Temperature distribution modeling in geothermal wellbore during circulation

Knowing temperature distribution in geothermal wells is important for design and management of the drilling operation. High temperatures reduce performance of drilling mud and it brings about many drilling problems. Also, high pumping power values are required due to the thermal expansion of the drilling fluid which leads to undesirable failures on all other equipment. This case is inevitable in geothermal wells. Therefore, it is important to know the temperature distribution along well depth in order to take precautions against possible risks and to estimate the energy feasibility accurately. In this study, a software was developed in MATLAB coding language based on heat transfer principles to accurately estimate the bottomhole temperature of well using the inlet-outlet mud temperatures while drilling. For the determination of the temperature distribution in the well, a software in Delphi coding language was developed and the two software were put in coordination in order to support each other. By using mud temperature data from an actual well, drilling was simulated and drilling temperatures were estimated along the well depth. A number of heat transfer approaches have been found with the comparison of estimates and actual values. It is observed that a uniform temperature distribution exists in radial direction according to the obtained results. It is also observed that temperature increase becomes steady after a certain depth around the top of well. Also it is detected that the Peclet (Pe) number plays an important role in heat transfer. A flow case was designed and investigated by using ANSYS software in order to determine whether a change occurs in the temperature difference according to the flow disturbances. It is concluded that temperature distribution does not change significantly due to the flow disturbances because of the small length scales of the geometries that disturb the flow comparing to the length scale of the well and it is concluded that temperature distribution calculation approach based on the heat transfer principles is acceptable. A number of references from the related literature are examined and summarized in the study. The theory of the related technique is mentioned and ideas and propositions for future studies are provided. More elaborate computational numerical analyses can be conducted for multi-phases non-Newtonian flows and different soil temperature gradient scenarios in the future.