川西坳陷沙溪庙组储集层致密化与天然气成藏耦合关系

Coupling Relationship between Reservoir Densification and Natural Gas Accumulation in Shaximiao Formation in Western Sichuan Depression

根据显微镜下观察分析与扫描电镜、电子探针、碳酸盐胶结物碳氧同位素等多种测试分析数据,结合埋藏史和构造演化史,明确了成岩作用及储集空间类型,建立了川西坳陷中侏罗统沙溪庙组不同类型储集层成岩演化序列。研究表明,不同类型储集层的储集特征和成岩演化具有一定差异:远物源富长石类储集层孔隙破坏作用主要为压实作用,储集空间以长石溶解的次生孔隙为主,储集层致密化时间较晚;近物源富岩屑类储集层孔隙破坏作用主要为压实作用和胶结作用,储集空间以剩余粒间孔为主,储集层致密化时间较早。通过包裹体相态、产状及均一温度分析,认为中侏罗统气藏具有多期油气充注的特点。不同类型储集层致密化与成藏时空耦合配置关系反映,远物源富长石类储集层整体具有成储成藏同时进行的特征,近物源富岩屑类储集层具有先致密化后成藏的特征。

Based on the observation under microscope and the analysis on the data of SEM, electronic probe, isotopes of carbon and oxygenin carbonate cements, and combined with the burial history and structural evolution history, the paper identifies the diagenesis and reser-voir space types and establishes diagenetic evolution sequences for different types of reservoirs of the Middle Jurassic Shaximiao formationin the western Sichuan depression. The study shows that different reservoirs have different accumulation characteristics and diagenetic evo-lutions. Compaction acted as the main destructive effect for the pores in far-from-provenance, feldspar-rich reservoirs whose reservoir spac-es were dominated by feldspar-dissolved secondary pores and the reservoir densification time was late; compaction and cementation actedas the main destructive effects for the pores in near-provenance, debris-rich reservoirs whose reservoir spaces were dominated by residualintergranular pores and the densification time of this kind of reservoir was relatively early. The analysis on phase, occurrence and homoge-neous temperature of inclusion indicates that the Middle Jurassic gas reservoirs are featured with multiple periods of hydrocarbon charging.The coupling relationship between reservoir densification and hydrocarbon accumulation reflects that the far-from-provenance, feldspar-rich reservoirs have a feature of hydrocarbon accumulation and reservoir forming simultaneously and the near-provenance, debris-rich reser-voirs is characterized by densification before reservoir forming.