Abstract:

Based on the analysis of the Upper Triassic structural evolution features in the western Sichuan Depression,a study of sedimentary reservoirs and trap development features is carried out in this paper.By using the theories and methods of pool-forming dynamics,we identify the main controlling factors of gas accumulation,divide plays,and present several pooling patterns.The Upper Triassic Xujiahe Formation in the western Sichuan Depression possesses the conditions for the development of giant or medium-sized gas pool/fields.The main controlling factors of gas accumulation in the Upper Triassic are abundant sources,relatively high gas generation intensity,favorable migration conditions,good timing of paleouplifts and paleoslopes,well-developed traps,widely-distributed thick reservoirs and favorable preservation and sealing conditions.Two plays are recognized in the Upper Triassic,including an upper play and a lower play.The lower one is featured by high pressure driving and low pressure attraction,while the upper one is characterized by capillary imbibition,migration and release of water-soluble gas and transporting by buoyancy through preferential pathways.Different modes have different dynamic mechanisms of pool-forming and different distribution characteristics.

Key words: main controlling factor, play, dynamic mode of hydrocarbon pooling, gas pool, Upper Triassic, western Sichuan Depression