WELL CLEANING TOOLS AND RELATED METHODS OF CLEANING WELLS IN OIL AND GAS APPLICATIONS

Abstract

A well cleaning tool includes a positioning device configured to control a position of the well cleaning tool within a well, a rotatable brush assembly configured to scrape a wall of the well, a capture device configured to catch debris dislodged from the wall by the rotatable brush assembly, and a fluid delivery assembly configured to deliver a cleaning fluid to the well.

Claims

1. A well cleaning tool includes: a positioning device configured to control a position of the well cleaning tool within a well; a rotatable brush assembly configured to scrape a wall of the well; a capture device configured to catch debris dislodged from the wall by the rotatable brush assembly; and a fluid delivery assembly configured to deliver a cleaning fluid to the well.

2. The well cleaning tool of claim 1, wherein the positioning device comprises a steerable assembly sub located at a downhole end of the well cleaning tool, and wherein the steerable subassembly is operable to: sense an end of the well; or detect an opening of a lateral of the well and direct the well cleaning tool to the lateral.

3. The well cleaning tool of claim 1, wherein the positioning device comprises a conveying device that is configured to move the well cleaning tool in a downhole direction or in an uphole direction within the well.

4. The well cleaning tool of claim 3, wherein the conveying device comprises: an elongate housing; and a plurality of traction arms that are carried on the elongate housing and adjustable between: a retracted configuration in which the plurality of traction arms are substantially collapsed against the elongate housing, and an extended configuration in which the plurality of traction arms are extended radially from the elongate housing toward the wall of the well to substantially contact the wall of the well.

5. The well cleaning tool of claim 1, wherein the positioning device comprises a flexible centralizer that is configured to radially center the well cleaning tool within the well.

6. The well cleaning tool of claim 1, wherein the rotatable brush assembly comprises a plurality of flexible brushes that extend radially from a central axis of the well cleaning tool toward the wall of the well.

7. The well cleaning tool of claim 6, wherein the plurality of flexible brushes are arranged in a helical pattern.

8. The well cleaning tool of claim 6, further comprising a motor assembly that is configured to rotate the rotatable brush assembly.

9. The well cleaning tool of claim 8, wherein the motor assembly comprises an electric motor and a gear arrangement configured to transfer rotational motion from the electric motor to the rotatable brush assembly.

10. The well cleaning tool of claim 1, wherein the debris comprises metallic debris, and wherein the capture device comprises an electromagnetic coil that is configured to attract the metallic debris.

11. The well cleaning tool of claim 1, further comprising: a noise detector that is configured to detect noise resulting from contact between the debris and a housing of the noise detector; and a surface expert system that is configured to further monitor behavior of the debris in the wellbore.

12. The well cleaning tool of claim 1, wherein the fluid delivery assembly comprises: a fluid hub body; first nozzles carried on the fluid hub body; and second nozzles carried on the fluid hub body.

13. The well cleaning tool of claim 12, wherein the first nozzles are arranged substantially equidistantly about a circumference of the fluid hub body, and wherein the second nozzles are arranged substantially equidistantly about the circumference of the fluid hub body.

14. The well cleaning tool of claim 12, wherein the first nozzles are oriented perpendicular to a central axis of the well cleaning tool, and wherein the second nozzles are oriented at an acute angle with respect to the central axis.

15. The well cleaning tool of claim 14, wherein the first nozzles are positioned downhole of the second nozzles.

16. The well cleaning tool of claim 14, wherein the first nozzles are positioned uphole of the second nozzles.

17. The well cleaning tool of claim 12, wherein each of the first nozzles and the second nozzles is configured to deliver a jet of fluid to the well at a selected pressure.

18. The well cleaning tool of claim 1, wherein the positioning device, the rotatable brush assembly, and the fluid delivery device are coupled to one another in a substantially in-line arrangement.

19. The well cleaning tool of claim 1, further comprising a control unit that is configured to control operations of one or more of the positioning device, the rotatable brush assembly, the capture device, and the fluid delivery device.

20. The well cleaning tool of claim 19, further comprising an electric cable that extends through the well cleaning tool to relay signals from the control unit.

Description

DESCRIPTION OF DRAWINGS

[0048] FIG. 1 is a side view of an example well cleaning tool with a conveying device in a retracted configuration.

[0049] FIG. 2 is a side view of the well cleaning tool of FIG. 1 with the conveying device in an extended configuration.

[0050] FIG. 3 is an enlarged side view of a portion of the well cleaning tool of FIG. 1.

[0051] FIG. 4 is a flow chart illustrating an example method of cleaning a well using the well cleaning tool of FIG. 1.

DETAILED DESCRIPTION

[0052] FIGS. 1 and 2 illustrate an example well cleaning tool 100 disposed within a well 101 of a rock formation 103. The well cleaning tool 100 is designed to remove debris 105 (shown in FIG. 3) that have accumulated along a wall 107 of the well 101. Such debris may include drill cuttings, sticky petroleum residues, sand, or other particulates that remain on the wall 107 after a drilling operation or that have formed during production of well fluid 109 (for example, oil and/or gas) at the well 101. The well cleaning tool 100 can be deployed to the well 101 (for example, on coiled tubing) and activated to scrape the wall 107 of the well to agitate the debris 105. The agitated debris 105 become dislodged from the wall 107 and can be carried away (for example, out of the well 101 in the uphole direction 110) with the well fluid 109.

[0053] The well cleaning tool 100 has a maximum diameter that is smaller than a minimum restriction of the well 101. The well cleaning tool 100 includes a control unit 160 that is located at the surface 111 of the rock formation 103 for controlling various other downhole components of the well cleaning tool 100 via signal communication carried on a wireline 136 that extends from coiled tubing on which the well cleaning tool 100 is deployed. For example, the well cleaning tool 100 includes a steerable assembly sub (SAS) 102 at a downhole end 104 for directing (for example, guiding) the well cleaning tool 100 forward (for example, in a generally downhole direction 106) into various lateral well sections and through a main section of the well 101. The well cleaning tool 100 also includes a conveying device 108 (for example, a tractor) for selectively moving the well cleaning tool 100 forward or backward (for example, in a generally uphole direction 110). The conveying device 108 includes an elongate housing 112 and multiple traction arms 114 that extend radially from the housing 112. In the example embodiment of FIGS. 1 and 2, the conveying device 108 includes four traction arms 114. However, in other embodiments, the conveying device 108 may include a different number of traction arms 114.

[0054] The housing 112 typically has a length of about 5 meters (m) to about 10 m, and the traction arms 114 typically have a length of about 10 centimeters (cm) to about 30 cm. The traction arms 114 may be placed in a retracted configuration in which the traction arms 114 are relatively collapsed against the housing 112 during tripping, as shown in FIG. 1. The traction arms 114 may alternatively be placed in an extended configuration in which the traction arms 114 extend radially from the housing 112 toward the wall 107 of the well 101 to grip the wall 107 and to radially center the well cleaning tool 100 within the well 101 during operation, as shown in FIG. 2. In the extended configuration, the traction arms 114 may be oriented at an angle of about 0 degrees to about 45 degrees from the housing 112. For example, once the well cleaning tool 100 reaches a section of the well 101 that is oriented at or above at least a threshold angle (for instance, upon reaching a highly deviated or horizontal well section), the traction arms 114 may be manually activated to help convey the well cleaning tool 100 forward. In some examples, the threshold angle may be at least about 60 degrees. In some embodiments, a desired maneuverability of the well cleaning tool 100 is achieved by the modularity of its various components, which may be connected by knuckle joints. For example, the shorter the axial length of the components of the well cleaning tool 100, the more flexible the well cleaning tool 100 is in movement and the higher is the well dog-leg that can be overcome by the well cleaning tool 100.

[0055] The well cleaning tool 100 also includes a brush assembly 168 with a shaft 116 that is equipped with multiple flexible brushes 118 for agitating the debris 105 along the wall 107. In order to ensure that the brushes 118 can make contact with the wall 107 of the well 101 to effect cleaning, the brush assembly 168 has a diameter that is larger than that of the well 101 when the brush assembly 168 is in operation. However, the brush assembly 168 is also flexible enough to pass through small restrictions within production tubing when the brush assembly 168 is not in operation. The well cleaning tool 100 typically has 1 to 100 brushes 118, and each brush 118 typically has a radial length of about 5 cm to about 50 cm. The shaft 116 typically has a length of about 0.5 m to about 10 m. The brushes 118 are continuously distributed about a circumference of the shaft 116 in a helical pattern (for example, a spiral pattern), such that when the shaft 116 is rotated, the brushes 118 rotate helically to agitate and thereby push the debris 105 in the uphole direction 110 within a flow of the well fluid 109. Accordingly, the well cleaning tool 100 further includes a motor assembly 120 for rotating the shaft 116. In other examples, the brushes 118 can push the debris 105 in the downhole direction 106 when the motor assembly 120 is rotated in an opposite direction.

[0056] Referring to FIG. 3, the motor assembly 120 includes a sealed housing 122 that contains an electric motor 124 and a gear arrangement 126 that transfers rotational motion from the electric motor 124 to a downhole end 128 of the shaft 116. The shaft 116 is equipped with a bearing 130 that secures the downhole end 128 of the shaft 116 to the motor assembly 120 within the housing 122. The shaft 116, the housing 122 of the motor assembly 120, the housing 112 of the conveying device 108, and the SAS 102 are all hollow structures through which the wireline 136 passes to deliver electrical signals originating from the control unit 160 to the respective components.

[0057] Another bearing 132 couples an uphole end 134 of the shaft 116 to a hollow pipe segment 138 through which the wireline 136 also passes. The well cleaning tool 100 further includes an electromagnetic (EM) coil 140 that attracts (for example, captures) metallic debris 105 dislodged from the wall 107 of the well 101 by the brushes 118, as well as a noise detector 142. The EM coil 140 typically has a diameter of about 3 cm to about 5 cm and a length of about 5 cm to about 50 cm. The noise detector 142 includes a hollow housing 144 and a detection device 146 located within the housing 144. The detection device 146 detects noise from debris 105 that hit the housing 144 as a manner of monitoring and estimating the amount of debris 105 that is being agitated by the brushes 118 and flowed within the well fluid 109. An expert system 170 is built into the control unit 160 so that the noise level and the rotational speed of the electric motor 124 may be monitored to prevent operational complications. In this manner, the expert system 170 helps to optimize the performance of the well cleaning tool 100. If the noise level becomes too high and the electric motor 124 begins to experience resistance to rotation, then a penetration speed of the well cleaning tool 100 should be slowed or stopped until most of the debris 105 has cleared. In some examples, the noise level may be monitored by both a decibel reading and a debris strike rate (for example, a strike count per minute or strike count per second). The noise detector 142 typically has a diameter of about 4 cm to about 10 cm and a length of about 10 cm to about 30 cm.

[0058] The well cleaning tool 100 also includes a bow centralizer 148 that is carried on the pipe segment 138. The bow centralizer 148 includes multiple flexible frame members 150 that are distributed about a circumference of the pipe segment 138. The frame members 150 behave like springs such that the bow centralizer 148 can accommodate a variety of tubing and borehole geometries as the well cleaning tool 100 is moved through the well 101. For example, the frame members 150 may remain in contact with the wall 107 of the well 101 to help radially center the well cleaning tool 100 within the well 101 as the bow centralizer 148 is squeezed through even highly deviated sections of the well 101. The bow centralizer 148 may have a maximum diameter of about 10 cm to about 50 cm in a resting state, but can flex to allow the well cleaning tool 100 to be squeezed through well sections with diameters as small as about 5 cm. The bow centralizer 148 typically has a length of about 0.25 m to about 0.5 m.

[0059] The well cleaning tool 100 further includes a fluid delivery device 166 with first and second sets of first and second nozzles 152, 154, respectively, for jetting (for example, forcefully flowing) fluidic substances that can aid in a cleaning operation carried out using the well cleaning tool 100. The nozzles 152, 154 are carried on and extend radially from a fluid hub body 158 of the fluid delivery assembly 166. The nozzles 152, 154 are arranged substantially equidistantly about a circumference of the fluid hub body 158. In the example embodiment of the well cleaning tool 100, the first nozzles 152 are positioned downhole of the second nozzles 154 and are oriented perpendicular to a central axis 156 of the well cleaning tool 100 to direct substances radially outward toward the wall 107 of the well 101. The second nozzles 154 are oriented at an acute angle with respect to the central axis 156 and are directed to deliver fluid in the uphole direction 110.

[0060] In some embodiments, either or both of the nozzles 152, 154 may be utilized at any given time, depending on operational needs. For example, during a tripping operation, the second nozzles 154 may be used to inject a fluid thickening agent 162 (for example, a viscosifier or a suspension agent) into an uphole-directed flow of the well fluid 109 to increase the viscosity of the well fluid 109 and thereby help carry heavy debris 105 away from the well cleaning tool 100. In other situations, such as during flow of the well 101, the first nozzles 152 may be used to jet a fluid thickening agent 162 or a dissolving fluid 164 (for example, acid, solvents, or hot fluids, such as steam) toward the wall 107 of the well 101 to dissolve or otherwise break down sticky petroleum residues that have accumulated along the wall 107, while the second nozzles 154 are used to jet the same fluid for carrying heavy debris 105 away from the well cleaning tool 100. Furthermore, in some embodiments, axial positions of the first and second sets of nozzles 152, 154 may be swapped as desired for operational goals.

[0061] In operation, the well cleaning tool 100 is deployed to and run into the well 101 (for example, on coiled tubing) with the conveying device 108 in the retracted configuration while the well 101 is flowed with well fluid 109. Various components of the well cleaning tool 100 may be subsequently operated as governed by the control unit 160 according to certain conditions present at the well 101. For example, sand, drill cuttings, and other debris particulates may be accumulated along the wall 107 of the well 101, with or without sticky petroleum residues.

[0062] In cases for which sticky petroleum residues are not accumulated in substantial amounts on the wall 107 of the well 101, the following process may be carried out. Once the well cleaning tool 100 reaches a target section within the well 101, the traction arms 114 of the conveying device 108 are placed into the extended configuration to stabilize and radially center the well cleaning tool 100 near the downhole end 104, while the bow centralizer 148 helps to stabilize and radially center the well cleaning tool 100 near an uphole end of the well cleaning tool 100. Furthermore, the electric motor 124, EM coil 140, and noise detector 142 are activated and the second nozzles 154 are opened to jet a fluid thickening agent 162 into the well fluid 109 at a relatively high pressure of about 50,000 kilopascals (kPa) to about 70,000 kPa. In general, the selected jetting pressure may be related to a local mechanical strength of the rock formation 103, which may be estimated from an openhole formation evaluation, such as acoustic logs. Lower pressure may be utilized for softer rock, while higher pressure may be utilized for harder rock. While the second nozzles 154 are open, the brushes 118 are operated to dislodge sand, drill cuttings, and other debris particulates on the wall 107 of the well 101.

[0063] Non-metallic debris may be carried away in the thickened well fluid 109, while the noise detector 142 monitors the noise generated by contact between the non-metallic debris and the housing 144 of the noise detector 142, and while the EM coil 140 catches metallic debris. Once the SAS 102 of the well cleaning tool 100 detects and reaches a downhole end of the well 101, the well cleaning tool 100 stops advancing to avoid contact damage, the electric motor 124 is deactivated, and the EM coil 140 is deactivated to dump the metallic debris (for example, to allow the captured metallic debris to fall to the downhole end of the well 101). The electric motor 124 may be optionally reactivated after dumping the metallic debris when the brushes 118 are far enough from the metallic debris while the well cleaning tool 100 is pulled in the uphole direction 110 to clean any remaining debris.

[0064] With the electric motor 124 and EM coil 140 deactivated and with the well 101 continuing to flow, the second nozzles 154 are adjusted to jet the fluid thickening agent 162 into the well fluid 109 at a relatively low pressure of about 10,000 kPa to about 30,000 kPa while the well cleaning tool 100 is pulled in the uphole direction 110 or otherwise withdrawn from the well 101. The well cleaning tool 100 may be run into and pulled within the well 101 while being operated as described above as many times as necessary to sufficiently clean the wall 107 of the well 101 (for example, to remove a sufficient amount of debris 105 from the wall 107 of the well 101). In some examples, the well 101 may be cleaned in this manner over a period of about 1 hours (h) to about 12 h, depending on, for example, the length of the well interval that needs to be cleaned. In some instances, a cleaning time may be related to a local mechanical strength of the rock formation 103.

[0065] In cases for which sticky petroleum residues are accumulated along the wall 107 of the well 101 in substantial amounts, the electric motor 124 and EM coil 140 are deactivated while tripping. Once the well cleaning tool 100 reaches a target section within the well 101, the traction arms 114 of the conveying device 108 are placed into the extended configuration to stabilize and radially center the well cleaning tool 100 near the downhole end 104, while the bow centralizer 148 helps to stabilize and radially center the well cleaning tool 100 near the uphole end of the well cleaning tool 100. Furthermore, both the first and second nozzles 152, 154 are opened to jet a dissolving fluid 164 into the well 101 at a relatively high pressure of about 50,000 kPa to about 70,000 kPa. The dissolving fluid 164 dissolves or otherwise breaks down the sand, drill cuttings, other debris particulates, and sticky petroleum residues on the wall 107 of the well 101. Once the SAS 102 of the well cleaning tool 100 detects and reaches the downhole end of the well 101, the well cleaning tool 100 stops advancing to avoid contact damage, and the first nozzles 152 are open at low pressure. Furthermore, if a specific lateral of a multilateral well 101 needs to be cleaned with the well cleaning tool 100, then the SAS 102 can direct the well cleaning tool 100 to that specific lateral to clean that lateral.

[0066] The second nozzles 154 are adjusted to jet the dissolving fluid 164 at a relatively low pressure of about 10,000 kPa to about 30,000 kPa while the well cleaning tool 100 is withdrawn from the well 101. The well cleaning tool 100 may be run into and pulled within the well 101 while being operated as described above as many times as necessary to sufficiently rid the wall 107 of sticky petroleum residues. In some examples, the well 101 may be cleaned in this manner over a period of about 1 h to about 12 h, depending on, for example, the debris that needs to be cleaned out and the length of the well interval that need to be cleaned. The well cleaning tool 100 is then run back into the well 101 and operated according to the steps described above for cases in which sticky petroleum residues are not accumulated along the wall 107 of the well 101 in substantial amounts. This stage of cleaning may also be carried out as many times as necessary to sufficiently remove other debris from the wall 107 of the well 101.

[0067] The above-described design and operational features of the well cleaning tool 100 provide several advantages over conventional well cleaning tools. For example, the well cleaning tool 100 has a dual functionality that addresses both sticky and non-sticky debris at the same apparatus and in a single cleaning operation, whereas conventional cleaning tools are designed to address only one of sticky or non-sticky debris, such that multiple cleaning tools and cleaning operations must be carried out to substantially rid the well of both types of debris. Additionally, the noise detector 142 of the well cleaning tool 100 allows convenient monitoring and estimation of the amount of debris 105 present within the well 101 while the well 101 is cleaned and without having to repeatedly remove the well cleaning tool 100 from the well 101 in order to assess the amount of debris, as is required when using conventional cleaning apparatuses that do not have a built-in debris-monitoring device. Furthermore, the well cleaning tool 100 helps to avoid a plug off condition, for which the well cleaning tool 100 cannot pass a plug off

[0068] FIG. 4 is a flow chart illustrating an example method 200 of cleaning a well (for example, the well 101). In some embodiments, the method 200 includes a step 202 for flowing well fluid (for example, the well fluid 109) within the well while running a cleaning tool (for example, the well cleaning tool 100) into the well. In some embodiments, the method 200 further includes a step 204 for injecting the well fluid with a fluid thickening agent (for example, the fluid thickening agent 162) through multiple nozzles (for example, either or both of the first and second nozzles 152, 154) of the well cleaning tool to form thickened well fluid. In some embodiments, the method 200 further includes a step 206 for dislodging metallic debris (for example, debris 105) and non-metallic debris (for example, debris 105) accumulated along a wall (for example, the wall 107) of the well with multiple brushes (for example, the brushes 118) of the cleaning tool. In some embodiments, the method 200 further includes a step 208 for carrying the non-metallic debris out of the well with the thickened well fluid. In some embodiments, the method 200 further includes a step 210 for capturing the metallic debris at a capture device (for example, the EM coil 140) of the cleaning tool.

[0069] While the well cleaning tool 100 has been described and illustrated with respect to certain dimensions, sizes, shapes, arrangements, materials, and methods 200, in some embodiments, a well cleaning tool that is otherwise substantially similar in construction and function to the well cleaning tool 100 may include one or more different dimensions, sizes, shapes, arrangements, configurations, and materials or may be utilized according to different methods. Accordingly, other embodiments are also within the scope of the following claims.