川西坳陷平落坝气田须二段气藏成藏研究

上三叠统领二段气藏是川西平落坝复式气田的主力气藏，储集层属小孔，细喉的细密砂岩。根据液态烃侵入之剩余面孔率以及与淀绿泥石的世代关系认为，油气运聚发生时原生粒间孔保存尚好，进油时间较早，液态烃的侵入改变了储集层的古物化环境，产生了大量次生孔隙，同时淀出的SiO2充填了原生孔隙空间，由沉积构造发展研究认为，J1末期平落坝构造已具雏型且烃源岩已成熟，J2末进入成烃高峰期，生、聚期同步；其后又经历了多次继承性隆升，褶皱，使构造闭合度增大，捕集油气能力增强，多期形成的裂缝系统沟通了生，储层及储集层内部的联系，既使后续生成的油气继续向圈闭中充流，又使气藏连通强而具统一的压力系统，高部位高裂缝率产大气，形成了受断裂，裂缝与构造双重因素控制的气藏。图3表1参4（兰大樵摘）。

The research on the formation of Upper Triassic Xuer gas reservoirof Pingluoba gas field in Chuanxi depression

The Upper Triassic Xuer reservoir is the main reservoir of Pingluoba composite gas field. Tight reservoir sandstone has the typical characteristics of small pore and thin throat. Based on the relationship between the remained areal porosity of liquid hydrocarbon invasion and the chlorite, as well as the evolution of pore space and the depth of autogeny quartz formation, the reservoir sandstone had the evidence of earlier inputting oil and more original intergranular pore (more than 11% areal porosity) when hydrocarbon migrated. The invasion of liquid hydrocarbon changed the palaeo physical and chemical environments, the numerous secondary pores were produced and the settling SiO_2 filled the original intergranular pores. From the historical research of sedimentary and structure in this area, it was recognized that Pingluoba structure was initially formed and the source rock reached low mature at the end of early Jurassic, mature at middle Jurassic, the same time of the accumulation as the hydrocarbon generation. The structure was later continuously upfolded, the structural closure enlarged, and hydrocarbon accumulation space increased. Multiple period fracture systems were formed which not only enlarged the reservoir space, but also connected the source rock and reservoir as well as the inner reservoir. The fracture system led the continuously generating hydrocarbons migrate to the closure and the gas reservoir possess good connection and consistent pressure gradient. High gas production from high fracture rate of high position of the structure shows the gas reservoir was controlled both by the fractures and the structural trap. The keys on the formation of Pingluoba Xuer gas reservoir are the early upfold of the structure, high porosity and permeability before the reservoir tight, rich gas source, fair composition of reservoir and seal and the same time of generation and accumulation of hydrocarbons.