西峰油田长8低渗致密储层微观特征

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

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。

The focus of oilfield development is in the reservoir and the core of reservoir recognition is microcosmic characteristics.Based on cast thin section,grain size analysis,X-ray diffraction,mercury intrusion and physical property test,the microscopic characteristics of Chang 8 low permeability tight reservoir in Xifeng oilfield were systematically studied,and the causes of low permeability tight reservoir were analyzed.The results indicate as follows.① Chang 8 reservoir is composed of medium-fine grained lithic feldspathic sandstone (62%) and feldspathic lithic sandstone (38%).The average content of quartz,feldspar and cuttings in the three-terminal component is 31.5%,29.7% and 27.6%,respectively.② The average content of rock interstitial substance is 11.2%,among which chlorite and iron calcite are the most developed,accounting for 66% of the total amount of interstitial substance;③ The pores are mainly intergranular pores (62.6%) and dissolved pores (34.2%).The throat is lamellar and curved,with an average pore diameter of 51μm and a median throat radius of 0.17 μm.The pore-throat combination is of fine pore-small throat type.④ Analysis shows that the low maturity of Chang 8 reservoir composition,high content of interstitial materials,small pore throat and relatively strong diagenesis are the main reasons for low permeability and tight reservoir.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.