鄂尔多斯盆地苏75区块山西组储层特征与发育主控因素

Reservoir Characteristics and Main Controlling Factors of Shanxi Formation in Block Su 75, Ordos Basin

摘要: 二叠系山西组作为苏75区块致密砂岩气主力勘探开发层位之一，现目前认识到该层位气藏厚度较大、领井产量高且有利区域已动用，为此亟需深化储层地质研究，为区域持续稳产奠定基础。利用目的层段取井岩心、铸体薄片、物性测试、地层埋藏史特征等资料分析了目的层段储层特征与储层发育主控因素。研究结果表明：研究区储层岩性主要为长石石英砂岩，少量岩屑石英砂岩。储层储集空间发育有原生孔隙、次生孔隙、微裂缝等，但主要以次生孔隙为主，占比达到总孔隙类型的90.58%，原生孔隙与微裂缝占比不足10%，总体上来说属于低孔低渗孔隙性储层。沉积作用、成岩作用、构造作用是研究区优质储层形成的主要控制因素，目的层段主要发育辫状河三角洲沉积相，持续深切的水流与侧向连续性较好的沉积相是储层发育的先决条件；成岩作用先发生胶结作用与压实作用使储层致密，然后发生溶蚀作用形成大量孔隙，是储层发育的核心条件；构造作用造成地层抬升沉降形成断裂，为地下流体与岩石颗粒发生溶蚀作用提供了场所，也为溶蚀流体的流动提供了有利通道，是储层发育的关键条件。

Abstract: The Shanxi Formation of the Permian System is one of the main exploration and development layers for tight sandstone gas in Su 75 block. Currently, it is recognized that the reservoir thickness is large, the well productivity is high, and the favorable areas have been developed. Therefore, it is urgently needed to deepen the reservoir geological research to lay a foundation for the continuous stable production of the area. Using the data of well core, thin section, petrophysical test, and geological burial history characteristics of the target layer, the reservoir characteristics and the main controlling factors of the reservoir development were analyzed. The research results show that the reservoir lithology in the study area is mainly quartzose sandstone with a small amount of clast-rich sandstone. The reservoir has developed primary porosity, secondary porosity, and microfractures, but the secondary porosity is the main type, accounting for 90.58% of the total pore type, while the primary porosity and microfractures account for less than 10%. In general, it is a low-porosity and low-permeability reservoir with a pore type. Deposition, diagenesis, and tectonic action are the main controlling factors for the formation of high-quality reservoirs in the study area, and the Shanxi Formation mainly develops braided river delta sedimentary facies. The continuous deep cutting water flow and the side-by-side sedimentary facies with good continuity are the prerequisites for the development of the reservoir; diagenesis first occurs in the form of cementation and compaction, making the reservoir dense, and then dissolution occurs to form a large number of pores, which is the core condition for the development of the reservoir; tectonic action causes the formation of faults, providing places for the dissolution of underground fluids and rock particles, and also providing favorable channels for the flow of dissolution fluids, which is the key condition for the development of the reservoir.