Semiquantitative Applications of Downhole-Temperature Data in Subsurface Surveillance

Abstract

Summary Permanent downhole-pressure and -temperature gauges have been installed in many intelligent wells worldwide, providing high-resolution and precision surveillance data about the performance of wells and reservoirs. Compared with the pressure data, the temperature data have been underused in the petroleum industry. In this paper, we first examine the measured downhole-temperature variation caused by the Joule-Thomson effect and infer the true reservoir temperature and the skin history from the temperature data. An analytical relationship between the temperature data and the skin is presented. Through the use of this relationship, many purposeful surveillance studies, such as monitoring the skin change of the well, can be conducted. Examples of such studies will be provided and discussed using some deepwater-field data. Furthermore, the downhole temperature can be used to detect whether water breakthrough occurs by means of matrix or fracture through use of the thermal retardation factor. When coupled with the production data and pressure-falloff (PFO) tests, the downhole-temperature data can be used to estimate the water-breakthrough time. The application of this analysis is of practical interest for subsea-well development because of the prohibitive costs and high risks of production logging.