BP Patents Blowout Preventer Testing
People of the Gulf, the country, and the world, are holding their breath as BP tests a new sealing cap on the blowout preventer.
The cap installed on the top of the well is basically a second blowout preventer. Charlie Petit at the Knight Science Journalism Tracker blog wonders in disbelief why this kind of gerryrigged oil spill stopper hasn't been on standby before now and hopes that these last two months of engineering lay the groundwork for a new generation of deepwater safety devices.
Perusal of the IP.com Intellectual Property Library discloses that, one week to the day of the Deepwater Horizon oil rig explosion causing a massive oil spill or leak from the Macondo Prospect oil field, BP received a patent for this blowout preventer testing system and method.
This invention relates to the general subject of production of oil and gas and, in particular, to methods and apparatuses for testing fluid systems.
BACKGROUND OF THE INVENTION
Current subsea Blow Out Preventer (BOP) testing practice (in U.S. “Oil and Gas Drilling Operation,” Subpart D, 30 C.F.R. Chapter II, current Edition; and generally worldwide) is to view shut-in test pressures on circular chart recorders and wait until a 5-minute period of reasonably stable pressures is obtained (see FIG. 1). Reasonably stable pressures must be greater than or equal to the required test pressure and allow for temperature-related pressure declines. Tests are initiated well in excess of required pressures. A 5-minute period of reasonably stable pressures is required as proof of non-leaking tests since, absent additional analysis, the periods of overtly declining shut-in pressures could be indicative of leaks in the systems. The basic chart recorder used on a majority of drilling rigs today was patented over one hundred years ago (Wittmer, G. X.: “Recording Apparatus for Fluid Meters,” U.S. Pat. No. 716,973).
In the United States under current regulations, subsea BOP tests, recorded on 4-hour 15,000 psi circular charts, are typically ended when pressure decline rates are in the range −4 to −3 psi/min. This is because the pressure trace begins to appear steady once pressure decline rates diminish to the range −4 to −3 psi/min, making this the as-practiced limit of circular chart resolution. Given the subjective nature of visual chart interpretation, tests are sometimes stopped at pressure decline rates as high as −5 psi/min and as low as −2 psi/min. A decline rate of −3 psi/min is representative of a high standard of current testing practice. The pressure at which this occurs is defined as Ps or the “pressure at stabilization.”
Industry trends toward deeper water, synthetic oil-based fluids, and subsurface conditions requiring increasingly higher test pressures all contribute to lengthy delays while waiting for pressures to stabilize during subsea BOP testing. Also, subsea BOP stacks with redundancy of components and use of multiple-diameter drill strings leads to greater numbers of tests that must be conducted.
Coincidentally, at least one of the patent drawings appears to relate specifically to tests the Deepwater Horizon oil rig almost four years before the explosion.
This Patent Application is related to a pending U.S. patent application filed on Dec. 22, 2004 under Ser. No. 11/025,415 and published as 2005/0269079 on Dec. 8, 2005. The teachings therein are incorporated herein by reference. This patent application claims the priority of a USA Provisional Patent Application filed on Feb. 1, 2007 under Ser. No. 60/887,739 and entitled “Improved Blowout Preventer System.”
