The Upper Permian Coalbed Methane Bearing System and its Sedimentary Control in Western Guizhou, China
Based on the observation of drilling cores and lab analysis, it is indicated that the formation of "unattached multiple superimposed coalbed-methane system" is controlled by sedimentary environment remarkably. This study demonstrates that the distribution of low-permeability rocks in coal-bearing strata plays a part of separating in the formation of "unattached multiple superimposed coalbed-methane system". The development of impermeable gas barrier is controlled by sedimentary environments, under which impermeable gas barrier of low porosity and low permeability in coal-bearing strata tends to form in the area from delta plain facies to delta front facies, resulting in vertical coalbed-methane bearing system becoming gradually complex. For its oxidized environment, delta plain area is not conducive to the formation of siderite and pyrite during the penecontemporaneous diagenesis and early diagenesis stages. The block performance of mudstone is relatively weakened, which is near to the maximum transgressive surface in the sequence, making the unattached coalbed methane bearing system connected to each other, constituting a relatively uniform coalbed methane bearing system. The vertical coalbed methane system is relatively simple in delta plain area. The impermeable gas barrier with low porosity and low permeability in the coal-bearing strata is relative development in the delta front where the vertical coalbed methane bearing system is more complex.
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维普
