An Interpretation of Precision Temperature Logs in a Deep Geothermal Well near Desert Peak, Churchill County, Nevada

Abstract

Three precision, continuous temperature logs were obtained in Philips Petroleum Company's deep geothermal well a few months after completion of drilling. The measurements were made in a small diameter tubing capped at the bottom and extending from the surface to near total depth in a the hole which ranged in diameter down to 20 cm. A 34 cm casing was cemented into place in the upper 901 m of the hole. The remainder of the hole was open, allowing the exchange of fluids among the many permeable zones encountered during drilling. Analysis of the temperature logs suggest the following: (1) the linearity of the temperature plot in the interval 200-900 m suggests the existence of a hydrothermal system of considerable antiquity. The high gradient an high heat flow in this interval require that heat be transported convectively to the as of this interval. (2) The interval between about 900 and 1300m exhibits anomalous warming since drilling. Although some of this warming represents a decay of the thermal disturbance due to invasion of cool drilling fluids, a part of it may represent an invasion of hot water into the hole which then descends along the hole and exits into many permeable zones at greater depth. This could, of course, obscure the true nature of the thermal regime of the rocks surrounding the lower part of the hole.