PLUG COMPRISING A DISC VALVE

Abstract: A plug (1) comprises a barrier portion (5) and a cutter mechanism (8) which can cut an aperture in the plug (5) when in place in a well by piercing the plug, cutting a portion of it and moving the cut portion from the fluid path through the plug.

Description: PLUG COMPRISING A DISC VALVE The invention relates to a plug and in particular, a plug for use in a borehole, such as an oil and/or gas well. When installing completion equipment, such as tubing into a well, such as an oil and/or gas well, it is commonplace to require to create a pressure differential between the inside and the outside of the tubing string. The purpose of this pressure differential is to test the tubing connections for pressure integrity and to pressure test the annular packers which are located between the outside of the tubing string and the inside of the casing lining the borehole. The annular packers prevent production fluids such as oil, gas and oil and gas mixtures flowing up the annulus between the tubing string and the casing. It may also be necessary to generate a pressure differential in order to activate hydraulically operated tools downhole. The current method of generating this pressure differential involves installing the tubing string into the well with the plug pre-installed in the tubing string, carrying out pressure testing of the tubing and annular packers and then opening, removing or destroying the plug in order to open the tubing string after the pressure operations have been completed. Current plugs include a bursting type plug which when pressurised above a certain level bursts in order to open a tubing string. However, this has the disadvantage that when the plug bursts a section of the plug will generally break free from the tubing string and this results in a piece of unwanted equipment at the bottom of the well which may cause problems at a later date. Other solutions include setting and retrieving traditional wireline type plugs in the tubing string and also use of a flap or ball type valve. The wireline type plugs have the disadvantage that they involve running wireline into the tubing after the pressure operations have been completed in order to retrieve the plug. With flap or ball type valves there is the problem that these type of valves restrict the internal diameter of the tubing and therefore decrease the efficiency of fluid production. Other approaches which have been suggested include plugs with in-built explosives which may be detonated after the pressure tests have been completed in order to open the tubing string and a plug with a barrier which dissolves after a protective membrane on the barrier is pierced. Both these solutions have problems associated with them. The exploding type plug has the disadvantage that it requires handling of explosives which is hazardous, especially in an offshore environment with flammable fluids present. The dissolving plug has the disadvantage that because of the type of materials which are used in the plug, the inherent strength of the barrier is relatively weak, especially as the membrane must be capable of being penetrated in order to permit well fluids to enter through the protective membrane and dissolve the substance of the plug. In accordance with a first aspect of the present invention, a plug for isolating a lower section of a well from an upper section of a well comprises a barrier portion which provides a barrier to fluid flow within the section of the well in which the plug is located and a cutting mechanism which may be activated to cut a section of the barrier portion and move the cut section of the barrier portion to permit the flow of fluid within the section of the well in which the plug is located. The plug may have a body member having a coupling to permit the body member to be secured within a well. In accordance with a second aspect of the present invention, a method of opening a plug located in a well comprises providing a cutter mechanism above a barrier of the plug and activating the cutter mechanism to cut a portion of the barrier and to subsequently move the cut portion of the barrier to allow flow of fluid past the plug. Preferably the cut section of the plug is moved adjacent an internal side wall of the well. However, this is not necessary, and it is sufficient for the cut section to be moved sufficiently to allow the passage of fluid. An advantage of the invention is that by cutting a portion of the barrier to facilitate opening of the barrier it is possible to use relatively strong materials for the barrier. In certain embodiments of the invention, the cut portion will move out of the flow path of fluid and will remain attached to the plug by a flap, rather than being cut off in its entirety, and this has the advantage that the cut section does not fall to the bottom of the well and obstruct later operations. Preferably, the plug is a plug which may be mounted in a conduit, such as a tubing string and the side wall of the well adjacent to which the cut portion of the barrier moves is an internal side wall of the conduit. Typically, the side wall against which the cut portion moves is recessed to minimise obstruction of the internal dimensions of the conduit after the plug has been opened. Preferably, the cutter mechanism comprises a portion of a cylinder and does not cut the barrier adjacent to the said internal side wall. Typically, the cutter mechanism includes a cutting blade which is tapered in a direction along the longitudinal axis of the well in which the plug is located. Preferably, the cutter is tubular and the blade may be tapered in both directions along an edge of the cutter. Typically, the cutter mechanism also includes a piercing device to pierce the barrier prior to cutting. Preferably the piercing device is a piercing formation on the cutting blade, such as the tip of the tapered blade . Preferably, the cutter mechanism includes a coupling profile which permits a wireline tool or other mechanical tool to be coupled to the cutter mechanism to activate the cutter mechanism. Typically, the plug also includes an activation device to activate the cutter. Preferably, activation of the cutter may be facilitated by hydraulic pressure within the well and typically, within the conduit in which the plug is located. Preferably, the activation mechanism includes a chamber filled with fluid which is typically gas which may be at atmospheric pressure. However, the means of activation of the cutter is not central to the invention, and the cutter can be actuated by, eg, explosives, ratchets and/or other such means capable of moving the cutter and the barrier relative to one another. Preferably, the plug also includes a releasable securing device which secures the cutter to the body member of the plug prior to activation of a cutter mechanism. Typically, the releasable securing device may comprise a shear pin. Preferably, the cutter mechanism may include a moveable sleeve and an indexing mechanism to permit pressure testing of a conduit in which the plug is located without activation of the cutter mechanism. Examples of a plug in accordance with the invention will now be described with reference to the accompanying drawings, in which:- Fig. 1 is a partial cross-sectional view through a length of tubing which includes a first example of a plug; Fig. 2 is a side view of a slotted sleeve for use in the tubing shown in Fig. 1; and Fig. 3 is a cross-sectional view through a portion of a second example of a plug. Fig. 1 shows a length of tubing 1 which comprises a threaded box end 2, a threaded pin end 3, an upper tubular body member 24 and a lower tubular body member 4. Mounted between the lower body member 4 and the pin end 3 is a steel plate barrier 5 which extends across a central bore 6 in the tubing 1. The barrier plate 5 is threaded onto the lower body member 4 and the pin end 3 by a cylindrical section 7. Mounted within the lower body member 4 adjacent to the plate 5 is a cutter 8 which is temporarily secured to the lower body member 4 by a shear pin 9 and has a cutting blade 10. The cutting blade 10 incorporates a piercing formation. Located above the cutter 8 is a moveable sleeve 11 which is secured to the lower body member 4 by locking dogs 12 and a lock sleeve 13. "0" ring seals 14 isolate a pressure chamber 15 from central bore 6 of the tubing 1. Located above the tubing 1 is an actuator mandrel 16 which is attached to a piston sleeve 17 by means of locking screws 18. A helical spring 19 is located between a shoulder 20 on the piston sleeve 17 and a shim 21 which is held in position between the upper body member 24, the lower body member 4, the actuator mandrel 16 and the piston sleeve 17. The upper end of the piston sleeve 17 has an upper piston sub 22 which includes an "0" ring seal 23. A port 25 in the upper body member 24 permits fluid in the annulus outside the tubing 1 to enter into fluid chamber 26 which is isolated from the other sections of the tool by "0" ring seals 23, 27. A slide bolt 28 moves in a slot 29 in a slotted sleeve 30 attached to the piston sleeve 17. The slotted sleeve 30 is shown in more detail in Fig. 2. The slotted sleeve 30 and slide bolt 28 permit pressure to be pumped into the tubing 1 and prevent the mandrel 16 being pushed into engagement with the sleeve 11 except, when the slide bolt 28 reaches position 31 in the slot 29. In use, the length of tubing 1 is connected into a tubing string and inserted into a well such as an oil or gas well. Pressure testing of the tubing string can then be performed as the barrier plate 5 prevents pressure escaping from the tubing string. After the pressure tests have been completed it is necessary to open the barrier plate 5 to permit fluid to pass through the tubing 1. In order to accomplish this, pressure within the tubing 1 is cycled to move the piston sleeve 17 up and down against the action of the biassing spring 19 until the slide bolt 28 enters position 31 in the slotted sleeve 30. When the slide bolt 28 enters the position 31 in the slotted sleeve 30, the piston sleeve 17 moves down until the mandrel 16 touches the locking sleeve 13. Further downward movement of the piston sleeve 17 then causes the locking sleeve 13 to move downwards with respect to the sleeve 11 thereby releasing dogs 12 from engagement with the lower body member 4 and permitting the sleeve 11 to be moved downwards to contact the cutter 8. The fluid chamber 15 is typically filled with a gas at atmospheric pressure and as the pressure in the bore 6 is many times greater than atmospheric pressure, the sleeve 11 will move down rapidly when the locking dogs 12 are released and hit against the cutter 8 causing shear pin 9 to shear and the cutter 8 to impact against the barrier plate 5. The piercing formation on the blade 10 will pierce the barrier plate 5 and then the blade 10 will cut through the barrier plate 5 around all but a small portion of the barrier plate 5. Hence, the blade 10 does not extend all the way round the cutter 8 and this permits the barrier plate 5 to be retained to the cylindrical section 7 by a small portion. Further downward movement of the cutter 8 then deflects the cut portion of the barrier plate 5 into a recess section in the box end 3, thereby moving the barrier plate 5 and opening the tubing to permit fluids to flow through the tubing 1. In addition, the cutter 8 has a profile 32 which permits a wireline jar to be engaged with the cutter and the cutter to be activated to cut and move the barrier plate 5 by mechanical activation if necessary or if desired. Fig. 3 shows a portion of a second example of a plug 40. In this example, a barrier 41 is integrally formed with side walls 42 which form part of a length of tubing. A cutter 43 is mounted within the side walls 42 and has a continuous edge blade 44. The cutter is symmetrical about the plane of the cross-sectional view of Fig. 3 and the cutter has a ridge 45 and a dulled portion 46 diametrically opposite each other. A recess 47 is provided in the side wall 42. In use, the plug 40 is operated and opened in a similar manner to the apparatus shown in Figs . 1 and 2. The ridge 45 acts as a piercing formation to pierce the barrier 41 and the blade 44 then cuts through the barrier 41 as it is pushed downwards. When the dulled portion 46 contacts the barrier 41, the dulled portion does not cut. Instead the dulled portion 46 pushes and bends the cut section of the barrier 41 into the recess 47 to open the plug 40. Modifications and improvements may be incorporated without departing from the scope of the invention.

Claims: Claims : 1. A plug for isolating a lower section of a well from an upper section of a well, the plug comprising a barrier portion which provides a barrier to fluid flow within the section of the well in which the plug is located and a cutter which may be activated to cut a section of the barrier portion and move the cut section of the barrier portion to permit the flow of fluid within the section of the well in which the plug is located. 2 A plug as claimed in claim 2 wherein the cut section of the plug is moved adjacent an internal side wall of the well. 3 A plug as claimed in claim 1 or claim 2 being mounted in a conduit and the side wall of the well adjacent to which the cut portion of the barrier moves is an internal side wall of the conduit. 4 A plug as claimed in any preceding claim, wherein the side wall against which the cut portion moves is recessed to receive the cut portion after the plug has been opened. 5 A plug as claimed in any preceding claim, wherein the cutter comprises a portion of a cylinder. 6 A plug as claimed in any preceding claim, wherein the cutter is adapted to leave the cut portion attached to the plug after operation of the cutter. 7 A plug as claimed in any preceding claim, wherein the cutter has a cutting blade which is tapered in a direction along the longitudinal axis of the well in which the plug is located. 8 A plug as claimed in any preceding claim, wherein the cutter is tubular. 9 A plug as claimed in claims 7 or 8, wherein the blade is tapered in both directions along an edge of the cutter. 10 A plug as claimed in any preceding claim, wherein the cutter includes a piercing device to pierce the barrier prior to cutting. 11 A plug as claimed in claim 10, wherein the piercing device is a piercing formation on the cutting blade. 12 A plug as claimed in any preceding claim wherein the cutter includes a coupling profile which permits a wireline tool or other mechanical tool to be coupled to and to activate the cutter. 13 A plug as claimed in any preceding claim, wherein the plug includes activation means to activate the cutter. 14 A plug as claimed in any preceding claim, wherein the cutter may be activated by hydraulic pressure within the well. 15 A plug as claimed in claim 13 or claim 14, wherein the activation means includes a chamber filled with fluid. 16 A plug as claimed in any preceding claim, which includes a releasable securing device which secures the cutter to a body member of the plug prior to activation of a cutter. 17 A plug as claimed in claim 16, wherein the releasable securing device comprises a shear pin. 18 A plug as claimed in any preceding claim, wherein the cutter includes a moveable sleeve and an indexing mechanism. 19 A method of opening a plug located in a well comprising providing a cutter above a barrier of the plug, activating the cutter mechanism to cut a portion of the barrier and subsequently moving the cut portion of the barrier to allow flow of fluid.

Inventors: RUBBO RICHARD PAUL, RUBBO, RICHARD, PAUL
Applicants: PETROLEUM ENG SERVICES, RUBBO RICHARD PAUL, PETROLEUM ENGINEERING SERVICES LIMITED, RUBBO, RICHARD, PAUL
Application year: 1997
Main classification: E21B34
IPC codes: E21B23, E21B29, E21B34