Abstract:

Geothermal field of petroliferous basin plays a very important role in oil and gas generation, transport and basin evolution. Qaidam Basin is an important oil and gas basin in western China, which is located in the northeast of the Himalayan tectonic domain. The study of the characteristic of geothermal field not only provides the scientific basis to intracontinental or intraplate continental dynamics and dynamics research in Qaidam Basin and its surrounding, but also is available to hydrocarbon generation, petroleum entrapment, the resources assessment, etc. Preliminary work of present geothermal field in Qaidam Basin mainly concentrated in the western basin, but a few in the northern and eastern Qaidam Basin, and the data used in the study were most obtained before the 20th century; the systematic research of present basin geothermal field is rare, and it is needed urgently to carry out the related research work. The advanced borehole temperature continuing acquisition system makes the measuring work of steady state temperature of deep well could be carried out in big scale and with high precision; using the Optical Scanning Method to test rock thermal conductivity, we obtained the batch, high precision rock thermal conductivity data, and 17 boreholes temperature profile. Studies show that the present geothermal gradient of Qaidam Basin is 28.6±4.6 ℃/km on average, that the geothermal gradient distribution is high in west and low in east and middle, and that the present terrestrial heat flow value of Qaidam Basin is 55.1±7.9 mW/m2 on average. The present terrestrial heat flow value of Qaidam Basin is higher than that of western China, such as Tarim and Junggar Basins, however, it is lower than the average regional terrestrial heat flow in China mainland, and it belongs to the warm basin as a whole. The distribution of geothermal field might be controlled by crustal structure, basin structures, etc.

Key words: geothermal gradient, thermal conductivity, heat flow, crustal structure, Qaidam Basin