庆城合水地区长8油层组储层成岩作用及孔隙演化

Diagenesis and Porosity Evolution of Chang 8 Oil Reservoir Group in Qingcheng-HeshuiArea

在钻井岩心观察的基础上,利用砂岩普通薄片、铸体薄片、扫描电镜、黏土矿物分析等多种方法,综合研究了庆城—合水地区长8储层成岩作用及孔隙演化特征。结果表明:1庆城—合水地区长8储层主要为一套三角洲前缘相砂岩,岩石类型为岩屑长石砂岩和少量的长石砂岩。2研究区长8储层砂岩主要经历了压实作用、胶结作用及后期溶蚀作用等成岩作用。3包裹体均一温度、黏土矿物组合、胶结物与孔隙类型特征等多种指标反应的成岩作用阶段已达到中成岩阶段A期。4早期压实作用是造成孔隙空间减少主要因素,平均损失率为21.58%,胶结作用造成的孔隙度平均损失率为6.89%,而后期溶蚀作用是改善砂岩储层的重要因素,平均孔隙度增加3.97%。庆城—合水地区长8段储层砂岩孔隙演化特征和成岩作用阶段的研究对低渗透致密储层的开发具有重要的意义。

On the basis of drilling core observation, the diagenesis teristics of the Chang 8 reservoirin Qincheng-Heshuiarea have and porosity evolution characbeen comprehensively studied through using ordinary thin section of sandstone, casting thin sections, scanning electron microscope, clay minerals analysis and other methods. The results show that. （1）the Chang 8 reservoir in Qingcheng-Heshui area is mainly a set of sandstones with delta front facies, which are composed by lithic arkose sandstone and a small amount of feldspar sandstone; （2）the sandstones of the Chang 8 reservoir have mainly experienced some diagenesis, such as compaction, cementation and later dissolution; （3）the diagenesis stage has reached the the stage of A period, which can be reflected by homogenization temperatures of inclusions, clay minerals content combination, ce- ment, pore types, and other indicators reaction; （4）Early compaction is the main factor for the decrease of pore space, with the average loss rate of 21.58%, and the average porosity loss rate caused by cementation is 6.89%. Butthe later dissolution is an important factor for improving the sandstone reservoir, which resulted in an average porosity incrasing rate of 3.97%. The research on the pore evolution characteristics and diagenesis stages of Chang 8 sandstone reservoir in Qingcheng-Heshui area plays an importantrole for the development of low permeability tight res- ervoirs.