Patent Publication Number: US-11021927-B2

Title: Well tool assembly

Description:
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. 
    
    
     
       DETAILED DESCRIPTION 
       Embodiments of the invention will be described in detail below with reference to the enclosed drawings, where: 
         FIG. 1  illustrates a perspective view of the well tool assembly in a run state, where the setting tool is illustrated schematically; 
         FIG. 2  illustrates a perspective view of the well tool assembly in the set state; 
         FIG. 3  illustrates a cross sectional view of the plugging tool in its run state; 
         FIG. 4  illustrates a side view of the plugging tool in its run state; 
         FIG. 5  illustrates a cross sectional view of the plugging tool in its set state; 
         FIG. 6  illustrates a side view of the plugging tool in its set state; 
         FIGS. 7 and 8  illustrates the well tool assembly in a well pipe in its run and set states respectively; 
         FIG. 9  illustrates an alternative embodiment where the inner mandrel device comprises a through bore; 
         FIG. 10  illustrates an alternative embodiment where the centralizing device is provided above the upper sealing device. 
     
    
    
     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 to  FIGS. 1 and 2 . Here, a well tool assembly  1  is shown comprising a setting tool  10  and a plugging tool  20 . 
     The setting tool  10  is shown schematically comprising an inner actuator  11  (drawn as an inner cylinder) and an outer actuator  16  (drawn as an outer cylinder) provided radially outside of the inner actuator  11 . The inner actuator  11  has an inner connection interface  12  in its lower end and the outer actuator  16  has an outer connection interface  17  in its lower end. The setting tool  10  is configured to provide relative axial motion between the inner and outer actuators  11 ,  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 tool  10  is considered known for a skilled person and will not be described further in detail herein. However, it should be noted that the setting tool  10  is configured to provide relative axial motion between the inner and outer actuators  11 ,  16  a number of times, without the need of retrieving the setting tool to surface. The setting tool  10 , as such, is known within the art and will not be described in any further detail here. However, a setting tool  10  suitable 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 actuators  11 ,  16  is to move the plugging tool  20  between its radially retracted state (shown in  FIG. 1 ) and its radially expanded state (shown in  FIG. 2 ). The radially retracted state is often referred to as the “run” state, as the plugging tool  20  is 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 tool  20  is in this state when set in the well (i.e. the plugging tool  20  is engaged with the inner surface of the well). 
     The plugging tool  20  comprises an inner mandrel device  21  and an outer housing device  26  provided radially outside of the inner mandrel device  21 . The inner mandrel device  21  has an inner connection interface  22  connected to the inner connection interface  12  of the setting tool  20  The outer housing device  26  has a outer connection interface  27  connected to the outer connection interface  17  of the setting tool  20 . The mandrel device  21  further comprises a bore B. 
     It should be noted that in  FIGS. 1 and 2 , the plugging tool  20  and the setting tool  10  are separated from each other. However, as is known for a skilled person, the setting tool  10  and the plugging tool  20  must be connected to each other in order to bring the plugging tool  20  between its radially retracted state and its radially expanded state. 
     The plugging tool  20  further comprises an upper sealing device  30 , a slips device  40 , a lower sealing device  50  and a centralizing device  60 . Each of the devices  30 ,  40 ,  50  and  60  can be brought between their radially retracted states of  FIG. 1  and their radially expanded states of  FIG. 2 . Each of these devices  30 ,  40 ,  50  and  60  are also provided radially outside of the mandrel device  21 . 
     It is now referred to  FIGS. 3 and 4  (retracted state) and  FIGS. 5 and 6  (expanded state). 
     The upper sealing device  30  comprises an upper section  31  connected to the outer housing device  26  and a lower section  32 . The upper section  31  comprises a first supporting element  37   a  and the lower section  32  comprises a second supporting element  37   b . An upper sealing element  35  is connected between the upper and lower sections  31 ,  32  of the upper sealing device  30  and circumferentially around and outside of the inner mandrel device  21 , between the first and second supporting elements  37   a ,  37   b . As is known, such sealing elements  35  may be made of a rubber or elastomeric or other suitable material. Axial movement of the upper and lower sections  31 ,  32  towards each other will cause a radial expansion of the sealing element  35 , where the supporting elements  37   a ,  37   b  are supporting the sealing element  35  in the radially expanded state. In the radially expanded state, the sealing element  35  is pressed towards the well pipe to prevent axial fluid flow in the annular compartment between the plugging tool  20  and the well pipe, more specifically in the annular compartment between the mandrel device  21  of the plugging tool  20  and the well pipe. Axial movement of the upper and lower sections  31 ,  32  away from each other will cause a radial retraction of the sealing element  35 . 
     The slips device  40  comprises an upper section  41  connected to the lower section  32  of the upper sealing device  30  and a lower section  42 . A slips element  45  is connected between the upper and lower sections  41 ,  42  of the slips device  40 . In the present embodiment, the slips device  40  comprises three, five or seven slips elements  45 . In the radially expanded state, the slips elements  45  are pressed towards the well pipe to prevent axial movement of the plugging tool  20  in relation to the well pipe. Each slips element  45  comprises a teethed outer surface  46  to improve its engagement with the inner surface of the well pipe. The slips device  40  also contributes to centralize the plugging tool  20  with respect to the well pipe, i.e. to provide that the longitudinal center axis I of the plugging tool  20  substantially coincides with the longitudinal center axis Iw (shown in  FIGS. 7 and 8 ) of the well pipe. 
     The slips element  45  is connected to the upper section  41  and the lower section  42  by means of slits provided in wedge-shaped surfaces, pivotably connections etc. Hence, relative axial movement of the upper section  41  and the lower section  42  towards each other is causing the slips element  45  to radially expand in relation to the inner mandrel device  21 . Relative axial movement of the upper section  41  and the lower section  42  away from each other is causing the slips element  45  to radially retract. 
     The lower sealing device  50  is similar to the upper sealing device  30  and comprises an upper section  51  connected to the lower section  42  of the slips device  40  and a lower section  52 . The upper section  51  comprises a first supporting element  57   a  and the lower section  52  comprises a second supporting element  57   b  with similar purpose as the supporting elements  37   a ,  37   b  described above. A lower sealing element  55  is connected between the upper and lower sections  51 ,  52  of the slips device  40 . In the radially expanded state, the sealing element  55  is pressed towards the well pipe to prevent axial fluid flow in the annular compartment between the plugging tool  20  and the well pipe. 
     The centralizing device  60  comprises an upper section  61  connected to the lower section  52  of the lower sealing device  50  and a lower section  62 . A centralizer element  65  is connected between the upper and lower sections  61 ,  62  of the centralizing device  60 . In the present embodiment, the centralizing device  50  comprises three centralizer elements  55 . In the radially expanded state, the centralizer element  65  is pressed towards the well pipe to centralize the plugging tool  20  together with the slips device  40 . 
     The upper and lower sealing devices  30 ,  50  is 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 device  40  is 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 device  60  is substantially equal to the slips device  40 , where the main difference is that the centralizer elements  65  have a smooth surface facing towards the inner surface of the well pipe. Another difference is that the number of centralizer elements  65  is lower (in this embodiment three) than the number of slips elements  45  (in this embodiment five). 
     The upper sealing device  30 , the slips device  40 , the lower sealing device  50  and the upper section  61  of the centralizing device  60  are axially displaceable downwardly and upwardly in relation to the mandrel device  21 . According to this feature, it is apparent that the plugging tool  20  does 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 tool  20  is ratchet-less. It should be noted that the setting tool  10  of the assembly  1  is ratchet-less as well. 
     In this embodiment, the centralizing device  60  is the lowest one of the devices  30 ,  40 ,  50 ,  60 . Here, the lower section  62  of the centralizing device  60  is fixed to the mandrel device  21 . By fixing the lower section  63  to the inner mandrel device  21 , the axial displacement of the devices  30 ,  40 ,  50 ,  60  in relation to the mandrel device  21  is limited. 
     Accordingly, the setting tool  10  can bring the plugging tool  20  from 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 assembly  1  to surface. Each time the plugging tool  20  is 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 device  40  is located between the upper and lower sealing devices  30 ,  50  and that the load is transferred from the sealing devices  30 ,  50  to the slips device. 
     Hence, when the plugging tool  20  is in the radially expanded state in the well pipe and the well pressure is higher below the lower sealing device  50  than above the upper sealing device  30 , the fluid pressure acting on the lower sealing device  50  will press the slips element  45  of the slips device  40  radially out towards the well pipe and hence prevent the plugging tool  20  to move in relation to the well pipe. 
     In the same way, when the plugging tool  20  is in the radially expanded state in the well pipe and the well pressure is higher above the upper sealing device  30  than below the lower sealing device  50 , the fluid pressure acting on the upper sealing device  30  press the slips element  45  of the slips device  40  radially out towards the well pipe and hence prevent the plugging tool  20  to move in relation to the well pipe. 
     In an alternative embodiment, the centralizing device  60  could be provided above the upper sealing device  30 . In such an embodiment, also the lower section  62  of the centralizing device  60  will be axially displaceable downwardly and upwardly in relation to the inner mandrel device  21 , i.e. the entire centralizing device  60  is axially displaceable downwardly and upwardly in relation to the inner mandrel device  21 . In such an embodiment, the lower sealing device  50  will be the lowest one of the devices  30 ,  40 ,  50 ,  60 , and the lower centralizing element  62  will be fixed to the mandrel device  21 . Hence, the also here, the axial displacement of the devices  30 ,  40 ,  50 ,  60  in relation to the mandrel device  21  is limited. And again, also here, the slips device  40  is located between the upper and lower sealing devices  30 ,  50 . 
     As shown in  FIGS. 3 and 4 , the lower section  62  of the centralizing device  60  is comprising a nose section  70  of the plugging tool  20 , where the lose section  70  is closing the bore B of the inner mandrel device  21 . 
     It is now referred to  FIGS. 3 and 5 . Here, it is shown that the upper sealing device  30  and the lower sealing device  50  each comprises a pressure or force distribution device  36 ,  56 . The pressure or force distribution device  36 ,  56  is 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 devices  36 ,  56  is to avoid that the radial expansion (caused by axial compression) of the sealing elements  35 ,  55  by means of the supporting elements  37   a ,  37   b ,  57   a ,  57   b  is reduced due to pressure variations and/or temperature variations etc. 
     In the present embodiment, the devices  30 ,  40 ,  50 ,  60  are connected to each other by means of bolts  81  provided in tangential bolt openings  82  as indicated in  FIGS. 1 and 3 . In  FIG. 1 , a tangential line I 80  is shown, indicating the direction of one of the tangential bolt openings  82 . Such bolt connections are known for the skilled person, for example from NO 340229 (also in the name of Interwell). 
     It is now referred to  FIGS. 7 and 8 , where the well tool assembly  1  described 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 device  30  or below the lower sealing device  50 . 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 device  30 . 
     A method for pressure testing of a section of a well W will be described below with reference to  FIGS. 7 and 8 . The well pipe is indicated with letters WP. 
     Initially, the setting tool  10  and the plugging tool  20  is assembled into the assembly  1  and lowered into the desired location in the well. The plugging tool  20  is in the retracted state during the lowering operation. 
     At the desired location, the setting tool  10  is actuated (by means of a topside signal, a pre-determined condition (desired depth, pressure, temperature etc.) to bring the plugging tool  20  to its radially expanded state. This is performed by moving the mandrel device  21  upwardly in relation to the outer housing  26  (or moving the outer housing  26  downwardly in relation to the mandrel device  21 ). Accordingly, the upper sealing device  30 , the slips device  40 , the lower sealing device  50  and the centralizing device  60  will be moved from their radially retracted state shown in  FIG. 7  to their radially expanded state shown in  FIG. 8 . 
     When set, the pressure testing can be performed. This is typically performed by increasing the pressure above the plugging tool  20 , thereby causing a higher pressure above the plugging tool  20  than below the plugging tool  20  and 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 tool  20  is decreased, thereby causing a higher pressure below the plugging tool  20  than above the plugging tool  20 . 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 device  50 . 
     After the pressure testing, the upper sealing device  30 , the slips device  40 , the lower sealing device  50  and the centralizing device  60  is brought from their radially expanded state to their radially retracted state again by means of the setting tool  10 . 
     Then, the well tool assembly  1  is moved to a new desired location in the well, and the procedure is repeated (expansion, testing, retraction, moving . . . ). 
     The setting tool  10  and the plugging tool  20  are 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 tool  20  are transferred from the upper and/or lower sealing devices  30 ,  50  to the slips device  40 . 
     Hence, the testing procedure is more efficient than prior art. 
     Alternative Embodiments 
     As the setting tool  10  and the plugging tool  20  described 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 to  FIG. 9 , illustrating an alternative embodiment of the plugging tool  20  described above. Here, the bore B of the inner mandrel device  21  is 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).