二连盆地巴音都兰凹陷阿尔善组云质岩储层特征

Characteristics of dolomitic reservoirs of A'ershan Formation in Bayindulan Sag,Erlian Basin

为研究巴音都兰凹陷下白垩统阿尔善组富油气云质岩储层特征,利用岩心、铸体薄片、阴极发光薄片、扫描电镜及X射线衍射等资料,对阿尔善组云质岩储层的岩性分类、储集空间类型、物性特征和成岩作用进行了研究。结果表明:阿尔善组云质岩储层主要分为两大类,即云质泥岩和云质砂岩,二者还可根据(铁)白云石的产状进一步细分。云质泥岩主要发育溶蚀孔隙、裂缝和晶间孔隙,孔隙度为4.4%~36.4%,平均为16.01%,渗透率为0.01~26.30 mD,平均为1.92 mD;云质砂岩主要发育溶蚀孔隙,孔隙度为1.1%~33.7%,平均为16.07%,渗透率为0.01~5 163.00 mD,平均为79.72 mD。云质泥岩以交代和溶蚀作用为主,成岩序列为:(铁)白云石的形成→有机酸生成→(铁)白云石的溶蚀;云质砂岩以溶蚀、胶结和交代作用为主,成岩序列为:轻度压实→石英次生加大→(铁)白云石胶结、交代→有机酸生成→(铁)白云石和长石的溶蚀。因此,研究云质岩储层特征对该区阿尔善组油气勘探具有重要意义。

A set of dolomitic reservoir developed in the Lower cretaceous A＇ ershan Formation of Bayindulan Sag, Erlian Basin. Based on the data of cores, cast thin sections, petrography, cathodoluminescence, SEM and X- ray diffraction, the lithologies, reservoir spaces types, physical properties and diagenesis of the dolomitic reser- voirs were studied. The result shows that the dolomitic reservoirs ofA＇ ershan Formation can be divided into two types in lithology： dolomitic sandstone and dolomitic mudstone, and these two types of lithology can be divided into more types according to the occurrence of dolomite or ankerite. The dolomitic mudstone developed dissolved pores, fractures and intracrystalline pores. The porosity of dolomitic mudstone is 4.4%-36.4%, with an average of 16.01%, and the permeability is 0.01-26.30mD, with an average of 1.92 mD. The main reservoir spaces developed in dolomitic sandstone are dissolved pores. The porosity of dolomitic sandstone is 1.1%-33.7%, with an average of 16.07%, and the permeability is 0.01-5 163.00 mD, with an average of 79.72 mD. Replacement and dissolution are the main diagenesis types developed in dolomitic mudstone, and the diagenesis sequence is the formation of dolomite and ankerite--→organic acid generation-＋dolomite dissolution. The main diagenesis types of dolomitic sandstone include dissolution, cementation and replacement, and the diagenesis sequence is： slight compaction-→ quartz secondary overgrowth-→cementation of dolomite and ankerite→organic acid generation→dissolution of dolomite, ankerite and feldspar.