Pore structure characteristics and logging recognition of tight sandstone reservoir of the second member of Xujiahe Formation in Anyue Area, central Sichuan

Petrologic characteristics, physical property, pore structure characteristics and classification standard of Xu-2 (the Second Member of Xujiahe Formation) Reservoir were studied by analyzing core, casting thin section, scanning electron microscope and mercury injection data. The logging response characteristics of different pore structure types were analyzed and summarised to build logging recognition criteria and then to identify pore structure types of each well in Anyue Area. The results show that the reservoir mainly develop intergranular, intragranular dissolved pore, matrix pore, intercrystalline pore and microfracture. Pore structure types are fine pores and throats, thin skewness of throat, poorly sorted, strong heterogeneity and poor connectivity of pore throats. Based on casting thin sections, physical property of cores, capillary pressure curves and combination of pores and throats, pore structures are divided into four types, including Type I large pore coarse throat structure, Type II intermediate pore medium throat structure, Type III intermediate pore fine throat structure and Type IV fine pore fine throat structure. Different pore structures have different physical properties. Type I has favorable gas potential and good percolation capacity, normally developed with structural fractures. Type II is most likely to correspond to relatively good physical property and high gas content. Type III and IV have poor storage capability, corresponding to bad reservoir or ineffective reservoir. © 2016, Central South University of Technology. All right reserved.