Managed Temperature Drilling: An Automated Real-Time Controller for Downhole Temperature Control in Geothermal and HPHT Wells

Abstract Drilling geothermal and HPHT wells is complicated by exposure of downhole tools to high temperatures. Pro-active downhole temperature management is therefore very important to prevent heat-related tool failure which can result in significant non-productive time and increased costs. Temperature management that relies heavily on surface cooling is currently mostly a manual process. This paper presents a control-oriented platform to achieve automated managed temperature drilling in real-time. For the controller, an improved reduced drift-flux model that considers temperature dynamics, interface mass transfer, and a new lumped pressure dynamics model is used. By considering these factors, the model is used to digitally twin the transient thermal behavior of geothermal wells. The improved temperature model is validated using experimental results from the Utah FORGE 16A(78)-32 dataset. To demonstrate the utility of the model, it is used in conjunction with a controller to simulate maintaining a sufficiently cool bottom-hole temperature for downhole tools in various drilling scenarios. These thermal control scenarios demonstrate that the model can be used for control design, which effectively controls the downhole temperatures during the well construction process. This paper presents the first control-oriented platform that automatically manages the downhole temperature in a geothermal or HPHT well. By using a model capable of real-time simulation, automatic and predictive control algorithms can be applied to reduce negative thermal effects during drilling, thereby significantly decreasing non-productive time events and the cost of constructing a geothermal well.