准噶尔盆地车排子地区下侏罗统八道湾组砂岩储层成岩作用与孔隙演化

Diagenesis and porosity evolution of sandstone reservoir in the lower Jurassic Badaowan formation in Chepaizi area,Junggar basin

准噶尔盆地车排子地区八道湾组油气勘探取得重大突破,但该地区成岩作用方面的研究还比较薄弱。根据岩石薄片及扫描电镜观察,确定车排子地区成岩作用类型及成岩事件发生顺序;根据阴极发光测试,确定方解石胶结物期次、石英次生加大发育程度及高岭石分布特征;根据X线衍射,确定黏土矿物组成及各矿物成分体积分数;根据氧同位素测试,确定自生方解石形成温度;采用反演回剥法研究储层孔隙演化过程。结果表明:储层主要经历压实作用,方解石、石英、黄铁矿等的胶结作用及长石和石英的溶蚀作用。方解石胶结物形成温度主要介于40~85℃,大致对应早成岩阶段A期的晚期至早成岩阶段B期;黏土矿物以高岭石为主,主要来源于长石的溶蚀;储层孔隙演化过程可以划分为3个阶段,即快速压实阶段、压实胶结阶段及压实溶蚀阶段。该研究成果为车排子地区八道湾组地层油气勘探提供地质依据。

A major breakthrough has been made in oil and gas exploration in the Badaowan formation in the Chepaizi area of the Junggar basin,but the diagenesis research in this area is still relatively weak.A comprehensive diagenesis study of the strata was conducted through various test methods.Thin section and SEM observation were conducted to determine diagenetic type and sequence.Cathodoluminscence(CL)was used to identify the period of calcite cementation,development degree of quartz overgrowth and distribution characteristics of kaolinite.The composition of clay minerals and the content of each mineral were determined by X-ray diffraction.Formation temperature of authigenic calcite cement was determined by oxygen isotope analysis.The evolution processes of reservoir porosity were quantitatively studied by inversion and back-stripping method.The results show that the reservoirs are mainly subjected to compaction,cementation of calcite,quartz,pyrite and the dissolution of feldspar and quartz.Formation temperatures of calcite cement range from 40℃to 85℃,corresponding to diagenetic stage between late eodiagenetic phase A and eodiagenetic phase B.Clay minerals are dominant with kaolinite due to feldspar dissolution.The process of reservoir porosity evolution can be divided into three stages:Rapid compaction stage,compaction-cementation stage and compaction-dissolution stage.The results provide a geological basis for the oil and gas exploration of the Badaowan formation in the Chepaizi area.