Dependence of fluid flow on cleat aperture distribution and aperture–length scaling: a case study from Gondwana coal seams of Raniganj Formation, Eastern India  

作　　者：Krishanu Bandyopadhyay Jyotirmoy Mallik Trishit Ghosh 

机构地区：[1]Indian Institute of Science Education and Research,Bhopal,India [2]Coal India Limited.Asansol.India

出　　处：《International Journal of Coal Science & Technology》2020年第1期133-146,共14页国际煤炭科学技术学报（英文）

基　　金：This is part of KB's doctoral research.This work is also a part of the pilot project for a project proposal(Project No:154)submitted to The Ministry of Earth Sciences(MoES);Government of India.The authors are grateful to the Indian Institute of Science Education and Research Bhopal(IISERB)for funding the necessary equipment and providing logistical support;We thank Coal India Limited(CIL)for their support and access to coal mines of Raniganj and Barakar coal fields;The authors are also thankful to Prof.S.K.Tandon of the Department of Earth and Environmental Sciences,USER Bhopal(Grant No.INST/EES/2016037);three anonymous referees and the Editor for their valuable comments that helped immensely to improve the manuscript;The authors have no conflict of interest while publishing this study.

摘　　要：Dimensions and mutual relationships amongst fracture(cleat)parameters such as maximum aperture width,average aperture width,length,spacing etc.control the connectivity within a fracture network and the fluid flow in a coal seam as the matrix permeability,here,is negligible.In this paper,we document cleat size distributions and investigate length–aperture relationships from coals of Raniganj coalfield in Eastern India.This coalfield has a proven extractable reserve of six billion tons of coal and holds immense potential to be one of the largest coal bed methane fields serving India’s growing energy needs.Here,cleat length(L)correlates with corresponding maximum aperture width(Dmax)in a power-law function with an exponent of 0.84(DmaxαL0.84)instead of the commonly observed exponents of 1 or 0.5 applicable for other natural‘opening-mode’fractures.The conventional wisdom pertains that laminar fluid flow(Q)through an isolated,smooth-walled,parallel-plate fracture,embedded in an impermeable matrix,is directly proportional to the cube of its aperture width(b,equivalent to Davg;cubic law:Qαb3).This assumes a linear relationship between length and fracture aperture.However,the modified relationship between cleat length and average aperture width changes the cubic law applicable for Raniganj coal seam and now fluid flow correlates with aperture width in a power-law function with an exponent of 4.25(Qαb4.25)instead of 3(cube).Such simplifications will come handy for the modeling and estimation of fluid flow as it will reduce the effort of cleat length measurement which is anyway difficult and can be misleading due to the risk of undersampling.

关 键 词：CBM CLEAT Coal PERMEABILITY Raniganj 

分 类 号：TD712.6[矿业工程—矿井通风与安全]