四川盆地元坝气田须家河组三段气藏致密钙屑砂岩储层发育机理

Development mechanism of tight calcarenaceous sandstone reservoir of the third member of Xujiahe Formation in Yuanba gas field of Sichuan Basin

元坝气田须家河组三段钙屑砂岩储层致密且非均质性强、产能差异大,利用岩芯、薄片及电成像资料,结合水动力条件、砂体厚度、岩石骨架、裂缝作用、裂缝主导等因素,初步明确该区钙屑砂岩优质储层发育机理。优质钙屑砂岩主要受沉积水动力强弱控制,碳酸盐岩岩屑含量、岩石粒度、砂体厚度是控制优质储层发育的基础,裂缝双重渗流作用是关键,砂体内部结构的非均性是裂缝发育的主导因素。综合研究认为,单层厚度小(<3 m)、累积厚度大(> 10 m)的刚性非均质叠置砂体具有勘探开发潜力。

The calcarenaceous sandstone reservoir of the third member of Xujiahe Formation in Yuanba gas field is tight and with strong heterogeneity. The reservoir productivity varies greatly. Based on core and electro-imaging data,thin section analysis,sedimentary hydrodynamic condition,sand thickness,particle size of rock matrix,fracturing,and the leading factor of fracture,the macro mechanism of high quality calcarenaceous sandstone reservoir has been defined preliminarily. The distribution of high calcarenaceous sandstone is manly controlled by the strength of sedimentary hydrodynamics. The distribution of high quality reservoir is based on the content of carbonate rock fragments,grain size and the sand thickness,and the double seepage action of fracture is the key. The structural heterogeneity within sand body is the main factor of fracture development. Comprehensive study shows that the rigid heterogeneous stacked sand bodies with single thickness smaller than 3 meters and accumulated thickness more than 10 meters have the potential of exploration and development.