The Insulated Drill Pipe - Field Experience and Thermal Model Validation

Abstract To drill deeper and hotter wells, such as for high temperature high pressure (HPHT) oil and gas or geothermal applications, proper management of bottomhole temperatures is critical to ensure survival of electronic tools and to improve drilling performance. The paper introduces a new type of the Insulated Drill Pipe (the "IDP") which minimizes heat transfer from the annulus into the drill pipe, to deliver drilling fluid to the bottomhole assembly (BHA) with substantially cooler circulating temperature than using the non-insulated drill pipe. An iterative design process was followed to develop a robust and cost-effective insulating material that can be applied to the inside and outside of the standard non-insulated drill pipe. After testing a series of different insulating materials in the lab and in the field as prototypes, a new coating system was chosen for the first generation of the IDP. Concurrently, a detailed thermal model was developed to estimate the expected cooling effect of the IDP. A full IDP string was manufactured in 2022 and was subsequently used in three field trials: a geothermal test well in New Mexico, the USA DOE FORGE project in Utah, and a US-based shale well. During field trials, mud inlet and outlet temperatures and measurement while drilling (MWD) temperatures were monitored. In some cases, mud chillers were used at the surface to decrease the inlet mud temperature. Both real-time and recorded MWD temperatures were obtained. At FORGE, recorded circulating temperatures at the MWD were reduced by up to 42 °C (75 °F), from 107 °C (225 °F) to 65 °C (150 °F) in formation temperatures exceeding 150 °C (300 °F). Analysis of wear and robustness of the insulating material were inspected on all joints of drill pipe and damage in vertical and deviated wells was minimal. High normal forces and friction in a horizontal well did result in significant damage to the coating which can be remedied through improved coating design. The thermal model was validated with the measured data and used to accurately predict the performance of IDP in future runs. This is the first extended field trial of the IDP, and the results demonstrate the value of the IDP to reduce mud temperatures downhole. The IDP allows for improved cooling of the BHA components, particularly electronics, and extends the operating window of existing MWD, electronic equipment and other BHA tools to deeper and hotter environments. This is critical for the HPHT wells and for deep and hot geothermal wells, reducing the cost of the instrumented BHAs for these wells, while improving downhole tool reliability, and reducing a frequency of tripping operations due to downhole failures. The developed thermal model can also provide maximal connection times by estimating the rate of borehole heating while rig pumps are off.