Transient numerical simulation of heat transfer processes during drilling of geothermal wells

Santoyo-Gutierrez, ER

Abstract

The transient thermal history of a well drilling system has been identified as one
of the main problems that the geothermal well drilling industry needs to solve. In
particular, the estimation of temperatures, in and around a geothermal well during
drilling (circulation) and shut-in (thermal recovery) conditions, is required.
To overcome this problem, a computer simulator (WELLTHER) has been
developed which uses a direct solution method to solve the finite difference equations
describing the transient heat transfer processes in a wellbore during drilling and shut-in
operations in the presence of the lost circulation to the formation. The new computer
simulator uses a numerical model to account for the transient convective heat transfer in
the formation surrounding a well, due to lost circulation. This feature of the present
simulator is important, since previous wellbore simulators consider the heat transfer
process in the formation (rock) as a merely conductive problem. The WELLTHER
simulator is capable of accounting for these losses at any point in the well and it has
been applied to the study of several Mexican geothermal wells. The results show that the
effect of lost circulation on the shut-in temperature profiles can be reproduced
satisfactorily. Likewise, a parametric analysis, carried out using the simulator,
indicates that a number of assumptions made in previous numerical models are invalid
and that certain factors ignored in previous models have a significant effect on the
dynamic wellbore temperature distribution.
Finally, a coupling of the new simulator with another computer code
(STATIC TEMP) can be used as a tool to infer more reliably the static formation
temperatures in geothermal systems.

Citation

Santoyo-Gutierrez, E. Transient numerical simulation of heat transfer processes during drilling of geothermal wells. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Sep 26, 2011
• Publicly Available Date: Sep 26, 2011
• Award Date: Jan 1, 1997