Abstract:

Based on drilling data, outcrop geologic survey around the area and laboratory test results of lots of rock samples, reservoir characteristics of Triassic Xujiahe Formation shale in the Sichuan basin are analyzed. Physical properties of the shale reservoir were tested by high pressure mercury intrusion method, nitrogen isothermal adsorption, and pulse permeability method. It is thought that Xujiahe Formation shale has a center of reservoir performance, and the porosity ranges from 0.95% to 4.77% with an average of 2.73%. A series of methods including direct observation method such as core and thin section observation, field emission scanning electron microscopy (FSEM) in combination with highpressure mercury injection, nitrogen isothermal adsorption experiment research have been used to research the reservoir space characteristics of Xujiahe Formation. Nanoscale matrix pore is the dominant reservoir space in the Xujiahe Formation shale, and pore with size less than 50 nm accounted for 83.9%. Matrix pores with pore size of 2100 nm include residual primary pores, intergranular pores, dissolved pores, and organic pores that only developed in local parts. Its pointed out that TOC content, clay mineral content and thermal maturity were the main controlling factors on reservoir characteristics of Xujiahe Formation shale.

Key words: continental shale, Xujiahe Formation, porosity characteristics, organic matter pore, surface area, porosity distribution