To address risk and uncertainties in difficult sidetrack operations in the Gulf of Suez in Egypt, a new method was implemented to identify and control the direction of the wellbore during the whipstock exit, and close to the liner, where standard directional measurements are compromised due to magnetic interference. Bending moment sensors were placed directly above the motor and only 26 ft behind the bit. These sensors delivered two perpendicular bending moment measurements referenced to gravity high side. Transmitted to surface via mud pulse telemetry, the two signals were further processed to deliver the well tool face and – with the help of a mathematical BHA model – the dogleg severity of the well.
In one case the well tool face confirmed the orientation of the whipstock and the window milled. However, in a second case, the measurement revealed a 40 degree deviation from the original whipstock orientation. The well plan was immediately adjusted to compensate for this deviation from plan. The dogleg severity information gave improved azimuth control when steering away from the existing well in sliding mode. As a result, both sidetracks achieved their directional objectives and could be steered into the target. The directional estimates derived from the bending moment measurements were later confirmed by the first valid MWD surveys and by gyroscopic survey measurements.
The paper will start with a detailed description of the directional challenges in this application. It will then introduce the concept of the bending moment measurements and the derived directional information, well tool face and dogleg severity. After a description of the implementation and directional execution of the sidetracks, the paper will conclude with a discussion of the benefits and the potential of this new directional control method, which could result in a reduction or even complete elimination of gyro runs during similar casing exits and significant rig time savings.