松辽盆地南部德惠断陷下白垩统营城组碎屑岩储层成岩作用及成岩相

Diagenesis and diagenetic facies of the lower Cretaceous Yingcheng formation sandstones in the Dehui fault depression in the southern Songliao basin,China

松辽盆地德惠断陷下白垩统营城组地层埋藏深度较大、成岩作用与非均质性强,致密化程度高,勘探风险大。采用普通薄片、铸体薄片、扫描电镜、X线衍射等测试分析方法,分析碎屑岩储层的岩石学特征、物性和成岩作用,根据影响储层物性的主控成岩作用类型和物性特征,结合沉积相(微相)划分成岩相。结果表明:德惠断陷营城组碎屑岩储层主要经历机械压实作用,硅质、碳酸盐(方解石)、黏土矿物和浊沸石胶结作用,以及长石和岩屑溶蚀作用。营城组碎屑岩储层成岩相划分为3种类型:压实致密相、碳酸盐胶结相、不稳定矿物溶蚀相。其中不稳定矿物溶蚀相含气性最好,广泛分布在水下分支河道和水上分支河道微相砂体中,属于建设性成岩相。压实致密相和碳酸盐胶结相导致储层致密,属于不利于储层发育的成岩相。研究结果可为研究区储层分类和评价提供依据。

The buried depth of the lower Cretaceous Yingcheng formation in the Dehui fault depression of the Songliao basin is large,the diagenesis and heterogeneity are strong,the degree of densification is high and the exploration risk is large.Through normal thin sections,casting thin sections,scanning eletron microscope(SEM),X-ray diffraction and other rock & mineral analysis technologies,we studied the lithology characteristics,reservoir physical properties,diagenisis and diagenetic facies of the lower Cretaceous Yingcheng formation sandstones in the Dehui fault depression in the Songliao basin.On the basis of analyzing the main controlling factors of diagenetic types and characteristics,combined with sedimentary facies(microfacies),we divided the diagenetic facies of the lower Cretaceous Yingcheng formation reservoir.The results showed that the reservoirs of the lower Cretaceous Yingcheng formation in the study area have mainly experienced mechanical compaction,cementation of siliceous,carbonate(calcite),clay minerals and laumonite,and dissolution of feldspar and debris.The diagenetic facies of the lower Cretaceous Yingcheng formation reservoir are divided into the following three types:Tight compaction facies;carbonate cemented facies;dissolution of unstable components facies.The dissolution of unstable components facies shows best gas-bearing properties,which belong to constructive diagenetic facies,and are widely distributed in the subaqueous distributary channels and subaerial distributary channels.Tight compaction facies and carbonate cemented facies corresponding to dense layer,belong to the unfavorable diagenetic facies for the reservoir.The results provide a basis for reservoir classification and evaluation in the study area.