Utilize Manage Pressure Drilling Equipment and Technique to Cement a Severely Depleted HPHT Reservoir in the North Sea

摘要

The paper describes the successful use of an advanced comprehensive managed pressure setup to run and cement a liner that covered reservoir layers with pressures ranging from no depletion to 130 bar depletion in the Kvitebjorn field in the North Sea. The setup, which was first used for drilling the same 8.5" section, included a rotary control head, use of Cs/K formate mud, automatic choke on return flow, and an advanced online dynamic flow and temperature model for calculation of choke pressure set-point. The model was also used for pre-calculations of various scenarios to be prepared for different eventualities. The paper describes methods and setup, planning and execution of operations, analyzes calculations vs. measured data, and discusses training and organizational aspects of conducting such a complex operation. The managed pressure setup was motivated by several occasions of losses, partly severe, in nearby wells, and a narrow drilling window. This is, to the authors' knowledge, the first time running and cementing a liner has been done with an automatic choke system controlled in real time by an online dynamic flow model. Managed pressure cementing has been done earlier on the Gullfaks field in the North Sea, but then with a manually operated rig choke based on pre-calculated pressures only. After having resolved a number of technical issues and trained thoroughly personnel for using the actual set-up, running and cementing liner could be conducted with good pressure control, and with no significant losses of drilling fluid. Later logging confirmed that the cement job was good. Important factors to ensure high probability of success included 1. thoroughly tested equipment and model, 2. good knowledge of limitations of the system, 3. comprehensive preparations, including pre-simulations and training, 4. detailed procedures, including contingencies, 5. good communication during operations