OTC 2013: Capping stack demonstrates well control

Michael Smith

Special Correspondent

HOUSTON – Officials with the Marine Well Containment Company and Shell Oil described results of a successful capping stack installation to control a potential runaway well in the Gulf of Mexico at the Offshore Technology Conference yesterday. 

Capping stacks are heavy, forged collars that can be placed on top of subsea wellheads to contain oil at the ocean floor.

After the Macondo incident in 2010, the US Department of Interior suspended new drilling permits for six months until tougher drilling rules were created. Several large oil companies set up the Marine Well Containment Company (MWCC) to prove the industry could control a deepwater oil spill.

Placing capping stacks at shore-side locations and training personnel to test and install such equipment is a condition of securing deepwater drilling permits today. MWCC supports oil and gas operators in the Gulf of Mexico, and is cited as the containment supplier for 103 deepwater well permits.

The industry demonstration of oil spill response “readiness” was requested by former DOI Secretary Ken Salazar in May 2012. The project involved staff from MWCC, Shell Oil, and the Bureau of Safety and Environmental Enforcement (BSEE). Admiral James Watson, the BSEE Director, was on hand to observe key parts of the exercise.

Shell Oil agreed to allow a subsea wellhead it owns to be used for the demonstration. The field test in July 2012 simulated “live” conditions. Within three days after BSEE officials triggered the spill event, a capping stack weighing 150 tons was being transported via a specially equipped vessel with an A-frame crane.

Once offshore, the capping stack was lowered 6,950 ft on wires using a landing system that compensates for “heave” or wave swells at the ocean surface. It was latched onto Shell’s simulated wellhead, where a pressure test confirmed the ability of the capping stack to control a well.

A video taken by remotely operated vehicles showed how robots made the required connections to install the capping stack and activate the pressure test.

Once the containment system was placed on the wellhead, the capping stack was slowly pressurized to simulate the conditions that may occur when a well receives gas pressure from the formation. The simulated well event held a pressure of 10,500 lbs. per square inch for 20 minutes.

The process of mobilizing the stack and ancillary equipment, transporting it to the well site in the Gulf, and installing it at the simulated well took about one week, according to Phil Smith of Shell Oil and Marty Massey of MWCC. This compares favorably to 91 days required to shut in the Macondo well in 2010.

Massey also reminded the OTC breakfast audience of 250 that water depth in Walker Ridge block 536 is 6,950 ft, or about 2,000 ft deeper than Macondo well operated by BP.

How soon should the test of oil spill containment with regulators at BSEE be repeated? “A three-year interval between tests seems about right,” indicated Massey. “But I think we’ll let someone else be the operator for the next one.”