The engineering necessity of achieving maximum cooling of the borehole during drilling and logging operations on geothermal wells prohibits the determination of equilibrium temperature in the sub surface before virtual rebound from the drilling disturbance some months after operations cease. Clearly, substantial economic benefits would accrue, in many cases, if a reasonable prediction of equilibrium temperature can be made while the rig is still over the borehole. tures are known to be present in the reservoir. the well is to be completed depends on its anticipated uses in the future. drilling of a confirmation well. Certain flow tests are desirable when commercial tempera- The manner in which Before the rig is released a decision must be made as to the Several methods have been worked out to predict equilibrium temperatures; all are based on (1) rebound following the physical law of logarithmic decay, and (2) rebound being by conductive processes. Perha s the most sophisticated method is one worked out by Albright (19'757; unfortunately, the amount of data required to apply the method is not generated in the course of normal dkilling operations. temperature rebound follows the same logarithmic decay law as does pressure buildup following a reservoir flow test, a Homer plot is suggested as a graphical method of predicting equilibrium temperature, and the Homer plot is a commonly used device. expression in several forms is given as the Lachenbruch-Brewer equations (1959, p. '79) which are applied herein.

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