Transient temperature field simulation and sensitivity factors analysis of riserless mud recovery system

The riserless mud recovery system (RMR) is different from conventional offshore drilling in that both the drill pipe and the return pipeline are exposed to seawater, which affects the entire temperature field distribution, and then affects the pressure field change of the whole system. Moreover, too low a temperature will lead to the emergence of gas hydrate. In order to accurately grasp the temperature field distribution and temperature regulation mechanism of the RMR system, a transient temperature field model was established considering frictional heat generation. The changing characteristics of temperature were discussed from two dimensions of time and space, and the influence of different factors on temperature was analyzed. The results show that the established transient temperature field model is more reliable and time-efficient. The variation of temperature with time and space is opposite in seawater and formation. Injection temperature and geothermal gradient are positively correlated with temperature. Displacement, drilling fluid density, and specific heat are positively correlated with temperature in the seawater section and negatively correlated with temperature in the formation section, while thermal conductivity shows the opposite trend. The research results can provide theoretical support for pressure control of the RMR system and the safe exploitation of hydrate.