Before a well is drilled in deep to ultradeep waters or environmentally sensitive areas, operators’ internal rules and regulatory agencies usually call for a contingency relief-well plan that includes dynamic-kill evaluation. Simulations for a worst-credible-blowout scenario often show that the pumping requirements exceed the capability of a relief-well rig, particularly when in deeper waters and/or where the reservoir is shallow. Installing a Relief Well Injection Spool (RWIS) between the wellhead and the blowout preventer (BOP) on a relief well provides additional inlets for pumping kill mud into the well at the seabed and ensures sufficient flow capacity to perform a high-rate dynamic kill. During the pumping operation, one or more additional high-pressure pumping vessels from remote locations are connected to the RWIS inlets using flex lines.

The RWIS system has been validated by hydraulic modeling using the OLGA-WELL-KILL simulator. Two hypothetical case studies, for shallow and deepwater wells, are presented here to show applications of the RWIS and the potential benefits. In both cases, a kill rate of 200 bpm is required at the relief well intersect to stop the uncontrolled flow from a blowout well. For both case studies, the benefit of the RWIS is pronounced and could prevent the need for two relief wells. Relief wells designed to control a deepwater blowout will require long choke and kill (C&K) lines, which could result in significant frictional loss during a dynamic kill with high pump rate. This flow restriction is mitigated by introducing additional inlets at the wellhead.