QUANTITATIVE ANALYSIS FOR NANOPORE STRUCTURE CHARACTERISTICS OF SHALES USING NMR AND NMR CRYOPOROMETRY

Based on the differences in pore structure characteristics between marine and continental shale in China, Weiyuan marine shale(1^#), Jiao Shiba marine shale(2^#), Yaoqu tuff(4^#) and Yaoqu continental shale(5^# and 6^#)were selected to study the pore structure characteristics using cold field emission scanning microscopy(FE-SEM) and nuclear magnetic resonance(NMR). Nuclear magnetic resonance cryoporometry(NMRC)was employed to represent nano-scale pore structure. This method can be extended to microns measurement combining nuclear magnetic resonance relaxation analysis to detect in detail the pore structure of shales under the different aperture scales. The smaller the test temperature gradient is, the finer the result of pore distribution is. Test results show decreasing porosity from sample 5^#, 2^#, 6^#, and 1^# to sample 4^#. NMRC, low field nuclear magnetic resonance(LFNMR), mercury intrusion porosimetry(MIP) and gas adsorption(GA)methods show good agreement of pore size distribution in their respective scope of application. Hence, the pore structure of the reservoir shale can be evaluated more accurately by combining NMRC, LFNMR with GA and MIP. Thus the nano-pores of continental shale(5^# Yaoqu shale) are clearly better developed and will more likely have a higher commercial exploitation value than those of marine shale.