Advanced Well Control Reduces Risk of a Blowout

Abstract

AbstractThere are still concerns about well control especially for operations in sensitive environments. Currently the final barrier while drilling oil and gas wells is a valve system (blowout preventer or BOP) located on top of wells. These valves can isolate wells by sealing around or shearing through obstructions in the well (e.g. drilling pipe and casing). If these valves fail or if some other barrier in a well fails, hydrocarbon loss to the environment is possible. Adding barriers capable of responding to a well control loss could alleviate these concerns. ExxonMobil is currently evaluating concepts to provide two additional methods to kill an out-of-control well. One utilizes rapid crosslinking polymers to form a polymer-plug seal inside a BOP after a failure. The other is to rapidly pump seawater into a well to produce back pressure that overpressures the entire well bore to keep hydrocarbons from escaping oil / gas bearing zones.Mixing dicyclopentadiene (DCPD) and other monomers with a ruthenium-based catalyst causes a rapid polymerization reaction that forms a high-strength, stable solid. These reactions can occur under extreme temperatures and pressures while withstanding significant contamination from other fluids and solids. The well-control concept is to rapidly pump the monomers and catalyst into a leaking BOP to form a polymer seal that prevents further flow.The seawater injection concept uses high-pressure and capacity pumps located on a surface vessel and a conduit from these pumps to a port on a BOP. If a blowout occurs, seawater at high rate is pumped in the BOP. If BOP seal failure is the reason for containment loss, then the seawater will overpressure the BOP and seawater will displace the hydrocarbons passing through the leak point. Seawater injection will also overpressure the entire wellbore to keep hydrocarbons from escaping anywhere in the well. For example, if a leak occurs deep in the well, seawater injection into the BOP will overpressure the entire well and the seawater will replace the hydrocarbon flowing through the leak point.We have conducted testing of the polymer plug concept at representative temperatures and pressures using a small-scale BOP. Polymer seals were formed when the scale BOP was flowing drilling mud, a crude-oil surrogate, and water. The seals held up to 5,000 psi pressure for almost 18 hours. We have completed modeling of the seawater injection concept to define pumping needs. This paper describes the current status of concept development.