Ultra-Deep Drilling Wellbore Temperature Model Considering Thermophysical Properties of Different Lithology

Abstract Deep and ultra-deep drilling encounters high-temperature and high-pressure formation, and the state of wellbore flow and heat transfer is complicated, so the wellbore temperature is difficult to describe accurately. The conventional wellbore-formation heat transfer model holds that the formation lithology is uniform and the thermophysical parameters are constant value. However, a variety of lithologies are drilled during the drilling, and the thermophysical parameters of the formation vary with lithology and temperature. In this paper, a wellbore-formation heat transfer model of the ultra-deep well is developed by considering the thermophysical properties of different formation lithologies. A mathematical model of wellbore-formation heat transfer is constructed based on the law of energy conservation. Then the lithology of the formation is extracted, and the thermophysical parameters matrix of the lithology is constructed, to be embedded into the heat transfer mathematical model. Finally, the finite difference method is used to solve the mathematical model. The real data of an ultra-deep well is used to verify the model. The results show that the error between the predicted results of the model and the measured is only 3%. The wellbore-formation heat transfer model established in this paper can accurately describe the evolution law of the wellbore temperature field.