Transient temperature prediction model of horizontal wells during drilling shale gas and geothermal energy

A transient temperature prediction model was established to analyze wellbore temperature distribution of horizontal wells during drilling shale gas and geothermal energy based on unsteady two-dimensional convection-diffusion equation and the model was discretized with finite volume methods and solved by owe relaxation iteration method. The validity of the model has been verified by field temperature data. The influence of drilling parameters on temperature distribution of drilling fluid were discussed. Results indicated that the closer to the bottom of the well, the smaller the rate of change of the drilling fluid temperature with depth. The temperature of the drilling fluid at the same well depth increases with the increasing horizontal section length, drilling fluid density, geothermal gradient and vertical depth. The temperature of the upper part of the wellbore increases with the increasing circulation time and drilling displacement, and the lower part of the wellbore decreases with the increasing circulation time and drilling displacement. Drilling fluid temperature inside the drilling string decreases with the increase in viscosity. However, drilling fluid temperature inside the annulus of the upper part of the wellbore increases with the increase of the viscosity while the drilling fluid temperature of the lower part of the wellbore decreases with the increasing viscosity.