Geothermal geological characteristics and geothermal resources evaluation of Huainan mining area

In order to explore the geothermal geological characteristics of Huainan mining area and the prevention and control measures of deep mine heat hazard,the temperature logging data of the exploration holes of Huainan mining ar- ea were systematically collected and analyzed. Based on the approximate steady-state temperature data,the temperature calibration curve in the thermometry hole bottom was fitted,and the temperature in the hole bottom of the simple ther- mometry well was corrected. The surrounding rock temperature of the underground roadway was measured by shallow hole temperature-measuring method. The geothermal gradient of each well field was calculated,and the terrestrial heat flow value of Huainan mining area was calculated by the thermal conductivity test results of 110 coal and rock samples of coal measure strata. The current geothermal field,the geothermal gradient and the terrestrial heat flow distribution map of Huainan mining area were compiled,and the distribution characteristics of the current geothermal field,the ge-othermal gradient and the terrestrial heat flow in this area and the thermophysical properties of coal measures rocks were comprehensively expounded. The geological structure control of the geothermal field distribution was discussed and the geothermal resources in this mining area were calculated. The results show that:① The temperature recovery in the bottom of the well and the static time of well-liquid of the Huainan mining area is in accordance with the expo-nential function relationship,and the correction formula for the temperature change in the bottom of the simple ther-mometry well is established accordingly. ② The geothermal parameters in the Huainan mining area are as follows:the geothermal gradient is from 1. 00 to 4. 00 ℃ / hm with an average value 2. 8 ℃ / hm;the terrestrial heat flow value va-ries from 31. 87 to 92. 68 mW / m2 with an average value 65. 50 mW / m2 ;the average temperature of the -500 m level is 29. 96 ℃ ,and the value of -1 000 m and -2 000 m level are 41. 84 ℃ and 69. 62 ℃ ,respectively;the thermal conductivity of rock is from 0. 37 to 5. 22 W / (m·K) with an average value 2. 93 W / (m·K). ③ The distribution of the geothermal gradient,the geothermal field and the terrestrial heat flow on the plane are generally higher in the east and north than that in the west and south. ④ The current geothermal field and the terrestrial heat flow distribution in the mining area are mainly controlled by the geological structure,which show three modes of controlling temperature by the geological structure including the fold type,the overthrust fault heat-resistance type and the water-conducting fault heat transfer type. ⑤ According to the results of geothermal resources evaluation,the resources of the geothermal reser-voir in this area are 2. 32 ×1016 kJ,the recoverable heat energy reserves are 2. 64 ×1015 kJ,and the mine water and mine return air waste heat recovery resources are from 0. 97×1013 to 1. 26×1013 kJ / a,and the geothermal reservoir be-longs to a renewable low-temperature heat source with significant potential benefits. The research results can provide a geological basis for the treatment of thermal hazard and the comprehensive development and utilization of geothermal resources in deep mining in Huainan mining area. Evaluation and utilization of geothermal resources and mine waste heat resources in the deep mine should be one of the development directions for the sustainable development of coal mining areas