GB2259317A - Method and apparatus for well closure - Google Patents

Abstract

A method and an apparatus where three valves are located in axially spaced relationship along the well bore. The lower valve 122 is opened and a boring tool is passed therethrough to bore through the outer casing 103b and into the well bore 100. The boring tool is removed and the lower valve 122 then acts as a bypass for oil or gas. The intermediate valve 121 is opened and the boring tool passed therethrough to bore through the well casing 103b into the well bore 100.The boring tool is removed and a bridge plug is inserted through the intermediate valve 121 to close the well bore above the lower valve 122. The boring tool is then passed through the upper valve 120 to cut through the well casing 103b into the well bore 100 and cement is passed through the upper valve 120 to fill the pipe above the bridge plug. Various forms of bridge plugs for closing the well bore may be used. <IMAGE>

Description

METHOD AND APPARATUS FOR WELL CLOSURE BACKGROUND OF INVENTION This invention relates to a method and an apparatus for well closure and is particularly useful for occasions when wellhead equipment is damaged and/or oil or gas is being discharged.

It is known from US-A-3738424 to provide two axially longitudinally spaced valves on a well casing and to drill via the valves into the well casing. Liquid nitrogen is then passed through the lower valve into the well bore and out of the other valve so that the section of the well bore between the two valves freezes the fluid or gas flowing in the pipe to close the flow thereof off.

However the United States reference is unable to bleed off fluid or gas within the well bore while plugging the well bore and, furthermore, the use of liquid nitrogen to form a temporary plug (which is all the plug of the U.S.

reference can be used for) leads to handling difficulties.

The present invention seeks to provide a method and apparatus for well closure in which the foregoing disadvantage is at least partially mitigated.

SUMMARY OF THE INVENTION According to this invention there is provided a method for well closure includingEthe steps of: contacting by mounting three valve means on an outer casing of a well bore in axially spaced relationship with respect to the well bore, opening the lower valve means and passing a boring means therethrough, boring through the outer casing into the well bore, removing the boring means and connecting an oil/gas bypass means to said lower valve means for permitting oil/gas diversion, passing said boring means through the intermediate valve means and cutting through the well casing into the well bore, withdrawing the boring means and passing a bridge plug through the intermediate valve means to close the pipe above said lower valve means so that the flow from the well bore is diverted through the lower valve means, passing the boring means through the upper valve means to cut through the well casing into the well bore, withdrawing the boring means and passing cement through the upper valve means to fill the well pipe above the bridge plug.

The well bore may be the annulus around a production pipe and/or the production pipe.

In one embodiment the bridge plug is filled with air or cement and in a further embodiment the bridge plug is made of rubber or elastomer having laterally running KEVLAR (RTM) threads.

Preferably the bridge plug is formed by a shaft inserted through the upper valve means, said shaft having an apertured top and being arranged to partially restrict flow in the well bore, and a hollow tube is inserted through the next lower valve means, the tube having an angled upper opening to provide a venturi effect above said angled upper opening, and elastomer or rubber members are passed along the tube and by virtue of pressure in the well bore and the venturi action, so the said members completely close gaps around the shaft to close the well. In such an arrangement cement is pumped through the upper valve means to seal the well.

In a further embodiment the bridge plug has an end curved to correspond to the internal contour of the well bore and a cross slot into which are located two oppositely directed slidable wings having outer edges contoured to abut the inside of the well bore, an aperture orthogonal to the slots is provided to permit well pressure to act between the wings so that the wings are forced radially outwardly to seal with the inside of the well pipe.

In another embodiment the bridge plug has an end curved to correspond to the internal contour of the well pipe and a cross slot into which are located two oppositely directed slidable wings having outer edges contoured to abut the inside of the well bore, and a push rod is provided to radially expand the wings into contact with the internal surfaces of the well bore surfaces.

Preferably the region adjacent the outer casing is excavated so that the valve means are located beneath the substrate surface. Advantageously the excavated surfaces are lined and overhead protection is provided.

According to a further aspect of this invention there is provided an apparatus for well closure comprising three valve means located on a well bore in axially spaced relationship with respect to said well bore, an aperture selectably openable through each said valve means to the inside of said well bore, a bypass means connected to said axially lower valve means for withdrawing oil/gas therethrough and a well bore sealing means locatable through said upper valve means to close the well bore above said lower valve means.

Preferably means are provided for blocking flow of gas or oil in the production pipe such as cement or a bridge plug formed by a rubber or elastomer balloon. Conveniently said blocking means is a balloon filled with cement or air.

Advantageously a bridge plug is formed between two adjacent valve means, an upper one of the two adjacent valve means having a shaft therethrough, said shaft having an apertured top and being arranged to partially restrict flow in the well bore, a hollow tube inserted through the adjacent lower valve means, the tube having an opening angled upwardly to produce a venturi effect, and elastomer or rubber members maintained in position by virtue of the venturi action to close the gaps around the shaft for closing the well.

In another embodiment said sealing means is a bridge plug having a curved end to correspond to the internal contour of the well pipe and a cross slot at an end thereof into which are located two oppositely directed slidable wings having outer edges contoured to abut the inside of the well pipe, said wings being operatively linked to an aperture in said well plug whereby well pressure acting through said aperture between the wings forces the wings radially outwardly to seal with the inside of the well pipe.

In a further embodiment the sealing means is a bridge plug having an end curved to correspond to the internal contour of the well pipe and a cross slot into which are located two oppositely directed slidable wings having outer edges contoured to abut the inside of the well pipe, and a push rod is provided to radially expand the wings into contact with the internal well pipe surfaces.

BRIEF DESCRIPTION OF DRAWINGS The invention will now be described with reference to the accompanying drawings in which: Figures l(a) and l(b) show side elevation and plan views of a direct approach trench used to reach the outer casing of a well bore; Figures 2(a) and 2(b) show side elevation and plan views of a through-and-spur trench used to reach the outer casing; Figure 3 shows a side view of a trench adjacent the outer casing of a well bore with equipment used during welding; Figure 4 shows three valve means, each comprising a valve and a spool, in axially spaced relationship with respect to the well bore mounted on the outer casing of the well bore; Figure 5 shows a cross-sectional view of a spool; Figure 6 shows a side elevation of a valve means mounted on to the well outer casing by welding; ; Figure 7 shows a diagrammatic view of a boring machine for direct attachment to a valve means comprising a spool and valve; Figure 8 shows details of the flanges and supports used in the boring machine of Figure 7; Figure 9 shows the boring machine in operation when attached to a valve means; Figure 10 shows a cross-sectional view of a well head with the boring means of the boring machine in operation, and an isolation plug inserted; Figures ll(a)-(c) show different types of bridge plug; Figure 12 shows a cross-sectional view of a well where the flow is through the production pipe and the annulus is clear and unpressurised, to illustrate the method and apparatus of the invention;; Figure 13 shows a cross-sectional view of a well where the production pipe is unsupported, and flow is through both annulus and production pipe, or annulus alone, to illustrate the method and apparatus of the invention; Figure 14 is a third cross-section view of a well to illustrate the method and apparatus of the invention; and Figures 15(a)-(f) show different types of bridge plug for use in the method and with the apparatus of the invention.

In the Figures like reference numerals indicate like parts.

DESCRIPTION OF PREFERRED EMBODIMENTS As exemplified in Figures 1 and 2, an approach trench is excavated from a safe distance to the outer casing of a well bore, this trench being, for example, approximately twelve feet wide. The trench descends with an inclined section 1 from the surface down to the working depth, then has a level section 2, 8 from the lower part of the descent to the outer casing 3. The working depth is typically twenty feet or more, however the actual depth will be decided by the engineer in charge. The approach direction of the trench depends on prevailing wind conditions to minimise the blowback of solid matter or fumes into the trench and is selected so that oil or flames are blown away from the excavation.The trench walls are lined with interlocking piling or coffer dam sections 4 supported by extension jacks 5 (ACROJACK type or similar) as required for safe working. The lower jacks are in cross grooves in the trench floor. Tread plates or ground plates 6 form the trench floor, and the upper edges of the piling protrudes above ground level to prevent ingress of water or oil. A mobile overhead protection assembly 7 in sections overlapping the excavation sides is progressed as the trench is prepared to provide overhead cover. This protection assembly can be fitted with cooling spray discharge nozzles, the overlap of the protection assembly allowing the water to discharge outside the excavations.

After completion of the approach trench, safety checks are carried out to secure the trench against collapse of walls and pumping equipment is operated if required to remove oil or cooling spray water.

Referring to Figure 3, a portable atmosphere chamber 30 is fitted and sealed to the casing 3. Into the portable atmosphere chamber is taken a closed circuit television camera 31, if required, bulkhead lights 32, welding equipment 36 and an air supply mask 37, with on-demand pipeline to the mask. Three pre-assembled spools 35 and three ball valves are taken to the casing 3 either using overhead block and tackle or a hand-operated lift truck 34 (HILIFT, TROLLEYLIFT or the like). Supply lines and pipes are connected and checked for correct operation and the welder is fitted with his air supply mask. The quickrelease entryway to the chamber is sealed and inert gas is supplied to bring the chamber up to pressure.

The spools 35 are then lifted one by one against the outer casing and mounted thereon by welding. Once all the spools have been welded, they are checked and allowed to cool before the ball valves are lifted and bolted to the flanges of the spools.

Turning to Figure 4, the valve means are shown in place, consisting of ball valves 41 bolted to the flanges of the spools 35, the spools being welded to the outer casing 3. A support bracket 40, also welded to the casing, is connected to the spools via pipe clamps 42 and adjustable pipe hangers 43.

Referring to Figure 5, the spools have a blind or undrilled flange 51 at one end, a spool body 52, and a drilled flange 53 at the other end. The face of the blind flange is machined so as to correspond with the casing outer periphery, and is provided with welding chamfers.

The hole pitches and sizes on the drilled flange correspond to the ball valve flanges and attachment bolts. Unions 54 are drilled and tapped and pressure sealed into the spool body 52. Secondary ball valves 55 are provided, these allowing entry for cutting fluid, coolant, brine or inert gas, insertion of a fibre optic camera unit, or attachment of a gauge for reading spool pressure. Further optional entryways 56 may be provided and these can be plugged until required, using sealing plugs with tab lock washers 57.

In Figure 6 the blind flange 51 is attached to the wellhead outer casing 3 by a running weld 61. When larger size spools are used welding tacks may be made inside in addition to the outside running welds. A ball valve 41 has a first flange 62 attached to the drilled flange 53 of the spool by bolts 63. The ball valve has a second drilled flange 64 at its opposite end.

Once the spools and ball valves are secured in position a boring machine is used to drill through the casing, by way of the spools and valves. Such a boring machine, as shown in Figures 7-9 consists of a further spool including a flange 71 for bolting to the valve 41, a secondary union and valve assembly 72, for allowing access for inspection, input of inert gas, an intermediate chamber 73 and a rear flange 74. A boring means cinluding a core cutter tool 75 is mounted on a chucking flange of a rotating drilling shaft. There is provided a circular flange 78 which may be bolted to the rear flange 74 of the further spool. The spindle for the core cutter tool passes through a stuffing box 79 which seals a housing spindle 80 to prevent oil/gas passing therethrough.A steady plate 81 for the housing spindle 80 has a central bronze bearing for the spindle with a key and is carried on support shafts 76.

The plate 81 may be locked on the support shafts to act as depth ccntrol. The boring shaft housing spindle 80 has a keyway to match the key in bushing of the steady plate to prevent rotation. A brass shear pin 82 shears in high torque situations resulting from excessive boring resistance to prevent damage to the boring machine motor 85. This pin 82 normally connects the drilling shaft in the housing spindle to the motor. A sliding steady plate 83, carrying the boring spindle and motor unit, can be translated along the support shafts by hydraulic, pneumatic, or electric motors, or by chain, sprocket and weight system. It has further bushings 84 (of SUSTAN or LEMPCO type). An end flange 86 and a front support 87 are supported by levelling screw jacks 88. Grease nipples 89 are provided.

Referring to Figure 8, this shows elevations of the front and rear flanges 71, 74, the steady plate 81 and end flange 86, and the sliding steady plate 83 respectively.

Turning to Figure 9, the end flange of the further spool of the boring machine is bolted to the flange 64 of the ball valve 41 and the circular flange 78, carrying the stuffing box is bolted to the rear flange 74 of the further spool. This brings the core cutter into the intermediate chamber 73.

The valve 41 is then opened to allow the boring means to cut the annulus casing or the production pipe.

Subsequently the boring means is withdrawn into the intermediate chamber 73, followed by closure of the valve 41 and releasing of overpressure in chamber 73 using the secondary union valve 72. Once this has been achieved the connection between flanges 74 and 78 is released and the flanges are separated to allow safe change of tool.

The boring machine described is used to cut through both casings and cement infills. It is important that leakage from the well is not allowed to enter the cement infills between casings and thus it is necessary to isolate the cement. To achieve this various types of bridge plugs have been designed.

Referring to Figure 10, the central production pipe 100 is surrounded by the annulus 101 and this in turn by the annulus casing 102. Around the annulus casing 102 is the inner casing 104, and in turn around the inner casing 104 is the outer casing 103. The space between the outer casing and the inner casing, and the inner casing and the annulus casing respectively is filled with cement inf ill 103 a, 103b. In the Figure, the core cutter 75 is shown having cut through casing and cement layers, being stopped upon reaching the outer face of the annulus casing 102.

The spool 35 and ball valve 41 are shown welded to the outer casing 3.

After the core cutter has reached the outer facing of the annulus casing 102, the core cutter is withdrawn, as herein described above, and a suitable heavy A.P.I. or ACME thread tapping tool is used to cut a thread 106. The tapping tool is withdrawn and a bridge plug fitted to a torquing tool. The bridge plug is in two parts, a compressible seal pad 107 which fits into a plug 108.

Typically, before insertion of the bridge plug, a pressure flush and an examination using a fibre-optic inspection camera unit or the like will be made using the secondary valve assembly on the spool 35. The core cutter 75 will of course remove the central cut mass by retention of the core and care will have been taken to ensure that cores are removed at suitable intervals.

The compressible seal pad 107 and plug 108 are driven into the threaded hole 106, after liberally coating with sealant, and torque is continued so as to expand the seal pad 107 by trapping the pad between the plug and the annulus casing 102. The pressure and torque are maintained until the sealant is fully hardened. The torquing tool is then removed and a smaller core cutter 109 is fitted. Thit is moved through plug 108 to cut through the centre of pad 109, the annulus casing 102 and the production pipe 100 if required.

Figures ll(a) and ll(b) show a circlip lock bridge plug 110, which can be used where there is no annulus flow.

This plug goes through to the production pipe 100 and sealed thereto by a compressible seal 107. It is externally threaded but has in addition a safe lock mechanism. Thus, in low pressure instances, a hole approximately perpendicular to the casing axis may be cut and the lock bridge plugs having deep circular grooves for cement sealing may be inserted. The head of the plug has an external groove into which is compressed a heavy spring circlip 111. The circlip is radially compressed by a thin spring steel retainer 112, the plug being driven home into the hole liberally coated with sealant. The composition seal 107 is fully compressed against the production pipe and held and then two pins 113 are activated to push back the circlip retainer, thereby allowing the circlip to radially expand and lock behind the outer casing.

Figure ll(c) is an automatic dog lock type of bridge plug which locks behind the outer casing wall 3 once the sealing plug is sufficiently compressed. A circlip 115 is fitted externally to compress and retain the tooth dogs 116. As shown, 117 is a circlip in compression. The device can be fed into an aperture but may not be withdrawn due to the circlip causing the tooth dogs to radially expand. Combinations of the threaded plug with retainer circlips or retention dogs may be used as appropriate.

Examples illustrating how the method according to the invention may be used will now be given: Referring to Figure 12, a boring means hereinafter referred to as a core cutter is inserted via the lower valve means 122 and used to cut through the casings and infills to open up into the production pipe. The core cutter is withdrawn and the valve of valve means 122 is shut. The boring means is removed and oil/gas bypass means shown) is attached to the flange of the valve means this bypass means running to a flare-off or a sand tank. The valve is then opened to allow partial oil/gas diversion from the production pipe. Alternatively, it may be possible to pump gas in via the secondary ball valve of the spool (see Figure 5) to equalise the oil/gas pressure up the well so that oil/gas from the well does not leave from the lowest assembly 122.A core cutter is then passed through the intermediate valve means 121 to cut through into the production pipe. The core cutter is removed and the valve of intermediate valve means 121 is closed. An extension spool (not shown) is connected to the valve flange, this extension spool containing an unexpanded bridge plug. An inert gas or liquid cement pressure connection is made and the bridge plug is driven through into the production pipe 100 and expanded to block the pipe. Upward flow is thereupon diverted via the lowest assembly 122. Additional pressure may be applied behind the bridge plug via the secondary ball valves (see Figure 5) on the spool of intermediate valve means 121, and the insertion tool is withdrawn back into the extension spool.

The valve on the intermediate valve means is then closed.

At this time the flow has been diverted through the lower valve means 122, and the bridge plug has fully closed all upward discharge. Upper valve means 120 is now used to allow a core cutter to cut through into the production tube 100, following which cement is injected to fill the tubing above the bridge plug. The valves on all three valve means 120, 121, 122 may now be closed and blank flanges fitted.

This closes the well in anticipation of possible fitting of new wellhead equipment and workover. If desired, to continue production temporarily via lower valve means 122, a production choke of the CAMERON or similar type may be fitted to the valve on the lower valve means 122.

Referring to Figure 13, bridge plugs are fitted through to the outer face of the annulus casing. The lower valve means 122 allows the core cutter to cut into the annulus, after which the cutter equipment is withdrawn.

The valve is closed, and a production choke may be fitted and bypass connections made to a flare-off or to sand pit tanking. The upper valve means 120 is now core-drilled through the annulus tubing and a centering fork used to centre the drilling through the production tube to the opposite annulus casing face. The cutter is withdrawn and a hollow, thick-walled high tensile tube with relief holes therein is inserted to support the production pipe. Using the intermediate valve means 121, a large core cutter is inserted to cut the annulus casing and to cut through and sever the production pipe. The production pipe 100 cannot drop, as it is held by the tube fitted in upper valve means 120. The large core cutter is withdrawn from the intermediate valve means 121 and a bridge plug of the inflatable type or an expanding composition solid bridge plug is inserted through the intermediate valve means 121.

A hydraulic connection is made to the secondary ball valve of the spool of the intermediate valve means 121. The main valve of that valve means is closed and a blank flange fitted. The ball valve and choke of lower valve means 122 are now fully opened to ensure well pressure relief. Main and secondary valves of the upper valve means 120 are closed and the bridge plug is forced forward and inflated or forcibly compressed through intermediate valve means 121 to close the upward well discharge. When upward discharge from the production pipe has ceased, the pressure on the bridge plug is locked to maintain the seal and the upper valve means is opened. Cement is pumped through the hollow tube supporting the upper section of the production pipe 100.It is then possible either to maintain temporary production through the lower valve means 122 and the choke, or shut and blank all the valves on all three valves to await workover.

Referring to Figure 14, a choke 141, of the CAMERON type, is in position at the lower assembly 122. In this instance the procedure is similar to that described herein with reference to Figure 13. The lower valve means 122, after initial use to ease pressure during the bridge plug expansion to close the well, is now connected to a pressurised brine or control mud supply. The brine or mud is forced into the annulus or production pipe to kill the well. The valves on the three valve means 120, 121, 122 are now closed and blank-flanged to await new wellhead equipment assembly and workover.

By use of the closed circuit television camera, the above operations may be remote-controlled if desired.

Suitable types of bridge plug will now be described with reference to Figure 15(a)-(f). Referring to Figure 15(a), a rubber balloon is inserted and inflated to provide a bridge plug. It will be appreciated that such a plug can only be used where the well pressure is virtually zero and so the plug of Figure 15(b) is sometimes used in which the rubber balloon is filled with cement. The advantage of filling the balloon with cement is that in the arrangement of Figure 15 (a) gas can leak from the balloon resulting in the balloon collapsing and the well opening to atmosphere.

Figure 15(c) shows a composition bridge plug made of rubber or elastomer material molded with laterally running KEVLAR threads. The plug is pushed into the production pipe or annulus, the pressure then increased to expand the plug to fill the well and the pressure locked on to keep the plug expanded. Such a KEVLAR plug may also be cement filled.

Figure 15(d) shows an alternative bridge plug in which the upper spool and valve have a steel shaft 154 is inserted having an apertured top opening 155 and a lower keyway 156 to ensure that the opening 155 is maintained upstream of the well. The shaft partially restricts the flow and diverts the well flow as described above. A hollow shoe tube 157 is inserted through the next lower spool and valve, the tube 157 having an angled opening 158 to produce a venturi effect above the opening 158.

Elastomer or rubber balls 159 are passed along the tube 157 and by virtue of pressure in the well and the venturi action, so the balls completely close gaps around the shaft 154 to close the well, the balls being deformed by well pressure. The upper shaft 154 then has cement 160 pumped therethrough to seal the well.

Figure 15(e) shows a snap valve bridge plug which has an end curved to correspond to the internal contour of the wellpipe and a cross slot 170 is provided into which are located two oppositely directed slidable metal wings having outer edges contoured to abut the inside of the wellpipe.

At 90 to the slots 170 is an aperture 171 to permit well pressure to act between the wings so that the wings are forced radially outwardly to seal with the inside of the wellpipe.

Figure 15(f) is similar to Figure 15(e) except that the slot 171 is not provided and instead a push rod 172 is provided to radially expand the wings into contact with the internal wellpipe surfaces.

Having described the invention, it will be understood that the present invention enables damage to a wellhead to be repaired or, for example a well fire to be extinguished, whilst maintaining the integrity of the well, i.e. without destroying the well strata. In this respect it is known in the prior art to pump cement down the well to the oil or gas strata which then necessitates a new well to be drilled. Such is of course extremely expensive and time consuming but by the present invention time and expense are saved.

For those skilled in the art it will be understood that the examples given of the method and equipment are not limited in use, various configurations can be used.

Additionally, as conditions at each well are likely to vary considerably the method steps and equipment can only be given in general outline.

Claims (19)

CLAIMS:

1. A method for well closure including the steps of: contacting by mounting three valve means on an outer casing of a well bore in axially spaced relationship with respect to the well bore, opening the lower valve means and passing a boring means therethrough, boring through the outer casing into the well bore, removing the boring means and connecting an oil/gas bypass means to said lower valve means for permitting oil/gas diversion, passing said boring means through the intermediate valve means and cutting through the well casing into the well bore, withdrawing the boring means and passing a bridge plug through the intermediate valve means to close the pipe above said lower valve means so that the flow from the well bore is diverted through the lower valve means, passing the boring means through the upper valve means to cut through the well casing into the well bore, withdrawing the boring means and passing cement through the upper valve means to fill the well pipe above the bridge plug.

2. A method as claimed in claim 1 wherein the well bore is the annulus around a production pipe and/or the production pipe.

3. A method as claimed in claim 1 or 2 wherein the bridge plug is filled with air or cement.

4. A method as claimed in any preceding claim wherein the bridge plug is made of rubber or elastomer having laterally running KEVLAR (RTM) threads.

5. A method as claimed in claim 1 wherein the bridge plug is formed by a shaft inserted through the upper valve means, said shaft having an apertured top and being arranged to partially restrict flow in the well bore, and a hollow tube is inserted through the next lower valve means, the tube having an angled upper opening to provide a venturi effect above said angled upper opening, and elastomer or rubber members are passed along the tube and by virtue of pressure in the well bore and the venturi action, so the said members completely close gaps around the shaft to close the well.

6. A method as claimed in claim 5 wherein cement is pumped through the upper valve means to seal the well.

7. A method as claimed in claim 1 wherein the bridge plug has an end curved to correspond to the internal contour of the well bore and a cross slot into which are located two oppositely directed slidable wings having outer edges contoured to abut the inside of the well bore, an aperture orthogonal to the slots is provided to permit well pressure to act between the wings so that the wings are forced radially outwardly to seal with the inside of the well pipe.

8. A method as claimed in claim 1 wherein the bridge plug has an end curved to correspond to the internal contour of the well pipe and a cross slot into which are located two oppositely directed slidable wings having outer edges contoured to abut the inside of the well bore, and a push rod is provided to radially expand the wings into contact with the internal surfaces of the well bore surfaces.

9. A method as claimed in any preceding claim wherein the region adjacent the outer casing is excavated so that the valve means are located beneath the substrate surface.

10. A method as claimed in claim 9 wherein the excavated surfaces are lined and overhead protection is provided.

11. An apparatus for well closure comprising three valve means located on a well bore in axially spaced relationship with respect to said well bore, an aperture selectably openable through each said valve means to the inside of said well bore, a bypass means connected to said axially lower valve means for withdrawing oil/gas therethrough and a well bore sealing means locatable through said upper valve means to close the well bore above said lower valve means.

12. An apparatus as claimed in claim 11 wherein the well bore is an annulus around a production pipe and/or the production pipe.

13. An apparatus as claimed in claim 11 wherein means are provided for blocking flow of gas or oil in the production pipe such as cement or a bridge plug formed by a rubber or elastomer balloon.

14. An apparatus as claimed in claim 13 wherein said blocking means is a balloon filled with cement or air.

15. An apparatus as claimed in claim 11 wherein a bridge plug is formed between two adjacent valve means, an upper one of the two adjacent valve means having a shaft therethrough, said shaft having an apertured top and being arranged to partially restrict flow in the well bore, a hollow tube inserted through the adjacent lower valve means, the tube having an opening angled upwardly to produce a venturi effect, and elastomer or rubber members maintained in position by virtue of the venturi action to close the gaps around the shaft for closing the well.

16. An apparatus as claimed in claim 11 wherein said sealing means is a bridge plug having a curved end to correspond to the internal contour of the well pipe and a cross slot at an end thereof into which are located two oppositely directed slidable wings having outer edges contoured to abut the inside of the well pipe, said wings being operatively linked to an aperture in said well plug whereby well pressure acting through said aperture between the wings forces the wings radially outwardly to seal with the inside of the well pipe.

17. An apparatus as claimed in claim 11 wherein the sealing means is a bridge plug having an end curved to correspond to the internal contour of the well pipe and a cross slot into which are located two oppositely directed slidable wings having outer edges contoured to abut the inside of the well pipe, and a push rod is provided to radially expand the wings into contact with the internal well pipe surfaces.

18. A method substantially as herein described with reference to, and as shown in, each of the embodiments of the invention shown in the accompanying drawings.

19. An apparatus substantially as herein described with reference to, and as shown in, each of the embodiments shown in the accompanying drawings.