ONS 2016: Can the industry finally say goodbye to nonshearable tubulars across the BOP?
BOP shearing technology just made a giant leap forward. The percentage of nonshearables crossing the BOP can now be reduced from an estimated 10% to about 2%, thus reducing safety and environmental risk and furthering the industry’s ability to comply with upcoming Bureau of Safety and Environmental Enforcement (BSEE) regulations. New BSEE rules address the need for improved shearing capability, putting a seven-year timeline for a mechanism coupled with each shear ram to position the entire pipe, completely within the area of the shearing blade and ensure shearing will occur any time the shear rams are activated.
Successful shear test of an off-center tool joint pin and box that was considered unshearable using conventional shearing technologies. Image: Schlumberger.
The industry has been increasingly plagued with nonshearable tubulars passing across the BOP during standard offshore drilling operations. While traditional shear rams can shear drill pipe and seal the open hole in a single stroke, they have unfortunately been limited in what can be sheared and sealed. Because tool joints, drill collars, screens, and other components in the drillstring have traditionally been considered nonshearable, a small percentage of nonshearable items passing through the BOP were allowed with mitigating procedures. But BSEE has since set a goal for the industry to find a suitable solution to the problem.
A critical component of any drilling program is the ability to shear, seal and stabilize the well to prevent blowouts. Shear rams are the means by which tubulars in the wellbore are sheared; this becomes essential in some cases. The ability to successfully perform this operation also allows a drilling rig to safely disconnect from the BOP stack and move offsite if the situation warrants.
As drilling environments have become more challenging, tubulars have increased in size and strength. Shear rams are being asked to cut heavier pipe. Not only does the additional wall thickness hurt shearability, but the wall thickness to outside diameter ratio has an effect on how the pipe deforms during and after the shear. Some components of the drillstring have become considered nonshearable, such as tool joints and drill collars. Additionally, the need to be able to shear pipe when it has buckled or become off center has increased the complexity of shearing.
New capability to shear hard banding, off-center tubulars
The Cameron BroadShear off-center tool joint shear rams advancement in casing shear enables tool joints (both through the pin/box and through hard banding) to be sheared with the pipe centered or to one side of the BOP. To simulate buckled pipe, the test used 4-in. plates at top and bottom of a single cavity BOP to hold the tubular firmly against the side where the choke/kill outlet was positioned. This rigidly held the pipe in place without allowing it to centralize except through pipe deformation. Engineered with enhanced metallurgy for exceptional strength and control, these rams enable shearing of casing diameters up to 16-in. Prior to the introduction of this new shearing technology, the industry was unable to shear hard banding or to shear with pipe forced to the sidewall and seal the well.
In a series of rigorous tests, a single set of the new BroadShear rams successfully sheared various drill string components seven times. These tests included through the pin/box, through the hard banding, as well as two off-center tests. In a separate test, another set of the rams successfully sheared off-center in a demonstration for BSEE. These rams were designed based on the Cameron SuperShear casing shear ram technology and fit in the same cavity as existing rams. Upgrading for the higher capacity can be performed in the field with no need to remachine bonnet components.
BSEE witnesses tests
The rams successfully sheared 6 5/8-in. FH tool joint, 8.50-in. OD x 4.00-in. ID, S-135, off center. In another set of shear tests, a single set of the new rams successfully sheared various drilling components seven times regardless of location in the bore. These were some of the hardest, thickest shear tests performed in the industry to date. They included through the pin/box, through the hard banding, and two off-center tests. According to engineering analysis, the new off-center tool joint shear ram reduces the risk of nonshearables across the BOP from approximately 10% to 2% at a hole depth of 25,000 ft.
The industry now has a head start on cutting through perceived nonshearable tubulars and lowering blowout risk. The day that development of new technology can successfully shear that remaining 2% of nonshearables may not be far off.
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