Abstract:

 In order to conduct a systematic study of thick dark mudstone and coal seams in the deep Late Paleozoic strata at the eastern foot of Taihang Mountains, Henan Province, taking the Late Paleozoic strata as the research object and using methods of sedimentology and sequence stratigraphy, the high resolution stratigraphic correlation and sedimentary facies division of the Upper Paleozoic Taiyuan Formation, Shanxi Formation and Xiashihezi Formation in the study area were carried out. A total of 5 rock types, 16 lithofacies types, 5 sedimentary facies and 10 sedimentary subfacies are identified. Three sequence boundaries and two key system tract boundaries were further identified, and 10 third-order sequences and corresponding system tracts were divided. Therefore, the sequence stratigraphic framework of coal measures strata in this area were established, the lithofacies paleogeographic characteristics in the isochronous stratigraphic framework were established, and its sedimentary evolution history was analyzed. It further defines the horizontal and vertical spatial distribution, evolution characteristics and the response relationship with the structure of each group of sedimentary facies, revealed that the sedimentation has a control relationship with all kinds of reservoirs, and established two typical coal accumulation models. On this basis, combined with gas logging data, the water and gas barriers and gas bearing systems are identified and divided within the sequence stratigraphic framework, the vertical distribution characteristics of coal seam gas content and the sealing characteristics of sequence structure on gas bearing systems are revealed, and the division of gas bearing systems of Late Paleozoic Coal measures are completed. There are two gas-bearing systems about Class I in sequence 2 of Taiyuan Formation and sequence 4 of Shanxi Formation.

Key words: Henan Province, Late Paleozoic, Taihang Mountains, sequence stratigraphy, sedimentary facies, principles of coal accumulation, gas-bearing system