Measurement and analysis of the thermal conductivities of rock samples from the Baiyinchagan Sag and Uliastai Sag, Erlian Basin, northern China

Thermal conductivity of rock plays a very significant role in the fields of geothermal related research. This paper is based on the thermal conductivity measurements of 129 borehole core samples, 98 newly measured and 31 collected, from the Baiyinchagan Sag and Uliastai Sag of the Erlian Basin, Inner Mongolia, northern China. The Erlian Basin is Mesozoic in age. Most samples belong to Cretaceous strata of mudstone, sandstone, conglomerate, callys and basalt with porosities ranging from 2% to 20%. They were taken from 117. 8m to 3159. 5m below surface where formation temperatures are estimated to be in the range from 13.5°C to 118. 6°C and pressures from 2. 89MPa to 77. 41MPa. The thermal conductivities of the dry core samples were first measured at room temperature and 1atm. The measured values were subsequently corrected for the effects of water saturation, temperature, and pressure according to their porosities and depths. The measured thermal conductivities fall in the range of 0. 89 ∼4. 91W/( m · K) with an increasing trend with depth. The mean lithologic thermal conductivities are 2. 08 ± 0. 36W/ ( m · K) for mudstone, 2. 28 ± 0. 50W/ ( m · K) for sandstone, 2.53 ±0. 44W/(m · K) for conglomerate, 4. 16 ± 0. 76W/(m · K) for callys, and 1.33 ± 0. 09W/(m · K) for basalt after water saturation and temperature-pressure corrections. Among the five sample categories, callys is of highest thermal conductivity, whereas basalt is of the lowest. The thermal conductivities of the Cretaceous strata in the Baiyinchagan Sag and the Uliastai Sag are 2. 00W/(m · K) and 2. 17W/(m · K), respectively. In conjunction with borehole temperature logging data, the heat flow density of the Erlian Basin is estimated to be 74 ∼85mW/m², substantially greater than the 61. 5mW/m²mean for the continental area of China. The results of this study enrich the geothermal conductivity data of the Erlian Basin, and lay a foundation for further investigations on the geothermal energy potential, deep thermal condition and thermal structure of the lithosphere of the study area.