Abstract: The development of hydrate reservoirs with horizontal wells has the characteristics of large producing range, high gas production rate, and high economic benefits. However, due to changes in downhole temperature, hydrates are prone to decompose during drilling, which induces instability of borehole wall. Based on the reservoir parameters and basic drilling parameters in the Shenhu area of the South China Sea, the heat transfer process in the wellbore during horizontal well drilling was studied, and the calculation model wellbore temperature profile during the mud circulation process was constructed. The influence law of displacement, density, initial temperature, and horizontal displacement of surface mud on wellbore temperature field was studied. The study finds that the mud injection displacement is the main factor that affects the temperature profile of the wellbore, while the mud density is the secondary factor. The greater the horizontal displacement, the more adequate the heat conduction between the mud and the formation in the wellbore. The research results can provide a reference basis for designing the mud parameters and designing well structure of horizontal wells in hydrate reservoirs in the Shenhu area of the South China Sea.

Key words: hydrate, horizontal well, drilling fluid, temperature field, Shenhu Area