Steerable Motor with Integrated Adjustable Gauge Stabiliser Provides Improved Directional Drilling Performance in the Middle-East

Abstract In high angle wells, control of hole inclination becomes the main concern for directional drilling operations rather than azimuth control. The use of a conventional steerable system to control inclination can introduce such problems as increased torque and drag due to the doglegs created, and poor hole cleaning when in sliding mode. These problems can in turn limit the amount of horizontal section that can be drilled. Adjustable gauge stabilisers have the ability to alter the gauge of the stabiliser without the requirement to pull out of hole. This type of stabiliser has been commonly used to assist in controlling inclination either in rotary assemblies or in steerable assemblies when run above a motor. Although positioning the adjustable gauge stabiliser above the motor has been successful in many applications, there are situations where an alternative may be required. With the stabiliser positioned above the motor, it is relatively far from the bit and thus the effects of its gauge change are limited. This in turn results in the changes of inclination possible being relatively small. It may then be impossible to change the wellbore path quickly enough in geological steering applications. This can be addressed by placing the adjustable gauge stabiliser below the motor, but reliability of both tool and motor suffer. Stresses on the motor bearing assembly can be high enough to cause problems such as premature bearing and drive shaft failures. By placing an adjustable gauge stabilser within the bearing housing of a steerable motor these problems have been overcome. The adjustable gauge stabiliser is therefore in a near-bit position. This means that changes in its gauge have the maximum effect on inclination. Stresses on the motor are also significantly reduced. This adjustable gauge motor has been run in the Middle-East in long horizontal sections. It was seen to result in significant improvements in overall drilling rates when compared to conventional steerable motor runs. The subject of this paper is the design and development of the adjustable gauge motor system. Case histories will presented that demonstrate the improved performance that was achieved.