A new transient simulation model and changing characteristics for circulating fluid temperature in a deepwater riserless mud recovery system

Abstract

In the ocean environment, the riserless mud recovery (RMR) system uses the return line as the return channel, resulting in the injection and return channels for the drilling fluid becoming two independent structures. Consequently, the RMR system exhibits different characteristics of circulating fluid temperature than conventional offshore drilling technology. To investigate this, a RMR system was divided into four simulation areas based on its structural characteristics, and a new transient simulation model was developed to simulate the circulating fluid temperature in each area. This study also explored the changing characteristics of the circulating fluid temperature under various sensitive factors, such as operating time, drilling fluid density, seawater depth, and pump rate, in both the time and space dimensions. Our results reveal that the transient simulation model developed is more suitable for simulating actual drilling situations than analytical solution models, and the simulation results are accurate. Furthermore, the distribution characteristics of circulating fluid temperature in the space dimension change with the operating time and drilling fluid density, but the trends and reasons for change vary between the two sensitive factors. Additionally, seawater depth mainly affects the circulating fluid temperature in each structure of the ocean environment when the RMR system is used for drilling in different sea areas, while its effect on the circulating fluid temperature in the formation environment structures is weak. Finally, pump rate mainly affects the circulating fluid temperature by changing its heat transfer time at a single space node, which is more remarkable than the frictional heat.