| Title | Geotrans: A Computer Code for Estimating Transient Temperatures in the Completion of Geothermal Wells with Drilling Fluid Losses |
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| Authors | Alfonso Garcia, Gilberto Espinosa, Edgar Santoyo, Pedro Mendoza and Isaias Hernandez |
| Year | 2000 |
| Conference | World Geothermal Congress |
| Keywords | geothermal wells |
| Abstract | The GEOTRANS computer code is described. It consists of a numerical simulator and a user interface for data input and analysis of results. The equations governing the dynamic heat transfer processes in a geothermal well under construction in the presence of lost circulation are solved. They describe flow of fluid in the drilling pipe and annulus, heat transfer in the drilling pipe metal wall and conductive and convective heat flow in the formation. Solution allows estimation of temperatures in and around a well as function of time and vertical and radial position. The model is closed using heat transfer and fluid friction correlations. Physical properties of drilling fluids (muds and water/air mixtures), cements, rocks and pipes, implemented via numerical routines or as databases complement the model. Numerical solution follows implicit finite differences and the Thomas algorithm is used for their solution Heat transfer in the formation is 2D and is solved via an ADI scheme. A unique feature of GEOTRANS is that it simulates drilling fluid losses at any position along the uncased wellbore and its effect is accounted for as thermal convection in the formation. GEOTRANS operates under Windows and data input can be done from a file, interactively or from the databases implemented. Program execution is controlled from the user interface. Data post-processing includes automated plotting of simulated temperatures as function of depth and time for the circulation and shut-in periods. Previous code validation was performed by comparison against data from the literature and analytical solutions. Results of application to the Mexican well H-26 from the Los Humeros geothermal field are presented. The shut-in logged temperatures were reproduced in the presence of lost circulation. GEOTRANS can be used to estimate formation temperatures and formation porosity by trial and error. |