Taking the Heat: Logging While Drilling at Extreme Temperatures

Abstract

Abstract As hydrocarbon reserves become scarcer, exploration and development efforts are increasing in locations where the downhole environment is hostile. This paper introduces a new measurement and logging while drilling (MLWD) system capable of operating at up to 200°C (392°F). In some areas of the world, operators are developing fields in which the great depth of the reservoir results in extremely high pressure. In other areas, the primary concern is the extremely high reservoir temperature. Such environments present challenges when running tools containing any type of electronics. These electronics must be protected from pressure and be either protected from heat or designed to tolerate high temperatures. High-temperature (HT) wireline logging tools have existed for many years. These tools mostly use flasking technology to insulate the electronics from high reservoir temperatures. The short duration of most wireline runs makes flasking a practical solution, but MLWD tools operate in the well for too long for this technology to remain effective. Instead, the electronics must be designed to operate at high temperatures without insulation. This requirement has previously limited the range of temperatures in which operators use measurement-while-drilling (MWD) and logging-while-drilling (LWD) tools. The new system contains electronics designed to operate at up to 200°C. It has undergone extensive field testing and has demonstrated its reliability over long periods of sustained high temperatures. The system comprises a base-services collar, providing real-time measurements of well trajectory, borehole pressure, drillstring dynamics, and natural formation gamma ray emissions. It also includes a set of additional collars, providing resistivity, density, and neutron-porosity measurements in zones where these have traditionally been unavailable. The new system has been used in multiple regions in multiple HT wells, delivering significant time and cost savings to operators. It has allowed the wells to be drilled more quickly as a result of the reduced need for temperature mitigation and has further reduced costs by eliminating or reducing the need for dedicated wireline logging runs.