WO2021234171A1

WO2021234171A1 - Downhole tool deployment

Info

Publication number: WO2021234171A1
Application number: PCT/EP2021/063720
Authority: WO
Inventors: Alan Thomson; Gordon Cunningham
Original assignee: Expro North Sea Limited
Priority date: 2020-05-22
Filing date: 2021-05-21
Publication date: 2021-11-25
Also published as: GB202217317D0; GB2610119A; GB202007671D0; US20230203901A1; CA3178906A1

Abstract

An apparatus for fitting to a wellbore, the apparatus comprising: a self-propelled downhole tool for deployment within the wellbore, and configured to propel itself along at least part of a length of the wellbore; and a lubricator for fitting to a wellhead of the wellbore via a valve system providing communication between the lubricator and the wellbore, and for housing the self-propelled downhole tool when in a stowed position, wherein the lubricator comprises an input port for receiving data from a remote unit, the input port being in electrical communication with the self-propelled downhole tool when in the stowed position, and wherein the received data comprises instructions for operating the self-propelled downhole tool, and associated self-propelled downhole tool, lubricator and method.

Description

Downhole Tool Deployment

Field of the invention

The invention relates to tools for use in downhole or wellbore environments, for example in the oil and gas industry. More specifically, the invention relates to downhole tools for use in well intervention or workover operations, and in specific arrangements may relate to self-propelled and/or autonomous downhole tools..

Background

In the oil and gas industry, well boreholes (“wellbores”) are drilled in order to access subsurface hydrocarbon-bearing formations. In order to control production from a given wellbore, a valve arrangement known as a Christmas tree is typically disposed on the wellhead, the valve arrangement comprising a number of flow control valves and safety valves configured amongst other things to control production, permit well isolation and control access of downhole tools and equipment into/from the wellbore.

During the operational life of a given well, it may be necessary to access the wellbore in order to perform remedial operations, known generally in the industry as intervention or workover operations.

However, while necessary, intervention operations pose a number of challenges for operators. For example, wellbores may be located in remote or relatively inaccessible locations, making them difficult and time consuming to access, particularly for intervention operations which require significant man-power to operate and/or which require equipment which by virtue of size or weight may be restricted or prevented by local infrastructure laws. Wellbores may also be located in areas of particular scientific or environmental sensitivity. The given location may also pose challenges in terms of how to protect the environment, intervention equipment and personnel.

An operator may wish to carry out intervention operations a number of times in order to mitigate deferred production or otherwise maintain production at optimal levels. One such intervention operation involves the removal of paraffin wax, asphaltenes and/or other solids, residues and the like which can accumulate in the wellbore over time and which reduce production or otherwise reduce the optimal operation of the well. In some instances, a given field may include a significant number of wells, some fields having hundreds of wells, making intervention operations difficult and in some cases prohibitively expensive to carry out regularly given the above factors and demands on personnel and equipment.

A number of intervention operations may be carried out using tools deployed on slickline. Typically, a tool is introduced to the well on a slickline through a stuffing box, which is designed to seal around the slickline to prevent well fluids and gases escaping. In known arrangements, the stuffing box includes a sheave or pulley assembly with a number of pulley wheels for guiding the slickline into the well. The slickline may be used to deploy the tool into the wellbore and/or to retrieve the tool from the wellbore.

Summary

According to the invention in an aspect, there is provided an apparatus for fitting to a wellbore. The apparatus may comprise a self-propelled downhole tool for deployment within the wellbore. The self-propelled downhole tool may be configured to propel itself along at least part of a length of the wellbore. The apparatus may comprise a lubricator for fitting to a wellhead of the wellbore. The lubricator may be fitted to the wellhead via a valve system providing communication between the lubricator and the wellbore. The lubricator may be for housing the self-propelled downhole tool when in a stowed position. The lubricator may comprise an input port for receiving data from a remote unit. The input port may be in electrical communication with the self-propelled downhole tool when in the stowed position. The received data may comprise instructions for operating the self-propelled downhole tool.

Optionally, the lubricator is configured to transfer the received data communications to the self-propelled downhole tool when in the stowed position.

Optionally, the input port comprises an electrical connector for connection to the self- propelled downhole tool when in the stowed position for creating an electrical connection between the input port and the self-propelled downhole tool. Optionally, electrical connector and/or the self-propelled downhole tool are configured such that the electrical connection is broken when the self-propelled downhole tool is not in the stowed position. Optionally, electrical connector and/or the self-propelled downhole tool are configured such that the electrical connection may be broken at a point during deployment of the self-propelled downhole tool. Such a point during deployment may be at the time the downhole tool leaves the stowed position, and in some arrangements may be later. After the electrical connection is broken, the self- propelled downhole tool may operate autonomously for part of or all of the deployment.

Optionally, the wellbore may form part of a flowing or producing well. Accordingly, the self-propelled downhole tool may be deployed in the flowing or producing well. The self-propelled downhole tool is able to drive itself into the wellbore against the flow.

Optionally, communications data is received by the input port and is transmitted to the self-propelled downhole tool via the electrical connection.

Optionally, the apparatus further comprises at least one sensor configured to sense one or more downhole parameters during deployment of the self-propelled downhole tool. The at least one sensor may comprise one or more of a camera or other light- based sensor, a temperature sensor and a pressure sensor. The skilled person will envisage other sensors that may be used. Accordingly, the one or more downhole parameters may comprise one or more of an image or light-based representation of the wellbore, a temperature sensed in the wellbore and a pressure sensed in the wellbore. The one or more parameters may be associated with a depth or other position in the wellbore and/or a time.

Optionally, the lubricator further comprises an output port for transmitting sensor data corresponding to the one or more sensed downhole parameters to the, or a separate, remote unit. Optionally, the output port comprises an electrical connector for connection to the self-propelled downhole tool when in the stowed position for creating an electrical connection between the output port and the self-propelled downhole tool. The output port may comprise at least part of the input port.

Optionally, the received data comprising instructions for operating the self-propelled downhole tool comprises one or more instructions based on the one or more sensed downhole parameters. Such instructions may have been determined by the, or a separate, remote unit receiving the sensor data. In this sense, “remote” encompasses a feature external to the wellbore and/or external to the output (or input) port.

Optionally, the received data communications comprise data instructing the self- propelled downhole tool to deploy within the wellbore. Such instruction may be arranged to be enacted immediately or at a later time.

Optionally, the data communications comprise one or more instructions setting deployment parameters for a deployment of the self-propelled downhole tool. The deployment parameters may comprise one or more of a depth to which the self- propelled downhole tool will be driven, a speed of drive of the self-propelled downhole tool, a sensor reading to take, an operation to undertake and a timing of any of the above or another deployment parameter. The skilled person will envisage other deployment parameters.

Optionally, the self-propelled downhole tool comprises a processor configured to store the one or more instructions and/or one or more preloaded instructions.

Optionally, the processor is configured to control the self-propelled downhole tool to undertake the one or more instructions and/or the one or more preloaded instructions.

Optionally, the processor is configured to determine one or more autonomous instructions based at least in part on the one or more sensed downhole parameters. That is, the processor may be configured to determine one or more deployment parameters (or instructions) without transmitting data associated with the sensed downhole parameters to a remote unit. The deployment parameters (or instructions) determined by the processor may relate to the current deployment and/or to future deployments.

Optionally, the processor is configured to control the self-propelled downhole tool autonomously.

Optionally, the one or more instructions comprise a plurality of instructions. Optionally, the plurality of instructions comprise a complete operation within the wellbore, including returning the self-propelled downhole tool to the stowed position.

Optionally, after deployment, the self-propelled downhole tool is configured to operate autonomously.

Optionally, after deployment, the self-propelled downhole tool has no direct and/or physical connection to the remote unit.

Optionally, the self-propelled downhole tool comprises a battery to provide power for propelling the self-propelled downhole tool and/or to provide power to the processor and/or sensors.

Optionally, the input port is further configured to receive electrical power from the, or a further, remote unit.

Optionally, the battery is chargeable when the self-propelled downhole tool is in the stowed position.

Optionally, the apparatus further comprises a sealed end cap fitted to a distal end of the lubricator, and the input port forms part of the end cap. The sealed end cap means that the lubricator, and therefore the wellbore, is sealed and is therefore at a lower risk of leaks.

Optionally, the input port comprises an electrical connector for fitting to an external cable.

According to the invention in an aspect, there is provided a self-propelled downhole tool for deployment within a wellbore. The self-propelled downhole tool may comprise a drive mechanism for propelling the self-propelled downhole tool along at least part of a length of the wellbore. The self-propelled downhole tool may comprise a receiver for electrical communication with an input port of a lubricator when the self-propelled downhole tool is in a stowed position. The self-propelled downhole tool may be configured to receive data communications from a remote unit for operating the self- propelled downhole tool. According to the invention in an aspect, there is provided a lubricator for fitting to a wellhead of a wellbore. The lubricator may be for fitting via a valve system providing communication between the lubricator and the wellbore. The lubricator may be for housing a self-propelled downhole tool when in a stowed position. The self-propelled downhole tool may be for deployment within the wellbore and may be configured to propel itself along at least part of a length of the wellbore. The lubricator may comprise an input port for receiving data from a remote unit, and for electrical communication with a receiver of the self-propelled downhole tool when in the stowed position. The received data may comprise instructions for operating the self-propelled downhole tool.

According to the invention in an aspect, there is provided a method for operating a self- propelled downhole tool within a wellbore. The self-propelled downhole tool may be configured to propel itself along at least part of a length of the wellbore. The method may comprise stowing the self-propelled downhole tool in a stowed position. In the stowed position, the self-propelled downhole tool may be received within a lubricator fitted to a wellhead of the wellbore. The lubricator may be fitted via a valve system providing communication between the lubricator and the wellbore. The method may comprise transmitting, from a remote unit, data communications for operating the self- propelled downhole tool. The method may comprise receiving, at an input port of the lubricator, the transmitted data communications, the input port being in electrical communication with the self-propelled downhole tool. The method may comprise deploying the self-propelled downhole tool based on the received data communications.

According to the invention in an aspect, there is provided a method for operating a self- propelled downhole tool within a wellbore. The self-propelled downhole tool may be configured to propel itself along at least part of a length of the wellbore. The method may comprise sensing, by at least one sensor, one or more downhole parameters. The method may comprise determining, based on the sensed downhole parameters, one or more instructions setting deployment parameters for a deployment of the self- propelled downhole tool. The method may comprise deploying the self-propelled downhole tool based on the determined instructions. The one or more instructions may be determined by a processor of the self-propelled downhole tool. The one or more instructions may be determined by a remote unit. Accordingly the method may comprise transmitting data relating to the sensed downhole parameters to the remote unit. The method may comprise stowing the self-propelled downhole tool in a stowed position. In the stowed position, the self-propelled downhole tool may be received within a lubricator fitted to a wellhead of the wellbore. The lubricator may be fitted via a valve system providing communication between the lubricator and the wellbore. The method may comprise, while the self-propelled downhole tool is stowed, transmitting, from the self-propelled downhole tool to a remote unit, the data relating to the sensed downhole parameters. The method may comprise determining, by the remote unit, one or more instructions setting deployment parameters for a deployment of the self-propelled downhole tool. The method may comprise transmitting, from the remote unit, data communications comprising the determined instructions. The method may comprise receiving, at an input port of the lubricator, the transmitted data communications, the input port being in electrical communication with the self-propelled downhole tool.

Brief description of the drawings

Figure 1 shows an isometric view of a wellhead with a lubricator fitted thereto;

Figure 2 shows an isometric view of a wellhead with a lubricator fitted thereto along with a plurality of remote units;

Figure 3a shows a section through part of a wellhead including a self-propelled downhole tool stowed within a lubricator;

Figure 3b shows a section through part of a wellhead including a self-propelled downhole tool during deployment; and

Figure 4 is a flow diagram of a method for operating a self-propelled downhole tool within a wellbore.

Detailed description

Referring first to Figure 1 of the accompanying drawings, there is shown an apparatus (e.g. an intervention system) 10 configured to perform an intervention operation in a wellbore 12. In the illustrated arrangement, the wellbore 12 is land-based having a wellhead valve arrangement in the form of a Christmas tree 14 disposed on a wellhead 16. The intervention system 10 is configured to deploy an intervention tool into the wellbore 12. In the illustrated arrangement, the intervention tool comprises a paraffin wax removal tool for cleaning paraffin deposits from the wellbore 12 and associated infrastructure and equipment. However, it will be recognised that the intervention system 10 may be configurable to perform a number of different intervention operations using a suitable intervention tool. In such cases, the intervention tool is typically be deployed on a slickline or wireline through a stuffing box, as with the tool.

As shown in Figure 1, the intervention system 10 comprises a tool housing in the form of a lubricator 20. In the illustrated arrangement, the lubricator 20 comprises a stand of three connected heavy wall tubing sections, the interior of the lubricator 20 defining a tool storage compartment configured to house the intervention tool.

As shown in Figure 1, the lubricator 20 is coupled to and disposed on top of the Christmas tree 14. The lubricator 20 is fitted to the wellhead via a valve system 22, which in the illustrated arrangement forms part of the lubricator 20. The valve system may also include the Christmas tree. The valve system 22 permits selective communication of tools and fluid between the lubricator 20 and the wellbore 12.

The exemplary valve system 22 shown has an upper control valve 24 and a lower control valve 26, which can be controlled independently. The valve system 22 provides a dual barrier between the lubricator 20 and the wellhead valve arrangement 14, and permits an upper valve 28 of the Christmas tree 14 to be maintained in an open condition.

The intervention system 10 is configurable between a tool stowed configuration in which the lubricator 20 is isolated from the wellbore 12 by the valve system 22 and an activated configuration in which the valve system 22 is open and the lubricator 20 communicates with the Christmas tree 14 and/or the wellbore 12 to permit deployment of the intervention tool by a tool deployment arrangement 30, as will be described below.

The tool deployment arrangement 30 is provided for deploying the intervention tool into the wellbore 12. The tool deployment arrangement 30 comprises a conveyance in the form of slickline or wireline 32 which is coupled to the intervention tool and which extends through an upper end portion of the lubricator 20 via stuffing box 34 - in the illustrated arrangement a dual chamber stuffing box - to ensure pressure integrity of the lubricator 20 and monitor any fluid/gas wire bypass.

The tool deployment arrangement 30 further comprises sheaves or pulleys 36, 38 for supporting the wireline 32. In the illustrated arrangement shown in Figure 1, pulley 36 is disposed on the lubricator 20 above the stuffing box 34 and pulley 38 is tied to wellhead 16, although it will be recognised that the pulleys 36, 38 may be disposed at other suitable locations.

Figure 2 shows an exemplary setup of an intervention apparatus or system at a wellhead. The Christmas tree, lubricator and valve system arrangement of Figure 2 may be the same or similar to that of Figure 1. A winch is provided as part of a wireline unit 40 and is operatively coupled to a drive which in the illustrated arrangement takes the form of a direct drive electric motor. In use, the drive rotates the winch in order to pay out the wireline 32 when it is desired to deploy the intervention tool 18 into the wellbore 12, and to reel in the wireline 32 when it is desired to retrieve the intervention tool from the wellbore 12. That is, the tool is deployed and retrieved using the wireline. In addition, weight bars may be positioned on the tool to drive it into the wellbore 12 when the wireline 32 is paid out. The weight bars take up considerable space in the lubricator 20.

As shown in Figure 2, the illustrated arrangement of an intervention apparatus further comprises a wireline power unit 42, a control power unit 44 and other ancillary equipment.

In Figure 1 (and similarly in Figure 2) a support arrangement in the form of support mast 58 supports the Christmas tree 14 and the lubricator 20.

In some arrangements, the intervention tool may form part of a self-propelled downhole tool for use in the wellbore 12. The self-propelled downhole tool may be configured to drive itself into the wellbore, powered by one or more motors. The one or more motors may be electric motors and may be provided with electrical power via a power supply similar to that shown in Figure 2. The self-propelled downhole tool may comprise a plurality of drive wheels. The drive wheels may be extendable on arms from a main body of the self-propelled downhole tool to engage an inner wall of the wellbore (or production tubing or casing). The drive wheels may be electrically or hydraulically driven.

Figures 3a and 3b show an apparatus 300 for deploying a self-propelled downhole tool 302 into a wellbore 304. In the example of Figure 3, the self-propelled downhole tool 302 is not deployed on a slickline or wireline. The self-propelled downhole tool 302 is configured to operate autonomously.

As used herein, the term “autonomous” in respect of operation of the self-propelled downhole tool 302 encompasses a self-propelled downhole tool that is instructed to deploy and undertake a task, and then requires no further instruction during that task in order to complete it. Completion of the task may include the self-propelled downhole tool returning to a start position, such as the stowed position. In some arrangements, an autonomous self-propelled downhole tool may also require no power (e.g. electrical power and/or hydraulic power) after deployment in order to complete the task. Accordingly, the self-propelled downhole tool may be configured, after deployment, to have no direct connection to any remote unit providing instructions to the self-propelled downhole tool. Direct connection in this context encompasses any communication of instructions, electrical power and/or hydraulic power to the self-propelled downhole tool from a remote unit via a physical medium, such as a wireline or slickline. The downhole tool 302 may also gather data using sensors and use that gathered data for control of the tool 302 without assistance from other apparatus outside the wellbore 304, e.g. from surface.

Figure 3a shows a top part of a Christmas tree 306, however a Christmas tree need not be used in all arrangements. Below the Christmas tree 306 and not shown in Figure 3a is the wellbore 304.

A valve system 308 is fitted to the Christmas tree 306 by a plurality of bolts 309, although other fixings may be used. As in Figures 1 and 2, the valve system 308 provides communication between the Christmas tree 306 and/or the wellbore 304, and a lubricator 310, which is fitted to a distal end of the valve system 308. The lubricator 310 is fitted to the valve system 308 by a plurality of bolts 311, although other fixings may be used. Communication between the lubricator 310 and the Christmas tree 306 may be fluid communication and/or communication allowing the self-propelled downhole tool 302 to pass from the lubricator 310 to the wellbore 304 and/or from the wellbore 304 to the lubricator 310. As in Figures 1 and 2, the valve system 308 comprises an upper valve 312 and a lower valve 314 that are controllable independently. In some arrangements, the valve system 308 may form part of the lubricator 310. In some arrangements, the valve system 308 may comprise a different number of valves, for example 1 or 3 valves. The Christmas tree may form part of the valve system 308.

As used herein, the term “distal” encompasses a feature of an apparatus that is positioned further away from the wellbore 304. The term “proximal” encompasses a feature that is positioned closer to the wellbore 304. For example, the valve system 308 is generally elongate and has a proximal end fitted to the Christmas tree 306 and a distal end fitted to the lubricator 310.

An end cap 316 is fitted to a distal end of the lubricator 310 by a plurality of bolts 317, although other fixings may be used. The end cap 316 is sealed. The end cap 316 comprises static features that form the seal. That is, the end cap 316 does not include a stuffing box or any mechanism through which a slickline or wireline can be passed and which a seal must be formed around. The end cap 316 comprises an input port 318 through which data communications and/or electrical power may be received. In the example shown in Figure 3, the input port comprises an electrical connector configured to be connected to an external cable 320. The electrical connector is secured to the end cap 316 so as to form a seal. The external cable 320 may be further connected to one or more remote units (not shown). The one or more remote units may be configured to supply data communications and/or electrical power to the apparatus 300 via the external cable 320. In other arrangements, the input port 318 may comprise one or more wireless communications devices. In some arrangements, the one or more wireless communications devices may be positioned elsewhere within the apparatus 300. It is also noted that the input port 318 may also be configured as an output port or a separate output port may be provided on the apparatus. An output port may be arranged to transmit data communications from the self-propelled downhole tool 302 and/or the lubricator 310 to one or more remote units. The lubricator 310 is configured to house the self-propelled downhole tool 302 when it is stowed. That is, the lubricator 310 is configured to house the self-propelled downhole tool 302 before deployment and/or after completion of a task or operation, such as an intervention operation.

The self-propelled downhole tool 302 may further comprise an electrical connector 322 that is configured for electrical connection to the input port 318. The input port 318 may comprise an electrical connector 324, which is configured to connect with the electrical connector 322 of the self-propelled downhole tool 302. Accordingly, an electrical connection may be established between the input port 318 and the self- propelled downhole tool 302. The lubricator 310, and in the specific arrangement of Figure 3a, the input port 318, is able to receive data communications and/or electrical power from one or more remote units (not shown) and may pass those data communications and/or the electrical power to the self-propelled downhole tool. In the example shown, the electrical connection is provided by the electrical connectors 322, 324 although other arrangements, e.g. a wireless data link, may be used. The data communications received by the lubricator 310, via the input port 318, comprise data for operation of the self-propelled downhole tool 302, as explained below.

The self-propelled downhole tool 302 may comprise a battery pack 326, which is configured to receive electrical power from the one or more remote units and store it. When the self-propelled downhole tool 302 is in the stowed position and electrical communication between the input port 318 and the self-propelled downhole tool 302 is established, the battery pack 326 may be configured to receive electrical power from the one or more remote units to charge it. The self-propelled downhole tool 302 may also comprise a memory 329 configured to store data received in the data communications from the one or more remote units. When the self-propelled downhole tool 302 is in the stowed position, the data communications may be transferred to the memory 329 of the self-propelled downhole tool 302 over the electrical connection via the input port 318.

The lubricator 310 may include one or more cleaning apparatus 330. The cleaning apparatus 330 may be positioned at a point in the lubricator 310 such that the self- propelled downhole tool 302 must pass the cleaning apparatus 330 when being deployed and/or when returning to the stowed position after deployment. That is, the cleaning apparatus 330 may be positioned at a more proximal location than the self- propelled downhole tool 302 when the self-propelled downhole tool 302 is in the stowed position. The cleaning apparatus may comprise one or more brushes or scrapers.

The lubricator 310 may have a reduced length over known lubricators. For example, the lubricator 310 may be short enough to fit between two decks of an offshore rig. This is possible at least partly because the weight bars used for known tool deployments are not required in exemplary arrangements disclosed herein, as deployment is made possible by the self-propulsion system of the downhole tool.

Figure 3a shows the self-propelled downhole tool 302 in the stowed position and received within the lubricator 310. The self-propelled downhole tool 302 is configured to propel itself along at least part of a length of the wellbore 304. That is, the self- propelled downhole tool 302 may propel itself along the wellbore 304 without receiving further electrical power and/or data communications from a remote unit during at least part of a time period when it is deployed. Accordingly, the self-propelled downhole tool 302 comprises a drive mechanism. The drive mechanism may comprise a motor. The drive mechanism may comprise one or more wheels 328 and/or caterpillar tracks, for example (although other means for propelling the self-propelled downhole tool will be clear to the skilled person). The motor may be an electric motor and may be powered by the battery pack 326. The motor may be configured to drive the one or more wheels 328, caterpillar tracks or other means. Further, the wheels 328, caterpillar tracks or other means may be positioned on arms extendable from a main body of the self- propelled downhole tool 302. The arms may extend until the wheels 328, caterpillar tracks or other means are in contact with a sidewall of the wellbore, which may comprise tubing, casing or an open hole.

The self-propelled downhole tool 302 may comprise docking features that engage with corresponding docking features 332 on the lubricator 310. The docking features 332 are arranged to retain the self-propelled downhole tool 302 in the lubricator 310 when stowed. Accordingly, the docking features 332 may comprise one or more detent mechanisms. The skilled person will be aware of a number of detent mechanisms and any may be used. As mentioned above, the self-propelled downhole tool 302 may comprise an electrical terminal 322 that is configured to communicate electrically with a corresponding electrical terminal 324 on the input port 318. When the self-propelled downhole tool 302 is stowed, the electrical terminal 322 of the self-propelled downhole tool 302 is able to communicate with the electrical terminal 324 of the input port 318. The electrical terminals 322, 324 may comprise electrical connectors configured to engage, antennas configured to communicate wirelessly, or another type of electrical terminal. The transfer of electrical power and/or data communications to the self-propelled downhole tool 302 may be via the electrical communication provided by the electrical terminals 322, 324.

In exemplary arrangements, the electrical terminals 322, 324 may form at least part of the docking features and/or detent mechanism. That is, the docking features may form an electrical connection between the self-propelled downhole tool 302 and the input port 318 and/or may control at least partly operation of the electrical terminals 322, 324 when the self-propelled downhole tool 302 is stowed. In exemplary arrangements, the electrical communication between the self-propelled downhole tool 302 and the input port 318 (or lubricator 310) is broken after deployment of the self-propelled downhole tool 302, e.g. after the detent mechanism is overcome.

As mentioned above, the self-propelled downhole tool 302 may comprise a battery pack 326. The battery pack 326 of the self-propelled downhole tool 302 may be charged by the electrical power received from the remote unit and passed to the self- propelled downhole tool 302 via the electrical terminals 322, 324. The battery pack 326 of the self-propelled downhole tool 302 may provide electrical power to the motor to drive the wheels 328, caterpillar tracks or other drive means, and/or to any sensors or other electrical equipment fitted to the self-propelled downhole tool 302.

The self-propelled downhole tool 302 may also comprise a processor 334. The processor 334 may be configured to control operation of one or more tools on the self- propelled downhole tool 302. For example, the self-propelled downhole tool 302 may include one or more of a camera, a temperature sensor, a pressure sensor or any other tool used in downhole operations. In a specific arrangement, the self-propelled downhole tool 302 may include a wax removal tool for the removal of paraffin wax build-up. The processor may also be configured to control the drive mechanism of the self-propelled downhole tool 302.

More specifically, the processor 334 may be configured to receive data communications from the lubricator 310, which may be via the input port 318, and to store the data in a memory for use during deployment to control the self-propelled downhole tool 302 and/or one or more tools located on the self-propelled downhole tool 302.

In some arrangements, the memory 329 may be configured to store data relating to one or more downhole parameters and sensed by the one or more sensors on the self- propelled downhole tool 302, such as a camera, a temperature sensor, a pressure sensor. When the self-propelled downhole tool 302 is in the stowed position and electrical communication is established with the input port 318, the self-propelled downhole tool 302 may transmit the stored sensor data to the one or more remote units. The data communications received from the remote unit may be based on the transmitted sensor data. In other arrangements, the processor 334 may be configured to determine one or more instructions for operating the self-propelled downhole tool 302 based on the sensor data. For example, during deployment the one or more sensors may measure an internal diameter of a casing or tubing of the wellbore 704. If the diameter is found not to be as expected in a particular area, the processor 334 of the self-propelled downhole tool 302 (and/or the remote unit if the sensed diameter is transmitted thereto) may determine that more wax cleaning (e.g. greater time) should be focused on that area. This may be done by the processor 334 without human intervention and/or the intervention of apparatus outside of the wellbore 304.

The processor 334 may be configured to control the self-propelled downhole tool 302 autonomously, e.g. without receiving any further data or instruction from the lubricator 310 or the remote unit for at least part of the period of deployment.

In specific arrangements, the self-propelled downhole tool 302 may be configured to undertake one or more well intervention or workover tasks. For example, the self- propelled downhole tool 302 may be configured deploy within the well bore and the paraffin wax removal tool may remove paraffin wax deposits from the wellbore 12 and associated infrastructure and equipment. In the exemplary arrangement shown in Figure 3a, the self-propelled downhole tool 302 also comprises a fishing neck 336 for removal of the self-propelled downhole tool dock 322 and self-propelled downhole tool 302 using a fishing tool, if necessary.

Figure 3b shows the system of Figure 3a with the self-propelled downhole tool 302 shortly after deployment.

In exemplary arrangements, the self-propelled downhole tool 302 may be configured to transmit data (e.g. sensor data) to surface and/or to receive data from surface using, at least in part, wireless EM communication and/or wireless acoustic communication.

Figure 4 shows a flow diagram of a method for operating a self-propelled downhole tool 302 within a wellbore 304. The self-propelled downhole tool 302 may be as described above. Accordingly, the self-propelled downhole tool 302 is configured to propel itself along at least a part of the length of the wellbore 304.

The method comprises stowing 400 the self-propelled downhole tool 302 in a stowed position. This may comprise docking the self-propelled downhole tool 302 in the lubricator 310, e.g. using the docking features discussed above. In stowing the self- propelled downhole tool 302, the docking feature of the self-propelled downhole tool 302 may engage with the corresponding docking features 332 of the lubricator 310. The detent mechanism may be engaged. Further, electrical communication is possible between the input port 318 and the self-propelled downhole tool 302 by way of the electrical terminals. In exemplary arrangements, the electrical terminals comprise electrical connectors 322 on the self-propelled downhole tool 302 that are configured to engage with electrical connectors 324 on the input port 318.

In this configuration, the upper and lower control valves 312, 314 may be in their closed configurations, thereby providing a dual barrier between the lubricator 310 and the Christmas tree 306/wellbore 304. The provision of the dual barrier beneficially permits the upper control valve of the Christmas tree 306 to be maintained in an open configuration. The method may include charging the battery pack 326 of the self-propelled downhole tool 302 when the self-propelled downhole tool 302 is in the stowed position. This may be done by electrical power received from one or more remote units via the input port 318 of the end cap 316.

The method further comprises transmitting 402 data communications from a remote unit and receiving 404 the transmitted data communications at the self-propelled downhole tool 302.

The data communications may include instructions for deployment of the self-propelled downhole tool 302 within the wellbore 304. More specifically, the data communications may include a plurality of instructions for the self-propelled downhole tool 302 to complete a task, such as an intervention or workover task. The instructions may comprise a set parameters for the completion of the task. For example, the data communications may include a plurality of instructions for the self-propelled downhole tool 302 to undertake a paraffin wax removal task, which may include operating the drive mechanism of the self-propelled downhole tool 302 to move the self-propelled downhole tool 302 to a required position within the wellbore 304, operating the paraffin wax removal tool, and operating the drive mechanism to return the self-propelled downhole tool 302 to the lubricator 310. In such circumstances, the parameters of the deployment may include a depth to which the self-propelled downhole tool 302 should travel, a type of operation to be conducted at that depth and/or the time for which the operation should be undertaken.

The plurality of instructions may be stored in the memory 329 of the self-propelled downhole tool 302, such that they may be implemented, e.g. by the processor 334, after the self-propelled downhole tool 302 has been deployed and there is no communication with the lubricator 310 or the remote unit. That is, the self-propelled downhole tool 302 may operate autonomously.

In some arrangements, a monitoring arrangement is provided, as illustrated in Figure 1. The exemplary monitoring arrangement comprises a flow sensor 60 and a pressure sensor 62. However, it will be recognised that in other arrangements the monitoring arrangement may comprise one or other of the flow sensor 60 and the pressure sensor 62, or other sensors alone or in combination. The monitoring arrangement also comprises a visual monitoring system in the form of a camera 64 which in the illustrated arrangement is disposed on the support mast 58. In use, the camera 64 may facilitate remote visual monitoring of the tool deployment arrangement. The monitoring arrangement may sense data, such as flow rate and/or pressure and provide the sensed data to the remote unit and/or the processor 334. The processor 334 and/or the remote unit may use the sensed data to determine instructions setting one or more deployment parameters, as discussed above.

In some arrangements, the instructions for undertaking a task may be preloaded into the memory 329 of the self-propelled downhole tool 302 before being fitted into the apparatus 300. In some arrangements, the instructions for undertaking a task may be determined by the processor 334, e.g. based on sensor data. In such arrangements, the data communications may include amendments to the preloaded instructions or processor determined instructions.

It will be appreciated that a plurality of different sets of instructions may be stored in the processor 334 of the self-propelled downhole tool 302 to allow the self-propelled downhole tool 302 to undertake a plurality of tasks.

The data communications may also include an instruction to deploy the self-propelled downhole tool 302. That is, the data communications may include an instruction to begin a deployment of the self-propelled downhole tool 302. Such a deployment may be one of one or more deployment programs stored in the memory 329. Instructions may be determined and sent manually, or may be determined and sent based on an intervention system configured to receive data, some of which may be sensor data from the wellbore, wellhead and/or vicinity of the wellhead, and determine whether the self-propelled downhole tool 302 should be deployed. Accordingly, the method may further comprise deploying 406 the self-propelled downhole tool 302 into the wellbore 304.

The data communications may also include instructions for operation of one or more other components of the apparatus 300, such as the valve system 308.

For example, on identifying that an activation event has occurred (e.g. a sensor detecting that the well flow rate has dropped below a threshold valve) the intervention system may enter an activated configuration to permit deployment of the self-propelled downhole tool 302 into the wellbore 304 by opening the lower and upper control valves 312, 314. The intervention system may ensure that the control valves 312, 314 have opened correctly and that pressure integrity has been maintained. The intervention system 300 may then transmit data communications to the lubricator 310, and then on to the self-propelled downhole tool 302 to deploy the self-propelled downhole tool 302 into the wellbore 304. The instructions may include data identifying a particular operation to be undertaken. On completion of the operation by the self-propelled downhole tool 302, which may be indicated by the self-propelled downhole tool 302 returning to the stowed position in the lubricator 310, the intervention system 300 may reconfigure from the activated configuration to a tool storage configuration by closing the upper and lower control valves 312, 314. Well pressure may then be vented from the lubricator 20.

It should be understood that embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention. For example, while in the described embodiments the systems and methods are directed to the removal of paraffin wax from a wellbore and associated infrastructure and equipment, it will be understood that the systems and methods may be used to perform any suitable intervention operation, including not exclusively well logging operations.

Claims

CLAIMS:

1. An apparatus for fitting to a wellbore, the apparatus comprising: a self-propelled downhole tool for deployment within the wellbore, and configured to propel itself along at least part of a length of the wellbore; and a lubricator for fitting to a wellhead of the wellbore via a valve system providing communication between the lubricator and the wellbore, and for housing the self- propelled downhole tool when in a stowed position, wherein the lubricator comprises an input port for receiving data from a remote unit, the input port being in electrical communication with the self-propelled downhole tool when in the stowed position, and wherein the received data comprises instructions for operating the self-propelled downhole tool.

2. The apparatus of claim 1, wherein the lubricator is configured to transfer the received data communications to the self-propelled downhole tool when in the stowed position.

3. The apparatus according to claim 2, wherein the input port comprises an electrical connector for connection to the self-propelled downhole tool when in the stowed position for creating an electrical connection between the input port and the self-propelled downhole tool.

4. The apparatus according to claim 3, wherein electrical connector and/or the self-propelled downhole tool are configured such that the electrical connection is broken when the self-propelled downhole tool is not in the stowed position.

5. The apparatus according to claim 3 or 4, wherein communications data is received by the input port and is transmitted to the self-propelled downhole tool via the electrical connection.

6. The apparatus according to any preceding claim, further comprising at least one sensor configured to sense one or more downhole parameters during deployment of the self-propelled downhole tool.

7. The apparatus according to claim 6, wherein the lubricator further comprises an output port for transmitting sensor data corresponding to the one or more sensed downhole parameters to the, or a separate, remote unit.

8. The apparatus according to claim 6 or 7, wherein the received data comprising instructions for operating the self-propelled downhole tool comprises one or more instructions based on the one or more sensed downhole parameters.

9. The apparatus of any preceding claim, wherein the received data communications comprise data instructing the self-propelled downhole tool to deploy within the wellbore.

10. The apparatus according to any preceding claim, wherein the data communications comprise one or more instructions setting deployment parameters for a deployment of the self-propelled downhole tool.

11. The apparatus according to claim 10, wherein the self-propelled downhole tool comprises a processor configured to store the one or more instructions and/or one or more preloaded instructions.

12. The apparatus according to claim 11, wherein the processor is configured to control the self-propelled downhole tool to undertake the one or more instructions and/or the one or more preloaded instructions.

13. The apparatus according to claim 11 or 12, when dependent directly or indirectly on any of claims 6 to 8, wherein the processor is configured to determine one or more autonomous instructions based at least in part on the one or more sensed downhole parameters.

14. The apparatus according to any of claims 11 to 13, wherein the processor is configured to control the self-propelled downhole tool autonomously.

15. The apparatus according to any of claims 10 to 14, wherein the one or more instructions comprise a plurality of instructions.

16. The apparatus according to claim 15, wherein the plurality of instructions comprise a complete operation within the wellbore, including returning the self- propelled downhole tool to the stowed position.

17. The apparatus according to any preceding claim, wherein, after deployment, the self-propelled downhole tool is configured to operate autonomously.

18. The apparatus according to any preceding claim, wherein, after deployment, the self-propelled downhole tool has no direct and/or physical connection to the remote unit.

19. The apparatus according to any preceding claim, wherein the self-propelled downhole tool comprises a battery to provide power for propelling the self-propelled downhole tool.

20. The apparatus according to claim 19, wherein the input port is further configured to receive electrical power from the, or a further, remote unit.

21. The apparatus according to claim 18 to 20, wherein the battery is chargeable when the self-propelled downhole tool is in the stowed position.

22. The apparatus according to any preceding claim, further comprising a sealed end cap fitted to a distal end of the lubricator, and the input port forms part of the end cap.

23. The apparatus according to claim 22, wherein the input port comprises an electrical connector for fitting to an external cable.

24. A self-propelled downhole tool for deployment within a wellbore, and comprising: a drive mechanism for propelling the self-propelled downhole tool along at least part of a length of the wellbore; and a receiver for electrical communication with an input port of a lubricator when the self-propelled downhole tool is in a stowed position, and configured to receive data communications from a remote unit for operating the self-propelled downhole tool.

25. A lubricator for fitting to a wellhead of a wellbore via a valve system providing communication between the lubricator and the wellbore, and for housing a self- propelled downhole tool when in a stowed position, the self-propelled downhole tool for deployment within the wellbore and configured to propel itself along at least part of a length of the wellbore, the lubricator comprising an input port for receiving data from a remote unit, and for electrical communication with a receiver of the self-propelled downhole tool when in the stowed position, and wherein the received data comprises instructions for operating the self-propelled downhole tool.

26. A method for operating a self-propelled downhole tool within a wellbore, the self-propelled downhole tool being configured to propel itself along at least part of a length of the wellbore , the method comprising: stowing the self-propelled downhole tool in a stowed position, in which the self- propelled downhole tool is received within a lubricator fitted to a wellhead of the wellbore via a valve system providing communication between the lubricator and the wellbore; transmitting, from a remote unit, data communications for operating the self- propelled downhole tool; receiving, at an input port of the lubricator, the transmitted data communications, the input port being in electrical communication with the self-propelled downhole tool; and deploying the self-propelled downhole tool based on the received data communications.