A Gear-Reduced Drilling Turbine Provides Game Changing Results: An Alternative to Downhole Positive Displacement Motor

Abstract

Drilling turbines, commonly referred to as Turbodrills, have historically been used for hard-rock applications in conjunction with diamond impregnated drill bits. Their use in North America land was typically restricted by rig stand-pipe-pressure limitations. Now, the latest generation rigs in North America land have sufficient stand pipe pressure to make use of Turbodrills. Reducing the bit speed of a Turbodrill can provide significant advantages. Reducing the bit speed and increasing torque makes the Turbodrill suitable for a wider range of drilling environments, including high-temperature wells. Turbodrills require no elastomer re-lines like Positive Displacement Motor (PDM) Power Sections, which are typically re-lined after every run in oil based mud. High-performance PDMs generate significant vibration which could reduce the life of measurement-while-drilling (MWD) systems. On the other hand, Turbodrills produce very little vibration, hence the life expectancy of bottom-hole assembly (BHA) components can be increased. Drilling with less vibration will lead to a more efficient drilling system and reduced non-productive time (NPT). This paper describes the operation, flow test and field test results from a new Gear-Reduced Drilling Turbine (GRDT). Key component in the GRDT were instrumented to gather critical information on vibration, shock, temperature and rotation speed in revolutions per minute (RPM).

Design and Output Performance Model of Turbodrill Blade Used in a Slim Borehole

“…HDR primarily consists of igneous or metamorphic rocks of high hardness and poor drillability, such as granite and gneiss; the temperature of a high-temperature geothermal reservoir is typically greater than 200 • C and can even reach 500 • C. When drilling a slim hole using a conventional drill, the amount of borehole friction is excessively high, thus making it difficult to pass the power to the bottom [4]. The common screw drill cannot be used under conditions of high temperature [5] with large rotational vibration. Practical work shows that an all-metal turbine drill with impregnated diamond bits [6] has good temperature adaptability and high efficiency in terms of the hard rock formations [7].…”