GEOTHERMAL REGIME OF SHALE GAS BEARING SEDIMENTARY BASINS IN THE YANGTZE AREAS, SOUTH CHINA

Shale gas has become an increasingly important source of natural gas in the world and has attracted much attention from the academic and industrial circles. Temperature and geothermal regime of the sedimentary basin is one key to assess the generation and preservation of the shale gas. Sedimentary basins in the Yangtze area of south China are considered to be the large shale gas potential areas; however, the accurate geothermal regime of the Yangtze area is still unclear. Here we combined the borehole temperature logging and other formation testing temperature data, with thermal properties of rocks from this area, to investigate the present-day geothermal regime of the Sichuan and Lower Yangtze basins. Our results show that the geothermal gradient of this area is between 18 K/km and 35 K/km, with an average of 30 K/km for the Lower Yangtze basin in the northeast and 22 K/km for the Sichuan basin in the southwest. Heat flow of the Sichuan basin ranges from 35.4 W/m² to 68.8 W/m², with an average of 53.2 W/m²; while most of the heat flow in the Lower Yangtze basin is between 54 W/m² and 72 W/m², and the average value is 60 W/m², suggesting that the Yangtze area is characterized by middle to high geothermal regime. In addition, according to the present-day geothermal regime mentioned above, the predicted formation temperature above 150 °C is available for formations with depth about 4000 m in the Lower Yangtze basin and 6000m in the Sichuan basin, which to a certain extent would represent the possible burial depth of the shale gas in the Yangtze area.

This work is financially supported by National 973 project (2012CB214703).