Types and Controlling Factors of Accumulation and High Productivity in the Upper Triassic Xujiahe Formation Gas Reservoirs, Sichuan Basin

Key words: 
• Sichuan Basin

Abstract: Because of the strong diagenesis, sandstone in Upper Triassic Xujiahe Formation is thick and tight, reservoir heterogeneity is very strong, various types of gas reservoirs are developed. Major developed eight conventional gas reservoirs and two unconventional gas reservoirs. The lithological gas reservoir, structurelithological reservoir having large scale and abundant reserves, are important gas reservoirs and mainly developed in the MidSichuan area; Water soluble gas reservoir with high yield and great potential is also developed, widely distributed in the gentle slope and the Depression in the centralwest Sichuan region, is the important development direction in Sichuan Basin. The Xujiahe Formation gas reservoirs adjacent the source, have high pressure, contain condensate oil and water, distributed widely, and their scale is large and relationship between water and gas is complex. As different areas have different characters of deposition, diagenesis and structure, the main controlling factors in gas accumulation are quite different. Therefore, the distribution of reservoir, tectonic background and the degree of fracture development are the major three controlling factors of the gas accumulation in Xujiahe Formation gas reservoirs, the main control factor of accumulation and high productivity is the effective combination of the three elements.