Patent Application
20200190930
The present invention relates to methods and apparatus for well abandonment and slot recovery and in particular, though not exclusively, to a method and apparatus for casing recovery.
When a well has reached the end of its commercial life, the well is abandoned according to strict regulations in order to prevent fluids escaping from the well on a permanent basis. In meeting the regulations it has become good practise to create the cement plug over a predetermined length of the well and to remove the casing. Current techniques to achieve this may require multiple trips into the well, for example: to set a bridge plug to support cement; to create a cement plug in the casing; to cut the casing above the cement plug; and to pull the casing from the well. A further trip can then be made to cement across to the well bore wall. The cement or other suitable plugging material forms a permanent barrier to meet the legislative requirements.
Each trip into a well takes substantial time and consequently significant costs. Combined casing cutting and pulling tools have been developed so that the cutting and pulling can be achieved on a single trip.
In the ideal scenario, such tools would cut the casing at a maximum depth and then pull a section of the longest length possible from the well on a single trip. However, the presence of drilling fluid sediments, cement, sand or other debris behind the casing can prevent the casing from being pulled.
US2015047845 to Well Technology AS describes a method of removing casing from a well, in which an annulus between the outside of the casing and the inside of a surrounding downhole body is at least partially filled by a viscous and/or solid mass, the method comprising:
This method advantageously washes out all material in the annulus between the outside of the casing and the inside of a surrounding downhole body, so that the casing is free to be cut and pulled without sticking. However, to ensure that all the viscous and/or solid mass is circulated up the annulus and out of the well, only short sections of casing can be washed, cut and pulled on each trip into the well. The process is thus started near the top of a section of casing, a short length of casing is perforated, washed and pulled, the casing being typically only a few metres in length. Additionally, the time taken to wash out the length of casing can be significant. The short length of casing is brought to surface and further trips are undertaken to perforate, wash, cut and pull subsequent lengths until the full length of the casing section is removed. The total time taken to remove the entire casing section is therefore very long.
Additionally, the viscous and/or solid mass is considered only to be old, settled-out drilling mud of large mud weight. In some cases, however, cement may be present, typically distributed unevenly, this may bridge the annulus between the outside of the casing and the inside of a surrounding downhole body at one or more points but not entirely around the circumference of the annulus. Washing will appear complete having occurred around the cement, but the cut casing section will be stuck due to the cement connectivity holding the casing to the surrounding outer body. This cement cannot be washed away as a fluid path exists around it.
In order to wash out greater lengths of casing, so that a longer length of casing can be pulled on a single trip, WO2015/105427 discloses a method for pulling out casing pipes or liner in a petroleum well, characterized by the combination of the following steps:
The actual section of casing pipe is a length of casing which is longer than the perforation gun so that casing of lengths of 10 to 100 metres can be perforated along the entire length and circumference. Advantageously the distance between the gaskets on the wash tool is significantly smaller than the perforated casing length and thus wash fluid expelled out through the perforations will return to the annulus between the drill pipe and the casing at locations above the wash tool, to be circulated to surface. The wash fluid will carry debris back into the annulus for return also which is much more efficient than the washing process of US2015047845. The smaller distance between gaskets and multiple perforations also provide the potential to remove any cement present.
However, there are a number of disadvantages with this technique. The perforations must begin at the top of the length of casing that is to be removed, otherwise the debris in the annulus between the casing and the formation above the perforations may prevent the casing being removed. The location of the top perforations then becomes critical as sufficient length of unperforated casing to engage the casing spear is required. Engaging a spear on perforated casing may cause collapse of the casing as its integrity has been lost by perforation. Indeed, in well abandonment the casing may be old and corroded so that making multiple perforations weakens the casing and, when pulled, lower sections may break off. Yet further, lengths of perforated casing are more difficult to handle on surface. Like the earlier patent application, this technique also teaches to begin at the top of the casing section and move down the wellbore.
It is therefore an object of the present invention to provide a method of removing casing from a well which obviates or mitigates one or more disadvantages of the prior art.
According to a first aspect of the present invention there is provided a method of removing casing from a well, in which an annulus between the outside of the casing and the inside of a surrounding downhole body is at least partially filled by debris, particles or cement or other binding substance connecting the outside of the casing and the inside of a surrounding downhole body, the method comprising:
In looking for a return at surface a circulation test is performed. In this way, it can be determined if fluid has managed to pass through material in the annulus between the outside of the casing and the inside of the surrounding downhole body and if it has, there is a possibility that the casing can be pulled. In this way, the method can be used to pull longer lengths of casing than for the prior art, by starting at a lower depth and testing to see if the longest length can be cut and pulled.
Preferably, the vibratory action is created by an agitator device. Such a device may be the Agitator™ system provided by National Oilwell Varco. More preferably, the vibratory action cyclically varies tension applied to the length of cut casing. It is considered that such a pulling force will be more effective in releasing stuck casing, particularly in the event that cement connectivity is present in the annulus. Additionally or alternatively, the vibratory action generates pressure pulses or pressure variations in fluid circulating fluid through the length of cut casing. Applying pressure pulses through the casing cut will assist in dislodging the debris, particles or cement or other binding substance in the annulus. The vibratory action therefore advantageously allows the longer lengths of casing to be pulled which would otherwise be considered as stuck if pulling was only undertaken by a casing spear.
If the circulation test is negative, and no return is detected at surface, the method includes repeating steps (c) to (h) at a shallower depth in the well. In this way, the steps are cycled until a positive circulation test is obtained. Thus the method will perforate and test at increasingly shallower depths until a first length of casing is cut and pulled. This advantageously speeds up the removal process as the steps of cutting and pulling do not occur until the longest length of casing that is likely to be free to pull is found. This is achieved on a single trip in the well.
Additionally, as washing through the perforations to circulate all the material to surface before a cut is made is not performed, the process is faster than the prior art by removing a separate washing step.
Preferably, upon pulling of a first casing section, steps (c) to (h) can be repeated at a greater depth to remove a second casing section. As the weight of material and casing will now be less, circulation may be achievable and further lengths of casing pulled.
Preferably, fluid is circulated through the cutting tool, the casing at the cut and up the annulus between the outside of the casing and the inside of the surrounding downhole body. In this way, material can be circulated out of the annulus between the outside of the casing and the inside of the surrounding downhole body during cutting and pulling of the length of cut casing. This can aid the cutting and pulling action.
By including a punch tool for making the perforations, step (d) can be performed before step (c) with the packer being set in advance of making the perforations as the punch tool can be operated without requiring circulation up the annulus between the string and the casing. In this way, well control is maintained during perforation. Additionally, the packer can advantageously be used to stabilise the punch tool in operation.
Preferably, tension is applied to the string to expand the packer. More preferably the tension is applied to operate the punch tool. In this way, the packer can be set in the same action as operating the punch tool.
Advantageously, there may be an anchor located on the string and the method includes the step of anchoring the string to the casing. In this way, the anchor can be used to pull tension against, assist in stabilising the punch tool, assist in stabilising the cutting tool and be used to grip and pull the cut casing to surface.
Optionally, the method includes an initial step of creating one or more upper perforations using the punch tool towards an upper end of the casing to be cut. Such upper perforations allow the migration of gas from the annulus between the casing and the downhole body. Advantageously, the upper perforations can be used as a return path to test for circulation when a wellhead seal assembly is in place. In such a case, the method may also include the step of pulling the wellhead seal assembly when the casing is pulled.
Optionally the method includes the step of creating one or more test perforations using the punch tool, such test perforations will be at a depth shallower than the third depth. Preferably the method then includes the step of performing a circulation test by circulating fluid between the perforations and the test perforations to detect circulation at surface. In this way, the method can include testing to identify a level of fill in the annulus between the casing and the surrounding downhole body.
Preferably, in step (g) the casing is cut by making a circumferential cut through the casing. In the preferred embodiment the cutting tool is a pipe cutter. Those skilled in the art will realise that other methods of casing cutting may be used such as jet cutting, laser cutting and chemical cutting.
Preferably, the string is a coiled tubing string. In this way, the cutting tool can be operated by rotation from surface. Alternatively, the string may be a drill string.
The surrounding downhole body may be the formation of the borehole. Optionally, the surrounding downhole body is a surrounding casing. The annulus is then the so-called B-annulus between the innermost casing and a surrounding casing.
The method may include setting the plug at the first depth to provide the seal across the bore of the casing. The method may include the step of setting the plug on the same trip as completing the other steps. In this way a further trip in the well is removed. Alternatively or additionally, the method may include pumping cement onto plug to provide the seal. In this way, the first depth will be at the top of the cement plug. The step of pumping cement may be completed on the same trip as setting the plug. In this way the number of trips is further reduced. Advantageously, the step of creating a vibratory action can be used when placing pumping the cement to aid even settlement of the cement.
The method may include the step of dressing a cement plug. In this way, the seal may be a cement plug already located in the well.
According to a second aspect of the present invention there is provided apparatus for the removal of casing from a well, comprising a string for running inside the casing, the string including a punch tool, a cutting tool, a packer, a casing spear and an agitator device.
In this way, the steps of setting the packer, operating the punch tool, testing for circulation behind the casing, cutting the casing and pulling the casing can be achieved on a single trip into the well.
Preferably, the agitator device is a pressure pulse-generator actuated by fluid being circulated through the string. Alternatively the agitator device is a tubular member for mounting on the string, the member comprising a flow modifier for producing cyclic variations in the flow of fluid therethrough and extension and retraction means adapted to axially extend or contract in response to said cyclic variations in the flow of fluid through the string. Preferably, the agitator device is the Agitator™ system provided National Oilwell Varco.
Preferably the casing spear comprises an anchor, the anchor being used to grip the inside surface of the casing. In this way, the string can be anchored to the casing and the cut casing can be pulled from the well.
Preferably the packer is a tension set packer. In this way, on setting the anchor below the packer, the packer can then be set by performing an overpull. The packer creates a two way seal in the annulus between the string and the inner wall of the casing.
Preferably, the punch tool is a tubing punch. In this way, single holes are punched from the casing without the use of explosives and without creating swarf and other cuttings. Circulation is also not required in the punch process.
Preferably, the cutting tool comprises a plurality of blades which are rotated to cut through the casing. In this way the cutting tool may be operated by rotating the string.
The apparatus may include one or more ports to allow fluid to pass radially out of the string as an alternative to exiting at the end of the string. Preferably, the ports are located on the punch tool. In this way, circulation can occur closest to the entry point through the casing to reduce the pressure drop for the return fluid path.
There may be a plug located at an end of the string. In this way, the seal at the first depth can be formed in the well on the same run as the punch, circulation test, cut and pull is achieved. The plug may be a bridge plug as is known in the art.
In the description that follows, the drawings are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form, and some details of conventional elements may not be shown in the interest of clarity and conciseness. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce the desired results.
Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as “including,” “comprising,” “having,” “containing,” or “involving,” and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps. Likewise, the term “comprising” is considered synonymous with the terms “including” or “containing” for applicable legal purposes.
All numerical values in this disclosure are understood as being modified by “about”. All singular forms of elements, or any other components described herein including (without limitations) components of the apparatus are understood to include plural forms thereof.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings of which:
Reference is initially made to
The punch tool 18, cutting tool 20, agitator device 24, packer 26 and casing spear 22 may be formed integrally on a single tool body or may be constructed separately and joined together by box and pin sections as is known in the art. Two or more parts may also be integrally formed and joined to any other part. While the packer 26 must be located above the punch tool 18, other parts may be in alternative order. For example, the agitator device 24 may be located below the others if any of the others operate by use of a drop ball as the agitator device 24 may not provide an uninterrupted throughbore.
Tool string 16 may be a drill string or coiled tubing having a central bore for the passage of fluid pumped from surface, as is known in the art.
The punch tool 18 may be any tool which can create individual holes in casing. Preferably this is achieved without explosives and may be achieved by applying tension to the tool 18. The punch tool 18 may create a single hole. Alternatively the punch tool creates a plurality of holes spaced around a circumference of the inner wall 34 of the casing 12. The cutting tool 20 may be any tool which is capable of cutting casing downhole in a well bore. A pipe cutter, section mill, jet cutter, laser cutter and chemical cutter are a non-exhaustive list of possible cutting tools. The packer 26 is preferably a tension set packer wherein an elastomeric band is compressed to expand radially outwards and seal across the annulus 32 between the string 16 and the inner wall 34 of the casing 12. The casing spear 22 is an anchor 40 arranged as a slip designed to ride up a wedge and by virtue of wickers or teeth on its outer surface grip and anchor to the inner wall 34 of the casing 12. In a preferred embodiment the cutting tool 20, packer 26 and casing spear 22 are the TRIDENT system as provided by the present Applicants.
The agitator device 24 is a circulation sub which creates fluid pulses in the flow passing through the device. This can be achieved by a rotating member or a rotating valve. In one embodiment the agitator device 24 includes a shock tool with extension and retraction means to apply a tensile load to the length of casing via the anchor 40. In a preferred embodiment the agitator device 24 is the Agitator™ System available from National Oilwell Varco. It is described in U.S. Pat. Nos. 6,279,670, 77,077,205 and 9,045,958, the disclosures of which are incorporated herein in their entirety by reference.
In
It will be recognised that other tools such as a bumper sub, logging tools, mills or drill bits may be incorporated on the tool string 16. Such tools are not illustrated on the figure merely to aid clarity.
In
In the embodiment shown in
Packer 26 is then expanded into sealing engagement with the inner wall 26 of the casing 12 at a location above the perforations 28, if this was not done before the punch tool 18 was operated. In a preferred embodiment the punch tool 18 and packer 26 are operated in a simultaneous action by applying tension to the string 16. Where the packer 26 is set before the punch tool 18, the packer 26 can be used to stabilize the punch tool 18 during the punching operation. With the packer 26 now set, a sealed section of the annulus 32 between the plug 36 and packer 26 is provided. This is illustrated in
Ports 30 are now opened to provide a circulation path for fluid from the throughbore 42 of the string 16, into the sealed section of annulus 32. Fluid pumped from surface at high pressure, will exit the string 16, enter the perforations 28 and try to find a path through the material 44 in the annulus 46 between the outer wall of the casing 12 and the inner wall of the bore 14. In
On a positive circulation test, the cutting tool 20 is activated and the casing 12 is cut. The cut can be made in any way, for example by slicing, milling, grinding, melting, dissolving or ablation as long as it achieves independent upper 48 and lower 50 lengths of casing 12. This is illustrated in
With the casing cut,
Pulling the tool string 16 out of the well bore 10 recovers the upper 48 length of casing 12. The wellbore 10 is now left with a permanent barrier, in the form of the plug 36, in the lower length 50 of casing 12. This is illustrated in
All the steps shown in
Referring now to
Thus on noting that a return is not recorded at surface and the circulation test is negative, the anchor 40 and/or packer 26 are released and the tool string 16 is pulled a distance out of the bore 14 to position the punch tool 18 at a shallower depth. This is as illustrated in
If the circulation test at
In the unlikely event of a positive circulation test, a cut being made and then the casing cannot be pulled, which may be due to a large amount of uneven cement distribution in the annulus 46, the spear 22 can be released and the method steps repeated with perforations at a shallower depth which will hopefully be above the stuck point. This will still be achieved on a single trip in the well bore 10.
Thus the method of the present invention provides for a single trip casing cutting and pulling system in which the tool string is run to a maximum depth, testing is performed via perforations to see if a circulation path to surface exits which is used to indicate the likelihood of being able to pull the casing at the perforated depth and pulling can be done with vibratory assistance. If circulation is not achieved, further perforations and testing are performed at progressively shallower depths until a positive circulation test is achieved and the casing is pulled. This is in direct contrast to the prior art systems which begin at a shallower depth and move to greater depths, washing, cutting and pulling casing sections at each step which means multiple steps into the well bore are required.
In the present invention once the casing section has been recovered, one could re-enter the lower length of casing and see if a circulation path to the cut can be found, now that a weight of material has been removed.
Further, as illustrated in
Perforations 58 advantageously allow the migration of gas from the annulus 46 between the casing 12 and the bore 14.
Further test perforations 60 can be made at different depths in the casing 12. The test perforations 60 are arranged to lie between the packer 26 and the perforations 28. In this way, a circulation test can be performed over a shorter length of casing between the two sets of perforations 28,60. This technique can be used to locate a fill level 62 of material 44 in the annulus 46.
The principle advantage of the present invention is that it provides a method of cutting and pulling the maximum possible length of casing in a single trip into a well bore.
A further advantage of the present invention is that it provides a method of cutting and pulling casing wherein the casing is cut and pulled only when an indication of the likelihood of being able to pull the casing is given.
It will be apparent to those skilled in the art that modifications may be made to the invention herein described without departing from the scope thereof. For example, the tool string may include a downhole pulling tool, such as the DHPT available from the present Applicants, or a jar to assist in pulling the cut casing from the well bore. Additionally, reference has been made to shallower and deeper, together with upper and lower positions in the well bore. It will be recognised that these are relative terms though a vertical well bore is illustrated the method and apparatus apply equally to deviated and horizontal well bores.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1707131.7 | May 2017 | GB | national |
| 1707135.8 | May 2017 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2018/051181 | 5/3/2018 | WO | 00 |
