上扬子盆地西南缘上组合气藏成藏过程分析

通过对代表上扬子盆地西南缘上组合气藏特征的平落坝、白马庙和观音寺3个典型气藏进行解剖，明确了中侏罗统沙溪庙组天然气分布特征。结合输导体系、流体包裹体成藏期次和构造演化研究成果，分析了气藏成藏过程，总结其成藏模式，以期为有利勘探目标区的选择及评价提供地质依据。上扬子盆地西南缘沙溪庙组气藏以构造-岩性和岩性气藏为主，天然气主要分布在沙溪庙组Ⅰ、Ⅱ、Ⅲ段，主要聚集于构造高点。油气成藏时间集中在93～72 Ma，发生过至少2幕油气充注。燕山运动是气藏形成的主要时期，其形成的断层是沟通气源的主要通道；喜山运动是气藏天然气调整的主要时期，喜山期逆冲断层的活动及构造高点的迁移是天然气调整的主要原因。不同构造区域成藏具有差异性：西部褶皱带断-砂匹配、构造、砂体物性是主要控藏因素，构造高点、断层封闭性控制其含气丰度；东部斜坡带断-砂匹配、构造、封闭断层是主要控藏因素，构造高点、砂体物性控制其含气丰度。

ACCUMULATION PROCESS OF THE UPPER GAS ASSEMBLAGE ON THE SOUTHWEST MARGIN OF UPPER YANGTZE BASIN

Three typical gas reservoirs, the Pingluoba, Baimamiao and Guanyinsi, selected from the upper gas reservoir assemblage on the southwest margin of the Upper Yangtze Basin, are studied for gas distribution in the Middle Jurassic Shaximiao Formation with the research results from gas transportation system, fluid inclusion accumulation period and tectonic evolution. The study has provided a solid geological basis for the determination and evaluation of favorable exploration target areas. The gas reservoirs, dominated by structural-lithologic and lithologic traps, are mainly accumulated in the structural highs of Sha I, Sha Ⅱ and Sha Ⅲ Members and deposited in the time span of 93-72 Ma, by two stages of hydrocarbon charging. Yanshan movement is the main period for the formation of gas reservoirs, active faults originated in the Yanshan movement provided channels connecting the source rocks and the gas accumulations. Himalayan movement is the main period for the adjustment of natural gas, the reverse fault activity and tectonic peak adjustment in the Himalayan movement led to the readjustment of gas reservoirs. The accumulation processes are different in different tectonic provinces. Fault-sand matching, structures and physical properties of sand bodies are the main controlling factors in the western fold belt, while structural high and fault sealing the main factors controlling the gas abundance; fault-sand matching, structures and sealing fault are the main controlling factors in the eastern slope belt, and the structural high and physical properties of sand bodies are the factors controlling the gas abundance.