Influence rule of geothermal temperature in medium-deep geothermal borehole and its prediction method
The initial formation temperature(IFT)and original geothermal gradient(OGG)are important parameters affecting the heat transfer calculation of medium-deep geothermal borehole,but the borehole temperature measured in a short time after borehole completion can not reflect IFT and OGG.In order to obtain IFT and OGG quickly and accurately,it's found by analyzing the log data that the drilling fluid circulation makes the temperature difference between the upper and lower inside the borehole smaller,resulting in a low geothermal gradient obtained when the borehole is not still.It is necessary to increase the static time to ensure the accuracy and reliability of IFT.However,in practical engineering,it is impossible to increase the drilling static time for a long time.And the relationship is determined between the fluid temperature in the drill string and the geothermal gradient through further analysis of heat transfer in the drilling fluid circulation process.Based on the establishment of the analytical solu-tion model of the transient heat transfer between drilling fluid and rock strata,the drilling fluid temper-ature after a short period of static time is calculated and the correlation coefficients are determined be-tween the calculation results and the drilling fluid temperatures measured after borehole completion,with both IFT and OGG being calculated quickly.The accuracy of the proposed method is verified by comparing with the data in literature and borehole logging results,which provides accurate data for the analysis of heat transfer between the medium-deep geothermal boreholes and rock strata and has practi-cal significance for the study of heat transfer performance of medium-deep geothermal boreholes.
万方数据
维普
