FIELD

The present invention relates to a system and method for plugging a well extending into a hydrocarbon bearing formation with a plug and pressure testing the plug after it has been set.

BACKGROUND

Oil and gas wells can generally either be production wells where hydrocarbons are produced and brought to the surface; injection wells where water, or other liquids or gas is injected into the well to boost reservoir pressure or for depositing fluids in the well; or exploration wells where hydrocarbon bearing formations are explored.

In all three types of wells, it is commonly required to set plugs inside the well tubulars to act as well barriers. A well barrier in intended to prevent the flow of hydrocarbons and contributes to well integrity and safety. Plugs that are set to act as well barrriers may be installed permanently or temporarily for a certain period of time.

An oil and gas well is constructed by drilling a long, relatively narrow, hole into a hydrocarbon bearing reservoir, using a drill bit attached to the end of drill pipe extending sometimes thousands of kilometres deep into the ground. Once the wellbore has been drilled, sections of tubular steel, casing or liner are inserted into the wellbore to strengthen the wellbore and prevent collapsing of the wellbore. Cement is injected between the outside of these tubulars and the wellbore and tubing is run to connect the wellbore to the surface, thereby allowing a path for the hydrocarbons to be extracted from the hydrocarbon bearing formation. For ease of reference, all of the above- mentioned tubulars, including the sections of tubular steel, casing sections, liner sections and tubing sections, are herein referred to as “tubulars”.

When a plug is set inside a tubular to act as a well barrier, once the plug has been set it is necessary to verify that the plug forms a sufficiently pressure-tight seal across the tubular. If the plug is not set properly such that it can withstand positive or negative pressures across it, the plug may become a serious liability with grave consequences if the plug fails in use. Currently, plugs are typically run into the well on wireline and set at their desired depth. A pressure testing tool may then be run into the well to perform a pressure test on the plug to ensure the integrity of the plug.

The journey taken by equipment from the surface to the point at which the equipment is used in the well is known as a trip. The time taken to perform a trip, either into or out of the wellbore, is extremely expensive, and there is a constant strive to making tripping of equipment faster or more efficient, which would greatly reduce cost.

Many efforts have been made in the prior art to trip more efficiently, or to make fewer trips to reduce costs.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow.

Patent document WO2018/068154 A 1 discloses a well abandonment tool comprising an elongate housing extending between top and bottom ends locatable within a wellbore having a longitudinal pumping cylindrical bore therein. The apparatus further comprises a wellbore seal located around the housing operable to engage upon the wellbore and to be expanded into contact therewith upon an upward motion of the housing so as to seal an annulus between the housing and the wellbore and a bridge plug engagement connector adapter to secure a bridge plug thereto at a position below the bottom end of the housing.

Patent document US2019/0284898A1 discloses a method of setting tandem releasable bridge plug system in a casing including assembling a tandem bridge plug string including a lower bridge plug and an upper bridge plug.

Patent document GB2555637A discloses methods and device for plug placement and verification in a well. This includes placing the tool at the formation to be plugged, inflating an expandable packer beneath the formation and then delivering plugging material, i.e. cement, above the packer to form the plug. There is a pressure sensor mounted under the packer, there may also be a temperature sensor above the packer.

SUMMARY

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention. According to a first aspect of the invention, there is provided a plug delivery and pressure test tool for delivering a plug to a wellbore or tubular and pressure testing the plug in a single trip, the tool comprising: an uphole end and a downhole end; a sealing element; a pressure adjustment means; and a plug attachment means located at or near the downhole end; wherein the plug attachment means is configured to carry a selectively expandable plug to a desired location in the wellbore or tubular and selectively release the plug from at or near the downhole end of the tool; the sealing element is configured to seal against an internal surface of the wellbore or tubular in use, thereby creating an isolated volume in use, between the sealing element and the plug; and the pressure adjustment means is configured to decrease the pressure in the isolated volume by moving fluid from the isolated volume to an upper fluid volume above the sealing element to create an underbalance in the isolated volume, thereby negatively pressure testing the plug in use.

The pressure adjustment means may be configured in use to adjust the pressure in the isolated volume by moving fluid from the upper fluid volume above the sealing element to the isolated volume to create an overbalance in the isolated volume, thereby positively pressure testing the plug.

The pressure adjustment means may be a pump or a piston or a pressure adjustment chamber.

The sealing element may be an expandable or conformable packer.

The sealing element may be expandable from a collapsed configuration to an expanded configuration, wherein in the collapsed configuration the sealing element is configured to be run into a wellbore or tubular without forming a seal with the internal surface of the wellbore or tubular, and in the expanded configuration the sealing element is configured to form a seal with the internal surface of the wellbore or tubular.

The tool may further comprise: a fluid inlet port; and a fluid outlet port; wherein the fluid inlet port is located between the sealing element and the plug attachment means, and is in fluid communication with the pressure adjustment means, and the fluid outlet port is located between the sealing element and the uphole end of the tool, and is in fluid communication with the pressure adjustment means.

Alternatively, the tool may further comprise: a fluid inlet port; and a fluid outlet port; wherein the fluid outlet port is located between the sealing element and the plug attachment means, and is in fluid communication with the pressure adjustment means, and the fluid inlet port is located between the sealing element and the uphole end of the tool, and is in fluid communication with the pressure adjustment means.

Alternatively, the tool may further comprise: a first fluid inlet and outlet port; and a second fluid inlet and outlet port; wherein the first fluid inlet and outlet port is located between the sealing element and the plug attachment means, and is in fluid communication with the pressure adjustment means, and the second fluid inlet and outlet port is located between the sealing element and the uphole end of the tool, and is in fluid communication with the pressure adjustment means.

The tool may further comprise: an upper pressure sensor configured to measure a pressure in the wellbore or tubular between the sealing element and the uphole end of the tool or at the uphole end of the tool in use, and/or; an intermediate pressure sensor configured to measure a pressure in the isolated volume in use.

The plug attachment means may comprise a shear pin and/or electromechanical latch and/or hydraulic locking mechanism.

The plug attachment means may be configured in use to selectively reattach the plug at or near the downhole end of the tool and carry the plug to a desired location in the wellbore or tubular.

The tool may further comprise a tubing cutter configured to selectively cut a tubular.

The tool may further comprise a tubing puncher configured to selectively form at least one aperture in a tubular.

According to a second aspect of the invention, there is provided a system for delivering and pressure testing a plug in a wellbore or tubular in a single trip, the system comprising: a tool according to the first aspect of the invention; a selectively expandable plug; wherein the plug is configured to be releasably attached to the plug attachment means in use.

The plug may be configured to seal against an internal surface of the wellbore or tubular in use, thereby creating a pressure tight seal.

The plug may be an expandable or conformable packer.

The plug may be expandable from a collapsed configuration to an expanded configuration, wherein in the collapsed configuration the plug is configured to be run into a wellbore or tubular without forming a seal with the internal surface of the wellbore or tubular, and in the expanded configuration the plug is configured to form a seal with the internal surface of the wellbore or tubular. The plug may be configured to be reattachable to the tool in use after the plug has been released from the tool.

The plug may comprises a lower pressure sensor configured to measure a pressure in the wellbore or tubular below the plug in use.

The system may further comprise a tubing cutter configured to selectively cut a tubular.

The system may further comprise a tubing puncher configured to selectively form at least one aperture in a tubular.

According to a third aspect of the invention, there is provided a method of assembling a system for delivering a plug to a wellbore and performing a pressure test on the plug in a single trip, comprising the steps of: providing a tool according to the first aspect of the invention; providing a selectively expandable plug configured to be releasably attached to the plug attachment means of the tool; and releasably attaching the plug to the plug attachment means.

According to a fourth aspect of the invention, there is provided a method of setting and pressure testing a plug in a single trip, comprising the steps of: providing a system according to the second aspect of the invention; releasably attaching the plug to the plug attachment means; running the system into a wellbore or tubular to a desired location in the wellbore or tubular; moving the plug to the expanded configuration to form a pressure tight seal in the wellbore or tubular; releasing the plug from the plug attachment means; lifting the tool uphole in the wellbore or tubular; moving the sealing element to the expanded configuration to form a pressure tight seal in the wellbore or tubular, thereby creating an isolated volume; and activating the pressure adjustment means to decrease the pressure in the isolated volume, thereby pressure testing the plug.

According to a fifth aspect of the invention, there is provided a method of pressure testing and setting a plug in a single trip, comprising the steps of: providing a system according to the second aspect of the invention; releasably attaching the plug to the plug attachment means; running the system into a wellbore or tubular to a desired location in the wellbore or tubular; moving the plug to the expanded configuration to form a pressure tight seal in the wellbore or tubular; moving the sealing element to the expanded configuration to form a pressure tight seal in the wellbore or tubular, thereby creating an isolated volume; activating the pressure adjustment means to decrease the pressure in the isolated volume, thereby pressure testing the plug; and releasing the plug from the plug attachment means.

According to the sixth aspect of the invention, there is provided a method of pressure testing and setting a plug in a single trip, comprising the steps of: providing a system according to the second aspect of the invention; releasably attaching the plug to the plug attachment means; running the system into a wellbore or tubular to a desired location in the wellbore or tubular; moving the sealing element to the expanded configuration to form a pressure tight seal in the wellbore or tubular; moving the plug to the expanded configuration to form a pressure tight seal in the wellbore or tubular thereby creating an isolated volume; activating the pressure adjustment means to decrease the pressure in the isolated volume, thereby pressure testing the plug; and releasing the plug from the plug attachment means.

According to a first clause, there is provided a plug delivery and pressure test tool for delivering a plug to a wellbore or tubular and pressure testing the plug in a single trip, the tool comprising: an uphole end and a downhole end; a sealing element; a pressure adjustment means; and a plug attachment means located at or near the downhole end; wherein the plug attachment means is configured to carry a selectively expandable plug to a desired location in the wellbore or tubular and selectively release the plug from at or near the downhole end of the tool; the sealing element is configured to seal against an internal surface of the wellbore or tubular in use, thereby creating an isolated volume in use, between the sealing element and the plug; and the pressure adjustment means is configured to increase or decrease the pressure in the isolated volume, in use, thereby creating a pressure differential across the plug to perform a pressure test of the plug.

The pressure adjustment means may be configured in use to adjust the pressure in the isolated volume by either: moving fluid from the isolated volume to an upper fluid volume above the sealing element to create an underbalance in the isolated volume, thereby negatively pressure testing the plug or moving fluid from an upper fluid volume above the sealing element to the isolated volume to create an overbalance in the isolated volume, thereby positively pressure testing the plug.

The pressure adjustment means may be a pump or a piston or a pressure adjustment chamber.

The sealing element may be an expandable or conformable packer. The sealing element may be expandable from a collapsed configuration to an expanded configuration, wherein in the collapsed configuration the sealing element is configured to be run into a wellbore or tubular without forming a seal with the internal surface of the wellbore or tubular, and in the expanded configuration the sealing element is configured to form a seal with the internal surface of the wellbore or tubular.

The tool may further comprise: a fluid inlet port; and a fluid outlet port; wherein the fluid inlet port is located between the sealing element and the plug attachment means, and is in fluid communication with the pressure adjustment means, and the fluid outlet port is located between the sealing element and the uphole end of the tool, and is in fluid communication with the pressure adjustment means.

The tool may further comprise: a fluid inlet port; and a fluid outlet port; wherein the fluid outlet port is located between the sealing element and the plug attachment means, and is in fluid communication with the pressure adjustment means, and the fluid inlet port is located between the sealing element and the uphole end of the tool, and is in fluid communication with the pressure adjustment means.

The tool may further comprise: a first fluid inlet and outlet port; and a second fluid inlet and outlet port; wherein the first fluid inlet and outlet port is located between the sealing element and the plug attachment means, and is in fluid communication with the pressure adjustment means, and the second fluid inlet and outlet port is located between the sealing element and the uphole end of the tool, and is in fluid communication with the pressure adjustment means.

The tool may further comprise: an upper pressure sensor configured to measure a pressure in the wellbore or tubular between the sealing element and the uphole end of the tool or at the uphole end of the tool in use, and/or; an intermediate pressure sensor configured to measure a pressure in the isolated volume in use.

The plug attachment means may comprise a shear pin and/or electromechanical latch and/or hydraulic locking mechanism.

The plug attachment means may be configured in use to selectively reattach the plug at or near the downhole end of the tool and carry the plug to a desired location in the wellbore or tubular.

According to a twelfth clause, there is provided a system for delivering and pressure testing a plug in a wellbore or tubular in a single trip, the system comprising: a tool according to the first clause; a selectively expandable plug; wherein the plug is configured to be releasably attached to the plug attachment means in use. The plug may be configured to seal against an internal surface of the wellbore or tubular in use, thereby creating a pressure tight seal.

The plug may be an expandable or conformable packer.

The plug may be expandable from a collapsed configuration to an expanded configuration, wherein in the collapsed configuration the plug is configured to be run into a wellbore or tubular without forming a seal with the internal surface of the wellbore or tubular, and in the expanded configuration the plug is configured to form a seal with the internal surface of the wellbore or tubular.

The plug may be configured to be reattachable to the tool in use after the plug has been released from the tool.

The plug may comprise a lower pressure sensor configured to measure a pressure in the wellbore or tubular below the plug in use.

According to a eighteenth clause, there is provided a method of assembling a system for delivering a plug to a wellbore and performing a pressure test on the plug in a single trip, comprising the steps of: providing a tool according to the first clause; providing a selectively expandable plug configured to be releasably attached to the plug attachment means of the tool; and releasably attaching the plug to the plug attachment means.

According to a nineteenth clause, there is provided a method of setting and pressure testing a plug in a single trip, comprising the steps of: providing a system according to the twelfth clause; releasably attaching the plug to the plug attachment means; running the system into a wellbore or tubular to a desired location in the wellbore or tubular; moving the plug to the expanded configuration to form a pressure tight seal in the wellbore or tubular; releasing the plug from the plug attachment means; lifting the tool uphole in the wellbore or tubular; moving the sealing element to the expanded configuration to form a pressure tight seal in the wellbore or tubular, thereby creating an isolated volume; and activating the pressure adjustment means to increase or decrease the pressure in the isolated volume, thereby pressure testing the plug.

According to a twentieth clause, there is provided a method of pressure testing and setting a plug in a single trip, comprising the steps of: providing a system according to the twelfth clause; releasably attaching the plug to the plug attachment means; running the system into a wellbore or tubular to a desired location in the wellbore or tubular; moving the plug to the expanded configuration to form a pressure tight seal in the wellbore or tubular; moving the sealing element to the expanded configuration to form a pressure tight seal in the wellbore or tubular, thereby creating an isolated volume; activating the pressure adjustment means to increase or decrease the pressure in the isolated volume, thereby pressure testing the plug; and releasing the plug from the plug attachment means.

According to a twenty first clause, there is provided a method of pressure testing and setting a plug in a single trip, comprising the steps of: providing a system according to the twelfth clause; releasably attaching the plug to the plug attachment means; running the system into a wellbore or tubular to a desired location in the wellbore or tubular; moving the sealing element to the expanded configuration to form a pressure tight seal in the wellbore or tubular; moving the plug to the expanded configuration to form a pressure tight seal in the wellbore or tubular, thereby creating an isolated volume; activating the pressure adjustment means to increase or decrease the pressure in the isolated volume, thereby pressure testing the plug; and releasing the plug from the plug attachment means.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the following drawings, in which:

Figure 1 shows a schematic of a standard wellbore;

Figure 2 shows the plug delivery and pressure test tool with the plug being run in hole;

Figure 3 shows the tool of Figure 2 with the plug in the expanded configuration;

Figure 4 shows the tool of Figure 2 with the plug released from the tool;

Figure 5 shows the tool of Figure 2 with the sealing element in the expanded configuration and the tool ready to perform a pressure test;

Figure 6 shows the tool of Figure 2 with the sealing element in the collapsed configuration and ready to run out of hole;

Figure 7 shows the tool being run out of hole with the plug left in the expanded configuration in the wellbore;

Figure 8 shows the plug left in the wellbore;

Figure 1a shows a schematic of a tubing string;

Figure 2a shows the plug delivery and pressure test tool with the plug being run into the tubing string; Figure 3a shows the tool of Figure 2a with the plug in the expanded configuration;

Figure 4a shows the tool of Figure 2a with the plug released from the tool;

Figure 5a shows the tool of Figure 2a with a tubing puncher in the tool activated to form apertures in the tubing string;

Figure 6a shows the tool of Figure 2a with the sealing element in the expanded configuration and the tool ready to perform a pressure test;

Figure 7a shows the tool of Figure 2a with the sealing element in the collapsed configuration and ready to run out of the tubing string;

Figure 8a shows the tool being run out of the tubing string with the plug left in the expanded configuration in the tubing string;

Figure 9a shows the plug left in the tubing string;

Figure 1b shows a schematic of a tubing string;

Figure 2b shows the plug delivery and pressure test tool with the plug being run into the tubing string;

Figure 3b shows the tool of Figure 2b with the plug in the expanded configuration;

Figure 4b shows the tool of Figure 2b with the plug released from the tool;

Figure 5b shows the tool of Figure 2b with the sealing element in the expanded configuration and the tool ready to perform a pressure test;

Figure 6b shows the tool of Figure 2b with a tubing cutter in the tool activated to form apertures in the tubing string;

Figure 7b shows the tool being run out of the tubing string with the plug left in the expanded configuration in the tubing; and

Figure 8b shows the plug left in the tubing string.

For clarity reasons, some elements may in some of the figures be without reference numerals. A person skilled in the art will understand that the figures are just principal drawings. The relative proportions of individual elements may also be distorted.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following is described examples of preferred embodiments illustrated in the accompanying drawings. Figure 1 shows a simplified schematic of a known wellbore construction configuration comprising a wellbore 100 configured within formation 101. The wellbore 100 extends from an uphole end 100’ to a downhole end 100”. It will be understood that in the presently described example a wellbore 100 is provided where the plug is to be set (as will be described later). However, in other examples the plug (not shown in Figure 1) may be set in another tubular used in the construction of the wellbore, for example in a liner, a tubing or a casing. Alternatively, the plug may be set in a liner, a tubing or a casing which has had a section milled or extracted such that the plug may extend through the milled or extracted portion to reach the wellbore 100 therebehind.

It will be understood by those skilled in the art that a myriad of equipment may be used in wellbore 100 which is omitted here in the interest of clarity.

Referring now to Figure 2, a tool 200 has been run into the wellbore 100. The tool 200 has been lowered into the wellbore 100 on an electric wireline 300 which provides power and communications between the tool 200 and the surface such that operators of the tool 200 at the surface can control the tool 200, as is well known in the art.

The tool 200 comprises a sealing element 201 which is configured to be operatively engageable with the internal surface of the wellbore 100 when in use in the wellbore 100. The sealing element 201 is an expandable packer in the presently described example. In other examples (not shown) the sealing element 201 may be a conformable packer. It will be understood that the sealing element 201 may be any component configured to be movable from a collapsed configuration, which allows the tool 200 to be run into the wellbore 100 without forming a seal with the wellbore 100 (or cement or casing attached to the internal surface of the wellbore 100, or other tubulars as previously described) and then moved to an expanded configuration, as will be explained with reference to later Figures.

Still referring to Figure 2, the tool 200 has an uphole end 200’ and a downhole end 200”. The electric wireline 300 is attached at the uphole end 200’ of the tool 200 such that the tool 200 can be lowered and lifted inside the wellbore 100, and such that a force in the uphole direction can be applied to the tool 200 when required, as will be explained later.

At the downhole end 200” there is releasably attached a selectively expandable plug 400. The plug 400 is attached to the tool 200 such that the plug 400 can be lowered into the wellbore 100 to a desired position where the plug 400 should be set, i.e. expanded, to provide a seal across the wellbore 100, as is shown in Figure 3. The plug 400 in the presently described example is an expandable packer. However, in other examples (not shown) the plug 400 may be a conformable packer. It will be understood that the plug 400 may be any component configured to be movable from a collapsed configuration, which allows the plug 400 to be run into the wellbore 100 without forming a seal with the wellbore 100 (or cement or casing attached to the internal surface of the wellbore 100, or any other tubulars or equipment as previously described) and then moved to an expanded configuration shown in Figure 3 to form a pressure tight seal against the wellbore 100. In this connection, the plug 400 may be operated in some examples by electrical connection (not shown) between the tool 200 and the plug 400 to move the plug 400 to the expanded configuration.

In other examples (not shown) hydraulic pressure may be provided by a pump 203 in the tool 200 with a connection (not shown) between the pump 203 and the plug 400 configured such that the pump 200 can selectively move the plug 400 to the expanded configuration by pumping hydraulic fluid into the plug 400. Regardless of the means by which the plug 400 is expanded, the plug 400 is selectively expanded by communication with the tool 200. The tool 200 may be programmed to locate and expand the plug 400 at a particular position in the wellbore 100 in some examples, or, as in the presently described example, may receive instructions via the electric wireline through a pre-determined communications protocol.

Once the plug 400 has been set at the desired location, the tool 200 can be released from the plug 400 by the operator selectively releasing the plug 400 from the tool 200 or by the tool 200 automatically releasing the plug 400 from the tool 200. In this connection, the tool 200 comprises a shear pin (not shown) releasably securing the plug 400 to the tool 200. When the plug 400 has been set and it is desired to release the plug 400 from the tool 200, the operator may lift the tool 200 on the electric wireline 300 with sufficient pull in the uphole direction such that the shear pin (not shown) breaks, thereby releasing the tool 200 from the plug 400. It will be understood that a selectively releasable connection between the plug 400 and tool 200 may be provided in a myriad of forms, and that the shear pin (not shown) used in the presently described example is merely one way of providing a selectively releasable attachment between the plug 400 and the tool 200. In other examples, a selectively releasable electro-mechanical latch may be provided to secure the plug 400 to the tool 200. In other examples, a selectively releasable hydraulic locking mechanism may be provided to secure the plug 400 to the tool 200.

Once the plug 400 has been released from the tool 200, the tool 200 can be lifted on the electric wireline 300 until the sealing element 201 is located at the desired location at which it will seal against the wellbore 100, as shown in Figure 4. As previously explained, in some cases the plug 400 is set in a milled or otherwise extracted portion of a casing and/or liner and/or tubing and cement barrier (not shown). In this connection, the sealing element 201 may be expanded against the inside of the casing or tubing or liner or the sealing element 201 may also be expanded against the wellbore 100 in some examples. Regardless of the well component which the sealing element 201 abuts against, the sealing element 201 is moved from a collapsed to an expanded configuration to form a pressure tight seal. Communication with the sealing element 201 in the presently described example is via the electric wireline 300. It will be understood that the tool 200 may be run in and out of the wellbore 100 using an alternative method of suspending and delivering the tool 200, such as on drill pipe or slickline, i.e. non-electric wireline. Where in some alternative methods of suspending and delivering the tool 200 into the wellbore there may not be provided an electrical connection to the surface which can also carry communications, then another communications method may be provided. In some examples mud pulse telemetry, acoustic waves or radio waves may be used. In other examples any other known and commonly used downhole communications technique, the configuration of which would be well within the capabilities of a person skilled in the art, may be used.

Once the sealing element 201 has been set in the expanded configuration shown in Figure 5 an isolated volume 500 is created between the sealing element 201 and the plug 400. The isolated volume 500 is separate from a first volume 501 above the sealing element 201 and a second volume 502 below the plug 400. It will be understood that the upper volume 501 may be a volume of wellbore fluid, or may be another isolated volume for a different purpose. The lower volume 502 is a volume of wellbore fluid within the wellbore 100 which may include casing and/or liner and/or tubing and/or cement, as previously described.

The lower volume 502 may extend for several thousand meters below the plug 400. Due to the location of the sealing element 201 providing a pressure tight seal against the wellbore 100, and the location of the plug 400 providing a pressure tight seal against the wellbore 100 therebelow, changes (increases or decreases) in pressure in the isolated volume 500 are applied to the plug 400, allowing a pressure test to be conducted on the plug 400 by adjusting the pressure within the isolated volume 500. It should be noted that in the presently described example, the sealing element 201 is moved to the expanded configuration around 3 metres above the plug 400. In some examples the sealing element 201 may be located closer to the plug 400. In other examples, the sealing element 201 may be located a greater distance from the plug 400, for example 5 metres or 10 metres or 20 metres. It will be understood that the greater distance between the plug 400 and the sealing element 201, the more wellbore fluid has to be extracted or injected to perform a pressure test on the plug 400, as will now be described.

As shown in Figure 5, the pump 203 is connected to an inlet port 204 in fluid communication with the isolated volume 500 and an outlet port 205 in fluid communication with the upper volume 501. The pump 203 is configured to pump fluid from the isolated volume 500 to the upper volume 501 , thereby reducing the pressure in the isolated volume 500 such that a negative pressure test on the plug 400 is conducted.

Alternatively to the arrangement shown in Figure 5, the pump 203 may be configured to pump fluid from the isolated volume 500 to a reservoir within the tool 200, thereby reducing the pressure in the isolated volume 500 such that a negative pressure test on the plug 400 can be conducted.

Although not shown in Figure 5, it will be understood that the pump 203 may be configured to pump fluid from the upper 501 volume to the isolated volume 500, thereby increasing the pressure in the isolated volume 500 such that a positive pressure test can be conducted. In this regard, the inlet port 204 shown in Figure 5 would be replaced by an outlet port, and the outlet port 205 shown in Figure 5 would be replaced by an inlet port. It will also be understood that the inlet port 204 and outlet port 205 may each have dual functionality, that is to say the inlet port 204 may act as an inlet port and the outlet port 205 may act as an outlet port when the pump 203 is pumping in one direction, and then the inlet port 204 may act as an outlet port and the outlet port 205 may act as an inlet port, such that the same inlet and outlet ports 204, 205 may be used to provide a positive and negative pressure test by simply reversing the direction of the pump 203. It will be well within the capabilities of a person skilled in the art to provide suitable modification to the inlet port 204 and outlet port 205 to provide this reversibility.

Referring again to the negative pressure testing arrangement shown in Figure 5, as the pressure in the isolated volume 500 is reduced, the plug 400 is pressure tested, i.e. the sealing performance at the plug 400 is tested, and if not sufficient, wellbore fluid or hydrocarbons will flow through or past the plug 400 to inside the isolated volume 500, thereby confirming that the seal provided by the plug 400 is not sufficient. In such cases it is likely that the plug 400 would be reset, or a new plug 400 would be delivered to the wellbore 100, possibly with further milling or cleaning of the wellbore 100 area where the plug 400 is to be set.

The tool 200 may, in some examples (not shown in the Figures), comprise an upper pressure sensor configured to measure a pressure in the wellbore 100 above the sealing element 201, i.e. in the first volume 501. Alternatively, or additionally, the tool 200 may comprise an intermediate pressure sensor configured to measure a pressure in the isolated volume 500. Alternatively, or additionally, the plug 400 may comprise a lower pressure sensor configured to measure a pressure in the wellbore 100 below the plug 400, i.e. in the second volume 502. In this connection, the plug 400 may comprise a wireless communications means configured to communicate the pressure in the wellbore 100 below the plug 400, in the second volume 502, to the tool 200, with the tool 200 comprising a respectively configured similar wireless communications means for receiving the communication from the plug 400. Communication with the upper pressure sensor and intermediate pressure sensor may be configured to be via the electric wireline 300, or where an electric wireline 300 is not used in alternative examples, via mud pulse telemetry, radio waves, or any other known and commonly used downhole communications technique, the configuration of which would be well within the capabilities of a person skilled in the art.

After one or more positive and/or negative pressure tests have been conducted with the sealing element 201 in the expanded configuration shown in Figure 5, the sealing element 201 is moved to the collapsed configuration shown in Figure 6. In the collapsed configuration, the sealing element 201 has a sufficiently slim profile such that the sealing element 201 can pass by any obstructions higher in the wellbore 100 such that the tool 200 can be removed from the wellbore 100. In some cases, such as in the presently described example, the sealing element 201 may not collapse to be completely flush with the body of the tool 200, and instead protrude slightly from the body of the tool 200.

As shown in Figure 7, the tool 200 is then lifted from within the wellbore 100. In some cases, the tool 200 may be lifted to another location in the wellbore 100 where a pressure test is to be performed. In other cases, the tool 200 is lifted out of the wellbore 100. As can be seen in Figure 8, when the tool 200 is removed from the wellbore 100 completely, or from the vicinity of the plug 400, the plug 400 is left in the wellbore 100 in the expanded configuration.

The above-mentioned system and method therefore deliver the plug 400 to the wellbore 100 and allow pressure testing of the plug 400 in a single trip. That is to say, the tool 200 and plug 400 are introduced into the wellbore 100 and run in to the wellbore 100 on the same electric wireline 300 at the same time, as opposed to running the plug 400 firstly and setting the plug 400 at the desired depth, and then running the tool 200 to perform the pressure testing of the plug 400.

Referring again to the selectively releasable attachment between the tool 200 and the plug 400 previously discussed. It will be understood that in some examples the selectively releasable attachment may also be capable of selectively reattaching the tool 200 to the plug 400 should the plug 400 fail the positive and/or negative pressure test, or should the plug 400 need to be moved or retrieved for another reason. In this connection, it would be highly desirable to retrieve the plug 400 at the same time as the tool 200 is removed from the wellbore 100. To do so, the tool 200 may comprise a selectively attachable attachment means, which may be incorporated into the selectively releasable attachment means or may be a separate component. That is to say, the attachment provided between the tool 200 and the plug 400 when the tool 200 and plug 400 are run into the wellbore 100 may be configured to selectively release the plug 400 from the tool 200 and selectively reattach the plug 400 to the tool 200. Alternatively, the selectively releasable attachment means and selectively attachable attachment means may be two separate components. Where the tool 200 is configured to reattached to the plug 400, the tool 200 is configured to also move the plug 400 from the expanded configuration to the collapsed configuration, thereby allowing the tool 200 to be able to lift the collapsed plug 400 through the wellbore 100 to the surface.

It will be within the capabilities of a person skilled in the art to determine suitable increases and/or decreases in pressure in the above-mentioned examples and in further examples not illustrated. As an example only, a pressure differential across the plug 400 of between 3000kPa and 15,000kPa may be used, for example a pressure differential of 10,000kPa may be used.

It will be appreciated that the pressure adjustment means shown is an example of a suitable pressure adjustment means. However, other pressure adjustment means may also be used. As another non-limiting example, the pressure adjustment means may be configured to increase or decrease the pressure in the isolated volume 500 by use of a pressure adjustment chamber in the tool 200. In this configuration, the pressure in the isolated volume 500 may be adjusted by extracting fluid from the isolated volume 500 into the pressure adjustment chamber to decrease the pressure in the isolated volume 500, or by delivering fluid to the isolated volume 500 from the pressure adjustment chamber to increase the pressure in the isolated volume 500. In some examples, the pressure adjustment chamber may be located inside the tool 200, or alternatively the pressure adjustment chamber may be located on an external surface of the tool 200.

Referring now to Figures 1a to 9a, an alternative example of a tool 200a is now described. The tool 200a comprises many similar features to the tool 200 described with reference to Figures 1 to 9, therefore like reference numerals (followed by “a”) are used to indicate like parts. However, the tool 200a is described in Figures 1a to 9a being delivered into a tubing string 100a to deliver and pressure test a plug 400a and an annular region behind the tubing, as is now explained.

Figure 1a shows a simplified schematic of a portion of a tubing string 100a configured within formation 101a. The tubing string 100a extends from an uphole end 100’a to a downhole end 100”a. In the presently described example the portion of the tubing string 100a provided in Figures 1a to 9a is where a plug is to be set and where at least one aperture is to be punched in the tubing to allow testing of the annulus behind the tubing string 100a, as will be described in detail.

It will be understood by those skilled in the art that a myriad of equipment may be used in the tubing string 100a which is omitted here in the interest of clarity.

Referring now to Figure 2a, a tool 200a has been run into the tubing string 100a. The tool 200a has been lowered into the tubing string 100a on an electric wireline 300a which provides power and communications between the tool 200a and the surface such that operators of the tool 200a at the surface can control the tool 200a, as is well known in the art.

The tool 200a comprises a sealing element 201a which is configured to be operatively engageable with the internal surface of the tubing string 100a when in use in the tubing string 100a. The sealing element 201a is an expandable packer in the presently described example. In other examples (not shown) the sealing element 201a may be a conformable packer. It will be understood that the sealing element 201a may be any component configured to be movable from a collapsed configuration, which allows the tool 200a to be run into the tubing string 100a without forming a seal with the tubing string 100a and then moved to an expanded configuration, as will be explained with reference to later Figures.

Still referring to Figure 2a, the tool 200a has an uphole end 200’a and a downhole end 200”a. The electric wireline 300a is attached at the uphole end 200’a of the tool 200a such that the tool 200a can be lowered and lifted inside the tubing string 100a, and such that a force in the uphole direction can be applied to the tool 200a when required, as will be explained later.

Still referring to Figure 2a, the tool 200a further comprises a tubing puncher 202a configured to selectively punch apertures in the tubing string 100a such that the annulus behind the tubing string 100a can be accessed and tested from inside the tubing string 100a.

In the presently described example, the tubing puncher 202a is a component of the tool 200a. It will be understood that in other examples the tubing puncher 202a may be provided as a separate component run in a string with the tool 200a. In such examples, the tubing puncher 202a may be connected to the tool 200a at the uphole end 200’a between the tool 200a and the wireline 300a, for example. It will be understood that other tools (not shown) may also be configured in the tool string, and the puncher 202a may be provided anywhere in the string in some examples. In examples where the puncher 202a is located above the tool 200a, the puncher 202a may be operated to perform a punching operation on the tubing string 100a before the tool 200a is lifted such that the sealing element 201a is above the punched apertures in the tubing string 100a, the purpose of which will be explained later. It is preferable that as in the presently described example shown in Figures 2a to 8a, the tubing puncher 202a is provided as a component of the tool 200a between the sealing element 201a and the downhole end 200”a, such that the sealing element 201a does not need to be lifted past the location of the punched apertures after the punching operation, as is required where the tubing puncher 202a is provided above the tool 200a in the tool string.

Still referring to Figure 2a, at the downhole end 200”a there is releasably attached a selectively expandable plug 400a. The plug 400a is attached to the tool 200a such that the plug 400a can be lowered into the tubing string 100a to a desired position where the plug 400a should be set, i.e. expanded, to provide a seal across the tubing string 100a, as is shown in Figure 3a. The plug 400a in the presently described example is an expandable packer. However, in other examples (not shown) the plug 400a may be a conformable packer. It will be understood that the plug 400a may be any component configured to be movable from a collapsed configuration, which allows the plug 400a to be run into the tubing string 100a without forming a seal with the tubing string 100a and then moved to an expanded configuration shown in Figure 3a to form a pressure tight seal against the tubing string 100a. In this connection, the plug 400a may be operated in some examples by electrical connection (not shown) between the tool 200a and the plug 400a to move the plug 400a to the expanded configuration.

In other examples (not shown) hydraulic pressure may be provided by a pump 203a in the tool 200a with a connection (not shown) between the pump 203a and the plug 400a configured such that the pump 200a can selectively move the plug 400a to the expanded configuration by pumping hydraulic fluid into the plug 400a. Regardless of the means by which the plug 400a is expanded, the plug 400a is selectively expanded by communication with the tool 200a. The tool 200a may be programmed to locate and expand the plug 400a at a particular position in the tubing string 100a in some examples, or, as in the presently described example, may receive instructions via the electric wireline through a pre-determined communications protocol.

Once the plug 400a has been set at the desired location, the tool 200a can be released from the plug 400a by the operator selectively releasing the plug 400a from the tool 200a or by the tool 200a automatically releasing the plug 400a from the tool 200a. In this connection, the tool 200a comprises a shear pin (not shown) releasably securing the plug 400a to the tool 200a. When the plug 400a has been set and it is desired to release the plug 400a from the tool 200a, the operator may lift the tool 200a on the electric wireline 300a with sufficient pull in the uphole direction such that the shear pin (not shown) breaks, thereby releasing the tool 200a from the plug 400a. It will be understood that a selectively releasable connection between the plug 400a and tool 200a may be provided in a myriad of forms, and that the shear pin (not shown) used in the presently described example is merely one way of providing a selectively releasable attachment between the plug 400a and the tool 200a. In other examples, a selectively releasable electro-mechanical latch may be provided to secure the plug 400a to the tool 200a. In other examples, a selectively releasable hydraulic locking mechanism may be provided to secure the plug 400a to the tool 200a.

Once the plug 400a has been released from the tool 200a, the tool 200a can be lifted on the electric wireline 300a until the tubing puncher 202a is located at the desired location at which it will form apertures in the tubing string 100a, as shown in Figure 4a. In some examples, it may not be necessary to lift the tool 200a at this stage if the tubing puncher 202a is already located at a suitable location to form apertures in the tubing string 100a. Furthermore, it will be appreciated that the tubing puncher 202a may form apertures in the tubing string 100a before the plug 400a is released from the tool 200a in some examples.

When the tubing puncher 202a is at the location where it is desired to form apertures in the tubing string 100a, the tubing puncher 202a is activated (as shown in Figure 5a) to form apertures 100”’a through the tubing string 100a (Figure 6a) to allow fluid communication between the inside of the tubing string 100a and the formation 101a or annulus surrounding the tubing string 100a.

The sealing element 201 a is then expanded against the inside of the tubing string 100a by moving the sealing element 201a from a collapsed to an expanded configuration to form a pressure tight seal (Figure 6a). Communication with the sealing element 201 a in the presently described example is via the electric wireline 300a. It will be understood that the tool 200a may be run in and out of the tubing string 100a using an alternative method of suspending and delivering the tool 200a, such as on drill pipe or slickline, i.e. non-electric wireline. Where in some alternative methods of suspending and delivering the tool 200a into the tubing string 100a there may not be provided an electrical connection to the surface which can also carry communications, then another communications method may be provided. In some examples mud pulse telemetry, acoustic waves or radio waves may be used. In other examples any other known and commonly used downhole communications technique, the configuration of which would be well within the capabilities of a person skilled in the art, may be used.

Once the sealing element 201a has been set in the expanded configuration shown in Figure 6a an isolated volume 500a is created between the sealing element 201a and the plug 400a. The isolated volume 500a spans the apertures 100”’a such that the annulus or formation behind the tubing string 100a can be pressure tested by adjustment of the pressure in the isolated volume 500a.

The isolated volume 500a is separate from a first volume 501a above the sealing element 201a and a second volume 502a below the plug 400a. It will be understood that the upper volume 501a may be a volume of wellbore fluid for example, or may be another isolated volume for a different purpose. The lower volume 502a may be a volume of wellbore fluid within the tubing string 100a. It will be understood that a plug may be set within a tubing string for myriad reasons and with myriad possible fluids within the tubing string 100a prior to setting. The term wellbore fluid here is used to refer to all possible fluids that may be within the tubing string 100a at the time of setting a barrier, i.e. a plug, across the tubing string 100a and is not intended to refer to a particular type of fluid. In this connection, it is not important what type of fluid is contained in the lower volume 502a below the plug 400a.

The lower volume 502a may extend for several thousand meters below the plug 400a. Due to the location of the sealing element 201a providing a pressure tight seal against the tubing string 100a, and the location of the plug 400a providing a pressure tight seal against the tubing string 100a therebelow, changes (increases or decreases) in pressure in the isolated volume 500a are applied to the plug 400a and the annulus or formation outside of the tubing string 100a in the locality of the apertures 100”’a formed by the tubing puncher 202a, allowing a pressure test to be conducted on the plug 400a and the annulus or formation by adjusting the pressure within the isolated volume 500a. It should be noted that in the presently described example, the sealing element 201a is moved to the expanded configuration around 3 metres above the plug 400a. In some examples the sealing element 201a may be located closer to the plug 400a. In other examples, the sealing element 201a may be located a greater distance from the plug 400a, for example 5 metres or 10 metres or 20 metres. It will be understood that the greater distance between the plug 400a and the sealing element 201a, the more wellbore fluid has to be extracted or injected to perform a pressure test on the plug 400a and the annulus or formation, as will now be described.

As shown in Figure 6a, the pump 203a is connected to an inlet port 204a in fluid communication with the isolated volume 500a and an outlet port 205a in fluid communication with the upper volume 501a. In the same way as previously described, the pump 203 pumps fluid from the isolated volume 500a to the upper volume 501a, thereby reducing the pressure in the isolated volume 500a such that a negative pressure test on the plug 400 and annulus or formulation is conducted.

Alternatively, the pump 203a may be configured to pump fluid from the isolated volume 500a to a reservoir within the tool 200a, thereby reducing the pressure in the isolated volume 500a such that a negative pressure test on the plug 400a and annulus or formation can be conducted.

Although not shown in Figure 6a, it will be understood that the pump 203a may be configured to pump fluid from the upper 501a volume to the isolated volume 500a, thereby increasing the pressure in the isolated volume 500a such that a positive pressure test can be conducted. In this regard, the inlet port 204a shown in Figure 6a would be replaced by an outlet port, and the outlet port 205a shown in Figure 6a would be replaced by an inlet port. It will also be understood that the inlet port 204a and outlet port 205a may each have dual functionality, that is to say the inlet port 204a may act as an inlet port and the outlet port 205a may act as an outlet port when the pump 203a is pumping in one direction, and then the inlet port 204a may act as an outlet port and the outlet port 205a may act as an inlet port, such that the same inlet and outlet ports 204a, 205a may be used to provide a positive and negative pressure test by simply reversing the direction of the pump 203a. It will be well within the capabilities of a person skilled in the art to provide suitable modification to the inlet port 204a and outlet port 205a to provide this reversibility.

Referring again to the negative pressure testing arrangement shown in Figure 6a, as the pressure in the isolated volume 500a is reduced, the plug 400a and annulus or formation is pressure tested, i.e. the sealing performance at the plug 400a is tested and the annulus or formation is negatively pressure tested to ensure that fluid does not flow through the annulus or formation when exposed to such negative pressure, and if not sufficient, wellbore fluid or hydrocarbons will flow through or past the plug 400 or through the annulus or formation to inside the isolated volume 500a, thereby confirming that the seal provided by the plug 400a is not sufficient or the annulus or formation is not sufficiently isolated. In such cases it is likely that remedial action would be taken to reset the plug 400a and/or improve the sealing in the annulus by for example performing a cement job.

The tool 200a may, in some examples (not shown in the Figures), comprise an upper pressure sensor configured to measure a pressure in the tubing string 100a above the sealing element 201a, i.e. in the first volume 501a. Alternatively, or additionally, the tool 200a may comprise an intermediate pressure sensor configured to measure a pressure in the isolated volume 500a. Alternatively, or additionally, the plug 400a may comprise a lower pressure sensor configured to measure a pressure in the tubing string 100a below the plug 400a, i.e. in the second volume 502a. In this connection, the plug 400a may comprise a wireless communications means configured to communicate the pressure in the tubing string 100a below the plug 400a, in the second volume 502a, to the tool 200a, with the tool 200a comprising a respectively configured similar wireless communications means for receiving the communication from the plug 400a. Communication with the upper pressure sensor and intermediate pressure sensor may be configured to be via the electric wireline 300a, or where an electric wireline 300a is not used in alternative examples, via mud pulse telemetry, radio waves, or any other known and commonly used downhole communications technique, the configuration of which would be well within the capabilities of a person skilled in the art.

After one or more positive and/or negative pressure tests have been conducted with the sealing element 201a in the expanded configuration shown in Figure 6a, the sealing element 201a is moved to the collapsed configuration shown in Figure 7a. In the collapsed configuration, the sealing element 201a has a sufficiently slim profile such that the sealing element 201a can pass by any obstructions higher in the tubing string 100a such that the tool 200a can be removed from the tubing string 100a. In some cases, such as in the presently described example, the sealing element 201a may not collapse to be completely flush with the body of the tool 200a, and instead protrude slightly from the body of the tool 200a.

As shown in Figure 8a, the tool 200a is then lifted from within the tubing string 100a. In some cases, the tool 200a may be lifted to another location in the tubing string 100a where a pressure test is to be performed. In other cases, the tool 200a is lifted out of the tubing string 100a. As can be seen in Figure 9a, when the tool 200a is removed from the tubing string 100a completely, or from the vicinity of the plug 400a, the plug 400a (in the expanded configuration) and apertures 100”a are left in the tubing string 100a.

The above-mentioned system and method therefore deliver the plug 400a to the tubing string 100a and allow pressure testing of the plug 400a and the annulus or formation behind the tubing string 100a in a single trip. That is to say, the tool 200a, plug 400a and tubing puncher 202a are introduced into the tubing string 100a and run in to the tubing string 100a on the same electric wireline 300a at the same time, as opposed to running the tubing punch 202a firstly, and then the plug, and then running the tool 200a to perform the pressure testing of the plug 400a and the annulus or formation behind the tubing string 100a.

It will be understood that the above-described method is just one way of using the tool 200a and that other ways of performing a tubing punching operation and pressure testing of the plug 400a and the annulus or formation behind the tubing string 100a in a single trip may be performed using the tool 200a. Some non-limiting examples of such methods are now described. In a first alternative example, the tool 200a may be run into the tubing string 100a and the tubing puncher 202a may be operated to form apertures in the tubing string 100a before the plug 400a is set. After the formation of apertures using the tubing puncher 202a and the setting of the plug 400a, the plug 400a and annulus or formation behind the tubing string 100a can be pressure tested in the manner previously described.

In a second alternative example, the tool 200a may be run into the tubing string 100a and the plug 400a may be set as previously described. In this example, there is an intermediate step of pressure testing the plug 400a within the tubing string 100a. This may be substantially as is performed in Figure 5 but for the tubing string 100a rather than the wellbore 100. After pressure testing the plug 400a in the tubing string 100a, the puncher 202a can be operated to form apertures in the tubing string 100a. After the setting of the plug 400a, pressure testing of the plug 400a in the tubing string 100a and formation of apertures using the tubing puncher 202a, the plug 400a and annulus or formation behind the tubing string 100a can be pressure tested in the manner previously described. This method allows the plug 400a integrity to be verified before apertures are punched in the tubing string 100a using the tubing puncher 202a.

The releasable attachment between the tool 200a and the plug 400a may be substantially as described in any of the examples discussed with reference to Figures 1 to 9, therefore the details are not described again in the interest of brevity.Again, it will be within the capabilities of a person skilled in the art to determine suitable increases and/or decreases in pressure in the above-mentioned examples and in further examples not illustrated. As an example only, a pressure differential across the plug 400a and the apertures 100”a of between 3000kPa and 15,000kPa may be used, for example a pressure differential of 10,000kPa may be used.

Referring now to Figures 1b to 8b, an alternative example of a tool 200b is now described. The tool 200b comprises many similar features to the tool 200a described with reference to Figures 1a to 9a, therefore like reference numerals (followed by “b” rather than “a”) are used to indicate like parts. In this connection, the tool 200b is for use in a tubing string 100b to deliver a plug 400b and make a cut in the tubing string 100b. The tool 100b is again run on electric wireline 300b. The tubing string 100b is configured within the formation 101b and extends from an uphole end 100’b to a downhole end 100”b. The tool 200a comprises a sealing element 201b as described in the previous examples, an uphole end 200’b and a downhole end 200”b and a tubing cutter 202b configured to selectively cut the tubing string 100b in preparation for subsequent removal of a portion of the tubing string 100b. T o stabilise the tubing cutter 202b and allow rotation of the tubing cutter 202b to perform the cut, there is also provided an expandable anchor 202’b which can be selectively expanded into engagement with the tubing string 100b when required. Furthermore, as described in detail with reference to previous examples, the tool 200b comprises an inlet port 204b, an outlet port 205b and a pump 203b to be able to perform a pressure test in the manner previously described.

In the presently described example, the tubing cutter 202b is a component of the tool 200b. It will be understood that in other examples the tubing cutter 202b may be provided as a separate component run in a string with the tool 200b. In such examples, the tubing cutter 202b may be connected to the tool 200b at the uphole end 200’b between the tool 200b and the wireline 300b, for example.

Once the plug 400b has been run in and released from the tool 200b and a pressure test has been performed in a similar manner to that previously explained with reference to the previous examples, the tool 200b can be lifted on the electric wireline 300b until the tubing cutter 202b is located at the desired location at which it will cut the tubing string 100b. The tubing string 100b can then be cut before the tool 200b is removed from the tubing string 100b, thus saving a subsequent trip to cut the tubing string 100b after the plug 400b has been set and the pressure test has been performed.

The process is now briefly explained with reference to each of Figures 1b to 8b in turn. In Figure 1b the tubing string 100b is ready to receive a plug and thereafter be cut ready for subsequent removal of a portion of the tubing string 100b. In Figure 2b the tool 200b is delivered into the tubing string 100b at the depth at which it is desired to set the plug 400b. In Figure 3b the plug 400b is expanded against the tubing string 100b. In Figure 4b the plug 400b is detached from the tool 200b and the tool 200b is lifted to the desired location to set the sealing element 201b and the sealing element 201 b is then set as shown in Figure 5b. A pressure test is then performed utilising the pump 203b and the inlet 204b and outlet 205b ports. After the pressure test is complete, the sealing element 201b is collapsed and the cutting of the tubing string 100b can commence. The anchor 202’b is expanded against the tubing string 100b and the tubing cutter 202b performs a cutting operation thereby forming a continuous cut 100”’b in the tubing string 100b (Figure 7b). The anchor 202’b and tubing cutter 202b can be collapsed into the tool 200b and the tool 200b is then raised out of the tubing string 100b leaving the pressure tested plug 400b and the cut 100”’b in the tubing string 100b, as shown in Figure 8b. It will be appreciated that the setting and pressure testing of the plug 400b and cutting of the tubing string 100b in one trip may provide significant time savings.

In highly deviated or horizontal wells, a wireline tractor may be used to deliver the tool 200, 200a, 200b and plug 400, 400a, 400b. It should be noted that the above- mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

CLAUSES

CLAUSE 1. A plug delivery and pressure test tool for delivering a plug to a wellbore or tubular and pressure testing the plug in a single trip, the tool comprising: an uphole end and a downhole end; a sealing element; a pressure adjustment means; and a plug attachment means located at or near the downhole end; wherein the plug attachment means is configured to carry a selectively expandable plug to a desired location in the wellbore or tubular and selectively release the plug from at or near the downhole end of the tool; the sealing element is configured to seal against an internal surface of the wellbore or tubular in use, thereby creating an isolated volume in use, between the sealing element and the plug; and the pressure adjustment means is configured to increase or decrease the pressure in the isolated volume, in use, thereby creating a pressure differential across the plug to perform a pressure test of the plug.

CLAUSE 2. The tool according to clause 1, wherein the pressure adjustment means is configured in use to adjust the pressure in the isolated volume by either: moving fluid from the isolated volume to an upper fluid volume above the sealing element to create an underbalance in the isolated volume, thereby negatively pressure testing the plug or moving fluid from an upper fluid volume above the sealing element to the isolated volume to create an overbalance in the isolated volume, thereby positively pressure testing the plug.

CLAUSE 3. The tool according to clause 1 or 2, wherein the pressure adjustment means is a pump or a piston or a pressure adjustment chamber.

CLAUSE 4. The tool according to any preceding clause, wherein the sealing element is an expandable or conformable packer.

CLAUSE 5. The tool according to any preceding clause, wherein the sealing element is expandable from a collapsed configuration to an expanded configuration, wherein in the collapsed configuration the sealing element is configured to be run into a wellbore or tubular without forming a seal with the internal surface of the wellbore or tubular, and in the expanded configuration the sealing element is configured to form a seal with the internal surface of the wellbore or tubular.

CLAUSE 6. The tool according to any preceding clause, further comprising: a fluid inlet port; and a fluid outlet port; wherein the fluid inlet port is located between the sealing element and the plug attachment means, and is in fluid communication with the pressure adjustment means, and the fluid outlet port is located between the sealing element and the uphole end of the tool, and is in fluid communication with the pressure adjustment means.

CLAUSE 7. The tool according to any of clauses 1 to 5, further comprising: a fluid inlet port; and a fluid outlet port; wherein the fluid outlet port is located between the sealing element and the plug attachment means, and is in fluid communication with the pressure adjustment means, and the fluid inlet port is located between the sealing element and the uphole end of the tool, and is in fluid communication with the pressure adjustment means.

CLAUSE 8. The tool according to any of clauses 1 to 5, further comprising: a first fluid inlet and outlet port; and a second fluid inlet and outlet port;wherein the first fluid inlet and outlet port is located between the sealing element and the plug attachment means, and is in fluid communication with the pressure adjustment means, and the second fluid inlet and outlet port is located between the sealing element and the uphole end of the tool, and is in fluid communication with the pressure adjustment means.

CLAUSE 9. The tool according to any preceding clause, further comprising: an upper pressure sensor configured to measure a pressure in the wellbore or tubular between the sealing element and the uphole end of the tool or at the uphole end of the tool in use, and/or; an intermediate pressure sensor configured to measure a pressure in the isolated volume in use.

CLAUSE 10. The tool according to any preceding clause, wherein the plug attachment means comprises a shear pin and/or electromechanical latch and/or hydraulic locking mechanism.

CLAUSE 11. The tool according to any preceding clause, wherein the plug attachment means is configured in use to selectively reattach the plug at or near the downhole end of the tool and carry the plug to a desired location in the wellbore or tubular.

CLAUSE 12. A system for delivering and pressure testing a plug in a wellbore or tubular in a single trip, the system comprising: a tool according to any of clauses 1 to 11 ; a selectively expandable plug; wherein the plug is configured to be releasably attached to the plug attachment means in use.

CLAUSE 13. The system according to clause 12, wherein the plug is configured to seal against an internal surface of the wellbore or tubular in use, thereby creating a pressure tight seal.

CLAUSE 14. The system according to clause 12 or 13, wherein the plug is an expandable or conformable packer.

CLAUSE 15. The system according to any of clauses 12 to 14, wherein the plug is expandable from a collapsed configuration to an expanded configuration, wherein in the collapsed configuration the plug is configured to be run into a wellbore or tubular without forming a seal with the internal surface of the wellbore or tubular, and in the expanded configuration the plug is configured to form a seal with the internal surface of the wellbore or tubular.

CLAUSE 16. The system according to any of clauses 12 to 15, wherein the plug is configured to be reattachable to the tool in use after the plug has been released from the tool.

CLAUSE 17. The system according to any of clauses 12 to 16, wherein the plug comprises a lower pressure sensor configured to measure a pressure in the wellbore or tubular below the plug in use.

CLAUSE 18. A method of assembling a system for delivering a plug to a wellbore and performing a pressure test on the plug in a single trip, comprising the steps of: providing a tool according to any of clauses 1 to 11; providing a selectively expandable plug configured to be releasably attached to the plug attachment means of the tool; and releasably attaching the plug to the plug attachment means.

CLAUSE 19. A method of setting and pressure testing a plug in a single trip, comprising the steps of: providing a system according to any of clauses 12 to 17; releasably attaching the plug to the plug attachment means; running the system into a wellbore or tubular to a desired location in the wellbore or tubular; moving the plug to the expanded configuration to form a pressure tight seal in the wellbore or tubular; releasing the plug from the plug attachment means; lifting the tool uphole in the wellbore or tubular; moving the sealing element to the expanded configuration to form a pressure tight seal in the wellbore or tubular, thereby creating an isolated volume; and activating the pressure adjustment means to increase or decrease the pressure in the isolated volume, thereby pressure testing the plug.

CLAUSE 20. A method of pressure testing and setting a plug in a single trip, comprising the steps of: providing a system according to any of clauses 12 to 17; releasably attaching the plug to the plug attachment means; running the system into a wellbore or tubular to a desired location in the wellbore or tubular; moving the plug to the expanded configuration to form a pressure tight seal in the wellbore or tubular; moving the sealing element to the expanded configuration to form a pressure tight seal in the wellbore or tubular, thereby creating an isolated volume; activating the pressure adjustment means to increase or decrease the pressure in the isolated volume, thereby pressure testing the plug; and releasing the plug from the plug attachment means.

CLAUSE 21. A method of pressure testing and setting a plug in a single trip, comprising the steps of: providing a system according to any of clauses 12 to 17; releasably attaching the plug to the plug attachment means; running the system into a wellbore or tubular to a desired location in the wellbore or tubular; moving the sealing element to the expanded configuration to form a pressure tight seal in the wellbore or tubular; moving the plug to the expanded configuration to form a pressure tight seal in the wellbore or tubular, thereby creating an isolated volume; activating the pressure adjustment means to increase or decrease the pressure in the isolated volume, thereby pressure testing the plug; and releasing the plug from the plug attachment means.