GB2582553A - Improvements in or relating to well abandonment - Google Patents

Improvements in or relating to well abandonment Download PDF

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Publication number
GB2582553A
GB2582553A GB1903803.3A GB201903803A GB2582553A GB 2582553 A GB2582553 A GB 2582553A GB 201903803 A GB201903803 A GB 201903803A GB 2582553 A GB2582553 A GB 2582553A
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United Kingdom
Prior art keywords
string
conduit
tool
downhole tool
annulus
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Granted
Application number
GB1903803.3A
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GB2582553B (en
GB201903803D0 (en
Inventor
Linklater James
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Ardyne Holdings Ltd
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Ardyne Holdings Ltd
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Priority to GB1903803.3A priority Critical patent/GB2582553B/en
Publication of GB201903803D0 publication Critical patent/GB201903803D0/en
Publication of GB2582553A publication Critical patent/GB2582553A/en
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Classifications

    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B37/00Methods or apparatus for cleaning boreholes or wells
    • E21B37/02Scrapers specially adapted therefor
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B33/00Sealing or packing boreholes or wells
    • E21B33/10Sealing or packing boreholes or wells in the borehole
    • E21B33/13Methods or devices for cementing, for plugging holes, crevices or the like
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B17/00Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B37/00Methods or apparatus for cleaning boreholes or wells

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Mining & Mineral Resources (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Mechanical Engineering (AREA)
  • Earth Drilling (AREA)

Abstract

A downhole tool having a tubular body 28 with an elongate section which is arranged on an axis being eccentric to a central axis of the tool and the string to which it is located in. Also disclosed is a method for the combined cleaning and plugging of an annulus in a well across a longitudinal section of the well were the annulus is located outside a conduit. Rotation of the string in the well creates a lateral force to vibrate the conduit together with washing and plugging fluids in the well and divert the fluids through perforations in the conduit to access the annulus. Embodiments describe the downhole tool used as a washing tool and/or cementing tool and creating pressure variations in the fluids. The tool may include radial ports 62e.

Description

IMPROVEMENTS IN OR RELATING TO WELL ABANDONMENT
The present invention relates to methods and apparatus for well s abandonment and in particular, though not exclusively, to apparatus to assist in and a method for perforating, washing and cementing an annulus across a longitudinal section of the well.
When a well has reached the end of its commercial life, the well is ao 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. As a well is constructed by locating conduits such as casing, lining and tubing into the well, the cement plug must extend over all annuli present in the well. In many cases all conduits are removed leaving the outer casing, including the annulus bounded by the formation.
One method of creating the cement plug is to mill away the inner conduit to expose the annulus behind the conduit and then pump cement into the enlarged area to create the cement plug. This method of section milling is expensive as the length of the cement plug is typically one to two hundred metres, removal of a section of conduit weakens the structure of the well, and several trips must be made into the well to change the milling head for different sizes of conduit i.e. casing used through the wellbore. An alternative method perforates the conduit and pumps cement through the perforations to travel up the annulus and thereby create a plug within the annulus. This 'perf and plug' arrangement has disadvantages in that material present in the annulus can restrict the flow and the adhesion of the cement and thus the required sealing of the plug is not achieved. The material present in the annulus may be various particles, deposits, for example so-called filter cake, and fluids remaining from previous downhole operations, including remaining drill cuttings, cement residues, baryte deposits and/or drill fluid.
GB2499172 to Hydra Systems AS discloses a method and washing tool for s combined cleaning of an annulus in a well across a longitudinal section of the well, and subsequent plugging of the longitudinal section, wherein the method comprises the following steps: (A) conducting a perforation tool into a casing to said longitudinal section; (B) forming holes in the casing along the longitudinal section; (C) by means of a washing tool conducted into the casing on a tubular work string, pumping a washing fluid through the tubular work string and out into the casing via the washing tool; (D) by means of a directional means associated with the washing tool, conducting the washing fluid out into the annulus via at least one hole at a first location within the longitudinal section, after which the washing fluid will flow via the annulus and onward into the casing via at least one hole formed in at least one second location within the longitudinal section; (E) pumping a fluidized plugging material out into the casing at the longitudinal section; and (F) placing the plugging material in the casing and in the annulus along the longitudinal section so as to plug the casing zo and the annulus.
W02015115905 to Archer Oil Tools discloses a bottom hole assembly (BHA) which enables a one trip procedure to set a bridge plug and release from that bridge plug with the BHA. A perforating gun is fired and a straddle tool above the gun is repositioned to wash the perforations as the opposed packer cups are moved along the perforations. At the end of the washing step a dropped ball closes a circulation port above the upper packer cups and the ball seat is blown out. A disconnect releases the lower part of the straddle tool with the lower packer cups that are uphole oriented. Cement can now be delivered past the upper packer cups and pressurized to squeeze the cement into the perforations using the upper cups to hold the pressure. Another ported sub above the upper cups has a port opened to prevent swabbing as the BHA is removed.
GB2499172 and W02015115905 provide the advantage of washing the s annulus prior to pumping the cement in a perf and plug method. In both cases the tools include 'directional means' in the form of packer elements such as swab cups which aim to direct the wash fluid through the perforations. The wash fluid is also ejected through nozzles in the tool at a high velocity so that it provides sufficient force to sweep the material so out of the annulus. A known disadvantage of these tools is that the swab cups can interfere with other functions as they prevent circulation between the tool and the perforated conduit. Additionally, the wash fluid experiences a high fluid velocity reduction on exiting the nozzles and thus may be ineffective at sweeping the material up and out of higher located perforations.
GB2563236 to the present Applicants discloses a method and apparatus for the combined cleaning and plugging of an annulus in a well across a longitudinal section of the well were the annulus is located outside a conduit in the well. The conduit is perforated over the longitudinal section.
Washing fluid is passed through the longitudinal section to clear material in the annulus before the longitudinal section is plugged. Pressure variations are created in the washing fluid by use of a flow modifier device to pulse the washing fluid. Embodiments include creating pressure variations in the plugging material. By creating pulses in the washing fluid a vibration assisted clean is achieved which improves the washing step to provide for better adhesion of the cement to the walls in creating the cement plug.
All these arrangements rely on getting both the washing fluid and the plugging material through the perforations and into the annulus.
A tool to aid in getting the cement to enter the perforations is disclosed in GB2505089 to Hydra Systems AS having a carrier body defined by an indefinite side portion extending between a first end portion and a second end portion, the carrier body being arranged to be set in motion by a s driving device; and at least one displacement member arranged on the carrier body, the displacement member being defined by the surface of the carrier body and a free end portion facing the inside of the casing, and the driving device being arranged to set the carrier body and the displacement member in motion in the bore of the casing, so that the fluidized plugging material is set in motion within the bore of the casing.
The displacement member is shown as a blade arranged helically around the body which sweeps the plugging material over the perforations as the blade is rotated with the body. For this arrangement to work effectively the blades are flexible, being made of rubber, and consequently construction is difficult to fit the blades on a metal tubular body.
GB2519240 to Hydra Systems AS describes a flushing tool for flushing in a well which aids in getting the washing fluid into the annulus. The flushing tool is arranged for connection to a lower portion of a string allowing through-flow; wherein the flushing tool is formed with at least one outlet allowing through-flow; wherein at least one of said at least one outlet is angled in such a way that an output jet thereof is non-normal to a longitudinal axis A of the flushing tool; wherein the flushing tool is formed with a plurality of outlets; and wherein the outlets are angled in such a way that the output jets thereof are distributed within +/-80 degrees from a plane which is normal to the longitudinal axis A of the flushing tool. By directing the fluid at non-normal angles from the longitudinal axis of the tool it can enter and clean the annulus more effectively. However, as the other prior art, the wash fluid experiences a high fluid velocity reduction on exiting the jets and thus may be ineffective at sweeping the material up and out of higher located perforations. If the tool is sized to locate the jets as close to the casing as possible, the reduced annulus between the tool and casing limits the returns flow path when running in and cementing.
It is therefore an object of the present invention to provide a downhole s tool which obviates or mitigates one or more disadvantages of the prior art.
It is a further object of the present invention to provide a method for the combined cleaning and plugging of an annulus in a well across a so longitudinal section of the 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 downhole tool, the tool comprising: a substantially tubular body having a through passage for fluid configured to locate in a string for running in a conduit in a well bore, the tubular body having: a first end being circular in cross-section, a second end being circular in cross section, and the first and the second ends being co-linear on a first zo central longitudinal axis of the string; and an elongate section being circular in cross-section and having a second central longitudinal axis; wherein the second central longitudinal axis is parallel to and offset from the first central longitudinal axis with the elongate section being eccentric to the zs first central longitudinal axis.
In this way, when the string is rotated there will be a high lateral force/vibration created in the fluid in the annulus between the string and the conduit, pipe or tubing, a sweeping of a line contact of the tool around the conduit to create bulk movement of fluid in the annulus and a diversion of fluid in the annulus through any perforations in the conduit.
Preferably, the elongate section has a diameter greater than a diameter of the first end. More preferably, a radius of the elongate section plus a separation distance between the first and second central longitudinal axes is greater than a radius of the conduit in which the tool is to be used. In s this way, the first central longitudinal axis will not be co-linear with a central longitudinal axis of the conduit and will follow a circular path on each rotation of the string causing the lateral displacement of the string. Preferably, a radius of the first end plus the separation distance between the first and second central longitudinal axes equals the radius of the so elongate section. In this way, a line contact along the downhole tool is provided. The line contact will contact the conduit on rotation due to the centrifugal force created by the eccentrically placed weights which provides a sweeping action through the fluids in the annulus between the downhole tool and the conduit. Preferably, the separation distance between the first and second central longitudinal axes is greater than half the difference between the diameter of the elongate section and the diameter of the conduit. In this way there is a small flow area around the elongate section.
Preferably the through passage is a cylindrical bore being co-linear on the first central longitudinal axis of the string. In this way, only the body of the elongate section is eccentric.
Preferably, the tool includes at least one outlet allowing through-flow; wherein at least one of said at least one outlet is angled to be normal to the first central longitudinal axis. In this way, as the outlet is perpendicular to the first central longitudinal axis, a radial jet is provided from the tool to facilitate washing or cleaning of the annulus behind the conduit.
Preferably, the tool includes at least one outlet allowing through-flow; wherein at least one of said at least one outlet is angled to be normal to the second central longitudinal axis. In this way, a radial jet is provided from the elongate section of the tool to facilitate washing or cleaning of the annulus behind the conduit.
s Preferably there are a plurality of outlets allowing through-flow. In this way, washing is provided around the elongate section of the tool. More preferably at least one outlet is provided over the extended distance. In this way, fluid from the outlet will be jetted directly through the perforations as the elongate section contacts the conduit during rotation.
There may be one or more outlets which are angled to be non-normal to the first central longitudinal axis. There may be one or more outlets which are angled to be non-normal to the second central longitudinal axis. By directing the fluid at non-normal angles from the longitudinal axes it can enter and clean the annulus more effectively.
Preferably, at least one end of the elongate section has a sloping outer surface angled to the second central longitudinal axis. In this way, the eccentric body is less likely to stick on run in or pulling out. More preferably, the sloping outer surface includes a milling surface. In this way the tool can remove perforation burrs on run in.
There may be a plurality of elongate sections in a spaced apart arrangement along the tubular body. In this way, the action of each elongate section can be simultaneously applied across a length of perforated conduit. More preferably, the extended distance of each elongate section, are parallel to each and line-up along the string.
Preferably the downhole tool further comprises the string and a plurality 30 of downhole tools are arranged on the string. In this way, the action of the eccentric body can be simultaneously applied across a length of perforated conduit. More preferably, the extended distance of each elongate section, are parallel to each and line-up along the string. Lining up may be achieved by clamping, splining or carsac connection. In this way, when the string is rotated there is a high lateral force creating vibration in the fluid in the annulus between the string and conduit.
s Additionally, the line contact as it sweeps the casing gives bulk movement of the fluids in the annulus between the casing and the string to improve mixing of the fluid.
Preferably, the string includes one or more perforation tools. Preferably, the perforation tools are perforation guns using explosives to create holes in the casing. Alternatively, the perforation tool is a tubing punch. In this way, a controlled number of holes may be punched from the conduit without the use of explosives and without creating swarf and other cuttings. Circulation is also not required in the punch process.
Preferably, the string includes a flow modifier. The fluid modifier may be a pressure pulse-generator actuated by fluid being circulated through the string. Alternatively, the flow modifier 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. Preferably, the flow modifier device is the AgitatorTM system provided National Oilwell Varco.
The string may include a cementing tool. Preferably, the cementing tool includes a plurality of radial ports. The cementing tool may include non-radial ports for the exit of cement. In this way, a stinger can form part of the cementing tool for the placement of cement in the conduit.
The string may include a washing tool. Preferably the washing tool is a 30 fluid jetting tool. The washing tool and cementing tool may be combined in the fluid jetting tool. In this way the fluidised plugging material can be distributed through the jetting tool.
Preferably, the fluid jetting tool includes a plurality of radial ports. The ports may include nozzles. In this way the pulsed washing/plugging fluid is accelerated on exiting the fluid jetting tool.
There may be a plug located on the string. In this way, a seal can be formed in the conduit at the end of the longitudinal section on the same run as the perf, agitated wash and agitated cementing is achieved. The plug may be a bridge plug as is known in the art.
Preferably, the string is a coiled tubing string. Alternatively, the string may be a drill string.
Preferably, the conduit is casing and the annulus is between the casing and the formation of the borehole. Optionally, the annulus is the B-annulus between inner casing and a surrounding casing.
According to a second aspect of the present invention there is provided a method for the combined cleaning and plugging of an outer annulus in a zo well across a longitudinal section of the well, said outer annulus being located outside a conduit in the well, comprising the steps: (a) perforating the conduit to form a plurality of holes in the conduit along the longitudinal section; (b) passing a washing fluid into the outer annulus through at least one of said holes; and (c) pumping a fluidized plugging material through at least one of said holes to fill the outer annulus and conduit with fluidized plugging material and thereby plug said well along at least said longitudinal section of the well: and characterised in that, the method includes the step of mounting at least one downhole tool according to the first aspect on a string run in the well and rotating the string and downhole tool to thereby cause the first central longitudinal axis of the downhole tool to describe a path around and separate from the second central longitudinal axis.
In this way, a lateral force is placed on the conduit as a contact line on s the eccentric elongate section sweeps an inner annulus between the string and conduit to create bulk mixing of fluid in the inner annulus, vibrating the conduit and diverting fluid through the perforations to the outer annulus. Additionally, either the wash fluid or the fluidized plugging material is better mixed and moved into the outer annulus to promote mixing and displacement of fluid within the outer annulus.
Preferably, the step of perforating is by operation of a perforating tool located on the string run into the conduit. The perforating tool may be a perforating gun as is known in the art. In this way, known tools may be used. Alternatively, the perforating tool may be a punch tool being combined with an anchor to allow the punch tool to be operated by tension. In this way, the annulus is accessed quickly and inexpensively compared to section milling the conduit. Perforation of the longitudinal section may be performed in stages over the longitudinal section. In this way, a perforating tool having a length shorter than the longitudinal section can be used and thus the length of the longitudinal section is not restricted by the perforating tool length.
Preferably, the step of passing the washing fluid through the outer annulus is by jetting washing fluid from ports in the at least one downhole tool. In this way the downhole tool can be used as the washing tool and the ports can contact the conduit to ensure washing fluid is jetted into the outer annulus. Alternatively, the step of passing the washing fluid through the outer annulus is by jetting washing fluid from ports in a washing tool located in the string. In this way, fluid from the washing tool which has not reached the outer annulus can be diverted into the outer annulus by the downhole tool.
Preferably the fluidized plugging material is cement. More preferably, the fluidized plugging material is pumped from surface through a cementing tool. The fluidized plugging material may be pumped through the string to s return up the inner annulus and diverted into the outer annulus by the at least one downhole tool. Alternatively, the fluidized plugging material may be passed out of ports in the at least one downhole tool.
The method may include the step of setting a bridge plug in the conduit. In this way, fluid entering the conduit is prevented from travelling downhole.
Preferably the method includes the step of creating pressure variations in fluid in the well. Preferably, the step of creating pressure variations is by use of a flow modifier device. More preferably, the pressure variations are pressure pulses created in the washing fluid. By agitating the washing fluid this will assist in dislodging stuck material in the annulus so that it can be lifted and swept from the annulus and so improve cleaning and the subsequent placing of cement.
Preferably, the method includes the step of creating pressure variations in the fluidized plugging material. In this way, the cement is encouraged to distribute more evenly through the annulus and conduit. More preferably, the step of creating pressure variations in the fluidized plugging material is by use of the flow modifier device. More preferably, the pressure variations are pressure pulses created in the fluidized plugging material. More preferably the flow modifier device is operated by pumping the fluidized plugging material through the device to thereby create pressure pulses in the fluidized plugging material. In this way, the flow modifier device can be used to assist both in washing and cementing.
The method may include providing the at least one downhole tool, perforating tool and the flow modifier device on the same string and performing the method on a single trip in the wellbore. Alternatively, the method may include providing the at least one downhole tool, the s perforating tool, the flow modifier device and the washing tool on the same string and performing the steps on a single trip in the wellbore.
The method may include providing the at least one downhole tool, the perforating tool, the flow modifier device, the washing tool and the cementing tool on the same string and performing the method on a single trip in the wellbore.
Preferably, the conduit is casing and the outer annulus is between the casing and the formation of the borehole. Optionally, the outer annulus is 15 the B-annulus between inner casing and a surrounding casing.
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 zo 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 drawing: Figures 1(a) and 1(b) are longitudinal and transverse cross-sectional views through a downhole tool in a conduit, according to an embodiment of the present invention; Figures 2(a)-(d) are longitudinal and transverse cross-sectional views through a downhole tool providing schematic illustrations of orientations of ports according to further embodiments of the present invention; Figure 3 is a schematic illustration of a string including five downhole tools according to an embodiment of the present invention; and Figures 4(a)-(h) illustrate a method for the combined cleaning and plugging of an annulus in a well across a longitudinal section of the well, carried out on a single trip in a well, according to an embodiment of the present invention.
Reference is initially made to Figures 1(a) and 1(b) of the drawings which illustrate a downhole tool, generally indicated by reference numeral 10, having an eccentric elongate section 12, according to an embodiment of the present invention.
Tool 10 is provided with a standard pin 14 and box 16 section at first 18 and second 20 ends respectively for connection in a string 15 as is known in the art. A throughbore 22 provides a passage of fluid through the tool 10 and the string 15 to which it is attached. This can be considered as a first tubular body 26 being circular in cross-section, as is known in the art. The throughbore 22 is aligned with the ends 18,20 on a first central longitudinal axis 24 which is the longitudinal axis through the tool 10 and the string 15. Between the ends 18,20 an elongate section 12 is provided ao which has a second tubular body 28, being circular in cross-section. A second central longitudinal axis 30, is through the centre of the second tubular body 28. Of note is that the second central longitudinal axis 30 is not co-linear with the first central longitudinal axis 24, instead being offset from and parallel to it so that the elongate section 12 is eccentric to the longitudinal axis of the tool 10 and the string 15.
The second tubular body 28 is of greater diameter than the first tubular body 26. In an embodiment, the radius C of the second tubular body 28 equals the radius B of the first tubular body 26 plus the displacement A of the second central longitudinal axis 30 from the first central longitudinal axis 24. This allows the outer surfaces 32,34 of the first and second tubular bodies 26,28 respectively to contact along a longitudinally arranged line 36 on the tool 10. A second longitudinally arranged line 38, on the outer surface 34 of the elongate section 12, which is directly opposite the first line 36, separated by the diameter of the second tubular body 28 provides a furthest extended contact line or point for the tool 10 from the first central longitudinal axis 24 and the axis of the tool 10.
The radius C of the second tubular body 28 is selected to be sized for the radius of the conduit 40 or casing into which the tool 10 is to be used. As an example, the casing may have a diameter of 217mm, the first tubular body has a diameter of 178mm and the second tubular body, a diameter of 208 -211mm. When the tool 10 is run-in the conduit 40 the axis 30 of the second tubular body 28 will lie close to the centre of the conduit 40 while the axis 24 of the tool 10 and the string 15 will lie to one side. In this way, the eccentric body 28 forces the string 15, to travel in a circular s path around the inside of the conduit 40 equivalently rotating around the second central longitudinal axis 30 while being separated therefrom by the separation distance A. As the weight is in the string 15 and first tubular body 26 along the first central longitudinal axis 24, the string 15 want to move towards the conduit by the centrifugal force applied as the string 15 is rotated. Consequently, the extended contact line 36 will want come close to or meet the inner surface 42 of the conduit 40. In a horizontal or deviated well, gravity will also cause the string 15 and tool 10 to position itself on the low side.
Rotation of the string and with it the tool 10, provides a sweeping action of the extended contact line 36 around the inner surface 42 of the conduit 40 which can be used to direct fluid in the inner annulus 46 through perforations 48 in the conduit 40 while also giving bulk movement of fluid to improve mixing thereof. As the eccentric elongate section 12 is circular in cross-section, the blades and protrusions which can stick in prior art arrangements are avoided via a simplified design which improves movement of the fluid through the perforations via squeezing as the tubular body rotates against the inner surface 42 of the conduit 40. The rotation also gives a high lateral force on the string 15 which induces vibration in the fluid and conduit 40, so increasing the mixing and distribution of fluid into the outer annulus 50 behind the conduit 40.
A further advantage of the tool 10 is in providing enhanced cleaning with washing fluid in the inner annulus 46. In a perf, wash and cement process a difficult step is in providing sufficient cleaning as normally washing only happens by fluid jetting at the washing tool so is very localized. At the tool 10, a smaller transverse flow area 52 will exist between the extended contact line 38 and the inner surface 42 of the conduit 40, than the transverse flow area 54 at the string 15. Consequently, fluid in the restricted transverse flow area 52 will experience a higher annular velocity and lower pressure than at area 54, creating localised s recirculation of fluid between the annuli 46,50 at the perforations due to the Bernoulli effect. This localised recirculation of fluid at the tool 10 will further enhance the cleaning.
At each end 56,58 of the elongate section of the tool 10, a sloping edge 60 is formed. The edge 60 may also be eccentric in that it is distinct at the extended contact line 38 and reduces as it moves away from the line around the tubular body 28 over the outer surface 34. By effectively smoothing the leading 56 and trailing 58 edges of the elongate section 12 this can aid run-in an POOH in operation. In an embodiment, at least the leading edge 56 has a milling surface applied thereto. Such a surface gives the tool a milling capability so that perforation burrs can be removed by rotation and longitudinal movement of the tool 10 in a perforated conduit 40.
In an embodiment of the tool 10, ports 62 are located through the tubular body 28 to provide a passageway for fluid from the throughbore 22 to the outer surface 34. The ports 62 may include nozzles so that fluid can be jetted from the tool 10 at the eccentric elongate section 12. Referring to Figures 2(a)-(d) there is illustrated orientations of ports 62 which may optionally be used on the tool 10. Though shown independently, one or more orientations can be used on a single tool 10. Figure 2(a) illustrates radial ports 62a originating from the first central longitudinal axis 24, being the axis of the tool 10. The ports 62a shown lie on a plane which is perpendicular to the axis 24. Also shown are radial ports 62b which covers the extended distance to exit the tubular body 28 at the contact line 38 and at contact line 36. In this way, fluid from ports 62b will be directed straight through perforations 48 as there will be no distance between the port 62b and the conduit 40 as the body 28 is swept around the annulus 46. In Figure 2(b) there is illustrated non-radial ports 62c which pass through the tubular body 28 and lie in a plane perpendicular to the axis 24. In Figure 2(c) ports 62d are shown which lie on a plane s perpendicular to the axis 24. Finally, in Figure 2(d) non-radial ports 62e are shown which lie at an angle to a plane perpendicular to the axis 24. It has been suggested that ports which are non-normal to a longitudinal axis provide more effective washing to the outer annulus 50 due to the different directions the fluid is jetted in through the perforations. It will be realised that a tool 10 including ports 62 can act as a washing tool. It will also be realised that a tool 10 including ports 62 can act as a cementing tool.
The string 15 may have a plurality of tools 10 aligned along a length.
They may extend over a longitudinal section of a conduit which is to be perforated and plugged. In this way, a perf wash and cement process can be speeded up as an individual tool does not have to be operated over the entire length of the perforated section, say 250ft (76.2m). Figure 3 shows five tools 10a-e arranged on a string 15. In this embodiment the string is a drill string formed of 7" (177.8mm) OD Drill collars or 7" pony collars as are known in the art. The tools 10a-e each have an 8.4" (213.4mm) OD at the elongate section 12. Of note is that the tools 10a-e are arranged so that the extended distance and contact lines 36,38 are co-linear so that the eccentric diameters line up and all extend from the string 15 in the same direction. The relative orientation of the contact lines 36,38 can be selected. While it is recognised that standard pin 14 and box 16 connections do not provide a fixed orientation, further connection means could be used such as clamping, splines or carsac style (castellated) connections could be used to fix the relative orientations between the tools 10a-e. Alternatively, the arrangement can be provided as a single downhole tool having five elongate sections spaced apart on a tubular body. The tubular section between each elongate section is of reduced diameter and is aligned on the first central longitudinal axis. Forming a single downhole tools allows the orientation of the elongate sections relative to each other to be fixed without the need for special connections.
s Reference is now made to Figures 4(a)-(h) of the drawings which illustrates a method for the combined cleaning and plugging of an annulus in a well across a longitudinal section of the well, carried out on a single trip, according to an embodiment of the present invention. Like parts to those in Figures 1 to 3 have been given the same reference numerals to aid clarity. In Figure 4(a) there is shown a cased well bore, generally indicated by reference numeral 70, in which conduit in the form of casing 72 lines the bore 74. A tool string 15 is run in the casing 72. Tool string 15 includes a perforating tool 76, a bridge plug/cement retainer 78, downhole tools 10a,b and a flow modifier device 80.
Component parts on the string 15 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. Other tools/parts may be present. The tools may be arranged in any order. For example, the flow modifier device 80 may be located below the others if any of the others operate by use of a drop ball as the flow modifier device 80 may not provide an uninterrupted throughbore. Additionally, the bridge plug 78 may be located at the end of the string 15.
Tool string 15 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 perforating tool 76 is a perforating gun which is known in the art. The perforating gun produces multiple holes 82 through the casing 72.
However, the perforating tool 76 may be any tool which can create individual holes 82 in casing 72. A punch tool may be used but would require an anchor in the string if it was to be set by tension.
The downhole tool 10a, as described herein with reference to Figures 1(a),(b) and 2(a)-(d) is configured as a washing tool or jetting tool and is therefore provided with a plurality of radial ports 62 through which fluid s can pass out of the tool 10a. The ports 62 may include nozzles to increase the velocity of the ejected fluid. The outer diameter of the tool 10a is sized so that ports 62 on the contact lines 36,38 of the eccentric elongate section 12 lie close to the wall 84 of the casing 72. This is done to encourage the fluid to pass directly into the holes 82 in the casing 72.
The flow modifier device 80 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 a preferred embodiment the flow modifier device 80 is the AgitatorTM System available from National Oilwell Varco.
It is described in US6279670, US77077205 and US9045958, the disclosures of which are incorporated herein in their entirety by reference. It will be appreciated that a surface device could be used to create cyclic pressure variations in the fluid and preferably pulses. The flow modifier device 80 may create fluid pulses at any desired frequency. A typical frequency range may be 5.5 Hz to 21 Hz.
Referring now to Figure 4(b), there is illustrated the perforating tool 76 positioned at a lower end 86 of a longitudinal section 88 selected over which a cement plug 90 is required. Guns have been actuated to create a spread of holes 82 through the wall 84 of the casing 72. The holes or perforations 82 are spaced circumferentially around the casing 72 and extend along the casing 72. The holes 82 provide multiple pathways between the annulus 50, bounded by the casing 72 and the formation 92, and the casing bore 94. The perforating tool 76 is pulled up to perforate the casing 72 at stages until it has provided holes 82 along the longitudinal section 88. Preferably, the placement of holes 82 extends above an upper end 96 of the longitudinal section 88. This is as illustrated in Figure 4(c). The annulus 50 is now accessible from the casing bore 94 along the full length of the longitudinal section 88. It will be appreciated that the perforation could be performed over the entire longitudinal section at one time. For this there may be a plurality of perforating guns s which extend over the full length of the longitudinal section so that the perforation holes can all be made together on a single detonation event.
At this stage, the perforating tool 76 is released from the string 15 and allowed to fall into the casing bore 94. In this way, the perforating tool 76 can be considered as sacrificial. However, it will be appreciated that the perforating tool could be recovered to surface on the tool string 15. In this arrangement the bridge plug 78 would be arranged below the perforation tool 76 and the plug 78 would likely be set before detonation occurs.
In the preferred embodiment, plug 78 is now set in the casing 72 below the perforated holes 82. Plug 78 creates a seal across the casing 72 and provides a sealed section to the casing 72 preventing the passage of fluids across the plug 78 in either direction. Plug 78 is a bridge plug 78.
Those skilled in the art will recognise that a cement retainer could be used in place of the bridge plug 78 with a stinger being located in the string 15 above the retainer. Once the plug 78 is set in the casing 72, the string 15 is detached from the plug 78 using known methods and the string 15 is pulled to position the downhole tool 10a at a lower end 86 of the longitudinal section 88.
It is noted that movement of the string 15 both longitudinally and via rotation will allow the milling surface on the edges 60 of the downhole tools 10a,b to remove burrs which may have been left at the holes 82 on the inner wall 84 by perforation.
The downhole tool 10a is now aligned with the holes 82 at the lower end 86 of the longitudinal section 88. Washing can now begin. A washing fluid, typically viscosified brine, is pumped through the string 15 from surface. The fluid will pass through the flow modifier device 80 to produce a pulsed fluid. The pulsed fluid will exit the downhole tool 10a through ports 62 and nozzles, if present. The ports 62 are arranged to be perpendicular to the axis of the string 15, but may be at any orientation as described with reference to Figures 2(a)-(d). In this way, pulsed fluid is passes directly from the downhole tool 10a through the perforated holes 82 in the casing 72. It can be seen that the eccentric elongate section 12 of the downhole tool 10a includes the ports 62 on the contact line 38 so that as the string 15 is rotated a minimal gap between the port 62 and the perforated hole 82 is provided. Similarly the contact line 36 at the reverse is forced against the wall 84 of the casing 72 as the string 15 is rotated in the well bore 70 as the axis 24 of the string 15 is forced off-centre by the presence of the eccentric elongate section 12 on each downhole tool 10a,b. In this way, there is a reduced fluid velocity reduction on the fluid exiting the downhole tool 10a at the contact lines 36,38. Additionally, the reduced diameter of the string 15 and the flow modifier device 80 compared to the downhole tool 10a at the contact line 38 provides for recirculation of fluid through the holes 82 by the Bernoulli effect as described hereinbefore. The reduced diameter of the string 15 also allows fluid to travel back into the casing bore 94 in the annulus 46 between the string 15 and the casing 72. The sweep of the eccentric elongate section 12 on the downhole tools 10a,b will additionally divert wash fluid in the casing bore 94 through the holes 82 and so improve the washing and cleaning step.
The pulsed washing fluid enters the annulus 50 between the casing 72 30 and the formation 92. Within the annulus 50 there is likely to be material 98 present in the form of various particles, deposits, for example so-called filter cake, and fluids remaining from previous downhole operations, including remaining drill cuttings, cement residues, baryte deposits and/or drill fluid. This material 98 can block the annulus 50 and adhere to the walls of the casing 72 and formation 92, thereby preventing cement from entirely filling the annulus 50 and adhering to the walls to s create adequate cement bonding.
The pulsing fluid being swept into and hitting the materials 98 in the annulus 50 will cause them to break-up and dislodge from each other and the walls of the casing 72 and the formation 92. Pulsing the fluid is more effective than having fluid at a constant pressure as the pressure variations in the fluid give a pumping action to the fluid. The lateral force caused on the fluid by rotation of the eccentric elongate section 12 on the downhole tool 10a,b will also cause vibrations in the fluid in the annulus 46. This pulsing and vibration action assists in forcing the materials out of position and sweeping them upwards and preferably back though the perforation holes 82 into the casing bore 94. Thus the annulus 50 at the ports 62 is cleared of material and the walls of the casing 72 and formation 92 are washed clean. This is as illustrated in Figure 4(d).
The string 15 is pulled out of the casing 72 so that the downhole tool 10a moves upwards across the longitudinal section 88, while ejecting pulsed fluid through the perforation holes 82. The movement can be staged so that the downhole tool 10a is rotated at a longitudinal position for some time before being moved to the next position. Alternatively the movement can be continuous but performed slowly enough to provide sufficient cleaning. This is as illustrated in Figure 4(e). The pulsed fluid will continue to flow up the annulus 50 to drain back into the casing bore 94 taking the materials 98 with it and thereby evacuating the annulus 50 of materials 98 leaving a clean annulus 50 over the longitudinal section 88. The downhole tool 10a will now be at the upper end 96 of the longitudinal section 88.
While a downhole tool 10a including a washing facility has been used, a separate washing/jetting tool as is known in the art may be located on the string 15 next to a downhole tool 10a to provide further washing if desired.
In the preferred embodiment a cement slurry is now passed down the string 15, through the flow modifier device 80 and out through the downhole tool 10a. A stinger may be located at the end of the exposed string 15 for the exit of cement slurry directly on the bridge plug 78 or cement retainer. Thus, the cement slurry is also pulsed by being passed through the flow modifier device 80. This agitates the cement so that it releases any gas to prevent pockets of empty space forming in the cement which could result in an incomplete cement plug. Agitation also encourages the cement slurry to enter the annulus 50 through the perforation holes 82 and better adhere to the formation 92. This is illustrated in Figure 4(f) with the cement slurry being allowed to travel up the annulus 46 between the string 15 and casing 72. At the downhole tools 10a,b rotation of the tool 10a,b will cause sweeping of the annulus 46 and so encourage the cement slurry to pass through the holes 82 into the annulus 50. The eccentric elongate section 12 on further rotation also creates a lateral cyclic force which vibrates the cement slurry and can cause vibration of the casing 72 also. This also assists in moving the cement slurry into the annulus 50 and completely filling the annulus 50.
The pulsed cement slurry is also released from the string 15 via the downhole tool 10a. The downhole tool 10a can therefore be used as a cementing tool as well as a washing tool by passing pulsed cement slurry through the ports 62. The pulsed cement slurry will be deposited in the entire casing bore 94 to the bridge plug 78 and through the perforation holes 82 to fill the cleaned annulus 50 along the entire longitudinal section 88. The string 15 is removed from well 70 and the downhole tools 10a,b are continuously rotated to distribute a calculated amount of cement slurry into the well 70, as illustrated in Figure 4(g). Once set, a cement plug 90 is formed across the longitudinal section 88. This is as illustrated in Figure 4(h).
It should be noted that while we refer to a cement plug as being required, the plug can be formed of any fluidised plugging material. A cement slurry is typically used but the Applicants are aware of gels and other materials which may be used alone or in combination with cement to provide a fluidised material which sets hard and bonds to both the casing 72 and the formation 92 of the well bore 70.
The principle advantage of the present invention is that it provides a downhole tool for the combined cleaning and plugging of an annulus in a well across a longitudinal section of the well in which enhanced cleaning and plugging material placement is achieved via rotation of an eccentric body in the casing.
A further advantage of the present invention is that it provides combined cleaning and plugging of an annulus in a well across a longitudinal section of the well in a single trip into a well bore.
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, like the washing tool, the string may include a separate cementing tool from the downhole tool. 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.

Claims (25)

  1. CLAIMS1. A downhole tool, the tool comprising: a substantially tubular body having a through passage for fluid s configured to locate in a string for running in a conduit in a well bore, the tubular body having: a first end being circular in cross-section, a second end being circular in cross section, and the first and the second ends being co-linear on a first central longitudinal axis of the string; an elongate section being circular in cross-section and having a second central longitudinal axis; wherein the second central longitudinal axis is parallel to and offset from the first central longitudinal axis with the elongate section being eccentric to the first central longitudinal axis.
  2. 2. A downhole tool according to claim 1 wherein the elongate section has a diameter greater than a diameter of the first end.
  3. 3. A downhole tool according to claim 1 wherein a radius of the elongate section is equal to a radius of the first end plus a separation distance between the first central longitudinal axis and the second central longitudinal axis.
  4. 4. A downhole tool according to any preceding claim wherein the through passage is a cylindrical bore being co-linear on the first central longitudinal axis of the string.
  5. 5. A downhole tool according to any preceding claim wherein the tool includes at least one outlet allowing through-flow; wherein at least one of said at least one outlets is angled to be normal to the first central longitudinal axis.
  6. 6. A downhole tool according to any one of claims 1 to 4 wherein the tool includes at least one outlet allowing through-flow; wherein at least one of said at least one outlets is angled to be normal to the second central longitudinal axis.
  7. 7. A downhole tool according to any preceding claim wherein at least one end of the elongate section has a sloping outer surface angled to the second central longitudinal axis.
  8. 8. A downhole tool according to claim 7 wherein the sloping outer surface includes a milling surface.
  9. 9. A downhole tool according to any preceding claim wherein the downhole tool further comprises the string and a plurality of downhole tools are arranged on the string.
  10. 10. A downhole tool according to claim 9 wherein the elongate sections of the downhole tools are aligned along the string.
  11. 11. A downhole tool according to claim 9 or claim 10 wherein the string, the string includes a flow modifier.
  12. 12. A downhole tool according to anyone of claims 9 to 11 wherein the string includes a fluid jetting tool.
  13. 13. A downhole tool according to anyone of claims 9 to 12 wherein the string includes one or more perforating tools.
  14. 14. A method for the combined cleaning and plugging of an outer annulus in a well across a longitudinal section of the well, said outer annulus being located outside a conduit in the well, comprising the steps: (a) perforating the conduit to form a plurality of holes in the conduit along the longitudinal section; (b) passing a washing fluid into the outer annulus through at least one of said holes; and (c) pumping a fluidized plugging material through at least one of said holes to fill the outer annulus and conduit with fluidized s plugging material and thereby plug said well along at least said longitudinal section of the well: and characterised in that, the method includes the step of mounting at least one downhole tool according to any one of claims 1 to 8 on a string, running the string in the well and rotating the string and downhole tool to thereby cause a lateral force to be placed on the conduit as the eccentric elongate section sweeps an inner annulus between the string and conduit to create bulk mixing of fluid in the inner annulus, vibrating the conduit and diverting fluid through the perforations to the outer annulus.
  15. 15. A method according to claim 14 wherein the downhole tool is selected to have a radius of the elongate section plus a separation distance between the first and second central longitudinal axes is greater than a radius of the conduit.
  16. 16. A method according to claim 14 or claim 15 wherein the step of perforating is by operation of a perforating tool located on the string run into the conduit.
  17. 17. A method according to any one of claims 14 to 16 wherein the step of passing the washing fluid through the outer annulus is by jetting washing fluid from ports in the at least one downhole tool.
  18. 18. A method according to any one of claims 14 to 16 wherein the step of passing the washing fluid through the outer annulus is by jetting washing fluid from ports in a washing tool located in the string.
  19. 19. A method according to any one of claims 14 to 18 wherein the fluidized plugging material is pumped through the string to return up the inner annulus and diverted into the outer annulus by the at least one downhole tool.
  20. 20. A method according to any one of claims 14 to 19 wherein the method includes the deburring perforations on the conduit using the at least one downhole tool.
  21. 21. A method according to any one of claims 14 to 20 wherein the method includes the step of creating pressure variations in the washing fluid in the well.
  22. 22. A method according to any one of claims 14 to 21 wherein the method includes the step of creating pressure variations in the fluidized plugging material.
  23. 23. A method according to any one of claims 14 to 22 wherein the method includes the step of setting a bridge plug in the conduit.
  24. 24. A method according to any one of claims 14 to 23 wherein the method is performed on a single trip in the wellbore.
  25. 25. A method according to any one of claims 14 to 24 wherein the conduit is casing and the outer annulus is between the casing and the formation of the borehole.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20230295993A1 (en) * 2021-05-13 2023-09-21 Baker Hughes Oilfield Operations Llc Separable tool with mill face, method and system

Citations (1)

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Publication number Priority date Publication date Assignee Title
GB2370054A (en) * 2000-12-14 2002-06-19 Halliburton Energy Serv Inc Abrasive slurry delivery apparatus

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2370054A (en) * 2000-12-14 2002-06-19 Halliburton Energy Serv Inc Abrasive slurry delivery apparatus

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20230295993A1 (en) * 2021-05-13 2023-09-21 Baker Hughes Oilfield Operations Llc Separable tool with mill face, method and system
US11959345B2 (en) * 2021-05-13 2024-04-16 Baker Hughes Oilfield Operations Llc Separable tool with mill face, method and system

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