Wellbore-formation transient temperature distribution considering heat transfer by fluid seepage while drilling in horizontal well

Currently, most wellbore-formation temperature field study only considers radial heat conduction in the formation, while neglecting temperature transfer caused by fluid seepage within the formation. Therefore, this paper investigates the impact of seepage between the wellbore and formation on heat transfer and develops a temperature prediction model suitable for horizontal wells. Secondly, detailed explanations are provided regarding the calculation methods for mechanical heat source term , hydraulic heat source term, drilling fluid rheological parameters, thermal physical parameters, and heat transfer coefficient in the model. Finally, the finite difference method is employed to solve the temperature model, and an analysis is conducted on the impact of mud density, formation permeability , seepage and drilling time on the annulus-formation temperature. The main conclusions are as follows: due to a large amount of mechanical friction, the temperature of the inclined section may exceed that of the initial position of the horizontal section. In the case of underbalanced drilling in high permeability formations, the consideration of seepage's influence on annulus temperature is paramount. Neglecting seepage results in a maximum error of 55.4 % in annulus temperature. The wellbore-formation temperature is positively correlated with formation permeability during overbalanced drilling, but negatively correlated during underbalanced drilling. The higher the drilling fluid density , the higher the wellbore-formation temperature. In the process of underbalanced drilling, there is minimal change in bottom hole temperature over time, while the wellhead temperature gradually increases. Conversely, during overbalanced drilling, the bottom hole temperature steadily rises as drilling progresses, with little variation observed at the wellhead. • Wellbore-formation temperature increases with permeability in overbalanced drilling and decreases in underbalanced drilling. • Wellbore-formation temperature is always positively correlated with the mud density. • Mud density and permeability affect temperature more in underbalanced drilling than in overbalanced drilling.