The present invention relates to a perforating tool for perforating a downhole well casing and relates to a packer apparatus for providing an annular seal in a downhole well bore. The present invention relates particularly, but not exclusively to a downhole work string incorporating such a perforating tool and/or packer apparatus and to a method of completion of a hydrocarbon well using such a work string.

In most oil and gas wells, steel casing is run through the productive zone as a conduit to keep the formation from breaking down and falling into the well bore. In order to produce oil and/or gas from the well, the casing must be perforated so the producing fluid can enter the well bore and be extracted. The most common technique for perforating a well casing is to use explosives and blow holes in the casing at predetermined intervals. However, it is desirable to be able to perforate a well casing in a more controlled and reliable manner.

It is also desirable to provide a reliable and repeatable method of fracturing formations to enable the production of oil and gas once the well casing has been perforated. To accomplish this, it is desirable to provide a packer apparatus that enables sections of perforated well casings to be reliably isolated and sealed to enable hydraulic fracturing to take place.

Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.

According to an aspect of the present invention, there is provided a perforating tool for perforating a downhole well casing, the tool comprising:

a body arranged to be disposed in a well casing and at least one cutter block moveable relative to the body between an inwardly retracted condition and an outwardly deployed condition to cut a perforation in the well casing;

an activation member disposed in the body, wherein the activation member is moveable relative to the body to move at least one said cutter block between the inwardly retracted condition and the outwardly deployed condition relative to the body;

a plurality of pistons arranged to move the activation member relative to the body, each said piston being disposed in a respective pressure chamber; and

wherein the activation member defines a bore disposed along a longitudinal axis of the body, and wherein a plurality of ports are formed in the activation member to enable fluid to flow from the bore to each said pressure chamber such that an increase in fluid pressure in the body increases fluid pressure in each said pressure chamber to move each of the plurality of pistons relative to the body and cause the activation member to move relative to the body.

This provides the advantage of a perforating tool that can be used to reliably cut perforations through a well casing. This is advantageous because when a casing has been placed in a well bore, and particularly in long horizontal well bores through tight formations, there is generally only a very small diameter, usually less than 4 inches, available for a downhole tool. As a result, there is a lack of hydraulic working area available in the downhole tool to provide a force for moving parts to operate.

Consequently, providing a plurality of pistons arranged to move the activation member relative to the body, each said piston being disposed in a respective pressure chamber arranged to be filled with fluid in response to an increase in fluid pressure in the body to move each of the plurality of pistons relative to the body and cause the activation member to move relative to the body increases the force available to the operator which provides a tool capable of perforating a well. This therefore enables the operator to use a downhole tool rather than explosives to perforate the well casing during completion operations.

By providing an activation member defining a bore disposed along a longitudinal axis of the body, and wherein a plurality of ports are formed in the activation member to enable fluid to flow from the bore to each said pressure chamber, this also provides a compact arrangement that can fit in the limited confines of a well casing to enable a plurality of pressure chambers to be operated to increase the force available to the operator for a given fluid pressure.

In a preferred embodiment, each said piston is disposed concentrically around the activation member.

This provides the advantage of helping to enable location of a plurality of pressure chambers in a downhole tool usable in small diameter well casings to increase working force available to the operator.

In preferred embodiment, each said pressure chamber defines an annular chamber arranged concentrically around the activation member.

This provides the advantage of helping to enable location of a plurality of pressure chambers in a downhole tool usable in small diameter well casings to increase working force available to the operator.

Each said pressure chamber may further comprise a stationary seal ring to provide a seal with the body for the respective pressure chamber.

The tool may further comprise a plurality ofannularannularly arrangedpressure ports formed through the body adjacent each said pressure chamber to enable each said piston to move relative to the body.

In a preferred embodiment, at least one said cutter block is slidably moveable along an inclined track to be moveable between the inwardly retracted condition and outwardly deployed condition, wherein the inclined track is inclined relative to a longitudinal axis of the body such that pulling the tool upwardly out of the well casing in which it is located pushes at least one said cutter block into the inwardly retracted condition.

This provides the advantage of minimising the likelihood of the perforating tool becoming stuck in the well casing. Since the action of pulling the perforating tool out of the well will push the cutter blocks along the inclined tracks and inwardly into the body, there is little chance that the perforating tool will become stuck with the cutter blocks in the outwardly deployed condition. This also provides the advantage that the cutter blocks can be manufactured with a relatively large length. This enables large perforations to be made in the well casing and could therefore prevent the requirement to pump acid down the well bore to break down casing cement after a perforation operation.

In a preferred embodiment, the tool further comprises at least one drive member disposed on the activation member to push at least one said cutter block along the inclined track in response to movement of the activation member.

The tool may further comprise a floating piston disposed in the bore, wherein the bore is filled with oil or another working fluid and the floating piston is moveable in the bore to change the pressure of the oil or other working fluid to cause movement of the activation member.

This provides the advantage that if the perforating tool is used in a work string that conducts hydraulic fracturing operations of the formation in which the well casing is located, the floating piston prevents fracturing sand and debris from entering the internal diameter of the perforating tool. This keeps the internal diameter of the perforating tool relatively clean and reduces the likelihood of malfunction as a result of debris interfering with the internal moving parts of the perforating tool.

According to another aspect of the present invention, there is provided a method of perforating a well casing, the method comprising use of a perforating tool as defined above to form a plurality of perforations through a well casing in use.

According to another aspect of the present invention, there is provided a downhole work string comprising:

a perforating tool as defined above; and

at least one cup tool disposed in the work string at a location above the perforating tool in use.

This provides the advantage that the work string can first be used to perforate the well casing and the string can then be lowered to position the cup tool or tools below the perforated section of well casing. With the work string in this position, high pressure pumping of hydraulic fracturing fluid can be commenced from the surface either between the casing and the work string in an annular configuration, or if a second cup tool is used, through the internal diameter of the work string using a ported sub to conduct a hydraulic fracturing operation.

This also provides the advantage that if the pumping pressure is high enough, the cutter blocks of the perforating tool will be deployed into the well casing to anchor the work string in position during the fracturing operation. This enables the isolation of a well bore that is exposed to high pressure and might therefore reduce the amount of fracturing fluid required. Consequently, it can be seen that this provides a highly advantageous work string that simplifies completion operations.

According to another aspect of the present invention, there is provided a downhole work string comprising:

a perforating tool as defined above; and

at least one packer apparatus disposed in the work string at a location above the perforating tool in use.

This provides the advantage that the work string can first be used to perforate the well casing and the string can then be lowered to position the at least one packer apparatus below the perforated section of well casing. With the work string in this position, high pressure pumping of hydraulic fracturing fluid can be commenced from the surface either between the casing and the work string in an annular configuration, or if a second packer apparatus is used, through the internal diameter of the work string using a ported sub to conduct a hydraulic fracturing operation.

This also provides the advantage that if the pumping pressure is high enough, the cutter blocks of the perforating tool will be deployed into the well casing to anchor the work string in position during the fracturing operation. This enables the isolation of a well bore that is exposed to high pressure and might therefore reduce the amount of fracturing fluid required. Consequently, it can be seen that this provides a highly advantageous work string that simplifies completion operations.

According to another aspect of the present invention, there is provided a method of completion of a hydrocarbon well in which a well casing has been disposed, the method comprising:

use of the perforating tool of a work string as defined above to form a plurality of perforations through the well casing in use;

lowering the work string to position at least one said cup tool or packer apparatus adjacent the plurality of perforations; and

pumping fracturing fluid down the hydrocarbon well to fracture the formation in use.

According to another aspect of the present invention, there is provided a packer apparatus for providing an annular seal in a downhole well casing or an open borehole, the apparatus comprising:

a body arranged to be disposed in a well casing;

an activation member mounted to the body, wherein the activation member is moveable relative to the body to deform an elastomeric packer element outwardly relative to the body to form an annular seal in a well casing in use; and

a plurality of pistons arranged to move the activation member relative to the body, each said piston defining a respective pressure chamber arranged to be filled with fluid in response to an increase in fluid pressure in the body to move each of the plurality of pistons relative to the body and cause the activation member to move relative to the body.

This provides the advantage of a packer apparatus that has a deformable elastomeric packer element that is deformable outwardly to form an annular seal in a well casing for use in fracturing operations and the like.

By providing a plurality of pistons arranged to move the activation member relative to the body, wherein each said piston defines a respective pressure chamber arranged to be filled with fluid in response to an increase in fluid pressure in the body to move each of the plurality of pistons relative to the body, this provides the advantage that the force that can be exerted on the packer element can be increased, particularly in casings having a small diameter, to ensure a reliable seal is formed. This helps to ensure packer seal integrity.

In a preferred embodiment, the body comprises a cylindrical member having an internal bore defining a longitudinal axis, and wherein each said piston is mounted concentrically to the body such that a plurality of ports formed in the body enable fluid to flow from the bore to each said pressure chamber.

This provides the advantage that the apparatus is modular and that further pistons can be added if more force is required. By mounting the pistons concentrically on the cylindrical body, it is actually the outer housing of the tool that moves relative to the body and further pistons can be stacked on the body if more force is required. This provides a versatile and adaptable packer apparatus.

In a preferred embodiment, each said pressure chamber defines an annular chamber arranged concentrically around the body.

This provides the advantage of providing a compact arrangement.

Each said pressure chamber may further comprise a stationary seal ring to provide a seal with the body for the respective pressure chamber.

The activation member may comprise a ramp adapted to slide under and deform outwardly a portion of said elastomeric packer element.

According to another aspect of the present invention, there is provided a method of providing an annular seal in a well casing or an open borehole, the method comprising use of a packer apparatus as defined above.

According to another aspect of the present invention, there is provided a downhole work string comprising:

a perforating tool as defined above; and

at least one packer apparatus as defined above disposed in the work string at a location above the perforating tool in use.

This provides the advantage that the work string can first be used to perforate the well casing and the string can then be lowered to position the at least one packer apparatus below the perforated section of well casing. With the work string in this position, high pressure pumping of hydraulic fracturing fluid can be commenced from the surface either between the casing and the work string in an annular configuration, or if a second packer apparatus is used, through the internal diameter of the work string using a ported sub to conduct a hydraulic fracturing operation.

This also provides the advantage that if the pumping pressure is high enough, the cutter blocks of the perforating tool will be deployed into the well casing to anchor the work string in position during the fracturing operation. This enables the isolation of a well bore that is exposed to high pressure and might therefore reduce the amount of fracturing fluid required. Consequently, it can be seen that this provides a highly advantageous work string that simplifies completion operations.

According to a further aspect of the present invention, there is provided a method of completion of a hydrocarbon well in which a well casing has been disposed, the method comprising:

use of the perforating tool of a work string as defined above to form a plurality of perforations through the well casing in use;

lowering the work string to position at least one said packer apparatus adjacent the plurality of perforations; and

pumping fracturing fluid down the hydrocarbon well to both activate the packer apparatus to form an annular seal in the well and fracture the formation in use.

Preferred embodiments of the present invention will now be described, by way of example only, and not in any limitative sense, with reference to the accompanying drawings in which:

FIG. 1ais a longitudinal cross-sectional view of a perforating tool of a first embodiment of the present invention showing the cutter blocks in the inwardly retracted condition;

FIG. 1bis a longitudinal cross-sectional view of the perforating tool ofFIG. 1ashowing the cutter blocks in the outwardly deployed condition;

FIG. 2ais a side view of the perforating tool ofFIGS. 1a and 1bshowing the cutter blocks in the inwardly retracted condition;

FIG. 2bis a side view of the perforating tool ofFIGS. 1a and 1bshowing the cutter blocks in the outwardly deployed condition;

FIG. 3ais a perspective view of the perforating tool ofFIGS. 1a and 1bshowing the cutter blocks in the inwardly retracted condition;

FIG. 3bis a perspective view of the perforating tool ofFIGS. 1a and 1bshowing the cutter blocks in the outwardly deployed condition;

FIG. 4is an end-on view of the perforating tool ofFIGS. 1a and 1bshowing the cutter blocks in the outwardly deployed condition;

FIG. 5ais a longitudinal cross-sectional close-up of the valve assembly of theaperforating tool ofFIGS. 1 to 4;

FIG. 5bis a perspective cross-sectional view corresponding toFIG. 5a;

FIG. 6ais a longitudinal cross-sectional close-up of the return spring assembly and drive member of the perforating tool ofFIGS. 1a and 1b;

FIG. 6bis a perspective view corresponding toFIG. 6a;

FIG. 7ais a longitudinal cross-section of the perforating tool ofFIG. 1acomprising a floating piston;

FIG. 7bis a longitudinal cross-section corresponding toFIG. 7ashowing the movement of the floating piston to deploy the cutter blocks;

FIG. 8is a side view of a cup tool;

FIG. 9is a longitudinal cross-section of a perforated well casing showing the cup tool ofFIG. 8disposed in a work string;

FIG. 10ais a longitudinal cross-section of a work string comprising the perforating tool ofFIGS. 7a and 7blocated below a cup tool in a perforated well casing;

FIG. 10bis a longitudinal cross-section corresponding toFIG. 10ain which the cutter blocks are deployed outwardly to perforate the well casing and provide an anchor for the work string in the well casing;

FIG. 11is a longitudinal cross-section of a work string using two cup tools to enable hydraulic fracturing to be performed through the internal diameter of the work string;

FIG. 12is a cross-sectional perspective close-up view of the two cup tools located in the work string ofFIG. 11;

FIG. 13is a longitudinal cross-section corresponding toFIG. 12;

FIG. 14ais a longitudinal cross-section of a packer apparatus for providing an annular seal in a well casing in which the elastomeric packer element is shown in the undeformed condition;

FIG. 14bis a longitudinal cross-section of the packer apparatus ofFIG. 14bin which the packer element is deformed outwardly;

FIG. 15ais a side view of the packer apparatus in the condition ofFIG. 14a;

FIG. 15bis a side view of the packer apparatus in the condition ofFIG. 14b;

FIG. 16ais a perspective cross-section corresponding toFIG. 14a;

FIG. 16bis a perspective view of the packer apparatus showing the packer element deformed outwardly;

FIG. 17is a longitudinal cross-section of a work string in which the perforating tool ofFIGS. 7a and 7band two packer apparatuses ofFIGS. 14 to 16are incorporated;

FIG. 18is a longitudinal cross-sectional view of the packer apparatuses of the work string ofFIG. 17showing a ported sub for use in fracturing operations;

FIG. 19ais a longitudinal cross-sectional view of a section of work stringuserusingtwo packer apparatuses in a well drilled in an open formation;

FIG. 19bis a longitudinal cross-sectional view corresponding toFIG. 19ain which the packer elements are deformed outwardly to form a seal in the open formation;

FIG. 20ais a longitudinal cross-sectional view of a second embodiment of a packer apparatus;

FIG. 20bis a longitudinal cross-sectional view of a packer apparatus ofFIG. 20ashowing the packer element deformed outwardly;

FIG. 21is a perspective cross-section corresponding toFIG. 20a; and

FIG. 22is a perspective cross-section corresponding toFIG. 20b.

