Embodiments described relate to coiled tubing for use in hydrocarbon wells. In particular, embodiments of coiled tubing are described utilizing a scale removal tool positioned at or near a downhole end thereof. In particular, embodiments of high pressure fluid dispensing “water jet” tools are described. These tools may employ downhole positionable fluid dispensing arms with respect to a wall of a well where scale buildup may be present.
Exploring, drilling and completing hydrocarbon wells are generally complicated, time consuming and ultimately very expensive endeavors. As a result, over the years increased attention has been paid to monitoring and maintaining the health of such wells. Significant premiums are placed on maximizing the total hydrocarbon recovery, recovery rate, and extending the overall life of the well as much as possible. Thus, logging applications for monitoring of well conditions play a significant role in the life of the well. Similarly, significant importance is placed on well intervention applications, such as clean-out techniques which may be utilized to remove debris from the well so as to ensure unobstructed hydrocarbon recovery.
Clean out techniques as indicated above may be employed for the removal of loose debris from within the well. However, in many cases, debris may be present within the well that is of a more challenging nature. For example, debris often accumulates within a well in the form of ‘scale’. As opposed to loose debris, scale is the build-up or caking of deposits at the surface of the well wall. For example, the well wall may be a smooth steel casing within the well that is configured for the rapid uphole transfer of hydrocarbons and other fluids from a formation. However, a build-up of irregular occlusive scale may occur at the inner surface of the casing restricting flow there through. Indeed, scale may even form over perforations in the casing, thereby also hampering hydrocarbon flow into the well from the surrounding formation.
Unfortunately, scale build-up within a well may take place in a fairly rapid manner. For example, it would not be uncommon for hydrocarbon production to decrease on the order of several thousand barrels per day once a significant amount of scale begins to accumulate at the well wall. Furthermore, while a variety of conventional techniques are available for addressing scale, hundreds of millions of dollars are nevertheless lost every year to the curing of scale problems. That is, as described below, current scale removal techniques remain fairly inefficient, leaving significant production time lost to the application of the techniques.
Scale build-up generally results from the presence of water within the well. This may be the result of water production by the well or the intentional introduction of water to the well, for example, by a water injector to enhance hydrocarbon recovery. Regardless, the presence of water may ultimately lead to mineral deposits such as calcium carbonate, barium sulfate, and others which may be prone to crystallize and build-up in the form of scale at the inner wall of the well as noted above. Due to the nature of the scale, chemical techniques such as the introduction of hydrochloric or other acids are often employed to break up the scale. Unfortunately, however, the introduction of acids is generally followed by a soak period which increases the amount of production time lost. Furthermore, acids may not be particularly effective at breaking up harder scale deposits and may even leave the well wall primed for future scale build-up. Therefore, mechanical techniques as described below are often employed for scale removal.
Scale may be removed by a variety of mechanical techniques such as the use of explosives, impact bits, and milling. However, these techniques include the drawback of potentially damaging the well itself Furthermore, the use of impact bits and milling generally fails to remove scale in its entirety. Rather, a small layer of scale is generally left behind which may act as a seed layer in encouraging new scale growth. As a result of these drawbacks, fluid mechanical jetting tools as described below may be most often employed for scale removal.
Water jetting tools are often deployed within a well to remove scale build-up as described above. A water jet tool may be dropped into the well via coiled tubing and include a rotating head for jetting water toward the well wall in order to fracture and dislodge the scale. The rotating head may include water dispensing arms that project outward from a central axis of the tool and toward the well wall. Additionally, in many cases, the water may include an abrasive in order to aid in the cutting into and fracturing of the scale as indicated.
For effective removal of scale with a water jetting tool as noted above, the water dispensing arms are securely pre-positioned with an outer diameter that is as close as possible to the scale. In this manner, the full force of the water may be substantially taken advantage of. Unfortunately, however, the thickness of the scale within the well may be quite variable. For example, there may be regions of the well with minimal scale buildup, whereas a maximum scale thickness of over an inch may be present in other regions of the well. In such a scenario, the arms of the water jet tool may be securely positioned at an outer diameter that is within about half of an inch of the maximum scale thickness. Thus, a water jet application of the tool through the well may remove a substantial amount of scale in well regions of maximum scale thickness. However, in other well regions of lesser scale thickness, scale buildup may remain largely unaffected.
The variability in scale thickness may largely determine the effectiveness of a given run through of the tool in the well. For example, the arms of the tool may be set with a drift ring retainer of a given outer diameter and the tool run through the well as part of the scale removal application. However, only a portion of the scale may be removed down to a certain level in regions of maximum scale thickness. Thus, the tool may then be removed from the well and the arms securely repositioned at a larger outer diameter with a larger drift ring retainer by an operator at the oilfield.
A subsequent run of the tool through the well may then take place. This process may continue several times until the scale is fully removed. Indeed, today there are about 30 different standard drift ring sizes that are commercially available so as to allow for a significant number of runs of the tool through the well with differently sized or positioned tool arms. Unfortunately, each of these separate runs through the well may take between about 5 and 12 hours or more, depending on the depth of the well. Thus, with the trend toward wells of greater depths, the time lost in order to resize the tool arms for continuing the scale removal is increasing. As such, the expense of the overall hydrocarbon recovery effort is substantially increasing as well.
A scale removal tool for use with coiled tubing is provided. The scale removal tool may be disposed at the end of coiled tubing and include a fluid dispensing arm for directing a fluid at a wall of a well for removal of scale thereat. The fluid dispensing arm may be of a configuration for adjustable positioning thereof relative to the wall of the well. In one embodiment, this adjustable positioning may be achieved by the use of a drift ring of adjustable diameter adjacent the fluid dispensing arm.
Embodiments are described with reference to certain coiled tubing operations employing a scale removal tool. The scale removal tool is configured for positioning downhole in a well for removing scale buildup from a wall of the well. In particular, the scale removal tool described is of a two armed configuration for water jet or ‘blasting’ scale from the well wall. However, a variety of alternative scale removal tool configurations may be employed. For example, the tool may have a different number of arms than two or be configured for delivery of fluids other than water alone, such as acids. Furthermore, the fluid may be a mixture of a variety of liquids including water, acid, and others, and may also include non-fluid particles mixed therein. For example, abrasive particles may be mixed in with the utilized fluid. Regardless, embodiments described herein include at least one fluid dispensing arm that is adjustably positionable relative to the well wall while located downhole in the well.
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In order to address the problems associated with scale 170 as noted above, a scale removal tool 100 is disposed at the end of the coiled tubing 155. The tool 100 includes fluid dispensing arms 101 disposed at the end thereof. The arms 101 may be employed for directing a fluid 350 radially toward the wall 185 for removal of any scale 170 thereat (see
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The well 180 of
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As detailed further below, the arms 101 may be dynamically guided by a drift ring 300 of adjustable diameter to achieve the arm diameter A depicted. In this manner, the arms 101 may be positioned relative to the wall 185 and the noted scale 170 for optimum scale removal without the need to remove the tool 100 from the well 180 to manually reposition the arms 101. As such, the arms 101 may display an initial arm diameter A suited for passage beyond the depicted restriction 183 and later repositioned to another larger arm diameter A better suited for scale removal near the perforation 193 as shown.
As indicated, the arms 101 may be guided by the drift ring 300 which is itself of adjustable diameter. It is of note that, while of adjustable diameter, the drift ring 300 is configured in a manner biased against the arms 101. That is, the drift ring 300 is configured with a closing tendency relative to the arms 101. This provides a degree of stability to the downhole end of the scale removal tool 100. However, this also means that in order to change diameter of the arms 101 are the scale removal tool 100 is configured to overcome this closing tendency of the drift ring 300 as described below.
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In the embodiment depicted in
Once opened to a given diameter, the arms 101 may be employed for an application as detailed below with reference to
As described above, the arms 101 are opened to a larger diameter without the need to remove the tool 100 in order to change the drift ring 300 to one of a larger size. Similarly, hydraulic pressure may be reduced to ultimately direct the j-slot mechanism 450 in an uphole direction. In this manner, the diameter of the drift ring 400 and arms 101 may be reduced. Again this is achieved without the need to remove the tool 100. Additionally, it is worth noting that employment of a j-slot mechanism 450 in this manner allows the change in positions to be achieved in a relatively stable manner with pins 455 moving from one secure location in a chamber 457 to another. In one embodiment, the adjacent chambers 457 are positioned relative to one another so as to attain between about 0.125 inch and about 0.75 inch increment changes in the diameter of the arms 101 from one chamber 457 to the next. For example, in one embodiment, the arms 101 are changed from a 2 inch diameter to a 2.5 inch diameter to a 3 inch diameter as the pins 455 move downhole from chamber 457 to chamber 457 to chamber 457.
Alternative positioning techniques may be employed. For example, the j-slot mechanism may have a variety of additional chambers 457, increasing the number of arm diameter sizes that may be achieved. Furthermore, while 30 different chambers 457 would seem to provide a sizing akin to conventional drift ring sizing options, in an even more practical embodiment, the j-slot mechanism 450 may itself be of an adjustable configuration. That is, the a j-slot mechanism 450 may be configured to achieve one range of arm diameter sizing during initial downhole use. Subsequently, the tool 100 may be removed from the well and the j-slot mechanism 450 adjusted to provide a different range of arm diameter sizing upon re-insertion into the well. Thus, a complete range of arm diameter sizing may be achieved without the need for upwards of 30 different conventional drift ring sizes.
In addition to alternative j-slot mechanism 450 configurations, arm diameter sizing may be directed through means aside from a j-slot mechanism 450. For example, a hydraulic mechanism or an electromechanical mechanism may be employed to more directly affect the positioning of the drift ring actuator 400 without the use of an intervening j-slot mechanism 450.
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In the above described advancing of the tool 100, the arms 101 may be positioned for traversing the narrowest effective diameter d′ at the location of the restriction 583. The arms 101 may then repositioned to a larger arm diameter A as the tool 100 encounters the first scale 170. With added reference now to
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Once the scale removal tool is positioned in the well with the arm diameter properly set, a scale removal application may be run in order to remove scale from a wall of the well as indicated at 665. However, as the profile of the well changes, the arm diameter may be reset to different diameters while the tool remains in the well as indicated at 675. In this manner, the arms of the tool may be positioned relative to scale at the well wall for optimum scale removal without the need to remove the entire tool from the well. Thus, substantial time and expense may be saved in performing the scale removal application.
Embodiments described hereinabove include a scale removal tool which may employ water jetting for removal of scale from a hydrocarbon well. While the dispensing arms may be securely pre-positioned for optimum scale removal at one location within the well, the arms may also be repositioned to another diameter in response to variable scale thickness within the well. Thus, scale removal need not take place with over the course of a host of multiple scale removal runs through the well. Rather, the repositioning of the arms allows for the operator to avoid removal of the tool from the well to achieve each new arm diameter setting. The resulting cost savings is enhanced further, depending on the depth of the well involved.
The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.