西峰油田长8低渗致密储层微观特征

油田开发的重心在储层,储层认识的核心在微观特征。利用铸体薄片、粒度分析、X衍射、压汞和物性测试等化验资料,系统研究了西峰油田长8低渗致密储层微观特征,分析了储层低渗致密原因。结果表明:(1)长8储层由中-细粒岩屑长石砂岩(占62%)和长石岩屑砂岩(占38%)构成,三端元组分中石英平均含量31. 5%、长石含量29. 7%、岩屑含量27. 6%;(2)岩石填隙物平均含量11. 2%,其中绿泥石及铁方解石最为发育,占填隙物总量66%;(3)孔隙以粒间孔(占62. 6%)和溶孔(占34. 2%)为主、喉道呈片状和弯片状,平均孔径51μm、中值喉道半径0. 17μm,孔喉组合为细孔-小喉型;(4)长8储层成分成熟度低、填隙物含量高、孔喉细小以及较为强烈的成岩作用是导致储层低渗致密的主要原因。研究成果深化了低渗致密储层地质认识,为西峰油田深入开发提供参考,并对类似油田储层微观特征研究提供借鉴。

Microscopic Characteristics of Chang 8 Low Permeability Tight Reservoir in Xifeng Oilfield

The focus of oilfield development is in the reservoir, and the core of reservoir recognition is microcosmic characteristics. The microscopic characteristics of reservoirs reflect the macroscopic characteristics of reservoirs, and ultimately reflect the physical properties of reservoirs. Chang 8 reservoir is the main production layer in Xifeng oilfield, which has the characteristics of low permeability, compactness and strong heterogeneity. At present, the microcosmic characteristics of reservoir are unclear, which restricts the efficient development process of oilfield. Therefore, the petrological, pore structure and physical properties of Chang 8 reservoir are systematically studied by using the experimental data of casting thin section, grain size analysis, X-ray diffraction, mercury injection and physical property testing. The results show that quartz (31.5%) is the main rock component of Chang 8 reservoir, followed by feldspar (29.7%). The average content of cuttings is 27.6%, and the content of fillings is 11.2%. The content of chlorite and iron calcite in the fillings is higher. The reservoir rock type is medium-fine lithic feldspar sandstone (62%) and feldspar lithic sandstone (38%). The reservoir space is mainly intergranular pore (62.6%). The pore throat combination (34.2%) is small pore, medium small throat type and poor pore throat connectivity. The analysis shows that low maturity of rock composition, high content of fillings, strong diagenesis and small throat are the main reasons leading to low permeability and compactness of reservoirs. The research results deepen the understanding of reservoir geology, provide reference for the further development of Xifeng Oilfield, and provide reference for the study of reservoir micro-characteristics of similar oilfields.