Design of thermal-insulated pipes applied in deepwater well to mitigate annular pressure build-up

Annular pressure build-up threatens deepwater well safety greatly, but the available mitigation methods are limited by well conditions and formation properties in some cases. Thermal-insulated pipes including casing and tubing are an alternative method due to low thermal conductivity. To optimize the application of thermal-insulted pipes, a model based on volume consistency and semi-steady approach is established to calculate the annular pressure in multiple annuli with thermal-insulated pipes. In the case well, the optimal setting depth is 2200 m, equal to cement top. Annular pressure decreases quickly when thermal conductivity is under 0.04 W/(m.k). Thermal-insulated pipes can reduce the rising speed of annular pressure as formation temperature increases. The effect of production rate can be ignored if it is higher than 400 t/d. The annular pressure of case well is reduced by as much as 63.97% and kept under maxim acceptable annular pressure in 10 years. Based on this model and analysis, a process is proposed to design the thermal pipes applied in deepwater well to mitigate annular pressure build-up. (C) 2015 Elsevier Ltd. All rights reserved.