Study On Distribution And Evaluation Methodology Of CBM (Coal Mine Gas) Resources In Coal Resource Depletiing Mine

Based on the comparison of coal and coalbeded methane (CBM) geologicalconditions, coal mining, abandoned mine management betwen China and foreigncountries, this thesis constructed two models--"Coal Mine Geological Model" and"Coal Mine Development Model"--to classify residual coal and residual gas, and tofurther analysis CBM migration as well as CBM enrichment rules during and aftercoal production. Besides, this thesis proposed a set of calculation methodologies,including "the Desorption Process Method" and "the Admissibility TaxonomyMethod" and bulit an initial CBM resource potential evaluation system, which weresuitable for the CBM in Chinese coal resource-exhausted mines. At last, takingLiangshuijing mine of Liuzhi mining area in Guizhou Province as example, this thesisdiscussed and evaluated its CBM migration, enrichment rules and resourceexploitation potential.The present study suggests that: Firstly, there existed remarkable differencesbetween China and foreign countries in terms of coal geology, CBM geology, coalmining conditions, especially the treatment to mine during its closing process and itsfollow-up management, indicating that the results of related studies abroad cannotdirectly apply to the evaluation and exploration of CBM resources in coalresource-exhausted mines at home. Secondly, CBM exploration in coalresource-exhausted mines undertaken domestically had not only advantages of a greatexploration potential, comparatively mature exploration technologies, but alsodisadvantages of weak basic researches, poor CBM preservation conditions. Thatmeans, during the coal mining process, the CBM in the working seam would spreadcontinuously towards working face and coal mine goaf because of concentrationdifference. While, in adjacent coal seams, due to various degrees of pressure reliefand desorption caused by their different distances to working seam, the desorbedCBM would diffuse into coal mine goafs as a result of gas pressure difference. Whenpermanent goaf formed or after caol mine closure, CBM in working and adjacentseams would eventually accumulate and preserved in mining cracked zone, or leakout to the ground if the capping conditions were poor in the accumulation area, ordissolve and run off when the underground water was of great moblility. TheAdmissibility Taxonomy Method is suitable for the CBM prediction in Chinese coalresource-exhausted mines which have not yet closed; while the Desorption Process Method is applicable to the CBM prediction in those have already closed.Taking15st coal as boundary, Liangshuijing coal mine were divided into twoseam groups--the upper group and the lower group, which formed two independentgas accumulating units respectively. In the upper seam group, along its updipdirection, a unified gas accumulating unit was formed in the1st,3st and7st mininggoaf cracked zone; in the lower seam group, along its updip direction, the unified gasaccumulating unit was in each mining goaf cracked zone. It is predicting that whenLiangshuijing mine was closed, the exploitable volume of CBM would reach1680.54ten thousand m3, with good CBM resource geology conditions and expoitationconditions, desirable preservation conditions and favourable economic marketconditions. All in all, the exploitaion potential of CBM in Liangshuijing mine wasoverall good.