Successful drilling of a high step-out ratio well with water-based mud in morecambe bay

The H9 well in Morecambe Bay was drilled in Block 110/2a to a total depth of 18,009 ft at true vertical depth of 3484 ft, giving a step-out ratio of 5.17. This represented a record step-out ratio for this area and was achieved using water-based drilling fluids. This achievement was made possible by careful planning, good drilling practices and the judicial use of lubricants. Normally an oil-based mud (OBM) would be used for a well of this type; however the field is in shallow water, close to shore in an environmentally sensitive area, precluding the use of OBM. Rotary steerable tools were employed to maintain the well path within a very thin (17-ft) reservoir. A total of 8,891 ft was drilled in the reservoir section and the well path only exited the reservoir once for a short length before being brought back. Although the well was planned to TD at 18,000 ft, it was not realistically expected to achieve over 15,000 ft. When drilling ceased, it was for geological reasons - the well path was dipped just prior to TD to assess reservoir thickness, which increased the torque significantly. Without this planned deviation, further drilling would have been possible. This paper describes the planning process, the drilling practices and the fluid characteristics that enabled the well to be successfully completed.