渤海BZ油田沙河街组低渗储层成岩作用及演化特征

Diagenesis and evolutionary characteristics of the low permeability reservoirs of the Shahejie Formation in BZ oilfield,Bohai sea

为解决渤海BZ油田沙河街组低渗油藏储层成因机理不明确及成岩作用定量化表征难的问题,利用岩心、岩石铸体薄片及扫描电镜等分析资料,对该油田沙河街组岩石学特征、储集空间、成岩作用、演化特征、演化阶段的定量表征进行了研究。结果表明:沙河街组储层岩石类型以岩屑长石砂岩为主,其中沙二段储层粒度分选、颗粒接触关系和储集空间类型均优于沙三段;沉积过程中主要发育机械压实及压溶、胶结和溶蚀等成岩作用,整体处于中成岩阶段A 2亚期,局部区域达到中成岩阶段B亚期;孔隙度演化分析表明,机械压实作用是沙河街组储层低渗的主要成因,在储层孔隙度损失过程中作用最大,其中沙三段相比沙二段机械压实作用更加明显,胶结和溶蚀作用对储层孔隙度损失和增加的影响基本相当。

In order to solve the problems of unclear formation mechanism and difficuly in quantitative characterization of diagenesis of low permeability reservoirs in Shahejie Formation in Bohai BZ oilfield,the analysis data of core,rock casting sheet and scanning electron microscope are used to study the petrological characteristics,reservoir space diagenesis and evolutionary characteristics and stages of the Shahejie Formation.The results show that the rock types of Shahejie Formation reservoirs are dominated by lithic feldspar sandstone.Reservoir grain⁃size sorting,particle contact relationship and reservoir space type of Es2 is better than the Es3;during the deposition process,the main diageneses such as mechanical compaction,pressure solution,cementation and dissolution are developed in A 2 substage of mesodiagenesis stage on the whole,and some local area reaches B substage of mesodiagenesis stage.The analysis of porosity evolution shows that mechanical compaction is the main cause of the low permeability for reservoirs of the Shahejie Formation.It plays an absolute destructive role in the process of reservoir porosity loss.Compared with Es2,mechanical compaction of Es3 is more obvious.The impact of cementation and dissolution reservoir porosity loss and increase is basically the same.