Patent Application
20220298886
The present invention relates to a downhole tool for punching a hole in a casing wall and injecting a sealant from an interior space of the casing to an annulus around the casing. The invention further relates to a method of injecting a sealant in an annulus around a casing in a borehole.
In the art of drilling and construction of boreholes in the earth, it is a common practice to install casing. The casing is generally cemented into place in the borehole by filling an annulus around the casing with cement. Over time, micro annuli or cracks may form in or adjacent to the body of cement in the annulus, which may cause unwanted leaks in the cement. Leaks may also be a result of bad displacement or shrinkage.
U.S. Pat. No. 2,381,929 describes a tool for sealing off the space between the wall of a borehole and its casing. The tool is adapted to perforate the casing, and also to inject sealing material (such as conventional cement or another hydrating material) into the space between the wall of the borehole and the casing through the perforation or perforations formed therein. The tool uses a punch which is forced through the casing.
After injecting the sealing material through the perforation, the punch is drawn back into the casing perforation. The punch is held in place by means of a screw made of relatively small section, which is designed to break under a tensile stress which is less than that required to withdraw the punch from the casing. Accordingly, when a force is applied to restore the perforating and injecting means to its normal position, the screw will break, leaving the punch jammed in the casing.
The tool of U.S. Pat. No. 2,381,929 suffers from a number of drawbacks. One is that the tool must be capable of exercising a tensile force on the punch. Moreover, the punch has to be drawn back into the casing before the sealing material has cured or hardened. The most important drawback, however, is that the seal created by the punch jammed in the casing is not guaranteed to succeed. If the seal is insufficient, the sealing material will flow back into the casing and thus risk leaving empty space in the annulus.
In one aspect, there is provided a downhole tool for punching a hole in a casing wall and injecting a sealant from an interior space of the casing to an annulus around the casing, comprising:
In another aspect, there is provided a method of injecting a sealant in an annulus around a casing in a borehole, said method comprising:
The drawing figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements.
The person skilled in the art will readily understand that, while the detailed description of the invention will be illustrated making reference to one or more embodiments, each having specific combinations of features and measures, many of those features and measures can be equally or similarly applied independently in other embodiments or combinations.
Disclosed is a downhole tool for punching a hole in a casing wall and injecting a sealant from an interior space of the casing to an annulus around the casing. It makes use of a sting which can be forced through the casing wall from within the tool, to thereby perforate the casing wall. The sting can already be fit tightly in the casing wall, as the fluid channel is available for sealant injection. The sealant can then be injected trough a fluid channel provided within the sting, and into the annular space around the casing. A check valve keeps the sealant in the annular space, and the sting itself does not have to be repositioned to avoid any backflow of sealant.
The sting can thus fit tightly in the perforation, and leak paths between the sting and the casing wall can be minimized. An advantage of this tool is that it allows for curing or setting of the sealant without loss of casing integrity in case of a pressure differential. In fact, a better seal can be created as the tool allows for a compressive pre-stress on the sealant in the annulus.
The check valve may be configured in an internal cavity within the sting. This way the check valve mechanism is protected from the force the sting takes when perforating through the casing. The check valve itself is shielded from mechanical load during perforation, which guarantees its operation during injection.
In a preferred embodiment, a distal end of the sting, including the check vale, may be severed from the tool and left behind in the casing wall when the tool is retracted. This provides a significant time saving opportunity over systems which need to stay in place during the curing or setting process.
A simplified illustration of the tool is provided in
The tool comprises a housing 5, which extends around a longitudinal axis A. Sting 10 comprises a fluid channel 12. Fluid communication can be established through the fluid channel 12, from within the tool housing 5 to an exterior of the tool housing. A press device 14 acts on the sting 10, to force the sting 10 in a radially outward direction from the tool housing 5, away from the longitudinal axis A, and preferably transversely to the longitudinal axis A. The sting 10 may perforate the surrounding casing wall 7.
Suitably, the sting 10 is assembled of an injection tube 15 of which the bore functions as the fluid channel 12, surrounded by a punch sheath 17. The materials of which the injection tube 15 and the punch sheath 17 are formed may be tailored to their respective functions. The injection tube merely contains the sealant, but in use is exposed ro only a relatively low mechanical load. Aluminium, or a composite polymer, may be suitable choices as a material for the injection tube 15. The punch sheath 17 on the other hand is forced through the casing wall 7, and should preferably be made of a much harder material such as tungsten carbide for example. As the sting 10 combines the functions of a perforating punch and an injection tube, it may be referred to as a punch and inject tube.
The press device 14 suitably comprises a piston which can be hydraulically powered. The piston may be integral to the sting 10 or engage with the sting 10 as for example illustrated in
The force applied by the sting to the casing wall should be sufficient to essentially shear off a cylindrical piece from the casing wall. The shear force in theory equals the circumference around the perforation times the wall thickness times the shear strength of the material. When there is cement behind the casing the force should also be sufficient to displace or deform the cement.
While a hydraulic press device is suitable for this purpose, many other options exist including mechanical presses. The cylinder piston assembly is illustrated in a very basic form in
A check valve 20 is arranged in the fluid channel 12. The check valve 12 is suitably configured in an internal cavity within the sting 10, fully shielded from external mechanical loading. The check valve 20 allows fluid communication in a direction from within the tool housing 5 to the exterior of the tool housing 5, but blocks fluid flow in opposite direction. The fluid channel 12 is connectable to a source of fluid sealant (not shown) via a sealant line 16. In the example of
A stop body 19 may be provided, which moves with the sting 10 in the radially outward direction until the stop body 19 engages with an inside of the casing wall 7 when the downhole tool 1 is activated within the casing 3. Herewith a fixed predetermined maximum penetration depth of the sting 10 relative to the casing wall 7 is guaranteed, regardless of the location of the tool housing 5 within the casing 3.
The sting 10 suitably comprises a release section 26, to sever a distal end 24 of the sting 10 (on the right hand side of the drawing) from the tool housing. The check valve 20 is arranged in said distal end 24 of said sting 10. The release section 26 comprises a frangible zone which may be provided by for example pre-cuts into the punch sheath 17. As shown in
The release section 26 is suitably outside of the tool housing 5 when the sting 10 has been forced out of the tool housing 5. Suitably, the release section 26 is then partly inside the casing wall 7 and partly inside the casing bore, so that it can break or shear off at the first exposed interface between to neighboring reinforcement rings 28 within the casing bore. The reinforcement rings 28 may be made of the same material as the remainder of the punch sheath 17.
In operation, the tool may be used as follows. The punch and inject tool 1 may be traversed through the bore of the casing 3, to a suitable location where an injection of sealant is desired. The sting 10 is then forced outward in a radially outward direction from the tool housing 5, away from the longitudinal axis A, and preferably transversely to the longitudinal axis A. The casing wall 7 is perforated with the sting 10.
Subsequently, the sealant is injected from within the tool housing 5 to an exterior of the tool housing and into an annular space around the casing 3. The sealant passes from a source (which may be integrated into the housing 5 or external to the housing 5), through the fluid channel 12 defined by the sting 10 and through the check valve 20 arranged in said fluid channel 12. During this phase of the operation, the distal end 24 of the sting 10 is tightly held in place by the casing wall 7. No fluids are required to pass through the perforation between the sting 10 and the casing wall 7.
The sealant may be a multi component composition (suitably an epoxy system) or any other liquid material which is capable of gaining sufficiently high viscosity or solidify after injection to create an adequate seal.
Alternatively, the sealant may be a single component resin system, which hardens by reaction with a wellbore fluid, such as water or brine. Such single component resin systems are described in, for example, EP application No. 20159582.4 filed 26 Feb. 2020, the disclosure of which is incorporated herein by reference. A suitable single component resin can be a moisture-curable polyurethane resin.
When a sufficient amount of sealant has been injected, the distal end 24 of the sting 10 may be severed. The check valve 20 is arranged in the distal end 24 of the sting 10 and thus it also remains behind stuck in the casing wall 7. The tool 1 may then be retracted through the bore of the casing 3, while leaving the distal end 24 behind. The sealant can then be left to cure or otherwise harden while the tool is already retrieved and prepared for a next round of operation.
The person skilled in the art will understand that the present invention can be carried out in many various ways without departing from the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19174667.6 | May 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/063116 | 5/12/2020 | WO |
