Blowout preventer

Abstract

A blowout preventer and method of closing a wellbore. The blowout prevented has a main body containing a wellbore, a passage transverse to the wellbore, a shearing device located in the passage; and a charge that, when activated, propels the shearing device along the passage and across the wellbore to close the wellbore and prevent a blowout.

Claims

1. A blowout preventer comprising: a main body containing a wellbore; a passage transverse to the wellbore; a shearing device located in the passage; a charge that, when activated, propels the shearing device along the passage and across the wellbore; and a concentric seal that extends in the direction of the wellbore to fluidly seal the passage from the wellbore, wherein the passage comprises a space between an initial location of the shearing device and the wellbore, and wherein the space between the initial location of the shearing device and the wellbore is at least as long as half a diameter of the wellbore.

2. The blowout preventer of claim 1, wherein the shearing device has a body section that substantially blocks the wellbore and substantially prevents passage of fluids through the wellbore, the shearing device comprising a cutting edge to cut through tubular sections in the wellbore.

3. The blowout preventer of claim 1, further comprising a retaining device that retains the shearing device in a predefined position in the passage until a sufficient force is exerted on the shearing device.

4. The blowout preventer of claim 3, wherein the retaining device comprises a shear pin.

5. The blowout preventer of claim 1, wherein the charge comprises a chemical propellant.

6. The blowout preventer of claim 5, wherein the charge is activated by an initiator.

7. The blowout preventer of claim 1, wherein the passage comprises a first portion on a first side of the wellbore and a second portion on a second side of the wellbore, and wherein the shearing device is initially located in the first portion of the passage on the first side of the wellbore.

8. The blowout preventer of claim 1, wherein a space between the initial location of the shearing device and the wellbore is longer than a diameter of the wellbore.

9. The blowout preventer of claim 8, wherein the space between the initial location of the shearing device and the wellbore is devoid of liquid.

10. The blowout preventer of claim 1, wherein the passage comprises a liner which fits within the passage.

11. The blowout preventer of claim 1, further comprising an arresting mechanism comprising an energy absorption mechanism adapted to absorb the energy of the shearing device once the shearing device has been propelled across the wellbore.

12. The blowout preventer of claim 11, wherein the arresting mechanism is disposed in the passage.

13. The blowout preventer of claim 11, wherein the arresting mechanism is disposed on an opposite side of the wellbore to the initial location of the shearing device.

14. The blowout preventer of claim 11, wherein the energy absorption mechanism has a front portion facing toward the shearing device, a rear portion, and a body of energy absorbing material located between the front portion and the rear portion, wherein the front portion of the energy absorption mechanism is configured to be attached to the shearing device.

15. The blowout preventer of claim 14, wherein a space behind the rear portion of the energy absorption mechanism is filled with hydraulic fluid.

16. The blowout preventer of claim 14, wherein the rear portion of the energy absorption mechanism contains a sliding piston which is movable within the passage.

17. The blowout preventer of claim 14, wherein a portion of the passage in which the energy absorption mechanism is disposed has a larger cross sectional area than a portion of the passage in which the shearing device is disposed prior to activation of the charge.

18. A method of closing a wellbore located within a main body of a blowout preventer, the method comprising: activating a charge to propel a shearing device along a passage transverse to the wellbore, such that the shearing device travels across the wellbore to inhibit the flow of wellbore fluids through the wellbore and shear any tubulars or downhole tools that may be present in the wellbore, wherein the shearing device is accelerated along the passage in a space between an initial location of the shearing device and the wellbore, and wherein the space is at least as long as half a diameter of the wellbore; and propelling the shearing device through a seal fluidly sealing the passage from the wellbore.

19. The method of claim 18, wherein the shearing device travels into an energy absorption mechanism located in the passage thereby absorbing kinetic energy of the shearing device.

20. The method of claim 19, wherein the absorbing the kinetic energy of the shearing device comprises hydraulically dissipating the kinetic energy.

21. The method of claim 18, wherein when the charge is activated, expansion of gases accelerates the shearing device along the passage, thereby imparting kinetic energy to the shearing device.

22. The method of claim 21, wherein an amount of kinetic energy imparted to the shearing device is sufficient to shear any device disposed in the wellbore without using energy from the expanded gases.

23. The method of claim 18, further comprising retaining the shearing device at the initial position until a sufficient expansion of the charge has occurred.

24. The method of claim 18, further comprising venting the activated charge into the wellbore.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To assist in understanding the present disclosure and to enable a person skilled in the art to put the present disclosure into practical effect, preferred embodiments of the present disclosure will be described by way of example only with reference to the accompanying drawings, wherein:

(2) FIG. 1 shows a sectioned view of a blowout preventer according to an embodiment of the present disclosure;

(3) FIG. 2 shows a cross section view of a blowout preventer prior to being activated;

(4) FIG. 3 shows a cross section view of a blowout preventer that has been activated;

(5) FIG. 4 shows a cross section view of a blowout preventer with the shearing device accelerating along the passage;

(6) FIG. 5 shows a cross section view of a blowout preventer with the shearing device piercing the seal;

(7) FIG. 6 shows a cross section view of a blowout preventer with the shearing device across the wellbore;

(8) FIG. 7 shows a cross section view of a blowout preventer with the shearing device contacting the energy absorption mechanism;

(9) FIG. 8 shows a cross section view of a blowout preventer with the energy absorption mechanism absorbing the kinetic energy of the shearing device;

(10) FIG. 9 shows a cross section view of a blowout preventer with the energy absorption mechanism pulling the shearing device clear of the wellbore; and

(11) FIG. 10 shows exploded views of a shearing device.

DETAILED DESCRIPTION

(12) With reference to FIG. 1, there is shown a sectioned view of a blowout preventer 100 according to an embodiment of the present disclosure. The blowout preventer 100 has a main body 110 having a wellbore 112. The blowout preventer 100 also has a passage 114 that is located transverse to the wellbore 112. A shearing device 116 having a cutting edge 118 is located in the passage 114 on a first side 120 of the wellbore 112. A charge in the form of a chemical propellant 122 is located between the shearing device 116 and an end cap 124. The chemical propellant 122 is adapted to propel the shearing device 116 along the passage 114 and across the wellbore 112, as will be described in greater detail below.

(13) A seal in the form of a cylinder 126 fluidly seals the passage 114 from the wellbore 112.

(14) An arresting mechanism in the form of an energy absorption mechanism 128 is located in the passage 114 on a second side 130 of the wellbore 112. The energy absorption mechanism 128 has a front portion 132 facing towards the shearing device 116, a rear portion 134 and a body of energy absorbing material 136 located between the front portion 132 and the rear portion 134. The energy absorption mechanism 128 is adapted to absorb the kinetic energy of the shearing device 116, as will be described in greater detail below. The rear portion 134 of the energy absorption mechanism 128 is a sliding piston, which can slide within the passage 114 on the second side 130 of the wellbore 112. As can be seen in FIG. 1 the passage 114 on the second side 130 of the wellbore 112 has a larger cross section than the passage 114 on the first side 120 of the wellbore 112. The portion of the passage 114 between the rear portion 134 of the energy absorption mechanism 128 and an end cap 138 is filled with hydraulic fluid.

(15) The operation of the blowout preventer 100 will now be explained with reference to FIGS. 2-8.

(16) With reference to FIG. 2, there is shown a cross section view of the blowout preventer 100 prior to being activated. As can be seen in FIG. 2, the chemical propellant 122 and shearing device 116 are located in the passage 114 on a first side 120 of the wellbore 112.

(17) FIG. 2 also shows an initiator in the form of a blasting cap 140 which is adapted to activate the chemical propellant 122. FIG. 2 also shows the cylinder 126 fluidly sealing the passage 114 from the wellbore 112.

(18) Around the wellbore 112 is located a wellbore sealing arrangement 142, which will be explained in more detail below.

(19) The energy absorption mechanism 128 is located within the passage 114 on the second side 130 of the wellbore 112.

(20) FIG. 3 shows a cross section view of the blowout preventer 100 where the chemical propellant 122 has been activated by the blasting cap 140. The shearing device 116 is held in place by a shear pin (not shown) until a sufficient expansion of hot gases has occurred after activation of the chemical propellant 122.

(21) FIG. 4 shows a cross section view of the blowout preventer 100 where a sufficient expansion of hot gases has occurred after activation of the chemical propellant 122 to shear the shear pin (not shown). At this stage, the shearing device 116 is accelerating along the passage 114 towards the cylinder 126 and wellbore 112.

(22) FIG. 5 shows a cross section view of the blowout preventer 100. At this stage, the shearing device 116 has begun to shear the cylinder 126. The shearing device will also shear any wellbore tubulars, tools, drill strings or the like which are present in the wellbore. The passage 114 on the first side 120 of the wellbore 112 contains a passage liner (not shown). The passage liner provides a close tolerance fit between itself and the shearing device 116. The liner controls the by-passing of the hot expanding gases from the exothermic reaction of the chemical propellant 122 and guides the shearing device 116 during its rapid acceleration and shearing phase of operation.

(23) FIG. 6 shows a cross section view of the blowout preventer 100. At this stage, the shearing device 116 has sheared through the cylinder 126 and anything else that may have been located in the wellbore 112. The upper portion of the shearing device 116 has channels (not shown) such that once the shearing device 116 is sufficiently across the wellbore 112, the expanding gases from the chemical propellant 122 are vented down into the wellbore.

(24) FIG. 7 shows a cross section view of the blowout preventer 100 where the shearing device 116 has connected with the front portion 132 of the energy absorption mechanism 128. An attachment mechanism (not shown) attaches the shearing device 116 to the front portion 132 of the energy absorption mechanism 128.

(25) FIG. 8 shows a cross section view of the blowout preventer 100 where the body of energy absorbing material 136 of the energy absorption mechanism 128 has crumpled to a predetermined amount, absorbing the kinetic energy of the shearing device 116. The hydraulic fluid in the passage 114 between the rear portion 134 of the energy absorption mechanism 128 and the end cap 138 dissipates any residual energy of the shearing device 116.

(26) The energy absorption mechanism 128 will retain the shearing device 116 in such a position that a sealing face (not shown) of the shearing device 116 is sufficiently aligned with the wellbore sealing arrangement 142. Once the shearing device 116 is sufficiently aligned with the wellbore sealing arrangement 142, the sealing arrangement 142 will firmly press a sealing ring (not shown) against the sealing face (not shown) of the shearing device 116, to stop the flow of wellbore fluids through the wellbore 112, securing the well. Once the well is secured, well control operations (for example choke and kill operations) can commence.

(27) Once well control has been re-established, the blowout preventer 100 can be de-activated as seen in FIG. 9. In FIG. 9, the sealing arrangement 142 retracts the sealing ring (not shown) from the sealing face (not shown) of the shearing device 116, then the hydraulic fluid in the passage 114 between the rear portion 134 of the energy absorption mechanism 128 and the end cap 138 is vented, pulling the energy absorption mechanism 128 along the passage 114 and the shearing device 116, which is attached to the front portion 132 of the energy absorption mechanism 128, clear of the wellbore 112.

(28) FIG. 10 shows exploded views of a shearing device 116. The shearing device 116 has a cutting edge 170. The cutting edge 170 is made of a very hard material such as metallic or ceramic alloys that can cut through tubular sections which may be present in a wellbore. The cutting edge 170 has a rib 172 extending around its sides and rear face. In the assembled form, the rib 172 sits in a slot 174 of the shearing device 116. The shearing device 116 has a body section 174 that in operation blocks a wellbore and prevents the mass passage of wellbore fluids through the wellbore. The shearing device 116 optionally has a sealing face 178 which is adapted to engage with a wellbore sealing arrangement to prevent passage of wellbore fluids. In an alternate embodiment (not shown), a sealing face may optionally be present on a upper portion of the shearing device.

(29) The shearing device 116 has two slots 180 which are adapted to attach to an energy absorption mechanism.

(30) A possible advantage of a blowout preventer according to the present disclosure is that the blow out preventer can be actuated without having to produce hydraulic forces to hydraulically push rams across the wellbore to close off the wellbore. Instead, the energy required to close the wellbore is contained in the charge in the blowout preventer where it is required.

(31) A possible advantage of holding the shearing device 116 in place by a shear pin is that this assists in the rapid acceleration of the shearing device 116 along the passage 114 once sufficient force has been generated by the expanding gases of the chemical propellant 122.

(32) A possible advantage of having the cylinder 126 fluidly sealing the passage 114 from the wellbore 112 is that the shearing device 116 can accelerate along the passage 114 unhindered by wellbore fluids or other liquids until the shearing device 116 starts to shear the cylinder 126.

(33) A possible advantage of using an energy absorption mechanism 128 is that excess kinetic energy of the shearing device 116 is not directly transferred into a structural portion of the blowout preventer 100.

(34) A possible advantage of pulling the shearing device 116, which is attached to the front portion 132 of the energy absorption mechanism 128, clear of the wellbore 112 is that the shearing device 116 does not have to be drilled through for wellbore operations to recommence.

(35) The foregoing embodiments are illustrative only of the principles of a blowout preventer according to the present disclosure, and various modifications and changes will readily occur to those skilled in the art. The present disclosure is capable of being practiced and carried out in various ways and in other embodiments. For example, individual features from one embodiment may be combined with another embodiment. It is also to be understood that the terminology employed herein is for the purpose of description and should not be regarded as limiting.

(36) In the present specification and claims, the word comprising and its derivatives including comprises and comprise include each of the stated integers but does not exclude the inclusion of one or more further integers unless the context of use indicates otherwise.