鄂尔多斯盆地典型煤相控制下煤储层孔裂隙特征OA

The deep Carboniferous-Permian strata of the Ordos Basin contain abundant coalbed methane resources,and an in-depth understanding of the development characteristics of pore and fracture systems in coal reservoirs is one of the keys to their efficient development.Focusing on typical coal facies in the basin,this study systematically collected different types of samples and applied multiscale reservoir characterization techniques to characterize in detail the macroscopic and microscopic pore structures and fracture-development characteristics of Carboniferous-Permian reservoirs of typical coal facies,thereby revealing the intrinsic coupling between coal-forming environments and pore and fracture characteristics.As indicated by the research results,coal facies are one of the core geological factors controlling the development of pore and fracture systems in deep coal reservoirs.Three coal facies are predominantly developed in the Carboniferous-Permian coal measures:low-lying swamp(reed)facies,wetland herbaceous swamp facies,and dry/wet forest swamp facies.The low-lying swamp(reed)facies contains abundant micropores,and its fracture system is characterized by major bedding fractures with long trace lengths and good connectivity.The pore system of the wetland herbaceous swamp facies is dominated by micropores,while its fracture network is characterized by the preferential development of vertical butt cleats and relatively good connectivity.In the dry/wet forest swamp facies,as the degree of water inundation decreases,the pore structure gradually changes from a bimodal distribution comprising micropores and mesopores to a unimodal distribution dominated by micropores,while the fracture network exhibits strong heterogeneity.Under deep-burial conditions characterized by high in-situ stress and intense compaction,coal facies constrain the original material composition,thereby influencing the mechanical properties of coal and the basis for fracture-network develop-ment,and controlling the preservation state of effective fractures and pore-throat connectivity.