Circulating Temperature Distribution Model Of Drilling Fluid In Geothermal Wells And Influencing Factors Of Research

Geothermal energy,as a green and efficient renewable energy source,has great potential for development.The development and utilization of geothermal energy cannot be separated from drilling work.The circulating temperature of drilling fluid in the wellbore of geothermal Wells has always been one of the most critical parameters.Accurate prediction of the circulating temperature of drilling fluid can ensure safe and rapid drilling,optimize drilling parameters and improve drilling efficiency.The Kabir model and Schoeppel model are two popular temperature prediction models.However,the two temperature prediction models have many limitations,and the actual formation temperature,thermophysical parameters and drilling fluid performance change with temperature are not taken into account.As a result,the final prediction results are often quite different from the actual values.Therefore,based on the traditional Kabir model,a new geothermal well drilling fluid temperature distribution model was established to reduce the prediction error and guide the optimization of the drilling process.In this paper,considering the formation temperature is not a single geothermal gradient and thermal physical property parameters change at the same time,attaches great importance to the performance of drilling fluid with temperature changes,to establish the coupling temperature characteristic of geothermal well drilling fluid circulating temperature distribution in the new model,designed the corresponding iteration steps with MATLAB parameterized,under the condition of positive cycle analysis it is concluded that the whole hole annulus cycle temperature is higher than the cyclic temperature inside the pipe,both in bottom hole temperature to achieve equal;The effect of changing formation temperature or drilling fluid performance on wellbore circulation temperature distribution was studied separately.It was found that the drilling fluid temperature deviation was larger when the formation temperature was calculated as a single gradient.Based on geothermal well drilling fluid temperature distribution model built in this paper,combined with the engineering practice setting parameter value scope,analysis of different drilling fluid mass flow rate,inlet temperature,cycle time and lost circulation under the condition of drilling fluid circulating temperature distribution,found that with the increase of mass flow rate and cycle time,borehole circulation temperature drop;As the inlet temperature rises,the circulating temperature in the well rises.Therefore,it is recommended to increase the mass flow of drilling fluid with large pumping capacity,increase cooling equipment on the ground,or improve the heat resistance of the drilling fluid system,etc.,so as to better"cool" the formation,so as to achieve the purpose of reducing the circulating temperature of drilling fluid in geothermal Wells.At the same time,the effect of the loss rate of drilling fluid and the position of the lost layer on the annulus temperature distribution is simulated.The results show that the continuous leakage phenomenon in the well will reduce the circulating temperature of drilling fluid in the annulus and drill pipe,which reflects the cooling effect of well leakage on drilling fluid,especially for some sections near the leakage layer at the bottom of the well,and the depth of the leakage layer can be judged by the inflection point of the temperature gradient distribution of drilling fluid in the annulus.