Sealing capacity of siderite-bearing strata: The effect of pore dimension on abundance and micromorphology type of siderite in the Lopingian (Late Permian) coal-bearing strata, western Guizhou province

We conducted a series of core observation, thin section evaluation, and integrated with low-temperature nitrogen adsorption/desorption, porosity, permeability, breakthrough pressure analysis of the siderite-bearing strata. This paper aims to discuss the sealing capacity of siderite-bearing strata as a function of siderite abundance and micromorphology type. The siderite-bearing strata can be potential gas barrier layers in multiply-superposed gas-bearing systems. In the transitional Lopingian coal-bearing succession of western Guizhou, the siderite content of siderite-bearing mudstone is 18.6-90.7% (wt.), with an average 53.4% (wt.). There are three morphologies of siderite, including S1 (gelatinous aggregates), S2 (microcrystal-silt size crystal aggregates), and S3 (sphaerosiderites). It shows that different abundance of siderite and type of siderite micromorphology affected the pore structure. The sealing capacity of siderite-bearing mudstone at the study area is somewhat or significantly larger, and the sealing capacity of the siderite-free mudstone is moderate. The development of siderite-bearing strata is controlled by the stratigraphy of the sequence.