For offshore wells, the regulatory agency requires the submission of a worst discharge analysis and relief well planning report. The ability to control the blow out under worst case blowout scenario shall be documented and is a requirement for the operators to successfully apply for a permit to drill in the US offshore fields.
As the water depths of offshore drilling operations are getting deeper and deeper, due to the increased frictional pressure losses in kill lines and formation fracture strength, bringing the blow out well under control with worst case discharge becomes more challenging. Operational parameters need to be carefully controlled to avoid exceeding the operational limitations such as breaking the formation or exceeding available pump capacity.
In this study, dynamic simulations of multiphase flow are carried out to evaluate the operational parameters during the kill process. The simulations account for transient changes including frictional pressure losses, U-tube effect and fluid density variations. By optimizing the operational sequence with regards to, kill mud density, pump flow rate, pump down staging, relief well drillstring and trajectory, blowout can be controlled without exceeding the operational window.
The paper shows the required volumes of the kill mud, required pump capacity, optimal flow rate arrangement, and minimum time required to get full kill mud return to the sea floor during the well kill operation. Through the aid of advanced transient software models, assessment of the required capacity to kill a blowout enables development of realistic contingency plans to ensure that well control can be re-established in case of an ultra-deep water worst blowout scenario.