Technical Field

[0001] The present invention relates to a shear/seal ram of blowout preventers.

The purpose of the shear/seal ram is to cut the drill string and seal the well bore in case of blowout.

Background Art

[0002] There is a requirement for shear/seal ram to be able to cut the heaviest drill string, the majority of the shear/seal ram designs share several inherent features that, in some cases make it impossible to safely cut the drill string and seal the well. Those features are among others:

a) The rams are working against well pressure and therefore at high pressures their effectiveness is impaired.

b) The shape of the blades is such that it cannot always effectively

move drill string into the centre of the BOP, for example, when the drill string is buckled under high well bore pressure.

Disclosure of the Invention

[0003] It is an object according to the present invention to provide a shear ram blow out preventer, which overcome the problems addressed above. In particular it is provided a shear ram blowout preventer at least comprising:

[0004] a valve housing with a first cylinder housing axially aligned with the

longitudinal axis of the valve housing and a gate valve opening

perpendicular to the first cylinder housing axis;

[0005] a first and a second piston rod arrangement where;

I. the first piston rod arrangement includes a first piston head arranged axially with the first piston rod arrangement at an end of the first piston rod arrangement, a first ram with a first blade opening remote of the first piston head of the first piston rod arrangement, and

II. the second piston rod arrangement includes a second piston head arranged axially with the second piston rod arrangement at an end of the second piston rod arrangement, a second ram with a second blade opening remote of the second piston head of the second piston rod arrangement.

[0006] The first and the second piston rod arrangement is in a slidable

engagement with each other both being arranged in the valve housing and the first cylinder housing, the first piston head of the first piston rod arrangement and the second piston head of the second piston rod arrangement are arranged in the first cylinder housing, the piston heads in the first cylinder housing are arranged with an axial distance, a high pressure inlet is arranged between the piston heads in the first cylinder housing thereby creating a double acting push and pull movement of the first and the second piston rod arrangement and resulting in an opposite movement of the first and the second ram.

[0007] In one aspect of the invention it is provided a shear ram blowout preventer with two cylinders thereby providing a double acting balanced shear ram blow out preventer, according to this aspect of the invention the shear ram blowout preventer further comprises:

• the valve housing comprises a second cylinder housings axially

aligned with the first cylinder housing and opposite and concentric arranged with respect to the first cylinder housing arranged remote of the gate valve opening;

• the first piston rod arrangement further includes a second piston

head arranged axially at an opposite end of the first piston head, the first ram with a first blade opening is arranged between the first and the second piston head, and

• the second piston rod arrangement further includes a first piston

head arranged axially at an opposite end of the second piston head, the second ram with a second blade opening is arranged between the first and the second piston heads;

the first and the second piston rod arrangement are both further arranged in the second cylinder housing, the first piston head of the second piston rod arrangement and the second piston head of the first piston rod arrangement are arranged in the second cylinder housing the piston heads in the first and the second cylinder housings are arranged with an axial distance, a high pressure inlet is arranged between the piston heads in each of the first and the second cylinder housings.

[0008] In another aspect of the invention it is provided a shear ram blowout

preventer, where the first and the second cylinder housing includes a low pressure return outlet arranged in a low pressure chamber part of the first and the second cylinder housings.

[0009] In another aspect of the invention it is provided a shear ram blowout

preventer where the first and the second piston rod arrangement further comprises a tubular section connected with the first piston heads, where the first piston heads have a concentric opening having the same or bigger internal diameter as the tubular, the first and the second piston rod arrangement is provided with a piston rod connected to the second piston heads, the piston rod having an outer diameter that is smaller than the internal diameter of the tubular thereby facilitating movement of the piston rod part of the piston rod arrangement inside of the tubular sections of the piston rod arrangement.

[0010] In another aspect of the invention it is provided a shear ram blowout

preventer where the first and the second ram is provided with openings with a diameter substantially similar to the diameter of the well bore of the gate valve opening.

[001 1] In another aspect of the invention, it is provided a shear ram blowout

preventer where the valve housing includes an upper bolt connection and a lower flange bolt connection with a collar.

[0012] In another aspect of the invention, it is provided a shear ram blowout

preventer where the valve housing is provided with first contact faces for slidable engagement with the first lower ram of the first piston rod arrangement and with second contact faces for slidable engagement with the upper second ram of the second piston rod arrangement.

[0013] In another aspect of the invention, it is provided a shear ram blowout

preventer where the well bore of the gate valve opening is provided with at least one cavity in its sidewalls for ring gaskets.

[0014] In another aspect of the invention, it is provided a shear ram blowout

preventer where at least one first cavity is arranged next to the first contact faces as a first cavity in the well bore opening. A first ring gasket can be arranged in the first cavity. The thickness of the first ring gasket in the wellbore coaxial direction can be smaller than the height of the cavity in the wellbore coaxial direction thereby creating a gap between the first ring gasket and the first cavity downstream of the contact faces.

[0015] In another aspect of the invention it is provided a shear ram blowout

preventer where the well bore of the gate valve opening is provided with a second cavity in its sidewalls for a second ring gasket, the second cavity is arranged next to the second contact faces upstream of the first and second ram.

[0016] According to the present invention it is also disclosed a method for sealing wellbores at least comprising the steps of:

providing a first cylinder house, where the first cylinder house is provided with a high pressure fluid inlet and two lower pressure outlets;

providing a first piston arrangement with a piston rod, a first ram and a first piston head;

providing a second piston arrangement with a second piston tubular rod, a circular concentric opening in the a first piston head of the second piston arrangement and a second ram;

assemble the first piston rod into the second piston tubular rod, thereby creating an assembly of two piston arrangement; inserting the assembly of the two piston arrangement into the first cylinder house so that the first and the second piston heads are axially spaced with the high pressure fluid inlet between them, thereby creating a push pull ram actuator with movement of the first and the second rams when a fluid pressure from the high pressure fluid inlet is higher than the pressure of the lower pressure outlets, and

assembly the push pull actuator to a valve housing.

[0017] In another aspect of the invention it is provided a method further

comprising the steps of: a) providing the first piston arrangement with a first piston tubular rod, a second piston head connected thereto where the second piston head have a circular concentric opening and where the second piston head is axially at the opposite end of the first piston head of the first piston arrangement;

b) providing the second piston arrangement with a second piston rod and a second piston head connected to the rod and arranged axially at the opposite end of the first piston head of the second piston arrangement;

c) assemble the second piston rod into the first piston tubular rod,

thereby creating an assembly of two piston arrangement; d) providing a second cylinder house, where the second cylinder house is provided with a high pressure fluid inlet and two lower pressure outlets;

e) inserting the assembly of the second piston head of the first piston arrangement and the second piston head of the second piston arrangement into the second cylinder house so that the piston heads in the second cylinder are axially spaced with the high pressure fluid inlet between them, thereby creating a two cylinder push pull ram actuator.

[0018] Other advantageous embodiments, aspects and details according to the present invention will become apparent by the accompanying claims.

Brief Description of the Drawings

[0019] In order to make the invention more readily understandable, the discussion that follows will refer to the accompanying drawings, in which

[0020] Fig. 1 , shows a shear ram blowout preventer in open configuration, i.e. the rams are retracted;

[0021] Fig. 2 shows working principles of a shear ram blowout preventer in closed configuration;

[0022] Fig 3 shows a piston rod arrangement, including two piston heads, a ram blade section, a piston rod section and a piston tubular section;

[0023] Fig 4 shows working principles of a shear ram blowout preventer in open configuration; [0024] Fig. 5 shows sections of a shear ram blowout preventer with sealing details, and

[0025] Fig 6 shows a principle of a balanced system with push and pull pistons. Detailed description of the Invention

[0026] In the following, the present invention will be discussed by describing

embodiments, and by referring to the accompanying drawings. However, people skilled in the art will realize other applications and modifications within the scope of the invention as defined in the enclosed independent claims.

[0027] It is disclosed a shear ram blowout preventer with balanced push and pull pistons, where the push and pull pistons is connected to ram blades. With reference to figure 6 it is shown a first and second piston head with an axial distance there between arranged in a cylinder housing. The first piston head is connected to a tubular the second piston head is connected with a piston rod. The piston rod of the second piston is inserted in the tubular of the first piston tubular arrangement. A high-pressure actuation fluid inlet is shown in the cylinder wall between the two piston heads. The volume between the piston heads is a high-pressure chamber when the shear ram blowout preventer works in a push and pull action for closing a wellbore. The cylinder includes two low-pressure vented chambers. The low-pressure vented chambers are in fluid connection with a low-pressure return system such as a one or more valves and one or more fluid vessels.

[0028] The piston rods and piston tubular is connected to ram blades, this is not shown in figure 6. The principles of one cylinder and two interacting push pull pistons can be extended to a double acting system with two cylinders. Figure 3 discloses a piston rod arrangement configured for a double acting balanced push pull system, i.e. extended to the two cylinder type.

[0029] Two piston rod arrangements as shown in figure 3 is assembled together in a double acting system. In one configuration, the piston heads can be dismounted by for example using a bolt arrangement. If the piston heads are removed it is easy to assemble the rod arrangements in a slidable configuration by inserting the rod 4 of one of the rod arrangements into the tubular 5 of the other rod arrangement and thereafter mount the piston heads. Figure 3 also shows the ram blade 8A with an opening for the well bore.

[0030] a shear ram blowout preventer First embodiment

[0031] According to the first embodiment, it is provided a shear ram blowout

preventer operating according to the principle shown in figure 6. The first embodiment can be illustrated in more detail as a "half shear ram blowout preventer 10 as shown in figure 1. A first cylinder 3A, two cylinder rod arrangements including ram blades 8A, 8B and one piston head 11 , 12 for each cylinder rod arrangement is included in the shear ram blowout preventer. The second cylinder housing 3B and its associated piston heads 13, 14 is omitted according to the first embodiment.

[0032] A high-pressure inlet can provide fluid at high pressure to the space

between the piston heads 11 , 12 in the first cylinder housing 3A during closing of the shear ram blowout preventer. The high pressure exerts a force to the piston heads 11 , 12 and thereby creating a push action on a first piston head 12 of a first piston rod arrangement and a pull action on a second piston head 11 of a second piston rod arrangement. The pull and push action will pull the upper ram blade 8B towards the wellbore 15 and seal it, simultaneously the push action will push the lower ram blade 8A towards the wellbore 15 and seal it. This push pull action provides a double acting sealing and cutting of the drill string during sealing of the wellbore 15.

[0033] A pressure seal 9 against wellbore when the ram blades 8A, 8B are closed is provided by a metal seal inserts 9 such as a ring gasket, located in the cavities between ram blades 8A, 8B and valve housing 1.

[0034] The employment of the "gate valve" principle ensures that the drill string is always inside the ram blade opening and therefore regardless of the drill string location and shape it will always be kept in optimal position against the cutting blade during gate closing. It also ensures a reliable seal against well bore pressure. [0035] Further details regarding operation of the shear ram blowout preventer is discussed below with reference to other embodiments of the present invention.

Second embodiment

[0036] The second embodiment of the present invention is shown in figure 1 - 5, and it includes two cylinder housings 3A,3B.

[0037] The pressure balanced double acting shear gate valve presented on Fig.1 , hereinafter referred to as a shear ram blowout preventer 10, operates as a gate valve. The gates or rams 8A, 8B are sealing the wellbore 15 and cutting the drill string, driven by the piston rod arrangements 11 , 12, 13, 14 towards the wellbore 15. The pistons 11 , 12, 13, 14 exert a force onto the ram blades 8A, 8B via brackets 6A, 6B, 7A, 7B. The force exerted by the pistons 11 , 12, 13, 14is created by pressure from hydraulic fluid that is pumped simultaneously into the cylinder housings 3A, 3B via an inlet 16 and channels from the inlet 16 to inlets/openings arranged between two pistons in the each cylinder housing 3A, 3B. End closures 2 are closing the ends of the valve housing 1 , thus providing a pressure barrier between wellbore cavity and the cylinders housing 3A, 3B. The end closures 2 also provides an axial fixture for the pistons rod arrangements 11 , 12, 13, 14, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B. A pressure seal 9 against wellbore when the gram blades 8 are closed is provided by a metal seal inserts 9 such as a ring gasket, located in the cavities between gram blades 8A, 8B and valve housing 1.

[0038] The employment of the "gate valve" principle ensures that the drill string is always inside the ram blade opening and therefore regardless of the drill string location and shape it will always be kept in optimal position against the cutting blade during gate closing. It also ensures a reliable seal against well bore pressure.

[0039] An operating principle of the pressure balanced double acting shear gate valve is shown in Fig.2. When an emergency occurs, the hydraulic fluid is pumped into both cylinders simultaneously, thus applying a pressure in the space between pistons and forcing the pistons in opposite directions; the pistons are exerting force on to the ram blades. The pistons are concentric where one piston is moving inside the other one. As it is illustrated in Fig. 3 an "inside piston" 4 of the piston rod arrangement 5A, 6A, 8A, 7A 4 exerts a pull action on to the gram blade 8A via bracket 7A. The pull action is provided by a high pressure in a second cylinder house 3B not shown in figure 3, but shown in figure 1 and 2. An "outside piston" 5A of the piston rod arrangement 5A, 6A, 8A, 7A 4 exerts a push action on to the gram blade 8A via bracket 6A, where the push action originates from a first cylinder house 3A.

[0040] The pressure balanced design is illustrated on the Fig. 4 with the ram

blades 8A, 8B in an open position. The force produced by the wellbore pressure is exerted in both directions and therefore cancels each other out. Therefore, an effective force exerted onto the drill string by closing of the gram blades 8A, 8B is independent of the wellbore pressure.

[0041] In order to establish seal that is reliable in all ranges of temperatures and fluid compositions, the metal seals with double piston effect, that is commonly used in heavy-duty valves. The double piston effect seal is illustrated on the Fig. 5. The double piston effect seal is increased with increased well bore pressure, and thus providing safe off pressure barriers in all operating conditions.

[0042] Reference list

A In combination with valve elements indicates lower ram blade

B In combination with valve elements indicates higher ram blade.

X Longitudinal axis of the shear ram blowout preventer, and the

piston rod arrangements

Z Wellbore axis

1 Valve housing

2 End closures of the valve housing (bonnet).

3A First cylinder housing

3B Second cylinder housing

4 Piston rod

4A Pull piston head in first cylinder

4B Pull piston head in second cylinder

5A Push piston head in first cylinder B Push piston head in second cylinder

A Bracket, transition between lower ram and piston rod/piston tubular.

B Transition between higher ram and piston tubular.

B Bracket, transition between higher ram and piston rod

A Lower ram blade, first ram

B Higher ram blade, second ram

Sealing, ring gasket.

0 Shear ram blowout preventer

1 Second piston head second piston rod arrangement

2 First piston head first piston rod arrangement

3 First piston head second piston rod arrangement

4 Second piston first piston rod arrangement

5 Wellbore / gate wall opening of shear ram blowout preventer.6 High pressure inlet to valve housing, in fluid connection with high pressure inlets to the first and the second cylinder housings