苏里格气田东南部盒8段致密砂岩储层特征及评价

Reservoir characteristics and evaluation of tight sandstone of He 8 member in southeastern Sulige Gas Field,Ordos Basin

召41井区是鄂尔多斯盆地苏里格气田东南部(苏东南)二叠系石盒子组盒8段致密砂岩气上产的主力区块,但单井产量低,产能差异大。运用铸体薄片、扫描电镜、阴极发光、高压压汞、物性分析、核磁共振、气水相渗等实验以及试气资料,对储层的岩石学特征、成岩作用、物性、孔隙结构和渗流特征进行了详细研究和分类评价,并探讨了储层类型与天然气产能之间的关系。结果表明,苏东南盒8段储层的岩石类型主要为岩屑石英砂岩,其次为岩屑砂岩和少量石英砂岩,填隙物基本上是胶结物,主要为伊利石、绿泥石、高岭石、硅质和铁方解石;成岩作用为压实压溶、胶结和溶解作用,已普遍进入中成岩B期阶段;孔隙类型主要为岩屑溶孔和晶间孔,其次是残余粒间孔;孔隙结构以粗孔-中喉型和细孔-小喉型为主;可动流体饱和度变化较大,且与物性密切相关,随物性变好而增大;综合储层物性、孔隙结构特征以及储层的沉积相带、砂体展布特征等,将苏东南盒8段储层划分为4种类型,天然气产能明显受储层类别的控制,且随储层类别的降低,天然气产能也逐渐降低。

Zhao 41 well area is the main gas producing area of tight sandstone of He 8 member in southeast Sulige Gas Field.However,the single well production is low and the productivity varies greatly.The petrological characteristics,diagenesis,physical properties,pore structure and seepage characteristics of reservoir were studied and evaluated by using data of cast thin sections,scanning electron microscope,cathodoluminescence,highpressure mercury injection,petrophysical analysis,nuclear magnetic resonance,gas-water relative permeability experiment and gas test,and the relationship between reservoirs type and natural gas productivity was discussed.The results show that the reservoir rocks of He 8 member in the study area are mainly lithic quartz sandstone,followed by lithic sandstone and a small amount of quartz sandstone,and the fillings is basically cements which are mainly illite,chlorite,kaolinite,siliceous and ferron calcite.Diagenesis is mainly compaction-pressure solution,cementation and dissolution,which has generally entered the stage B of middle diagenesis.The pore types are mainly secondary pores such as debris dissolved pores and intercrystalline pores,followed by residual intergranular pores,and the pore structure mainly consists of coarse pore-middle throat and fine pore-small throat.The saturation of movable fluid varies greatly,which is closely related to physical properties and increases with the improvement of physical properties.Based on the characteristics of reservoir physical properties,pore structure,sedimentary facies zone and sand body distribution,the reservoir of He 8 member in the study area was divided into four types.The productivity of natural gas is obviously controlled by reservoir types,and with the decline of reservoir type,the productivity of natural gas gradually decreases.