Method for shearing pipe and providing a compression seal
The method of providing blowout preventer shear rams which will shear pipe then provide a face-to-face compression seal comprising providing an upper shear ram having an upper shear ram blade and a pipe lifter, providing a lower shear ram having a lower shear ram blade, and a pipe lifter, providing a face-to-face seal, moving the upper and lower shear rams into the bore towards one another, shearing the pipe in the bore of the blowout preventer, engaging the upper sheared portion of the pipe with the pipe lifters, lifting the upper sheared portion of the pipe with the pipe lifters to a position above the face-to-face seal, engaging the face-to-face compression seal to effect a seal across the bore.
This invention relates to the method of providing shear rams which will shear the pipe and then lift the sheared section of pipe above the shear plane to allow a face-to-face compression seal between the rams.
CROSS-REFERENCE TO RELATED APPLICATIONSNot applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot applicable
REFERENCE TO A “MICROFICHE APPENDIX”Not applicable
BACKGROUND OF THE INVENTIONDeepwater offshore drilling requires that a vessel at the surface be connected through a drilling riser and a large blowout preventer stack to the seafloor wellhead. The seafloor wellhead is the structural anchor piece into the seabed and the basic support for the casing strings which are placed in the well bore as long tubular pressure vessels. During the process of drilling the well, the blowout preventer stack on the top of the subsea wellhead provides the second level of pressure control for the well. The first level being provided by the weighted drilling mud within the bore.
During the drilling process, weighted drilling mud circulates down a string of drill pipe to the drilling bit at the bottom of the hole and back up the annular area between the outside diameter of the drill pipe and the inside diameter of the drilled hole or the casing, depending on the depth.
Coming back up above the blowout preventer stack, the drilling mud will continue to travel back outside the drill pipe and inside the drilling riser, which is much large than the casing. The drilling riser has to be large enough to pass the casing strings run into the well, as well as the casing hangers which will suspend the casing strings. The bore in a contemporary riser will be at least twenty inches in diameter. It additionally has to be pressure competent to handle the pressure of the weighed mud, but does not have the same pressure requirement as the blowout preventer stack itself.
As wells are drilled into progressively deeper and deeper formations, the subsurface pressure and therefore the pressure which the blowout preventer stack must be able to withstand becomes greater and greater. This is the same for drilling on the surface of the land and subsea drilling on the surface of the seafloor. Early subsea blowout preventer stacks were of a 5,000 p.s.i. working pressure, and over time these evolved to 10,000 and 15,000 p.s.i. working pressure. As the working pressure of components becomes higher, the pressure holding components naturally become both heavier and taller. Additionally, in the higher pressure situations, redundant components have been added, again adding to the height. The 15,000 blowout preventer stacks have become in the range of 800,000 lbs. and 80 feet tall. This provides enormous complications on the ability to handle the equipment as well as the loadings on the seafloor wellhead. In addition to the direct weight load on the subsea wellheads, side angle loadings from the drilling riser when the surface vessel drifts off the well centerline are an enormous addition to the stresses on both the subsea wellhead and the seafloor formations. Similarly pipe sizes and weights have increased as well.
Shear rams within these blowout preventers are utilized to shear pipe only in emergency cases when there is no other solution to securing a subsea well installation. Securing the well involves both the steps of shearing the pipe in half and then providing a seal across the well bore. Ideally a single blowout preventer ram will be equipped with shear rams which upon actuation will shear and seal in a single movement and then provide a seal which is compression set. Being compression set is beneficial as the extreme destructive nature of cutting high strength pipe in half tends to damage any kind of seal, and a compression set seal is the most “self-healing” type of seal. The high pressures generated by being compression set will tend to seal over many defects in the seal.
It can be sometimes presumed that the sheared section of pipe above the shear ram will be yanked out of the seal area upon shearing if the pipe is in its normal tension is a subsea drilling system. This is not always true, and was not true in the 2010 Gulf of Mexico Macondo blowout case when the incapacitated rig could not pick up anything.
One solution provided for this is to have a seal which seal in the shear plane as a face seal. This seal is dependent upon not scratching the seal or the mating seal surfaces, and that no shrapnel from the shearing operation gets in the way so it is a less reliable seal.
Another solution which has been provided is to literally bend the pipe out of the way. This has worked on some section of pipe, but with extreme high strength pipe and connections used today, there is great difficulty in bending the pipe and coupling sections.
The ideal goal is to simply shear the pipe and have the sheared pieces not in the way of a face-to-face compression seal.
BRIEF SUMMARY OF THE INVENTIONThe object of this invention is to provide blowout preventer shear rams which will shear pipe in the bore of the blowout preventer.
A second object of this invention is to provide blowout preventer shear rams which will seal in a face-to-face compression seal.
A third object of this invention is to provide shear rams which will raise the shear section of pipe above the shear plane above the sealing area.
Another object of this invention is to provide a secondary seal which will independently seal across the interface of the shear rams if the primary seal fails.
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Blowout preventer stack 60 is landed on a subsea wellhead system 64 landed on the seafloor 66. The blowout preventer stack 60 includes pressurized accumulators 68, kill valves 70, choke valves 72, choke and kill lines 74, choke and kill connectors 76, choke and kill flex means 78, and control pods 80.
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The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
Claims
1. The method of providing blowout preventer shear rams which will shear pipe in the bore of the blowout preventer and then provide a face-to-face compression seal comprising
- providing an upper shear ram having an upper shear ram blade and a pipe lifter,
- providing a lower shear ram having a lower shear ram blade, and a pipe lifter,
- providing a face-to-face seal on at least one of the upper shear ram or the lower shear ram,
- placing the upper shear ram and lower shear ram in ram pockets in a blowout preventer on opposite sides of the bore of the blowout preventer, the pipe lifters being in an initial position,
- moving the upper and lower shear rams into the bore towards one another,
- shearing the pipe in the bore of the blowout preventer into an upper sheared portion and a lower sheared portion,
- engaging the upper sheared portion of the pipe with the pipe lifters,
- lifting the upper sheared portion of the pipe with the pipe lifters to a position above the face-to-face seal,
- engaging the face-to-face compression seal to effect a seal across the bore.
2. The method of claim 1, further comprising the face-to-face compression seal engages at least one of the upper shear ram or the lower shear ram blade.
3. The method of claim 1, further comprising the pipe lifters are pivoted.
4. The method of claim 3, further comprising the pipe lifters are pivoted on an axle,
- the shear ram bodies are provided with a body cylindrical surface,
- the pipe lifters are provided with a lifter cylindrical surface about the axle,
- the loading from the lifting of the upper sheared pipe section is supported by the lifter cylindrical surface loading against the body cylindrical surface.
5. The method of claim 1, further comprising the initial contact between the lifters and the pipe to be sheared is above the pivot point of the lifters.
6. The method of claim 1, further comprising when the shear rams no longer are in contact with the sheared pipe, the lifters will return to the initial position by force of gravity.
7. The method of claim 1, further comprising when the shear rams no longer are in contact with the sheared pipe and the lifters do not return to the initial position by force of gravity, the lifters will engage the blowout preventer body upon returning to the pockets in a blowout preventer on opposite sides of the bore of the blowout preventer and be forced to return to the initial position.
8. The method of claim 1, further comprising porting is provided across the face of at one of the shear rams and porting is placed in the blowout preventer body to allow sealant to be pumped across the face of the shear rams to seal when the face-to-face compression seal does not seal.
Type: Application
Filed: Jul 27, 2021
Publication Date: Feb 2, 2023
Inventor: Benton Frederick Baugh (Houston, TX)
Application Number: 17/386,415