BATTERY OPERATED AUTONOMOUS SCALE REMOVAL SYSTEM FOR WELLS

Abstract

An autonomously operated well intervention tool system includes a lubricator sealingly affixable to an upper end of a well. The lubricator has a latch at an upper end thereof. A well intervention tool system is releasably matable with the latch. The well intervention tool system comprises a wellbore intervention device at a longitudinal end thereof. The lubricator has at least one isolation valve to close fluid communication between the well and the lubricator.

Description

BACKGROUND

This disclosure relates generally to the field of a non-tethered autonomous well intervention tool system for removing scale and similar from a wellbore. The wellbore can be subsea, on an offshore platform or on land. More specifically, the present disclosure relates to a battery operated electrical tool for dissolving mineral build-up in a wellbore, where the tool is stored, deployed from and received in a lubricator and charging system mounted on top of a wellhead (Christmas tree). The wellbore intervention tool system may also perform other wellbore operations, e.g., production logging, setting and retrieval of plugs, and other intervention operations known in the art. The system may operate without the presence of a human operator at the well site, either remotely operated or autonomously at pre-determined times.

Buildup of scale and paraffin is a frequent problem in producing hydrocarbon wells, where such build up causes drop or total halt of production as well as malfunction of wellbore completion components, for example, downhole safety valves. To remove scale and paraffin deposits, wireline is rigged up on top of the wellbore, followed by an intervention where electrical or mechanical impact based tools are run into the wellbore to hammer loose the scale or cut the paraffin built up. This is a slow process due to the nature of the tools being used, but not least due to the time required to rig up and down the intervention valves, lubricator and so on. In addition, well production is lost due to the required well “shut in” (stopping of fluid production) during rigging operation. The process may also be expensive, where the cost of performing an intervention in a subsea well can amount to tens of millions of United States dollars, plus a significant lost income for the duration of the intervention.

Due to the foregoing considerations, failures of wellbore components, for example, downhole safety valves, also take place as a result of intentionally infrequent scale removal, causing the production tubing, etc., to become partially or completely non-functional.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. illustrates scale in a tube, where it can be understood that this will reduce or totally prevent flow through a tube as well as cause wellbore components to malfunction.

FIG. 2 illustrates a wellhead with an attached wellhead (“christmas tree”) and a lubricator/valve system installed on top of the christmas tree. Within the lubricator, a wellbore intervention tool system is mounted. Scale build up is indicated within a conduit called production tubing.

FIG. 2A shows an enlarged view of an example intervention tool system

FIG. 3 illustrates that valves in the lower end of the lubricator system have been opened, followed by a wellbore intervention tool moving into the wellbore.

FIG. 4 illustrates that one or both valves in the lower section of the lubricator system have been closed, so that the well can be flowed at a low rate with the intervention tool being downhole. Scale removal may be started.

FIG. 5 illustrates that the intervention tool is transported up-hole, either by producing the well or by a built in propulsion drive.

FIG. 6 illustrates that the intervention tool has latched into the top section of the lubricator/valve system, with both valves closed and well brought back to normal production.

DETAILED DESCRIPTION

Therefore the present disclosure sets forth a possible solution to removing scale or paraffin in a well where the scale or paraffin removal is performed more frequently than may be performed using conventional wireline conveyed tools. Increased frequency of scale or paraffin deposits may prevent excessive buildup of such scale or paraffin deposits. Scale or paraffin removal at more frequent intervals may be performed by a system mounted on top of the wellhead, where a lubricator, isolated from the wellhead by valves built into the lower section of the intervention system, contains a scale or paraffin removal tool that can be deployed into the wellbore when required.

The wellbore tool intervention system may include a scale or paraffin removal tool with required ancillary instrumentation attached, such as, for example, a battery package, a wet-mating electrical coupler, a propulsion system, etc. The wellbore tool intervention system may be deployed into the wellbore from a storage place within the lubricator and may be returned to the lubricator by causing fluid to flow from the formations external to the well thence into the well. In some embodiments, the wellbore intervention tool system may contain a propulsion system built in that returns the wellbore tool system to the lubricator when required.

Electrical, hydraulic or pneumatic operated impact (e.g. hammer, so called “broach” and similar) based scale removal tools can be coupled to the wellbore intervention tool system. A wellbore intervention tool system according to the present disclosure allows more frequent wellbore scale or paraffin removal operations than would be ordinarily performed using interventions from a vessel, workover rig or a drilling rig. More frequent deposit removal may result in the scale or paraffin deposits being of less extent than would occur with less frequent intervention; such more frequent deposit removal ensures improved production of hydrocarbons from the well.

To perform a wellbore intervention, pressure equalizing between the wellbore and the lubricator may be performed, followed by opening of valves between the lubricator and the wellhead. This will enable the wellbore intervention tool system to drop, or drive down, into the wellbore where it reaches a restriction caused by scale or paraffin. Then the removal of such restriction will be commenced, until the restriction has been removed or until an internal power source (e.g., batteries) is exhausted. When the foregoing takes place, the wellbore intervention tool system may be transported up to the lubricator again by a built in “swab cup” that uses fluid flow from the wellbore to lift the wellbore intervention tool system. When reaching the wellhead, the wellbore intervention tool system will be further pushed up into the lubricator and latch onto a holding device and/or an electrical coupler enabling battery recharging.

After the wellbore intervention tool system has been returned to the lubricator, the valves between the lubricator and the wellhead can be closed and pressure tested, so that the well can commence fluid production again.

When scale or paraffin removal is required again, the above sequence may be repeated.

For those skilled in the art of wellbore interventions, it will be understood that the method described herein may also be used for other type interventions, e.g., memory type production logging, and other intervention operations.

FIG. 1. illustrates scale 14 in a tube 12. The tube 12 may be, for example, a wellbore production tubing or “velocity string.” It will be appreciated that the scale 14 will reduce or totally prevent flow through the tube 14. The scale 14 may also cause wellbore components to malfunction. Such scale needs to be removed, where various methods can be used, as for example mechanically breaking the scale, pulsed electrical energy pulverizing the scale, release of scale-dissolving chemicals, or abrasive means such as milling.

FIG. 2 illustrates a wellhead 20, for example a sea bottom wellhead with an attached christmas tree (e.g., valves 30 and 32). A lubricator system 22 may be affixed to the upper end of the wellhead. The lubricator system 22 may include isolation valves 22A such as gate valves to selectively pressure isolate the lubricator system 22 from the wellhead 20. The isolation valves 22A may be operated by respective actuators 22B. The actuators 22B may be electrically, pneumatically or hydraulically operated, for example. The lubricator system 22 may include pressure equalization valves 28 that connect the interior of the lubricator system to below each of the isolation valves 22A. The pressure equalization valves 28 may also be actuated electrically, hydraulically or pneumatically. The isolation valves 22A and the pressure equalization valves 28 may be operated by a controller 29. The controller 29 may be operated using, for example, telemetry from the water surface or electrical connection using a remotely operated vehicle (ROV). The lubricator system 22 may also include a pressure relief valve 24 to enable release of pressure from the interior of the lubricator system after the well intervention tool system 10 is retrieved into the lubricator system 22. The pressure relief valve 24 may also be electrically, hydraulically or pneumatically operated and may be controlled by the controller 29.

The upper end of the lubricator system 22 may include a sealing cover 22D that is retained in place on the upper end of the lubricator system 22 and is pressure sealed. The sealing cover 22D may include an automatically operable latch 22E to retain the wellbore intervention tool system 10 when it is retrieved into the lubricator system 22. The latch 22E may include electrical connections (not shown separately) for providing electrical power to the wellbore intervention tool system 10, e.g., to recharge batteries therein (see FIG. 2A).

The sealing cover 22D may have a profile for a retrieval and running tool, a receptacle 22F for an electrical cable from an external power source as well as various sensors for monitoring pressure, etc. It may also contain a telemetry system for transmitting and receiving commands and data from a surface vessel or the like. The sealing cap 22D may also be removed, so that a wellbore intervention pressure control system (with riser, etc.) can be landed on top of the lubricator system 22, followed by the possibility of deploying and setting plugs and other equipment in the wellbore. Setting a plug within a tubing hanger or further down into the wellbore tubing 14 may enable a safe removal of the complete lubricator system 22 if such is required.

The isolation valves 22A valve system on the lower end of the lubricator system 22 may be used for pressure testing of the lubricator system 22 and enable the well to operate normally without subjecting the lubricator system 22 to wellbore production fluids and pressure when the wellbore intervention tool system 10 is not in use.

FIG. 2A shows the wellbore intervention tool system 10 in more detail. The wellbore intervention tool system 10, hereinafter “tool” for convenience, may include a self-contained power supply 10E such as batteries within a pressure sealed housing 11. A control and power module 10F disposed in the housing 11 may be used to operate a wellbore intervention device 10A. In the present embodiment, the wellbore intervention device may be a scale removal device disposed proximate the bottom of the housing 11. The scale removal device may be any type known in the art, including a chemical storage and release mechanism, motor-rotated blades or abrasive mills, electric shock (sparker) discharge devices, acoustic devices, heater(s) to remove paraffin deposits, or any other such device for removal of deposits in the tubing (12 in FIG. 1). The tool 10 may include combinations of any or all of the foregoing as well. The tool 10 may include a propulsion device 10G, such as a fluid operated jet or a propeller to cause the tool 10 to move within the tube 14 during operations if gravity is insufficient to move the tool 10 downwardly to the depth of any obstruction, and to return the tool 10 to the lubricator system (22 in FIG. 2) if fluid flow from the well is insufficient to lift the tool 10. The housing 11 may include annular seals 10D such as swab cups to enable free movement of the tool 10 downwardly, but may seal to engage the interior of the tubing (14 in FIG. 1) to enable fluid flow into the well to lift the tool into the lubricator system (22 in FIG. 2). The upper end of the housing 11 may include a mating latch 10B to engage the latch (22E in FIG. 2) in the lubricator system sealing cover (22D in FIG. 2). The housing 11 may include centralizers 10C to enable relatively free movement of the tool 10 in the tubing (14 in FIG. 2) and to keep the tool 10 centered in the tubing for proper operation of the scale removal device.

Scale or paraffin build up may be indicated within the production tubing (14 in FIG. 2), for example, by a decrease in fluid production from the well. Thus it may be necessary to deploy the tool 10. The tool 10 may be installed into the lubricator system (22 in FIG. 2) prior to installing the lubricator system (22 in FIG. 2) onto the wellhead (20 in FIG. 2) or the tool 10 may be installed into the lubricator system (22 in FIG. 2) by unlatching and removing the sealing cover (22D in FIG. 2). Retrieval of the tool 10 may be performed by unlatching and retrieving the entire lubricator system with the tool 10 inside the lubricator system, or by unlatching the sealing cover (22D in FIG. 2) and retrieving the tool 10. It is also possible to perform tool replacement using an ROV in marine operations where the wellhead is on the water bottom.

In other embodiments, the wellbore intervention device 10A may be any other type of wellbore tool, including, without limitation, a production logging instrument, a plug or packer setting tool or a video camera.

FIG. 2 shows the tool 10 engaged with the latch 22E and the isolation valves 22A and pressure equalization valves 28 closed so that the well can operate normally. When it is determined that deployment of the tool is necessary, FIG. 3 illustrates that the pressure equalization valves 28 may be opened to equalize pressure in the well with the pressure in the lubricator system 22. The isolation valves 22A may then be opened and the latch 22E may be released to enable the tool 10 to move downwardly through the well tubing 14. Movement of the tool 10 into the wellbore may be by gravity or by a propulsion device (10G in FIG. 2A) in the tool 10. It is also here illustrated that the tool performs scale or paraffin removal.

FIG. 4 illustrates that one or both of the isolation valves28 has been closed, so that well can be flowed at low rate with the tool 10 being in the wellbore. Scale or other deposit removal may then be started by operating the deposit removal device 10A. When the tool 10 reaches the area of restriction caused by scale or paraffin, the tool 10 performs the removal of this restriction as explained above. As the deposits are removed and the flow restriction is alleviated, the tool 10 will by move further down into the wellbore by gravity (or by use of the propulsion device 10G in FIG. 2A, e.g., for highly inclined or horizontal wells) The tool 10 control and power module (10F in FIG. 2A) may include an internal mechanism that detects length of free fall, e.g., integrating accelerometers or an integrating velocity meter and/or area with no unwanted restriction. The power and control module may be programmed to enable the tool 10 to stop itself, e.g., by energizing its swab cups (10D in FIG. 2A), a mechanical breaking mechanism or the propulsion device (10G in FIG. 2A.

A device preventing the tool 10 from going further into the wellbore than a selected depth may also be installed in the wellbore, for example, a narrow internal diameter packer or similar restriction. Such a device can be set up to trigger the power and control module (10F in FIG. 2A) to cause the tool 10 to return the lubricator/system 22. An example of such device may be a contact switch, shown at 13 in FIG. 2A which would not be triggered by scale or other deposits, but would be triggered by contact with a packer or similar internal diameter restriction.

FIG. 5 illustrates that the tool 10 is transported up-hole, either by producing the well at low flow rate or by the propulsion device (10G in FIG. 2A). The isolation valves 28 are opened to enable the tool 10 to enter the lubricator system 22.

FIG. 6 illustrates that the tool 10 has latched into the lubricator system 22 on the latch 22E in the sealing cover 22D. At such time the isolation valves 28 may be closed and the well brought back to normal production. The tool 10 is now coupled to the electrical coupler (part of latch 22E) in the sealing cover 22D so that the batteries (10E in FIG. 2A) can be charged. In some embodiments it may be possible to retrieve logged data and transmit new commands to the tool 10 through the electrical connector 22F.

After the isolation valves 28 are closed, pressure inside the lubricator system 22 may be released using the pressure relief valve 24. Such may be performed prior to any required removal of the sealing cap 22D or the lubricator system 22 from the wellhead 20.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

1. An autonomously operated well intervention tool system, comprising:

a lubricator sealingly affixable to an upper end of a well, the lubricator comprising a latch at an upper end thereof;

a well intervention tool system releasably matable with the latch, the well intervention tool system comprising a wellbore intervention device at a longitudinal end thereof; and

wherein the lubricator comprises at least one isolation valve to close fluid communication between the well and the lubricator.

2. The system of claim 1 wherein the latch comprises an electrical connector to enable supply of electrical power to the well intervention tool system.

3. The system of claim 1 wherein an electrical connector is located anywhere within the lubricator system.

4. The system of claim 1 wherein the wellbore intervention device comprises a scale removal device.

5. The system of claim 1 wherein the wellbore intervention device comprises at least one of a production logging instrument and a plug or packer setting tool.

6. The system of claim 1 wherein the well intervention tool system comprises at least one swab cup on an exterior surface thereof to enable lifting the well intervention tool system by upward movement of fluid in the well.

7. The system of claim 1 wherein the well intervention tool system comprises a powered propulsion unit to enable movement of the well intervention tool system along an interior of the well.

8. The system of claim 1 wherein the lubricator comprises at least one equalization valve in a fluid communication line extending between the well and the lubricator.

9. The system of claim 1 wherein the lubricator comprises at least one pressure relief valve configured to selectively vent pressure inside the lubricator.

10. The system of claim 1 wherein the scale removal device comprises at least one of a chemical storage and release mechanism, motor-rotated blades, motor-rotated abrasive mills, an electric shock discharge device, an acoustic device and a heater.

11. The system of claim 1 wherein the well intervention tool system comprises means for automatically stopping the well intervention tool system at a selected position in the well.

12. A method for performing intervention operations in a well, comprising:

latching a well intervention tool system in a lubricator, the lubricator comprising at least one isolation valve at a well connection end thereof, the lubricator comprising at least one pressure equalization valve, the lubricator comprising at least one pressure relief valve;

closing the at least one isolation valve;

affixing the lubricator to an upper end of a well;

opening the at least one pressure equalization valve to impart pressure in the well to an interior of the lubricator;

opening the at least one isolation valve;

releasing the well intervention tool system to move into the well to selected depth therein;

operating a wellbore intervention device on the well intervention tool system; and

returning the well intervention tool system to the lubricator.

13. The method of claim 12 wherein the returning the well intervention tool system to the lubricator comprises lifting the well intervention tool system using flow of fluid in the well.

14. The method of claim 12 wherein the returning the well intervention tool system to the lubricator comprises operating a propulsion device in the well intervention tool system.

15. The method of claim 12 further comprising closing the at least one isolation valve, opening a pressure relief valve to vent pressure from within the lubricator and removing the lubricator from the well.

16. The method of claim 12 further comprising closing the at least one isolation valve, opening a pressure relief valve to vent pressure from within the lubricator, removing a sealing cap from an upper end of the lubricator and retrieving the well intervention tool system from within the lubricator.

17. The method of claim 12 further comprising attaching an electrical cable to a connector forming part of a latch used to retain the well intervention tool system in the lubricator and applying electrical power to the electrical cable to recharge at least one battery in the well intervention tool system.

18. The method of claim 12 wherein the wellbore intervention device comprises a scale removal device.

19. The method of claim 12 wherein the wellbore intervention device comprises at least one of a production logging instrument and a packer or plug setting tool.