Experimental investigation of the pore structure of triassic terrestrial shale in the Yanchang Formation, Ordos Basin, China

摘要

The Yanchang Formation was deposited in a terrestrial environment in the late Triassic period. It consists of organic-rich shales that possess hydrocarbon resources for both conventional and tight gas sand plays in the Ordos Basin. The identified source rocks have become horizontal drilling targets as an active shale gas play. Although limited, the current study suggests that the physics of its porous media is far more complicated than that of marine shales in either North America or China, which calls for detailed characterization. In this study, a series of laboratory experiments were conducted on 20 samples from Chang 7 and Chang 9 members of the Yanchang Formation to characterize the pore structure of the terrestrial shale, including the mercury injection capillary porosimetry (MICP) test, low-pressure N-2 adsorption test, X-ray diffraction mineralogy (XRD) test, and geochemical analysis. Moreover, petrographical analysis was performed to obtain field-emission scanning electron microscopy (FE-SEM) images in order to identify different types of pores, as well as their correlations with mineral constituents and organic matter.