Upgrading Amerada-Type Survey Clocks for High-Temperature Geothermal Service

Abstract

The "Amerada" type subsurface recording gauges have been use by the oil and gas industry for many years. These mechanical logging instruments are currently used by the growing geothermal industry. As the gauges were designed for service in low temperature oil and gas wells, a significant number of failures are occurring at elevated geothermal temperatures. The spring driven mechanical survey clocks appear to be the primary cause of the failures. The clock mechanism tend to stop or lock up when exposed to temperatures as high as 300°. This paper summarizes a project at was undertaken to upgrade the survey clocks to 300°C capability. The major problems causing clock failure were identified and corrected by straightforward design modifications together with special lubrication of the moving parts. Several clocks so modified performed reliably, both during laboratory oven tests and during field tests that were performed in actual geothermal well at temperatures up to 330°C.