basin. Acta Petrolei Sinica, 2011, 32(5): 775-782.

[4] Daniel M J, Ronald J, Tim E R, . Unconventional Shale Gas Systems: The Mississippian Barnett Shale of North Central Texasas One Model for Thermogenic Shale Gas Assessment. AAPG Bulletin, 2007, 91: 475-499.

[5] Dong D Z, Cheng K M, Wang S Q, . An Evaluation Method of Shale Gas Resource and Its Application in the Sichuan Basin. Natural Gas Industry, 2009, 29(5): 33-39.

[6] Fu X D, Qing J Z. Evaluation on Excellent Marine Hydrocarbon Source Layers in Southeast Area of the Sichuan Basin-An Example from Well D-1. Petroleum Geology and Experiment, 2008, 30(6): 621-628.

[7] Guo T L, Liu R B. Implications from Marine Shale Gas Exploration Breakthrough in Complicated Structural Area at High Thermal Stage: Taking Longmaxi Formation in Well JY1 as an Example. Natural Gas Geoscience, 2013, 24(4): 643-651.

[8] Hao F, Zou H Y. Cause of Shale Gas Geochemical Anomalies and Mechanisms for Gas Enrichment and Depletion in High-Maturity Shales. Marine and Petroleum Geology, 2013, 44: 1-12.

[9] Hao F, Zou H Y, Lu Y C. Mechanisms of Shale Gas Storage: Implications for Shale Gas Exploration China. AAPG Bulletin, 2013, 97(8): 1325-1346.

[10] Huang J L, Zou C N, Li J Z, . Shale Gas Generation and Potential of the Lower Cambrian Qiongzhusi Formation in the Southern Sichuan Basin, China. Petroleum Exploration and Development, 2012, 39(1): 69-75.

[11] Jarvie D M, Hill R J, Ruble T E, . Unconventional Shale-Gas Systems: The Mississippian Barnett Shale of North-Central Texas as One Model for Thermogenic Shale-Gas Assessment. AAPG Bulletin, 2007, 91(4): 475-499.

[12] Jia C Z, Zhang M, Zhang Y F. Unconventional Hydrocarbon Resources in China and the Prospect of Exploration and Development. Petroleum Exploration and De velopment, 2012, 39(2): 129-136.

[13] Li J Z, Dong D Z, Chen G S, . Prospects and Strategic Position of Shale Gas Resources in China. Natural Gas Industry, 2009, 29(5): 11-16.

[14] Liang C, Jiang Z X, Yang Y T, . Shale Lithofacies and Reservoir Space of the Wufeng-Longmaxi Formation, Sichuan Basin, China. Petroleum Exploration and Development, 2012, 39(6): 691-698.

[15] Liang D G, Guo T L, Bian L Z, . Some Progresses on Studies of Hydrocarbon Generation and Accumulation in Marine Sedimentary Regions, Southern China (Part 3): Controlling Factors on the Sedimentary Facies and Development of Palaeozoic Marine Source Rocks. Marine Geology, 2009, 14(2): 1-19.

[16] Liang D G, Guo T L, Bian L Z, . Some Progresses on Studies of Hydrocarbon Generation and Accumulation in Marine Sedimentary Regions, Southern China (Part 2): Geochemical Characteristics of Four Suits of Regional Marine Source Rocks, South China. Marine Geology, 2009, 14(1): 1-15.

[17] Liang D G, Guo T L, Bian L Z, . Some Progresses on Studies of Hydrocarbon Generation and Accumulation in Marine Sedimentary Regions, Southern China (Part 1): Distribution of Four Suits of Regional Marine Source Rocks. Marine Geology, 2008, 13(5): 1-16.

[18] Lin B Q, Wang T. Forecasting Natural Gas Supply in China: Production Peak and Import Trends. Energy Policy, 2012, 49: 225-233.

[19] Liu S G, Sun W, Li Z W, . Tectonic Uplifting and Gas Pool Formation since Late Cretaceous Epoch, Sichuan Basin. Natural Gas Geoscience, 2006, 19(3): 293-300.

[20] Loucks R G, Reed R M, Ruppel S C, . Morphology, Genesis and Distribution of Nanometer-Scale Pores in Siliceous Mudstones of the Mississippian Barnett Shale. Journal of Sedimentary Research, 2009, 79(11–12): 848-861.

[21] Modica C J, Lapierre S G. Estimation of Kerogen Porosity in Source Rocks as A Function of Thermal Transformation: Example from the Mowry Shale in the Powder River Basin of Wyoming. AAPG Bulletin, 2012, 96(1): 87-108.

[22] Pan R F, Huang X S. Shale Gas and Its Exploration Prospects in China. China Petroleum Exploration, 2009, 14 3 125.

[23] Ross D J K, Bustin R M. Characterizing the Shale Gas Resource Potential of Devonian-Mississippian Strata in the Western Canada Sedimentary Basin: Application of an Integrated Formation Evaluation. AAPG Bulletin, 2008, 92(1): 87-125.

[24] Tao S, Wang Y B, Tang D Z, . Hydrocarbon-Generation in Cambrian-Silurian High- to Over-Mature Source Rocks, Middle and Upper Yangtze Region, China. Energy, Exploration & Exploitation, 2012, 30(1): 19-42.

[25] Wang L S, Zou C Y, Zheng P, . Geochemical Evidence of Shale Gas Existed in the Lower Paleozoic Sichuan Basin. Natural Gas Industry, 2009, 29(5): 59-62.

[26] Wang S J, Wang L S, Huang J L, . Accumulation Conditions of Shale Gas Reservoirs in Silurian of the Upper Yangtze Region. Natural Gas Industry, 2009, 29(5): 45-50.

[27] Wang S Q, Chen G S, Dong D Z, . Accumulation Conditions and Exploitation Prospect of Shale Gas in the Lower Paleozoic Sichuan Basin. Natural Gas Industry, 2009, 29(5): 51-58.

[28] Zhang J C, Li Y X, Nie H K, . Geologic Setting and Drilling Effect of the Shale Cored Well Yuye-1, Penshui County of Chongqing. Natural Gas Industry, 2010, 30(12): 114-118.

[29] Zhang J C, Nie H K, Xu B, . Geological Condition of Shale Gas Accumulation in Sichuan Basin. Natural Gas Industry, 2008, 28(2): 151-156.

[30] Zhu X. The View of Zhu Xia of Chinese Petroliferous Basins Tectonics, 1986 Beijing: Petroleum Industry Press, 81-82.