Pore Structure Characteristics of Non-Marine Shale in Ordos Basin, China

Unlike marine shale, the non-marine (lacustrine) shale deposits are with frequent sand and mud interbed, large gross thickness, interlayers development and etc. In order to study reservoir properties, adsorption, permeability, porosity, gas storage and migration of such shale, experimental study of porosity character with the core sample of Mesozoic Triassic Yanchang Formation shale in Ordos Basin of China and contrastive study of this non-marine shale porosity characters and marine shale porosity character in north America and China were integrated in this paper. In experimental study, high pressure (up to 200 MPa) mercury porosimetry analysis determined the porosity, pore diameter and its size distribution, and specific surface area; different pressure permeability tests with nitrogen medium were taken to analysis the permeability with Klinkenberg correction; SEM images were observed to characterize the micro pore structures, and to describe the geometry, connectivity and fillings of pores. By combining all above experimental result, core structure features was comprehensive analyzed and gas-bearing properties of shale was evaluated. In contrastive study, experimental and literature data of pores feature in non-marine shale and marine shale, including permeability, porosity, pore size, and SEM images, were compared to analyze the development and structure of shale porosity in different sedimentary environment. Studies show that lacustrine shale has considerable gas storage capacity, and various types of porosities were observed on SEM images. Expectable, it could get considerable gas output. However, non-marine shale with extremely low permeability has adjacent porosity (accessible porosity 2.27%) to that of marine shale, which is attributed to the poor rate of pore connectivity in non-marine shale.