Blowout Contingency Decision-Making Leveraging Reservoir/Wellbore Pressure Modeling: Cap-and-Restrain or Cap-and-Divert?

Summary After the MC 252–1 “Macondo Well” blowout on 20 April 2010 in the Gulf of Mexico, notable efforts were placed on subsea-well capping and containment to improve the industry’s response to offshore-blowout events. The thrust of this paper is an investigation of the role that forward modeling and monitoring of the reservoir and wellbore pressures can play in determining the best practice to kill a blown well. A novel workflow is presented for supporting blowout contingency by assisting decision-making across different post-blowout intervention strategies integrating reservoir simulation, wellbore mechanics, and the surface equipment’s operating limits. Caused by the unique set of challenges of each blowout incident, a well-intervention method proven effective in one scenario may not be optimal for the next—it could lead to failure, or be unimplementable. Proper response to a well-control event of this type is divided into two broad categories. The first category is “Cap-and-Restrain,” which requires forward modeling of the wellbore-pressure buildup, identifying the critical post-blowout discharge flowrates, above which it is safe to shut-in the subsea-capping stack (SCS). The second category is “Cap-and-Divert,” which requires the SCS to remain partially or completely open after its installation on the blown well’s damaged blowout preventer (BOP), with the flow being diverted to an external storage unit. The SCS is shut-in later once it is confirmed that the well’s integrity can handle the backpressure of the controlled discharge without any “underground blowouts” triggered by tensile failures on exposed locations along the wellbore. This work focuses on the methods and processes planned to contain a subsea blowout, either by Cap-and-Restrain or by Cap-and-Divert, using a workflow employing a generic, multipurpose, 3D, two-phase (water/oil) reservoir simulator [Program for Integrated Modeling of Petroleum Systems (PIMPS3D2P), written in MATLAB® of The MathWorks, Inc.]. Once the feasibility of SCS deployment and landing is evaluated, the implementation of a shut-in procedure becomes vital for reaching the static well conditions required. Our workflow has been applied a posteriori to the Macondo Well’s blowout scenario, as an illustrative example.