Prediction of geotemperatures in coal-bearing strata and implications for coal bed methane accumulation in the Bide-Santang basin, western Guizhou, China

Abstract

The geothermal fields of coal-bearing strata have become a key topic in geological research into coal and coal bed methane (CBM). Based on temperature data from 135 boreholes that penetrate the Upper Permian coal-bearing strata in the Bide-Santang basin, western Guizhou, the precisions of geothermal predictions made using a geothermal gradient model and a gray sequence GM(1,1) model are analyzed and compared. The results indicate that the gray sequence GM(1,1) model is more appropriate for the prediction of geothermal fields. The GM(1,1) model is used to predict the geothermal field at three levels with depths of 500, 1000, and 1500 m, as well as within the No. 6, No. 16, and No. 27 coal seams. The results indicate that the geotemperatures of the 500 m depth level are between 21.0 and 30.0 °C, indicating no heat damage; the geotemperatures of the 1000 m depth level are between 29.4 and 44.7 °C, indicating the first level of heat damage; and the geotemperatures of the 1500 m depth level are between 35.6 and 63.4 °C, indicating the second level of heat damage. The CBM contents are positively correlated with the geotemperatures of the coal seams. The target area for CBM development is identified.