准噶尔盆地SN31井区白垩系清一段一砂组沉积相及储层主控因素分析

准噶尔盆地SN31井区白垩系清水河组地层厚度大多在300 m以上,储集体横向和纵向变化较大,不同砂层组的储集性能、物性主控因素及其空间展布规律的研究不够精细,难以满足油气勘探开发特别是滚动评价的需求。综合岩心观察、薄片鉴定、测井和录井资料分析、扫描电镜分析等多种技术方法,研究了清一段一砂组的岩石学特征、物性特征、各目的小层的沉积微相分布特征及储层物性主控因素。结果表明:清一段一砂组储层以细砂岩、砂砾岩、粗砂岩和中砂岩为主,成分成熟度较低,结构成熟度中等,储层物性较好,属于中孔中渗储层;研究区主要发育辫状河三角洲前缘水下分流河道、河口坝、席状砂沉积,并以水下分流河道微相的砂砾岩、粗砂岩和中砂岩储层物性最好;该区储层物性主要受到沉积作用的控制,成岩作用的影响较小,优质储层主要发育于辫状河三角洲前缘水下分流河道沉积微相中。

Fine analysis of sedimentary facies and main controlling factors of reservoir in the first sand group of 1st member of Cretaceous Qingshuihe Formation in SN31 well area of Junggar Basin

The first sand group of 1 stmember of Cretaceous Qingshuihe Formation in SN31 well area of Junggar Basin has thick strata. The lateral and vertical variations of sand bodies restrict the process of exploration,development and rolling evaluation in this area. Based on core observation,thin section,logging and logging data,scanning electron microscopy(SEM)and other technical methods,the lithological characteristics,physical characteristics,distribution characteristics of sedimentary microfacies of the first sand group of 1 stmember of Qingshuihe Formation,and main controlling factors of physical properties of reservoir have been studied. The results show that the reservoir of the first sand group in 1 stmember of Qingshuihe Formation are composed of finegrained sandstone,sandy conglomerate,coarse sandstone and medium sandstone,with low component maturity,middle structural maturity and good physical properties,which is emphatically defined as medium porosity and medium permeability reservoir. The study area developed the underwater distributary channel,river mouth bar and sheet sand deposits of braided river delta front,and the best physical properties such as sandy conglomerate,coarse sandstone and medium sandstone reservoir are mainly developed in underwater distributary channel microfacies. The physical properties of reservoir in the study area are mainly controlled by sedimentation,and diagenesis has little influence on physical properties of reservoir. The underwater distributary channel of braided river delta front is favorable microfacies for the development of high-quality reservoirs.