**3. Methodology**

A total of 28 exploration wells were selected as research objects in this study, drilled from 2013 to 2017 by the China United Coalbed Methane Corporation. In total, more than 818-m-long conventional cores were received from 28 wells, diffusely covering the developed intervals of the tight sandstone gas reservoirs in coal-bearing formation; additionally, all the wells were logged with a set of comprehensive wireline surveys and cuttings. The cores have been macroscopically examined and described at 1-cm scale to obtain information on lithology, sedimentary structures, and geometric features of the organic-rich clasts. Samples have been collected from the shallow marine shelf, barrier coast and fluvial-delta deposits in all the three coal-bearing formations, thus providing sufficient geological information to undertake a comprehensive study of ORCs.
