Sedimentary Enviroment Of Shanxi Formation And Its Impact On CBM Enrichment In Gujiao Mining Area

The theory and method of sequence stratigraphy, petrology, sedimentology, gas geology, coalbed gas geology and other disciplines was applied in this paper. The sedimentary facies, sequence stratigraphy, lithofacies palaeogeography, relations between sedimentary environment and coalbed gas enrichment of Shanxi Formation in Gujiao mining area was researched with the observation and study of the drilling cores GS-26, D13-4 and GS-3, combined with a comprehensive analysis of 100 drilling and gas content of them. According to the study to facies mark, two deposition phases of delta plain, delta front sub-facies and eight related microfacies were identified, and its characteristics are summarizes.By identification to sequence boundaries, transgressive surface, the largest transgressive surface, Shanxi Formation is divided into three third-order sequences, 8 system domains. Sequence stratigraphic framework was established through the study to more than 100 ports in drilling region. Characteristics of sedimentary evolution of Shanxi Formation were discussed within the sequence stratigraphic framework. On this basis,the depositional model of Shanxi formation are summarized.Taking the study area of 2# coal gas content as an example, which aims at discussing the relationships between the sedimentary environment including other factors and CBM enrichment. Sedimentary environment has effect on CBM enrichment, it firstly mainly embodied in the coal thickness, roof and floor thickness of mudstone and coal, etc. Except that, it also disscusses other factors involving tectonic evolution, fold development area, the development of fault features, coal seam buried depth and hydrogeological conditions.