川西坳陷东坡中江气田沙溪庙组复杂“窄”河道致密砂岩气藏高产富集规律

High-yield enrichment laws of Shaximiao Formation tight sandstone gas reservoir of complex "narrow" channel in Zhongjiang Gas Field,in the eastern slope of West Sichuan Depression

四川盆地西部中江气田中侏罗统沙溪庙组气藏为川西地区第2大中浅层气藏,是一个以三角洲平原—前缘河道砂沉积为主的致密砂岩气藏,具有河道窄、砂体薄、储层致密、非均质性强以及气水分布异常复杂等特点,给气藏的开发评价及建产选区带来极大难度。为此,通过对该气田不同产能井及其所在河道和层系逐一由点到面的解剖,分析其构造及其演化特征、断砂配置关系以及储层物性等因素对单井产能的影响,明确了中江气田复杂"窄"河道致密砂岩气藏高产富集的4个主要控制因素为断层、构造、河道砂岩及储层物性;通过分析各控制因素的综合作用,建立了不同河道砂岩的天然气动态富集模式,并从中提炼出2种高产富集动态模式,即构造主控模式中的"有效断砂配置+优势古构造+优质储层"组合和岩性主控模式中的"有效断砂配置+优势古构造+物性封堵+优质储层"的组合,为该气藏的高效开发奠定了基础。

The gas reservoir of Middle Jurassic Shaximiao Formation in Zhongjiang Gas Field is the second largest middle-shallow gas reservoir in western Sichuan Basin. It is a tight sandstone gas reservoir with delta plain-frontal channel sand as the main deposit. It is characterized by narrow channel, thin sand body, tight reservoir, strong heterogeneity and extremely complex gas/water distribution, which bring great difficulty to the development evaluation and productivity construction zone selection of this gas reservoir. In this paper, the production wells of Zhongjiang Gas Field and the channels and series of strata where these wells are located were dissected one by one from the point to the plane, and the effects of structural and evolutionary characteristics, fault-sandbody match relation- ships and reservoir physical properties on the single-well productivity were analyzed. It is ascertained that the high-yield enrichment of tight sandstone gas reservoir of complex ＂narrow＂ channel in Zhongjiang Gas Field is mainly dominated by four factors, i.e., fault, structure, channel sand and reservoir physical property. After the combined effects of all control factors were analyzed, several dynam- ic natural gas enrichment models of channel sand were established, and two high-yield dynamic enrichment models were extracted, i.e., the structure dominated combination of ＂effective fault-sandbody match ＋ predominant palaeostructure ＋ quality reservoir＂ and the lithology dominated combination of ＂effective fault-sandbody match ＋ predominant palaeostructure ＋ physical property sealing ＋ quality reservoir＂. It provides the basis for the efficient development of gas reservoirs.