Laboratory studies of non-marine shale porosity characterization

Abstract

Porosity characterization is the basic and very important research direction in shale core experimental study because it affects the gas reserves and the design of fracturing treatment. In this paper, laboratory studies of porosity characters with non-marine shale core samples from Mesozoic Triassic Yanchang Formation in Ordos Basin of China are investigated. To analyze the porosity characters, like porosity and pore size distribution, mercury porosimetry and gas adsorption test are carried out and compared. SEM images of horizontal surface and vertical cross section in shale samples were observed and analyzed to characterize the micro pore structures, describe the geometry and connectivity of pores. This paper concludes that pores in this non-marine shale samples are dominated by mesopores, secondly by macropores and rarely micropores. Nitrogen adsorption test is better than mercury intrusion method to measure shale pore size properties. Pores and micro cracks of shale mainly exist in intergranular spaces of minerals and in the border between two minerals. Moreover, non-marine shales having less nanoscale pores and lower porosity than marine shale is partly caused by low maturity of organic matter.