Problems Associated with Application of a Wellbore Heat TransmissionComputer Code

Abstract

An analysis of the discrepancies between actual temperature surveys and results obtained from a wellbore heat transmission computer code are presented for recent workover operations in well EE-2 at the Fenton Hill Hot Dry Rock Geothermal site. Several sources of error in modeling the thermal behavior of wellbores are considered. These are errors in the estimation of in-situ properties, particularly thermal conductivity, the failure to include frictional heating effects when high flow rates are involved, and error in reporting the flow rate history. These errors were also found to have a cumulative effect. A sensitivity analysis of the computed results to each error type is presented for countercurrent flow. It is concluded that all the errors considered can cause temperature discrepancies between measured and computed temperature. Well bore codes should have provisions for variable thermal properties and frictional heating. In addition, modeling efforts should be coordinated with periodic temperature surveys so cumulative errors can be minimized.