NMRI test on two-phase transport of gas-water in coal seam
煤层中气水两相运移的NMRI试验研究

An advanced non-destructive measurement technique(NMRI technique)was applied for the first time in the research of two-phase transport of gas-water in coal seam.The home-made triaxial osmoscope which is made up of non-magnetic polycarbonate material and can change confining pressure,axial pressure and pore pressure,was placed into the magnetic cavity of NMRI instrument.Through the tests on gas driving water and water driving gas,the flow law of gas and water was real-time observed.Mainly based on the test of water driving gas as an example,the development of molding coal sample and NMR triaxial osmoscope was demonstrated.The experiment process of water driving gas and parameters were demonstrated.NMRI images of molding sample in horizontal cross-section along the driving direction were obtained by NMRI instrument.The results from images were analyzed and compared.Some novel laws were obtained as the following:(1)the leading edge of water driving has inconsistency.This certified the important previous conclusion that the storage of methane mainly was absorbed in inner surface of pore from NMRI technique;(2)the existence of dominant driving pathway was tested and the way kept almost fixed.The pathway is apt to exist in the edge of coal samples where pore and fracture fully develop;(3)the variation of water flow determines the transport velocity of leading edge of water driving and it has lag effect;(4)the effectiveness of the first driving is better than the second driving;and(5)the subsequence of water driving gas are from trunk fractures to branch fractures,then to branch pores.