Well tool assembly

The invention relates to a well tool assembly (1) comprising a setting tool (10) and a plugging tool (20). The plugging tool (20) comprises:

FIELD OF THE INVENTION

The present invention relates to a well tool assembly comprising a setting tool and a plugging tool. The well tool assembly is used for pressure testing of a well. The present invention also relates to a method for pressure testing a well. In particular, the well tool assembly and method is used for pressure testing of different zones in the well.

BACKGROUND OF THE INVENTION

During operations in hydrocarbon producing wells, there is a need to test different zones in the well. In one situation, one zone in the well may be producing water instead of oil/gas. It is then necessary to determine the location of that water-producing zone and thereafter to isolate that water-producing zone of the well. The operation of determining the location of such a zone is often time-consuming. One common way of doing this is to lower and set a plugging tool at an initial location in the well. The setting tool is then retrieved to surface, whereafter the content of the well fluid from the formation above the plug is analyzed to check if the initial location was the correct location. If not, the plugging tool is released by a releasing tool, retrieved to surface and a new plug is run to a new location before setting of the plugging tool again. Some plugging tools requires the releasing tool and the plugging tool to be retrieved to surface and reconfigured before a setting tool is used to set the plugging device again.

Another operation performed in such wells is a pressure test of the tubing itself, to check for leakages in the tubing pipe joints. Another type of pressure test is the pressure test of the gas lift valves.

Such plugging tools are typically using a ratchet mechanism to lock the plugging tool in its set (radially expanded) state, even if the setting tool is still connected to the plugging tool. This is necessary, as setting tools has a limited setting force. As an example, some setting tools have a setting force of 15 tons. However, when set, the differential pressure over a sealing element of such a plugging tool may be as high as 70 000 lbf (corresponding to a weight of 31 tons), which will press the setting tool upwardly and destroy the setting tool. The disadvantage with the ratchet mechanism is that, when set, it is cumbersome to reset again, as this typically requires a disassembly of the tool. Hence, it is often the resetting of the ratchet mechanism which is causing the number of runs needed during the abovementioned operations.

Hence, it is an object of the invention to provide a simple and efficient well tool assembly for testing zones in a well. A further object is to provide a well tool assembly which may be run by means of wireline, e-line or similar, i.e. without drill pipe or without coiled tubing. Yet a further object is to provide a well tool assembly where the setting tool is capable of bringing the plugging tool between its run state and its set state a number of times, while the setting tool and plugging tool are connected to each other. Of course, it is an object that the plugging tool should be able to withstand a high pressure without any risk of destroying the setting tool. Yet a further object is to provide a well tool assembly without a ratchet mechanism. Another purpose of the present invention is to provide a method for pressure testing of a well which is efficient and fast.

SUMMARY OF THE INVENTION

The present invention relates to a well tool assembly comprising a setting tool and a plugging tool, where the setting tool comprises:an inner actuator having a inner connection interface in its lower end;an outer actuator having a outer connection interface in its lower end, where the setting tool is configured to provide relative axial motion between the inner and outer actuators, thereby causing the plugging tool to be moved between its radially retracted state and its radially expanded state;
where the plugging tool comprises:an inner mandrel device having a inner connection interface connected to the inner connection interface of the setting tool;an outer housing device provided radially outside of the mandrel device having a outer connection interface connected to the outer connection interface of the setting tool;an upper sealing device comprising an upper sealing element provided axially between an upper section and a lower section;a slips device comprising a slips element provided axially between an upper section and a lower section;a lower sealing device comprising a sealing element provided axially between an upper section and a lower section;a centralizing device comprising a centralizer element provided axially between an upper section and a lower section;
where the devices are provided radially outside of the mandrel device;
where the devices are connected to each other;
where the slips device is provided axially between the upper and lower sealing devices;
where the centralizing device is provided below the lower sealing device or above the upper sealing device;
where, when the centralizing device is provided below the lower sealing device:the upper sealing device, the slips device, the lower sealing device and the upper section of the centralizing device are axially displaceable downwardly and upwardly in relation to the mandrel device;the upper section of the upper sealing device is connected to the outer housing device and the lower section of the centralizing device is fixed to the inner mandrel device;
or where, when the centralizing device is provided above the upper sealing device:the centralizing device, the upper sealing device, the slips device and the upper section of the lower sealing device are axially displaceable downwardly and upwardly in relation to the mandrel device;the upper section of the centralizing device is connected to the outer housing device and the lower section of the lower sealing device is fixed to the inner mandrel device.

Accordingly, there are two different options with respect to where the centralizing device is located.

In one aspect, the assembly is a pressure testing well tool assembly for pressure testing of a section of a well. However, the assembly can be used for other purposes as well.

The plugging tool is a ratchet-less plugging tool, as all parts of the devices are axially displaceable downwardly and upwardly in relation to the mandrel device, with the exception of the lower section of the lowermost device, which are fixed to the inner mandrel device.

In one aspect, the lower section of the lowermost device is comprising a nose section of the plugging tool, where the lose section is providing a closing of a bore through the inner mandrel device. In an alternative embodiment, the bore is a through bore. Also here, a nose section can be provided to ease the lowering of the plugging tool into the well, where the bore through the mandrel device is continued through the nose section.

In one aspect the upper sealing device and the lower sealing device each comprises a pressure or force distribution device.

In one aspect, when the plugging tool is in the radially expanded state in a well pipe, and the well pressure is higher below the lower sealing device than above the upper sealing device, the fluid pressure acting on the lower sealing device will cause the slips device to radially expand the slips element radially out towards the well pipe.

In one aspect, when the plugging tool is in the radially expanded state in a well pipe, and the well pressure is higher above the upper sealing device than below the lower sealing device, the fluid pressure acting on the upper sealing device will cause the slips device to radially expand the slips element radially out towards the well pipe.

In one aspect, the outer housing and the devices are connected to each other by means of bolts inserted into tangential bolt openings of the respective upper and lower sections.

The present invention also relates to a method for pressure testing of a section of a well, the method comprising the steps of:

a) lowering a well tool assembly comprising a setting tool and a plugging tool to a desired location in the well, the plugging tool comprising inner mandrel device, a outer housing device, a upper sealing device, a slips device, a lower sealing device and a centralizing device;
b) bringing, by means of the setting tool, the upper sealing device, the slips device, the lower sealing device and the centralizing device from their radially retracted state to their radially expanded state;
c) performing the pressure testing by increasing the pressure below and/or above the plugging tool;
d) bringing, by means of the setting tool, the upper sealing device, the slips device, the lower sealing device and the centralizing device from their radially expanded state to their radially retracted state;
e) moving the well tool assembly to a new desired location in the well;
f) repeating steps b-d.

Preferably, the setting tool is connected to the plugging tool during all steps a-f.

The terms “upper”, “above”, “below” and “lower” is used in the document to define positions in a well. “Upper” and “above” in the context of this document mean closer to the well opening and “lower” further away from the well opening. These terms apply both when the well has a vertical and horizontal orientation.

A “ratchet mechanism” is a well known mechanism for tools used in oil and/or gas wells. The ratchet mechanism may have many different designs, but the main principle is that relative axial movement between an inner pipe with respect to an outer pipe is allowed in one direction only, while relative axial movement in the opposite direction is prevented. One example of such a “ratchet mechanism” is known from WO 2016087641 in the name of Interwell.

It is now referred toFIGS. 1 and 2. Here, a well tool assembly1is shown comprising a setting tool10and a plugging tool20.

The setting tool10is shown schematically comprising an inner actuator11(drawn as an inner cylinder) and an outer actuator16(drawn as an outer cylinder) provided radially outside of the inner actuator11. The inner actuator11has an inner connection interface12in its lower end and the outer actuator16has an outer connection interface17in its lower end. The setting tool10is configured to provide relative axial motion between the inner and outer actuators11,16.

This relative axial motion may for example be provided by an electric actuator, for example an electric motor powered by a battery. In such an embodiment, the setting tool may be lowered into the well by means of a wireline. Alternatively, the setting tool may be lowered into the well by means of an e-line for transferring signals (and possibly also electric power, replacing the need for a battery) between the setting tool and topside.

In yet an alternative embodiment, the relative axial motion is provided by an hydraulic actuator, for example a hydraulic pump connected to an electric motor powered by a battery.

The setting tool10is considered known for a skilled person and will not be described further in detail herein. However, it should be noted that the setting tool10is configured to provide relative axial motion between the inner and outer actuators11,16a number of times, without the need of retrieving the setting tool to surface. The setting tool10, as such, is known within the art and will not be described in any further detail here. However, a setting tool10suitable for use in the assembly of the present invention may for example be of the type presently used in the EST tool (Electronic Setting Tool) marketed by Interwell.

The purpose of the relative axial motion between the inner and outer actuators11,16is to move the plugging tool20between its radially retracted state (shown inFIG. 1) and its radially expanded state (shown inFIG. 2). The radially retracted state is often referred to as the “run” state, as the plugging tool20is in this state when run into or lowered into the well. The radially expanded state is often referred to as the “set” state, as the plugging tool20is in this state when set in the well (i.e. the plugging tool20is engaged with the inner surface of the well).

The plugging tool20comprises an inner mandrel device21and an outer housing device26provided radially outside of the inner mandrel device21. The inner mandrel device21has an inner connection interface22connected to the inner connection interface12of the setting tool20The outer housing device26has a outer connection interface27connected to the outer connection interface17of the setting tool20. The mandrel device21further comprises a bore B.

It should be noted that inFIGS. 1 and 2, the plugging tool20and the setting tool10are separated from each other. However, as is known for a skilled person, the setting tool10and the plugging tool20must be connected to each other in order to bring the plugging tool20between its radially retracted state and its radially expanded state.

The plugging tool20further comprises an upper sealing device30, a slips device40, a lower sealing device50and a centralizing device60. Each of the devices30,40,50and60can be brought between their radially retracted states ofFIG. 1and their radially expanded states ofFIG. 2. Each of these devices30,40,50and60are also provided radially outside of the mandrel device21.

The upper sealing device30comprises an upper section31connected to the outer housing device26and a lower section32. The upper section31comprises a first supporting element37aand the lower section32comprises a second supporting element37b. An upper sealing element35is connected between the upper and lower sections31,32of the upper sealing device30and circumferentially around and outside of the inner mandrel device21, between the first and second supporting elements37a,37b. As is known, such sealing elements35may be made of a rubber or elastomeric or other suitable material. Axial movement of the upper and lower sections31,32towards each other will cause a radial expansion of the sealing element35, where the supporting elements37a,37bare supporting the sealing element35in the radially expanded state. In the radially expanded state, the sealing element35is pressed towards the well pipe to prevent axial fluid flow in the annular compartment between the plugging tool20and the well pipe, more specifically in the annular compartment between the mandrel device21of the plugging tool20and the well pipe. Axial movement of the upper and lower sections31,32away from each other will cause a radial retraction of the sealing element35.

The slips device40comprises an upper section41connected to the lower section32of the upper sealing device30and a lower section42. A slips element45is connected between the upper and lower sections41,42of the slips device40. In the present embodiment, the slips device40comprises three, five or seven slips elements45. In the radially expanded state, the slips elements45are pressed towards the well pipe to prevent axial movement of the plugging tool20in relation to the well pipe. Each slips element45comprises a teethed outer surface46to improve its engagement with the inner surface of the well pipe. The slips device40also contributes to centralize the plugging tool20with respect to the well pipe, i.e. to provide that the longitudinal center axis I of the plugging tool20substantially coincides with the longitudinal center axis Iw (shown inFIGS. 7 and 8) of the well pipe.

The slips element45is connected to the upper section41and the lower section42by means of slits provided in wedge-shaped surfaces, pivotably connections etc. Hence, relative axial movement of the upper section41and the lower section42towards each other is causing the slips element45to radially expand in relation to the inner mandrel device21. Relative axial movement of the upper section41and the lower section42away from each other is causing the slips element45to radially retract.

The lower sealing device50is similar to the upper sealing device30and comprises an upper section51connected to the lower section42of the slips device40and a lower section52. The upper section51comprises a first supporting element57aand the lower section52comprises a second supporting element57bwith similar purpose as the supporting elements37a,37bdescribed above. A lower sealing element55is connected between the upper and lower sections51,52of the slips device40. In the radially expanded state, the sealing element55is pressed towards the well pipe to prevent axial fluid flow in the annular compartment between the plugging tool20and the well pipe.

The centralizing device60comprises an upper section61connected to the lower section52of the lower sealing device50and a lower section62. A centralizer element65is connected between the upper and lower sections61,62of the centralizing device60. In the present embodiment, the centralizing device50comprises three centralizer elements55. In the radially expanded state, the centralizer element65is pressed towards the well pipe to centralize the plugging tool20together with the slips device40.

The upper and lower sealing devices30,50is considered known in the art and will not be described in any further detail here. However, a sealing device suitable for use in the plugging tool of the present invention may for example be of the type presently used in the Matrix platform plug marketed by Interwell.

The slips device40is considered known in the art and will not be described in any further detail here. However, a slips device suitable for use in the plugging tool of the present invention may for example be of the type presently used in the Matrix platform plug marketed by Interwell.

The centralizing device60is substantially equal to the slips device40, where the main difference is that the centralizer elements65have a smooth surface facing towards the inner surface of the well pipe. Another difference is that the number of centralizer elements65is lower (in this embodiment three) than the number of slips elements45(in this embodiment five).

The upper sealing device30, the slips device40, the lower sealing device50and the upper section61of the centralizing device60are axially displaceable downwardly and upwardly in relation to the mandrel device21. According to this feature, it is apparent that the plugging tool20does not comprise a ratchet mechanism, as the ratchet mechanism described above only allows relative axial displacement in one direction (either upwardly or downwardly). Hence, the plugging tool20is ratchet-less. It should be noted that the setting tool10of the assembly1is ratchet-less as well.

In this embodiment, the centralizing device60is the lowest one of the devices30,40,50,60. Here, the lower section62of the centralizing device60is fixed to the mandrel device21. By fixing the lower section63to the inner mandrel device21, the axial displacement of the devices30,40,50,60in relation to the mandrel device21is limited.

Accordingly, the setting tool10can bring the plugging tool20from its radially retracted state to its radially expanded state and back to the radially retracted state a number of times without the need for bringing the assembly1to surface. Each time the plugging tool20is in the radially expanded state, the plugging tool is able to withstand high relative pressures over the plugging tool, in both directions. This is possible due to the fact that the slips device40is located between the upper and lower sealing devices30,50and that the load is transferred from the sealing devices30,50to the slips device.

Hence, when the plugging tool20is in the radially expanded state in the well pipe and the well pressure is higher below the lower sealing device50than above the upper sealing device30, the fluid pressure acting on the lower sealing device50will press the slips element45of the slips device40radially out towards the well pipe and hence prevent the plugging tool20to move in relation to the well pipe.

In the same way, when the plugging tool20is in the radially expanded state in the well pipe and the well pressure is higher above the upper sealing device30than below the lower sealing device50, the fluid pressure acting on the upper sealing device30press the slips element45of the slips device40radially out towards the well pipe and hence prevent the plugging tool20to move in relation to the well pipe.

In an alternative embodiment, the centralizing device60could be provided above the upper sealing device30. In such an embodiment, also the lower section62of the centralizing device60will be axially displaceable downwardly and upwardly in relation to the inner mandrel device21, i.e. the entire centralizing device60is axially displaceable downwardly and upwardly in relation to the inner mandrel device21. In such an embodiment, the lower sealing device50will be the lowest one of the devices30,40,50,60, and the lower centralizing element62will be fixed to the mandrel device21. Hence, the also here, the axial displacement of the devices30,40,50,60in relation to the mandrel device21is limited. And again, also here, the slips device40is located between the upper and lower sealing devices30,50.

As shown inFIGS. 3 and 4, the lower section62of the centralizing device60is comprising a nose section70of the plugging tool20, where the lose section70is closing the bore B of the inner mandrel device21.

It is now referred toFIGS. 3 and 5. Here, it is shown that the upper sealing device30and the lower sealing device50each comprises a pressure or force distribution device36,56. The pressure or force distribution device36,56is known for a skilled person, for example from NO 339646 (also in the name of Interwell). NO 339646 is hereby incorporated by reference. The purpose of the force or pressure distribution devices36,56is to avoid that the radial expansion (caused by axial compression) of the sealing elements35,55by means of the supporting elements37a,37b,57a,57bis reduced due to pressure variations and/or temperature variations etc.

In the present embodiment, the devices30,40,50,60are connected to each other by means of bolts81provided in tangential bolt openings82as indicated inFIGS. 1 and 3. InFIG. 1, a tangential line I80is shown, indicating the direction of one of the tangential bolt openings82. Such bolt connections are known for the skilled person, for example from NO 340229 (also in the name of Interwell).

It is now referred toFIGS. 7 and 8, where the well tool assembly1described above is used as a pressure testing well tool assembly for pressure testing of a section of a well. A “section of a well” is here referring to a section of a well above the upper sealing device30or below the lower sealing device50. This “section” can be a length of a well pipe, (to check the integrity of pipe joints etc. Alternatively, if the well pipe is perforated, this “section” can be a zone of the well (i.e. the formation surrounding the well pipe is also pressure tested). It should be noted that the section of a well may also be located above the upper sealing device30.

A method for pressure testing of a section of a well W will be described below with reference toFIGS. 7 and 8. The well pipe is indicated with letters WP.

Initially, the setting tool10and the plugging tool20is assembled into the assembly1and lowered into the desired location in the well. The plugging tool20is in the retracted state during the lowering operation.

At the desired location, the setting tool10is actuated (by means of a topside signal, a pre-determined condition (desired depth, pressure, temperature etc.) to bring the plugging tool20to its radially expanded state. This is performed by moving the mandrel device21upwardly in relation to the outer housing26(or moving the outer housing26downwardly in relation to the mandrel device21). Accordingly, the upper sealing device30, the slips device40, the lower sealing device50and the centralizing device60will be moved from their radially retracted state shown inFIG. 7to their radially expanded state shown inFIG. 8.

When set, the pressure testing can be performed. This is typically performed by increasing the pressure above the plugging tool20, thereby causing a higher pressure above the plugging tool20than below the plugging tool20and then monitor the pressure to check if the pressure is maintained at the desired level. If the pressure is not maintained at the desired level, for example the pressure is decreasing, this will normally represent an indication of a leakage. It is also possible to perform a test where pressure above the plugging tool20is decreased, thereby causing a higher pressure below the plugging tool20than above the plugging tool20. Again, the pressure is monitored for a period of time.

The measurement of the pressure is measured by a topside sensor, or a sensor provided below the lower sealing device50.

After the pressure testing, the upper sealing device30, the slips device40, the lower sealing device50and the centralizing device60is brought from their radially expanded state to their radially retracted state again by means of the setting tool10.

Then, the well tool assembly1is moved to a new desired location in the well, and the procedure is repeated (expansion, testing, retraction, moving . . . ).

The setting tool10and the plugging tool20are connected to each other during these tests without any need to retrieve them to surface and without any risk of damaging the setting tool, as pressure differences over the plugging tool20are transferred from the upper and/or lower sealing devices30,50to the slips device40.

Hence, the testing procedure is more efficient than prior art.

Alternative Embodiments

As the setting tool10and the plugging tool20described above are connected to each other during the pressure testing operation, the well tool assembly could be assembled as one unit.

It is now referred toFIG. 9, illustrating an alternative embodiment of the plugging tool20described above. Here, the bore B of the inner mandrel device21is a through bore. This embodiment can be used for well stimulation operations, fracking operations, washing operations (washing of perforations in well pipe, washing of screen etc).