鄂尔多斯盆地下寺湾地区长6砂岩储层成岩作用研究

Diagenesis of Chang 6 reservoir of Xiasiwan area in Ordos Basin

通过岩石薄片、铸体薄片鉴定、扫描电镜、X射线衍射、镜质体反射率等资料,对鄂尔多斯盆地下寺湾地区长6油层组的储层特征及成岩作用阶段进行了研究,揭示成岩作用与孔隙演化在空间上的演化规律.研究结果表明:下寺湾地区长6储层主要处于晚成岩A期,主要成岩作用有机械压实作用、胶结作用、交代作用、裂缝作用;机械压实作用强烈是导致该储层早期孔隙丧失的根本原因;晚成岩阶段铁方解石胶结作用是造成储层物性非均质性严重的主要因素;溶蚀作用、绿泥石衬里、破裂作用对储层物性起建设性作用;储层孔隙类型主要有残余粒间孔、长石溶孔和岩屑溶孔,次为微孔隙及裂缝孔隙.最后,分析储层成岩演化序列和孔隙演化史.

In order to reveal the spatial evolution rule of diagenesis and porosity evolution,the characteristics and diagenesis stage of the Chang 6 reservoir are studied based on the data analysis of rock section,casting thin-section,scan electron microscope,X-ray diffraction and vitrinite reflection of Xiasiwan area in Ordos Basin.The results show that the Chang 6 reservoir is in the late diagenesis phase A;and main diageneses include compaction,cementation,metasomatosis and cataclasis.The intense compaction is the primary cause leading to pore loss of the reservoir in early period;the cementation of ferrocalcite in late diagenetic stage is the main factor leading to the severe heterogeneity of reservoir physical property;dissolution,grain-coating chlorite,and cataclasis have constructive effect on the reservoir physical property.The pore types of the Chang 6 reservoir mainly include primary remained intergranular pore,feldspar dissolved pore and lithic dissolved pore,secondly micropore and fracture pore.Finally,reservoir diagenetic evolutionary sequence and the history of reservoir pore evolution are analyzed.