Abstract: Wellbore transient circulation temperature is of great importance in the selection of rotary steering tool during the deep shale gas horizontal well drilling process. A wellbore transient temperature model was established with consideration of heat exchange mechanism between the wellbore and the formation and the principle of energy conservation. The effects of circulation time, flow rate, horizontal length and drilling fluid inlet temperature on the annulus transient temperature were analyzed. The shale gas horizontal well trajectory control method was optimized, and then the measures for reducing the bottom hole circulation temperature were proposed. The results show that the annulus drilling fluid temperature in the upper part increases with the increase of circulation time and flow rate, while the drilling fluid temperature in the lower part decreases. As the horizontal length increases, the annulus drilling fluid circulation temperature increases, and the longer the horizontal length, the lower the cycle cooling effect. With the increase of the drilling fluid inlet temperature, the drilling fluid outlet temperature increase, but the drilling fluid temperature in the lower part changes little. When the vertical length is more than 4 000 m, the rotary steering drilling tool can be used with the short horizontal length, and the downhole motor with LWD measuring tool is recommended for long horizontal length and bottom hole circulation temperature is higher than 135℃. The bottom hole circulation temperature can be reduced by increasing the circulation time and flow rate and using the circulating while tripping-in, so as to ensure that and the rotary steering tool and LWD tool are within the safe working temperature.

Key words: deep shale gas, horizontal well, wellbore temperature, transient heat transfer, rotary steering, LWD