GB2520494A

GB2520494A - Method and apparatus for sealing a subterranean bore-hole

Info

Publication number: GB2520494A
Application number: GB1320490.4A
Authority: GB
Inventors: Peter James
Original assignee: Cintec International Ltd
Current assignee: Cintec International Ltd
Priority date: 2013-11-20
Filing date: 2013-11-20
Publication date: 2015-05-27
Also published as: GB201320490D0

Abstract

A method of sealing a borehole includes inserting an extraction pipe 14 into the borehole. The pipe 14 has a sleeve 16 which covers an outer portion of the pipe 14 and a settable slurry is introduced into the sleeve 16 to cause expansion of the sleeve 16 away from the outer surface of the pipe 14 towards the wall of the borehole. The sleeve 16 is permeable to the slurry to allow liquid to seep through, and to substantially seal the pipe 14 to the borehole along a portion of the outer surface of the pipe 14.

Description

METHOD AND APPARATUS FOR SEALING A SUBTERRANEAN BORE-HOLE

The present invention relates to a method and an apparatus for sealing a subterranean bore-hole and particularly, but not exclusively, to a method and an apparatus for sealing a subterranean bore-hole to minimise any cross-contamination of subterranean fluids.

The extraction of oil and gas principally involves drilling a subterranean bore-hole to the oil or gas reserve is location. Once the bore-hole is created, there is a risk that the gas and/or oil and/or other fluid disposed at various subterranean strata may enter the bore-hole and traverse the hole leading to a cross-contamination of subterranean fluids.

In the process of tracking for example, there is a risk that the shale gas which is forced to escape from the subterranean rocks may enter the water table and thus lead to a contamination of drinking water.

We have now devised a method and apparatus for sealing a subterranean bore-hole to minimise any cross-contamination of subterranean fluids.

In accordance with a first aspect of the present invention, there is provided a method of sealing a subterranean bore-hole to minimise any cross-contamination of subterranean fluids, the method comprising the steps of: -inserting an extraction pipe, for the extraction of a subterranean fluid, into the bore-hole through an open end toward a distal end of the hole, the pipe comprising a sleeve which extends over at least a portion of an outer surface of the pipe and which is securable at a distal end thereof to an outer surface of the pipe; -introducing a settable slurry into the sleeve to cause expansion of the sleeve away from an outer surface of the pipe toward the wall of the bore-hole, the sock being formed from a material which is permeable to the slurry to allow the liquid to seep through the sock, to substantially seal the pipe to the bore-hole along at least a portion of the outer surface of the pipe.

In an embodiment, the settable slurry is introduced into the sleeve to cause the sock to expand toward the wall of the bore-hole, in a direction which is from a distal end of the bore-hole to the proximal end of the bore-hole.

In a further embodiment, the method further comprises reducing a pressure in the bore-hole whilst said introducing step is taking place, to encourage the slurry to seep through the sleeve, to substantially fill the space between the extraction pipe and the bore-hole. The pressure may be reduced by inserting a vacuum pipe into the bore-hole for the removal of air therein.

In an embodiment, the vacuum pipe extends within the bore-hole and is arranged to reduce the pressure outside of the sleeve compared with inside of the sleeve, from a first pressure to a second pressure thereby creating a pressure differential between the outside of the sleeve and the inside of the sleeve to cause a flow of the settable slurry from the inside of the sleeve to the outside of the sleeve, and to inhibit pressure build-up in the sleeve as the slurry is introduced.

The method may further comprise sealing the open end of the bore-hole, such as with a plug, to maintain a reduced pressure within the bore-hole.

In accordance with a second aspect of the present invention, there is provided apparatus for sealing a subterranean bore-hole having, to minimise any cross-contamination of subterranean fluids, the apparatus comprising an extraction pipe for the extraction of a subterranean fluid and a sleeve which extends over at least a portion of an outer surface of the pipe and which is securable at a distal end thereof to an outer surface of the pipe, the sleeve being arranged to receive a settable slurry for sealing at least a portion of the outer surface of the pipe to the bore-hole.

In an embodiment, the apparatus further comprises a plurality of injection pipes disposed along an outer surface of the extraction pipe for introducing the settable slurry into the sleeve. The injection pipes preferably extend to different positions along the extraction pipe for selectively introducing the slurry into the sleeve at different locations along the pipe.

The settable slurry may comprise a micro-concrete, such that the concrete can cause the sleeve to expand to fill any holes and/or bridge cavities along the bore-hole, and thus compact and bond the extraction pipe to the wall of the bore-hole. In an embodiment, the extraction pipe is formed of stainless steel.

Preferably, the sleeve is expandable and is preferably formed of Kevlar®.

In a further embodiment, the apparatus further comprises at least one vacuum pipe which extends into the bore-hole. The apparatus may further comprise a plug, which is arranged to seal the open end of the bore-hole to the outer surface of the pipe, to maintain a reduced pressure within the bore-hole.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure la is a schematic illustration of a cross-section of an apparatus for sealing bore-hole according to an embodiment of the present invention; Figure lb is a schematic illustration of the apparatus illustrated in figure 1 a, located within a bore hole; Figure 2a is a flow chart sequencing the steps associated with a method of sealing a bore-hole according to a first embodiment of the present invention; and, Figure 2b is a flow chart sequencing the steps associated with a method of sealing a bore-hole according to a second embodiment of the present invention.

Referring to figures la and lb of the drawings, there illustrated an apparatus 10 foi sealing a subterranean bore-hole 12 having an open proximal end 12a and a distal end 12b, to minimise any doss-contamination of subterranean fluids (not shown). The appalatus 10 comprises an extraction pipe 14 which may be formed of stainless steel, which is arranged to extend within the boie-hole 12 and as such comprises an outer diameter which is less than the diameter of the boie-hole 12. The pipe 14 complises an expandable sleeve 16, which may be formed of Kevlar® and which extends around an outer surface of the pipe 14, along at least a portion of the length of the extraction pipe 14. In an embodiment, the sleeve 16 is securable to a distal end of an outer surface of the pipe 14, along a circumference thereof, using a clip 18 or other suitable fastener, for example. In a further embodiment however, the sleeve 16 may be rigidly secured to the extraction pipe 14 via a weld or adhesive (not shown), for example.

The apparatus 10 fuithei comprises a plurality of injection pipes 20a-c which extend along the length of the extraction pipe 14 for introducing a seftable slurry (not shown), such as a micro-concrete into the bore-hole 12 into the sleeve 16, namely between the sleeve 16 and the outer surface of the extraction pipe 14. The injection pipes 20a-c extend from a proximal end of the extiaction pipe 14, and terminate at different distances along the length of the extraction pipe 14, so that the slurry may be selectively introduced into the sleeve 16, at different locations along the extraction pipe 14.

Bore-holes 12 formed for the extraction of subterranean fluids are typically formed by drilling the earth and the diameter of the drill core (not shown) used to form the hole 12 is selected to be larger than the outer diameter of the extraction pipe 14. Referring to figure 2a of the drawings, there is illustrated a flow chart sequencing the steps of a method bOa of subsequently sealing the bore-hole 12 to minimise any cross-contamination of subterranean fluids, such as oil, water and gas, according to a first embodiment of the present invention.

The method 100 complises inserting the pipe 14 comprising the sleeve 16 into the bore-hole 12 at step 110 thiough the open proximal end 12a theieof so that a distal portion of the extraction pipe 14 becomes suitably located along the length of the bore-hole 12. A settable slurry is then pumped from a slurry source (not shown) via a pumping arrangement (not shown) into one or more of the injection pipes 20 for introducing the slurry into the sleeve 16 at step 120. In this embodiment, the slurry is first introduced at a distal location within the bore-hole 12 and then at progressively more proximal locations toward the open end 12a of the bore-hole 12, by switching the supply of the slurry to different injection pipes 20a-c via a switching arrangement (not shown) at step 130. This introduction of the slurry into the bore-hole 12 according to this sequence is found to minimise any trapping of air pockets within the sleeve 16, and the bore-hole 12, by squeezing the air within the bore-hole 12 toward the open end 12a of the bore-hole 12.

As the slurry is introduced into the sleeve 16, the sleeve 16 is forced to expand and contact the wall of the bore-hole 12. As further slurry is introduced the sleeve 16 further expands into holes (not shown) along the length of the wall of the bore-hole 12 and bridges any cavities (not shown) formed therein, so that the extraction pipe 14 becomes sealed to the wall of bore-hole 12. The slurry further bonds the extraction pipe 14 within the bore-hole 12 to provide for a secure extraction of subterranean fluids therealong. In an embodiment, the sleeve 16 may be permeable to the slurry, such that the slurry can pass out from the sleeve 16 to contact the wall of the bore-hole 12 to further improve the sealing ability.

In a second embodiment, as illustrated in figure 2b of the drawings, the method lOOb further comprises applying a vacuum within the bore-hole 12 as the slurry is introduced to further encourage the expansion of the sleeve 16 and thus the passage of the slurry, toward the wall of the bore-hole 12. In this embodiment, the open end 12a of the bore-hole 12 is first sealed with a plug 22 at step 111 and a vacuum pump (not shown) is used to evacuate air from within the bore-hole 12, via a vacuum pipe 24 which extends into the bore-hole, at step 112. Accordingly, once the plug 22 has been fitted, the slurry is introduced into the sleeve 16 via the injection pipes 20 at step 120 and the slurry which emerges from the injection pipes subsequently fills the sleeve 16 so that the sleeve 16 expands, eventually to make contact with the wall of the bore-hole 12. At the same time the vacuum pump (not shown) evacuates air from within the bore-hole 12 via the vacuum pipe 24 to reduce the air pressure within the bore-hole 12 to further improve the seepage of the slurry through the fabric of the sleeve 16. The vacuum pipe 24 further inhibits any undesirable build-up of pressure in the hole 12.

In this second embodiment, the sleeve 16 is arranged to fill with slurry in a direction which is toward the location of the open end 24a of the vacuum pipe 24 within the bore-hole 12. Accordingly, in situations where the open end 24a of the vacuum pipe 24 is located at a distal end of the extraction pipe 14, the slurry is arranged to fill the sleeve 16 in a direction which is toward the distal end of the extraction pipe 14, rather than toward the proximal end of the extraction pipe 14, as described in connection with the first embodiment.

In either of the above described embodiments, one the sleeve 16 has been filled with the slurry, the injection pipes 20 and, where necessary, the vacuum pipe 24 are removed at step 140 and the slurry is allowed to set at step 150. Once the slurry has set, the extraction pipe 14 becomes securely positioned within the bore-hole 12 and sealed within the hole 12, such that subterranean fluids cannot leak into the bore-hole 12 and pass to different subterranean strata resulting in a cross-contamination of subterranean fluids. From the foregoing therefore is it evident that the above described method and apparatus provide for a simple yet effective sealing of subterranean bore-holes.