HYDRAULICLY LOCKED TOOL

Abstract

A downhole tool and method of use are described; the tool has a sleeve assembly that slides within the tool body under the action of a hydraulic pressure differential; the sleeve assembly has a control neck portion and a first hydraulic reservoir defined between a first end of the control neck portion and a second hydraulic reservoir defined between a second end of the control neck portion and the body; a purge conduit extending between the first and second hydraulic reservoirs and an electromechanical control valve across the purge conduit is used to regulate fluid flow along the purge conduit; the electromechanical control valve can communicate with sensors, through which control systems transmit information to the control valve.

Description

HYDRAULICLY LOCKED TOOL FIELD OF INVENTION The invention relates to a downhole tool that has a drive mechanism with a hydraulically movable element with selective locking capability. BACKGROUND OF THE INVENTION In oil and gas industry drilling operations, drilled wells are provided for hydrocarbon reserves. Drilling, completion, maintenance, and extraction operations associated with such wells require the use of a wide variety of equipment operating within the wellbore in a production string. This equipment frequently includes mechanical tools that must be remotely controlled from the surface, for example, to switch the equipment between one or more states. Many of these operations require fluid circulation to a particular part of the well, such as drilling fluid, steam, or chemical treatments. The fluids are typically pumped through the production string. Control over some tools can be achieved using fluid in the production string by dropping objects, such as a ball or dart, into the string to selectively block the internal diameter of a tool and apply backpressure to actuate a mechanism. For example, a ball can fall onto a seat, and the pressure can displace the seat and an associated downhole sleeve or redirect fluid to actuate a mechanism operatively coupled to the sleeve. Many tools utilize this general means of actuation, including, for example, circulation tools with circulation ports operable by moving a sleeve; or downhole reamers or scraping / cleaning tools that have reaming or cleaning elements actuated by moving a sleeve. One problem with tools that selectively block an internal diameter through the drill string is that the internal diameter is then unavailable for other operations. This can be addressed by blowing the ball or dart through the hole, but since a typical well can only tolerate a limited number of such objects, this in turn usually requires that the ball or dart be captured and retrieved, or drilled out. ινΐΛ / a / zuzz / ui ¿jo / An additional problem is that it is desirable to operate multiple tools on a single production string to minimize the number of trips. When several tools generally share the same drive principle, this can limit the number of tools that can operate together, increasing the total time and cost of downhole operations. US Patent 2010 / 089583 describes a bottom reaming tool in which a central piston is hydraulically displaced to deploy the tool's crushing arms. A chamber is defined between the piston and the tool body, divided into upper and lower portions by a friction joint. As the piston is displaced, fluid is dissipated between the upper and lower portions of the chamber through a passage to accommodate its changing volume. A solenoid valve in the passage is actuated to open it and allow the piston to move. However, this arrangement results in a significant radial thickness of the tool. Hence the need remains for a means to operate or control a downhole tool that addresses or mitigates one or more of these problems. BRIEF DESCRIPTION OF THE INVENTION In accordance with a first aspect of the invention, a downhole tool is provided comprising: a body that has a through hole; A sleeve assembly capable of sliding within the body between a first position and a second position, under the action of hydraulic pressure and / or a bias arrangement; and the body comprising a control neck portion arranged around the sleeve assembly; when a first hydraulic reservoir is defined between the sleeve assembly and the body above a first end of the control neck portion and the body, and a second hydraulic reservoir is defined between the sleeve assembly and the body below a second end of the control neck portion and the body; where the control neck portion further comprises; A purge conduit that generally extends longitudinally between the first and second hydraulic reservoirs; and an electromechanical control valve across the purge conduit configured to regulate fluid flow along the purge conduit. The first hydraulic reservoir, bleed line, and control valve, and the second hydraulic reservoir are separated longitudinally along the tool. When the control valve is open, the fluid in the reservoirs can pass through the bleed line between the first and second hydraulic reservoirs, allowing the sleeve assembly to move between the first and second positions under the action of hydraulic pressure and / or elastic bias. When the control valve is closed, the fluid cannot pass between the first and second reservoirs, preventing any change in its volume. Opening and closing the control valve can thus be used to regulate the movement of the sleeve assembly. Additionally, the control valve can be closed to hydraulically lock the sleeve in position.Furthermore, the longitudinal arrangement of the control neck portion, in particular the purge duct and control valve, and the hydraulic reservoirs, is radially compact. Reference is made herein to the fact that the purge passage extending longitudinally between the first and second hydraulic reservoirs is distinct from prior art arrangements in which a passage is located radially outside either of such cylinders or reservoirs. That is to say, the first and second hydraulic reservoirs may have internal and external radial dimensions around the longitudinal axis of the tool, wherein the purge passage does not pass radially within or outside the internal or external dimension along any part of its length. The control neck portion may include the entire purge duct. The first hydraulic reservoir can be defined between a first end of the control neck portion and the body. The second hydraulic reservoir can be defined between a first end of the control neck portion and the body. The first and second hydraulic reservoirs may be defined in part by adjacent surfaces of the sleeve assembly. The tool may comprise one or more sensors, configured to detect a signal or series of signals. The electromechanical control valve may communicate with one or more of the sensors and is operable to open and / or close upon detection of a predetermined control signal or signals detected by the sensor(s). The tool may comprise any suitable sensor or combination of sensors. The tool comprises one or more sensors configured to detect a downhole condition, such as pressure, flow rate, temperature, etc. The tool may comprise a pressure sensor, flow sensor, accelerometer, acoustic sensor, or similar device. Consequently, when the tool includes a pressure and / or flow sensor, the electromechanical control valve can be controlled from the surface by pumping to increase the hydrostatic pressure in the wellbore and / or to create fluid flow into the wellbore and / or out of the tool. Where the tool includes an accelerometer, the electromagnetic control valve can be controlled by moving the tool longitudinally or rotationally, or by shifting or rotating the production string to which the tool is connected. In some embodiments, the electromechanical control valve is connected or has the ability to be connected to a cable line, and control signals can be transmitted through the cable line in use. The tool may also include a control system configured to open and close the control valve. The control system may communicate with the electromagnetic control valve and one or more sensors or cable lines, as the case may be. It will be understood that the electromechanical control valve, or the control system in particular, may be configured to respond to a combination of such control signals and / or a combination of signals from more than one sensor, to help eliminate any unwanted actuation of the electromagnetic control valve. In some embodiments, for example, the tool comprises an accelerometer configured to detect rotational signals, and the control system is configured to actuate the valve in response to a series of two or more periods of rotation and / or counter-rotation separated by predetermined time intervals. The processing resource or logical control required by the control system to effect such control over the electromagnetic control valve will be well known to the person skilled in the art. The sleeve assembly may be elastically biased to one or the other of the first and second positions by an elastic biasing element (or elements) acting between the sleeve assembly and the body. For example, a spring or other suitable elastic biasing element(s) may be arranged in the first and / or second hydraulic chamber. Elastic biasing may be between opposing lips or ledges (e.g., an annular lip) within the first and / or second reservoir, or any other suitable formation known in the art. One or more elastic biasing elements may be provided to act between the body and the sleeve assembly anywhere within the tool, other than in the hydraulic reservoirs. The sleeve assembly can be slid under the action of hydrostatic pressure within the bore, that is, a differential static pressure between the bore and the outside of the tool body. Consequently, the sleeve can move, pressurizing the bore. In some embodiments, the first hydraulic reservoir may communicate with the borehole and the second hydraulic reservoir may communicate with an exterior of the body (for example, via a purge port or ports through the body). In operation, the borehole may be pressurized to create a pressure differential between the borehole and the exterior of the body, to displace the sleeve assembly to the second position (when the control valve is open). The tool may further comprise a first tertiary hydraulic reservoir and / or a second tertiary hydraulic reservoir defined, at least in part, between the sleeve assembly and the body above and below the first and second hydraulic reservoirs, respectively. The first tertiary hydraulic reservoir can communicate with the borehole. The second tertiary hydraulic reservoir can communicate with an exterior of the wellbore. Providing tertiary hydraulic reservoirs separates the first and second hydraulic reservoirs from the fluid in the borehole or wellbore and can prevent debris or chemical treatments from entering the first and second hydraulic reservoirs, which could otherwise cause blockage or damage to the bleed line and control valve in certain downhole applications. The first tertiary hydraulic reservoir may be at least partially open at its upper end. The first tertiary hydraulic reservoir may communicate with the borehole via one or more pressure ports through the sleeve assembly. The first tertiary hydraulic reservoir may be separated from the first hydraulic reservoir by a first balancing piston. The first balancing piston may be integrally formed with the adjacent part of the valve assembly, or it may be fixed to it. For example, the first balancing piston may be generally shaped like a neck around the sleeve assembly, retained by retaining screws, bolts, or similar fasteners. The first balancing piston can be slidable with respect to the sleeve and body assembly between a first upper end stop and a first lower end stop. Such a sliding relationship can provide a degree of damping. The second tertiary hydraulic reservoir may be separated from the second hydraulic reservoir by a second balancing piston. The second balancing piston may be integrally formed with the adjacent part of the screen assembly, or it may be fixed to it. The first balance piston can be slidable with respect to the sleeve assembly and body between a second upper end stop and a second lower end stop. The sleeve assembly can be slidable under the action of a dynamic pressure differential. The sleeve assembly can be slidable under the action of a dynamic pressure differential along the tool (i.e., longitudinally). The sleeve assembly can be slidable under the action of a dynamic pressure differential through a flow restriction with the perforation defined by the sleeve assembly. The fluid flowing through the perforation creates a dynamic pressure differential sufficient to move the valve assembly. At least a portion of the through-hole length may be defined by the sleeve assembly. At least a portion, and in some embodiments the entire portion, of the through-hole defined by the sleeve assembly may have a diameter that is smaller than an upstream portion of the production string, whether it is an upstream portion of the tool, or an upstream tubular length of the tool, etc. Provision of each of: a flow restriction; communication of the first hydraulic reservoir (or first tertiary hydraulic reservoir as the case may be) with the borehole; and communication of the second hydraulic reservoir (or second tertiary hydraulic reservoir as the case may be) with and outside the body; provides that the sleeve assembly moves under the action of either a hydrostatic pressure in the borehole or a dynamic differential depression as described herein. The experienced person will understand that pumping fluid can increase both the hydrostatic pressure in the tool and create a dynamic pressure drop. Providing communication between the second hydraulic reservoir, or tertiary hydraulic chamber, and the outside of the tool can therefore better facilitate the movement of the sleeve assembly when fluid is pumped. For example, this can allow for relatively minimal flow restriction when moving the valve assembly by pumping or circulating fluid through the tool. The control neck portion may be integrally formed with an adjacent body portion. The control neck portion may be fixed to the body, for example by a locking key threaded through the body into the control neck portion, or by any other suitable means such as welding, pressure screws, or line fittings. The first and second hydraulic reservoirs may be defined in part by the upper and lower ends of the control neck portion and adjacent surfaces of the sleeve assembly. The control neck portion may comprise the first and second outwardly extending protrusions, wherein an upper face of the first protrusion portion defines a lower end of the first hydraulic reservoir, and a lower face of the second protrusion portion defines an upper end of the second hydraulic reservoir. The control neck portion, and in particular the first and second projection portions thereof, may be provided with one or more seals for sealing against an internal body surface, for example, one or more O-rings. The control neck may comprise one or more internal seals for sliding sealing between the control neck portion and the adjacent portion of the sleeve assembly, such as sliding contact seals. The purge passage may generally extend longitudinally through one or more parts of the control neck portion. The first and second protrusion portions may comprise the upper and lower end regions of the purge passage. An intermediate region of the purge passage may be defined by one or more hydraulic lines, optionally connected to the protrusion portions (by threaded compression fits, for example), or extending through it. The electromechanical valve may be connected to one or more hydraulic lines. The control neck portion may include one or more recesses, or portions of reduced diameter, between the upper and lower ends of the control neck portion. Recesses or reduced-diameter sections provide space to house additional equipment. At least one intermediate section of the purge line may be located in the recess or reduced-diameter section. In some embodiments, the electromechanical control valve is located in a recess or reduced-diameter section. In some embodiments, a control system may be located in a recess or reduced-diameter section. As discussed earlier, the electromechanical control valve can be switched on and controlled via cable line from the surface. In some versions, however, the electromechanical control valve is battery-powered. The tool, accordingly, includes a battery pack. The control neck portion may house the battery pack. The battery pack may be located in a recess or reduced-diameter portion of the control neck portion. When present, the control system and one or more sensors communicate with and are powered from the battery pack. The movement of the sleeve assembly between the first and second positions can change the tool between an activated and deactivated condition. The tool may comprise one or more circulation ports. The movement of the sleeve assembly between the first and second positions may open and close the one or more circulation ports (i.e., switch the ports between deactivated (closed) and activated (open)). The sleeve assembly may comprise one or more sleeve ports that communicate with the through-bore through the sleeve assembly to an exterior of the sleeve assembly. The body may comprise one or more circulation ports that extend radially through the body to an exterior of the body. In one of the first and second positions of the sleeve assembly, the one or more sleeve ports and the one or more circulation ports may be longitudinally misaligned, such that the tool is in an off condition in which the fluid in the through-hole does not communicate with the outside of the body. ινΐΛ / a / zuzz / ui ¿jo / In the other of the first and second sleeve assembly positions, the one or more sleeve ports and the one or more circulation ports may be longitudinally misaligned with each other or with a defined intermediate chamber between the sleeve assembly and the body, such that the tool is in an activated condition in which the fluid in the through-hole communicates with the fluid outside the body. In the activated condition, fluid may be pumped through the production string and circulated through the one or more sleeve ports and the one or more circulation ports to the outside of the tool. The sleeve assembly can be operatively connected to an actuator, such as a linear actuator or a hydroelectric piston actuator, to change the condition of the additional device between an off and an on state. The sleeve assembly can also be directly operatively coupled to the additional device to change its condition between an off and an on state. The additional apparatus may include any downhole apparatus, including, but not limited to, an expandable stabilizer, expandable packer, deployable cleaner, crushing or scraping apparatus, deployable arms of a reaming apparatus, a deployable anchor, a deflection wedge, and other out-of-well tools. The range of downhole apparatus and the means available for operationally connecting it to a slip sleeve will be well known to a person skilled in the art. In some embodiments, the tool can be used as a housing cleaner or scraper, with sleeve-fed, deployable cleaning elements generally as described in European Patent Applications PCT / EP2015 / 056540 or PCT / EP2019 / 053345, which are incorporated herein by reference. In some embodiments, movement of the sleeve assembly from the first to the second position externally releases the spring-loaded, skewed cleaning elements from an inactive condition, in which they lie recessed within the body, to an activated position in which the cleaning elements extend radially from the body and can be used to clean or scrape a housing.The cleaning elements can, in the first portion of the sleeve assembly, be hooked to the sleeve assembly in the deactivated position and the movement of the sleeve assembly to the second position releases the hook, as described in Co-Pending Application PCT / EP2019 / 053345. The tool may comprise one or more circulation ports and sleeve ports, and the sleeve may be operatively coupled to the additional downhole apparatus. For example, the tool may comprise both deployable cleaning elements and circulation ports with the ability to be selectively opened as described herein. The tool may comprise more than one additional downhole apparatus. ινΐΛ / a / zuzz / ui ¿jo / The movement of the sleeve assembly between the first and second positions can change the condition of more than one downhole appliance, or it can change the condition of one or more additional downhole appliances and circulation ports between their respective deactivated and activated conditions. The condition of the respective circulation ports and / or additional downhole equipment can generally change simultaneously when the sleeve assembly moves between the first and second positions. In some embodiments, the sleeve assembly can be operated to move between the first and second positions and one or more defined third positions. The sleeve assembly can also be operated to move between the first position, the second position, and a defined third position that is intermediate between the first and second positions. Where the tool comprises more than one deactivated condition and more than one corresponding activated condition, switching between an activated condition and a deactivated one can be achieved in some embodiments by moving the sleeve assembly between the third position and one of the first and second positions.The tool may be configured, for example, to activate a downhole device, such as deployable cleaning elements, on the movement of the sleeve assembly between the first and third positions, and to open the circulation ports or activate an additional downhole device, on the movement of the sleeve assembly between the third and second positions. In some embodiments, one or more third positions may be defined by closing the electromechanical control valve and hydraulically locking the sleeve assembly in a defined third position. The tool may comprise a sensor, such as an optical sensor or a mechanical switch, to detect when the valve assembly is in the third position and cause the electromechanical control valve to close. The tool can be configured to cause the electromechanical control valve to close automatically under certain circumstances. For example, the electromechanical control valve can be configured to close after a predetermined amount of time has elapsed since it opened. Alternatively, or additionally, it is configured to close automatically when the sleeve assembly reaches the first and / or second position. The tool may be equipped with one or more sensors to detect the position of the sleeve assembly. In some configurations, an accelerometer or acoustic sensor used to detect control signals may also be configured to detect the position of the sleeve assembly, for example, when the sleeve assembly makes contact with an end stop and creates a vibration or sound. iviA / a / zuzz / ui ¿óor The control system can be configured to effect such automatic closure of the electromechanical control valve. The sleeve assembly can be of unitary construction (with some auxiliary apparatus, such as gaskets or similar). The sleeve assembly may comprise a single sleeve, to which balance pistons are optionally mounted. The valve assembly may comprise multiple sleeves connected end-to-end; for example, threaded together. The body may be of unitary construction (i.e., formed as a single piece), optionally with the exception of the control neck portion, where present, any downhole apparatus which may be mounted or coupled to the body. The body may be a mandrel, generally tubular. The body may comprise multiple body portions connected end-to-end. The tool body may include connectors for attaching the tool to the production string above and below the tool. Any suitable connectors may be used, such as threaded pin connectors, as known to those skilled in the art. According to a second aspect of the invention, a method is provided for moving a sliding sleeve assembly of a downhole tool between a first position and a second position, wherein a first hydraulic reservoir is defined between the sleeve assembly and a tool body above a first end of a control neck portion of the body, and a second hydraulic reservoir is defined between the sleeve assembly and the body below a second end of the control neck portion; wherein the control neck portion comprises a purge conduit generally extending longitudinally between the first and second hydraulic reservoirs; the method comprising: Generate a hydrostatic pressure differential between the through-hole and an outside of the tool; and / or generate a dynamic pressure differential in the through-hole through the tool or through a flow restriction defined by the sleeve assembly; open a control valve (such as an electromechanical control valve); flow hydraulic fluid between the first and second hydraulic reservoirs, generally longitudinally along the purge duct, by means of the control valve; and close the control valve to hydraulically lock the valve assembly in the first and second positions. iviA / a / zuzz / ui ¿jo / The steps can be conducted in any appropriate order. For example, the pressure differential can be created before or after the control valve is opened. The method may comprise emitting a control signal or signals to open and close the control valve. The method may comprise emitting a control signal or signals to one or more sensors in communication with the electromagnetic control valve. The method may comprise creating a downhole condition to emit a control signal to a sensor. The downhole condition may comprise, for example, pressurizing the drilling fluid through the borehole, moving the tool longitudinally and / or rotationally, for example, by operating the production string or rotating the drill string as described herein with respect to the first aspect. For example, the tool may comprise an accelerometer in communication with the electromechanical control valve, and the method may comprise emitting a rotational signal to the accelerometer by rotating the tool. In some modalities, the electromechanical control valve, or a control system that communicates with it, is configured to respond with one or more sequences of rotational signals (or other downhole conditions or wireline signals), such as a predetermined sequence of rotations and / or counter-rotations separated by non-rotating periods. The method may comprise controlling the electromechanical control valve by means of a line connection. The method may comprise controlling the control valve via more than one of the downhole or wireline conditions. The sleeve assembly can be elastically biased to either the first or second position. Accordingly, the method may comprise moving the sleeve assembly from the first to the second position under the action of either the hydraulic pressure differential or an elastic bias member; and moving the sleeve assembly from the second to the first position under the action of the other hydraulic pressure differential or elastic bias member. Where the method includes multiple steps of moving the sleeve assembly between the first and second chamber positions, it shall be understood that the method may comprise additional steps of opening and closing the control valve. The pressure differential can be a hydrostatic pressure differential between the borehole and the outside of the tool. The method may involve generating the hydrostatic pressure differential by creating hydrostatic pressure inside the borehole. The tool is generally cylindrical and can thus be considered to have a longitudinal axis extending the length of the tool. The term radially refers to an orientation perpendicular to the longitudinal orientation, for example, radially with respect to the longitudinal axis. Although the tool may have a longitudinal axis, it need not be completely symmetrical about the longitudinal axis, and downhole equipment, control neck portion components, etc., may be distributed asymmetrically around the longitudinal axis. Herein, reference is made to an end (e.g., a first end or a second end) of a tool feature, such as the body, sleeve assembly, control neck portion, etc., in relation to the longitudinal dimension. Thus, a first end of a given feature is necessarily longitudinally separated from the second end. Terms such as "above" and "below" are used in relation to the longitudinal orientation of the production string or tool. A feature that is above another feature is placed along the production string (or tool) closest to the surface, and a feature that is below another feature is placed along the production string (or tool) farthest from the surface—regardless of the wellbore or drill hole's orientation relative to the vertical. BRIEF DESCRIPTION OF THE DRAWINGS Non-limiting exemplary modalities will now be described in relation to the following drawings in which: Fig. 1A shows a longitudinal cross-sectional side view through a top portion of a modality of a downhole tool with a sleeve assembly in a first position; Fig. IB shows a cross-sectional view of a top portion of a downhole tool modality with a sleeve assembly in a second position; Fig. 2 shows a perspective view of a downhole tool sleeve assembly, with the control neck portion omitted for clarity; Figure 3 shows a perspective view of the control neck portion of the downhole tool; and Fig. 4 shows a perspective cross-sectional view of the downhole tool body. ινΐΛ / a / zuzz / ui ¿jo / DETAILED DESCRIPTION OF THE INVENTION With reference to Figs. 1A, 1B and 2 to 4, the downhole tool includes a body 100 and a through hole 102, 102a. The body includes a control collar portion 15, which in the embodiment shown is formed as a separate unit (see Fig. 3) which is secured within the body 100 by a locking key 6, which engages with a recess 31 on the outer surface of the control collar 15. A sleeve assembly 200 (shown in perspective view in Fig. 2) generally consists of an upper sleeve 4 threaded to a lower sleeve 8 by means of the respective external threaded region 19 of the upper sleeve and an internal threaded region 20 of the lower sleeve 8. The upper and lower sleeves 4, 8 are provided with hexagonal formations 71, 74 to facilitate such coupling. In alternative embodiments, the sleeve assembly may comprise a single sleeve or a greater number of sleeves. A portion 102a of the through-hole 102 is defined by the sleeve assembly. The diameter of the hole 102a through the sleeve assembly is smaller than the diameter of the hole 102 above and below the sleeve assembly defined by the body 100. The control neck portion 15 is arranged around a lower region 74 of the upper sleeve 4. As shown in Fig. 4, in the configuration shown, body 100 includes lower 1, middle, and upper 3 sections, which are threaded together using conventional male 25 and female 24 bolt connectors. For clarity, the upper and lower body sections are omitted from Figs. 1A and 1B. A first hydraulic reservoir 29 is defined between the sleeve assembly 200 and the body 100 above the control neck portion 15 (on the left in Figs. 1A and 1B). A second hydraulic reservoir 30 is defined between the sleeve assembly 200 and the body 100 below the control neck portion 15 (on the right in Figs. 1A and 1B). In the embodiment shown, the first and second hydraulic reservoirs 29, 30 are defined by the upper and lower ends 60, 61 of the control neck portion, adjacent to the outer surfaces of the upper sleeve 4 and the body surfaces 100. The first and second hydraulic reservoirs are also partly defined by the ends of the first and second balance pistons, the function of which will be discussed in further detail below. The sleeve assembly 200 is slidable within the body 100 between a first position, shown in Fig. 1A, and a second position, shown in Fig. 1B. In the first position, the upper end 33 of the upper sleeve 4 abuts the lower end 32 of the upper body section 3, which acts as an end stop. In the second position, a butt shoulder 13 around the upper sleeve 4 meets an opposite butt shoulder 14 extending from the top end of the control collar 15. The sleeve assembly 200 is spring-loaded to the first position shown in Fig. 1A by a coiled spring 23. The spring is arranged in the first hydraulic reservoir 29 and acts between the upper face 60 of the control neck 15 and a shoulder 204 around the upper sleeve 4. The tool also includes a first balance piston 10 and a second balance piston 5. The balance pistons 5, 10 are, in the embodiment shown, sliding relative to the sleeve assembly 200 and body 100 and consequently include the inner and outer seals 58, 59. It is understood that the balance cylinders are optional and are omitted in alternative embodiments, and in still additional embodiments are fixed relative to the sleeve assembly. A lower end of the first balancing cylinder 10 defines the upper end of the first hydraulic reservoir 29. An upper end of the first balancing cylinder 10 defines a lower end of a first tertiary hydraulic reservoir 108, between the body and the sleeve 4. The first tertiary hydraulic reservoir communicates with the orifice 100 at its upper end, by means of a ring defined between the upper sleeve 4 and the upper body section 3. The first balance cylinder 10 is slidable along the sleeve 4 between the shoulder 204 and the lower end of the upper body section 3. An upper end of the second balance cylinder 5 defines the lower end of the second hydraulic reservoir 30. A lower end of the second balance cylinder 5 defines an upper end of a second tertiary hydraulic reservoir 34. The second tertiary hydraulic reservoir communicates with an exterior of the body by means of bleed ports 11 through the middle body section 2. The lower end of the secondary tertiary hydraulic reservoir 34 is defined by the friction joint 74. The second balance cylinder is slidable along the lower 74 portion of sleeve 4 between an inner shoulder 104 of the mid-body section 2, and the lower end face 61 of the control collar 15. The neck 100 includes fill ports 28, 22 through which the first and second hydraulic reservoirs are filled with hydraulic fluid. The ports are then plugged. The first tertiary hydraulic reservoir 108 is filled with fluid at orifice 100, and the second tertiary hydraulic reservoir 34 is filled with fluid from the well. Balancing pistons 5, 10 isolate the first and second hydraulic reservoirs 29, 30 from the entry of unwanted fluids or debris. In alternative configurations (not shown), the hydraulic reservoirs 29 and 30 communicate with the orifice and exterior of the tool, respectively. Additional configurations include completely sealed hydraulic reservoirs. Figure 3 shows control neck 15 in additional detail. The control neck portion 15 further comprises a purge conduit extending between the first and second hydraulic reservoirs 29, 30. The purge conduit is defined partly by openings extending through the control neck 15 and partly by hydraulic lines. The neck has upper and lower projection portions 15a, 15b at the first and second ends of the neck 15. Projection portions 15a, 15b define the first and second ends 60, 61 of the neck 15. A superior channel 56 extends through the upper projection portion, extending from the upper end face 60, exiting into a recess 15c between projection portions 15a, 15b. Similarly, a lower channel 57 extends through the lower projection portion 15b, extending from the lower end face 61 and exiting into the recess 15c. The upper and lower channels thus communicate with the first and second hydraulic reservoirs 29, 30. The hydraulic lines 53 placed within the recess 15c are connected by threaded compression couplings 52 to the upper and lower channels 56, 57. The hydraulic lines 53 each also connect to a solenoid valve 51, which has a solenoid 54. End regions of the purge duct are thus defined by the upper and lower channels 56, 57 and an intermediate region of the purge duct is defined by the hydraulic lines 53, with the solenoid valve 51 being located in the purge duct. The first and second hydraulic reservoirs 29, 30 each have a minimum and maximum radius and the full length of the purge conduit is within the maximum and minimum radius of the reservoirs. The solenoid (i.e., electromechanical) valve 51 includes an accelerometer (not shown) and a control system (not shown), whereby control over the valve 51 can be effected by means of rotational signals received by the accelerometer, as described herein. The control neck 15 also includes a battery pack 55 that communicates with and powers the valve 51. The battery pack is housed within an adjacent recess between the upper and lower protruding portions of the neck 15. The control neck has a central bore sized to slide into the valve assembly 200 (and the lower portion 75 of the upper sleeve in particular). The protruding portions 15a, 15b are sized to be received within the body 100. Gaskets 58 are provided around the protruding portions to seal between the neck 15 and the body 100. Gaskets are also provided to slide into the control neck 15 and the sleeve assembly 200. The movement of the sleeve assembly between the first and second positions will now be described with reference to Figs. 1A and 1B. In use, the tool will be connected to a production string and run in a well. The electromagnetic control valve is opened by rotating the tool (from the surface, via the production string) to transmit rotational control signals to the accelerometer. The fluid is pumped through the production string. The section 26 of orifice 102, defined by the upper body section 3 above the upper end 33 of sleeve assembly 200, is wider in diameter than the orifice 102b through the sleeve assembly. Fluid flowing through orifice 102 into the narrower section 102a, defined by sleeve assembly 200, creates a dynamic pressure differential. The hydrostatic pressure in orifice 102, 102a, also increases, resulting in a static pressure differential between the orifice and the well outside the body. When the static pressure differential, the dynamic pressure differential, or their combined effects overcome the resistance of spring 23, the sleeve moves to the second position. With control valve 51 open, the hydraulic fluid is generally able to flow longitudinally from the second hydraulic reservoir 30, along the purge duct 57, 53, 56 and into the first hydraulic reservoir. It should be noted that if valve 51 is closed, such pumping of fluid through the production string (as may be required for other downhole operations, e.g., in relation to other equipment running on the production string) might not cause movement of the sleeve, since the fluid might not be able to flow between the first and second hydraulic reservoirs and the sleeve might be hydraulically blocked. If, as is typically the case, the balance cylinders are at their upper end stops, or between their upper and lower end stops, fluid is also displaced into the first tertiary hydraulic reservoir 108 and out of the second tertiary hydraulic reservoir. Either the fluid exchange between the first and second hydraulic reservoirs and the flow into and out of the first and second tertiary hydraulic reservoirs can be speed-limiting (typically the orifice can be pumped / pressurized such that the flow through the bleed passage is speed-limiting), such that the movement of the floating balance cylinders 10, 5 independent of the sleeve 4 provides a degree of damping. When the sleeve assembly 200 reaches the second position shown in Fig. 1B (and the balance cylinders 5, 10 are at their lower end stops), the solenoid control valve 51 is closed. This prevents fluid flow along the bleed line and hydraulically locks the sleeve assembly in the second position. With the valve closed, any subsequent pressure changes in the borehole 100 or well outside the tool, which act on the balance cylinders 5, 10, cannot cause further movement of the sleeve assembly. The control valve can close automatically after a predetermined time has elapsed since the sleeve moved into the opening. Alternatively, or in addition, additional rotary signals can be transmitted to the accelerometer to close the control valve. The accelerometer (or optionally additional sensors or circuit breakers) can also be configured to detect sleeve discharge in the second position. The valve control system can be configured to close the valve under any of these circumstances. When the control valve 51 is open again (by rotation of the tool) and pumping / fluid circulation in the orifice 100 has ceased, the spring 23 drives the sleeve back towards the first portion shown in Fig. 1A and the fluid flows from the second hydraulic reservoir 30 back into the first hydraulic reservoir 29 along the purge conduit 56, 53, 57. The fluid is also drawn into the second tertiary hydraulic reservoir 34 by means of the purge port 11. Where cessation of pumping causes a negative pressure differential between the outside of the tool and the orifice 100, the floating balance pistons 5, 10 can move independently relative to the sleeve 4 towards their upper end stops, thus damping the movement of the sleeve. In use, as discussed above, the total volume of the first and second reservoirs 29, 30 is constant and the volume increases from the first tertiary hydraulic reservoir 108 which corresponds to the volume decreases from the second tertiary hydraulic reservoir 34. The movement of the sleeve between the first and second positions changes the tool's state from an inactive to an active state. The mode shown is a fluid circulation tool. With reference to Figs. 2 and 4, the sleeve assembly 200 includes an arrangement of sleeve ports 18 which extend through the lower sleeve 8 of the bore 102a. The sleeve ports 18 are separated from the second tertiary hydraulic reservoir 34 by a friction joint 72 provided with external gaskets 58 against the body (to which it is attached, generally as described above in relation to the control neck) and internal planks (not shown) around the lower sleeve 8. ινΐΛ / a / zuzz / ui ¿jo / The lower body section 1 is provided with an arrangement of upward-facing circulation ports 7. Internal gaskets 59 are positioned on either side of it, which seal around the sleeve 8. When the sleeve is in the first position, the sleeve ports 18 are misaligned with and above the circulation ports 7 and separated from them by internal seals 59a. The seals 59a isolate the orifice 102a from the ports 7 and thus from the outside of the tool. The circulation tool is in an off condition when the sleeve is in the first position. When the sleeve assembly is in the second position, the sleeve ports 18 move into alignment with the circulation ports 7 such that the hole 102a communicates with the outside of the tool through ports 7, 18 and the circulation tool is in an activated condition. In alternative modes, the circulation tool may be in an inactive condition when the tool is in the second position. In alternative configurations, the sleeve can be operationally coupled to additional downhole equipment, such as cutters or scrapers, which are caused to move outward under the sleeve's movement. For example, an outer surface of the sleeve or an inner face of one or more cleaning elements can be augmented. Stabilizer elements can similarly be operationally coupled to a sleeve. In still additional embodiments, reaming arms or indeed various additional downhole devices known in the art can be connected to the body and triggered to be activated by movement of the sleeve. Although exemplary embodiments have been described herein, these may not be considered as limited to the possible modifications and variants within the scope of the invention as described herein and recited in the appended claims.

Claims

1. A downhole tool comprising: a body having a through-hole; a sleeve assembly capable of sliding within the body between a first position and a second position, under the action of hydraulic pressure and / or a bias arrangement; and the body comprising a control neck portion disposed around the sleeve assembly; wherein a first hydraulic reservoir is defined between the sleeve assembly and the body above a first end of the control neck portion and the body, and a second hydraulic reservoir is defined between the sleeve assembly and the body below a second end of the control neck portion and the body; wherein the control neck portion further comprises: a purge conduit generally extending longitudinally between the first and second hydraulic reservoirs;and an electromechanical control valve across the purge conduit configured to regulate fluid flow along the purge conduit.

2. The tool according to claim 1, further characterized in that the first hydraulic reservoir is defined between a first end of the control neck portion and the body and / or wherein the second hydraulic reservoir is defined between a second end of the control neck portion and the body.

3. The tool according to claim 1 or 2, further characterized in that it comprises one or more sensors and / or a cable line in communication with the electromechanical control valve, wherein the electromechanical control valve is operable to open and / or close upon detection of a predetermined control signal or signals by the sensor or sensors or received by means of the cable line.

4. The tool according to claim 3, further characterized in that the electromechanical control valve is controllable by moving the tool longitudinally and / or rotationally.

5. The tool according to claim 3 or 4, further characterized in that it comprises a control system that communicates with the electromagnetic control valve and the one or more sensors or cable line, wherein the control system is configured to open and close the control valve.

6. The tool according to any preceding claim, further characterized in that the sleeve assembly is elastically biased towards one or the other of the first and second positions, by an elastic bias element acting between the sleeve assembly and the body.

7. The tool according to claim 6, further characterized in that the elastic bias element comprises a spring arranged in the first and / or second hydraulic chamber.

8. The tool according to any preceding claim, further characterized in that it additionally comprises a first tertiary hydraulic reservoir and / or a second tertiary hydraulic reservoir defined, at least in part, between the sleeve assembly and the body above and below the first and second hydraulic reservoirs, respectively.

9. The tool according to any preceding claim, further characterized in that the sleeve assembly is slidable under the action of a hydrostatic pressure differential between the orifice and an exterior of the tool body.

10. The tool according to claim 9, further characterized in that the first hydraulic reservoir communicates with the orifice and the second hydraulic reservoir communicates with an exterior of the body by means of one or more purge ports through the body.

11. The tool according to claim 9, when dependent on claim 8, further characterized in that the first tertiary hydraulic reservoir communicates with the orifice and the second tertiary hydraulic reservoir communicates with an exterior of the body.

12. The tool according to claim 11, further characterized in that the first tertiary hydraulic reservoir is terminated open at its upper end; or wherein the first tertiary hydraulic reservoir communicates with the orifice by means of one or more pressure ports through the sleeve assembly.

13. The tool according to any preceding claim, when dependent on claim 6, further characterized in that the first tertiary hydraulic reservoir is separated from the first hydraulic reservoir by a first balancing piston and the second tertiary hydraulic reservoir is separated from the second hydraulic reservoir by a second balancing piston.

14. The tool according to claim 13, further characterized in that the first and / or second balance piston is slidable with respect to the sleeve assembly and the body between the respective upper and lower end stops.

15. The tool according to any preceding claim, further characterized in that the sleeve assembly is slidable between the first and second positions under the action of a dynamic pressure differential along the tool or through a flow restriction within the orifice defined by the sleeve assembly.

16. The tool according to any preceding claim, further characterized in that the purge conduit generally extends longitudinally through one or more parts of the control neck portion, wherein at least an intermediate region of the purge conduit is defined by one or more hydraulic lines, and wherein the electromechanical valve is connected to one or more hydraulic lines.

17. The tool according to any preceding claim, further characterized in that the control neck portion includes one or more recesses, or more reduced diameter portions, between the upper and lower ends of the control neck portion; wherein an intermediate region of the purge conduit and the electromechanical control valve is loaded into a recess or reduced diameter portion.

18. The tool according to any preceding claim, further characterized in that the movement of the sleeve assembly between the first and second positions can change the tool between an off condition and an on condition.

19. The tool according to claim 18, further characterized in that it comprises one or more circulation ports, wherein the movement of the sleeve assembly between the first and second positions opens and closes the one or more circulation ports.

20. The tool according to claim 19, further characterized in that the sleeve assembly comprises one or more sleeve ports communicating with the through-hole through the sleeve assembly to an outside of the sleeve assembly, and the body comprises one or more circulation ports extending radially through the body to an outside of the body, wherein, in one of the first and second positions of the sleeve assembly, the one or more sleeve ports and the one or more circulation ports are longitudinally misaligned, such that the tool is in an off condition in which the fluid in the through-hole does not communicate with the outside of the body;and in the other of the first and second positions of the sleeve assembly, the one or more sleeve ports and the one or more circulation ports are longitudinally aligned, with each other or with a defined intermediate chamber between the sleeve assembly and the body, such that the tool is in an activated condition in which the fluid in the through-hole communicates with the fluid outside the body.

21. The tool according to any of claims 18 to 20, further characterized in that the sleeve assembly is operatively coupled to the downhole apparatus additionally to change the condition of the apparatus further between an off condition and an on condition, when the sleeve assembly moves between the first and second conditions.

22. The tool according to any of the preceding claims, further characterized in that the sleeve assembly is operable to move between the first and second positions and one or more defined third positions, wherein the one or more third positions are optionally defined by closing the electromechanical control valve and hydraulically locking the sleeve assembly in the defined third position.

23. A method for moving a sliding sleeve assembly of a downhole tool between a first position and a second position, wherein a first hydraulic reservoir is defined between the sleeve assembly and a tool body above a first end of a control neck portion of the body, and a second hydraulic reservoir is defined between the sleeve assembly and the body below a second end of the control neck portion; wherein the control neck portion comprises a purge passage; the method comprising: generating a dynamic pressure differential along the tool or through a flow restriction within the orifice defined by the sleeve assembly, and / or generating a hydrostatic pressure differential between the through-hole and an exterior of the tool; opening a control valve, such as an electromechanical control valve;to flow hydraulic fluid between the first and second hydraulic reservoirs, generally longitudinally along the bleed line, by means of the control valve; and to close the control valve to hydraulically lock the valve assembly in the first and second positions.

24. The method according to claim 23, further characterized in that it comprises emitting a control signal or signals to open and / or close the control valve.

25. The method according to claim 24, further characterized in that it comprises emitting the control signal or signals to one or more sensors in communication with the electromagnetic control valve.

26. The method according to claim 25, further characterized in that it comprises an accelerometer in communication with the electromechanical control valve and the method comprises emitting a rotational signal to the accelerometer by rotating the tool.

27. The method according to any one of claims 23 to 26, further characterized in that it comprises generating the hydrostatic pressure differential by generating a hydrostatic pressure within the orifice and by flowing fluid between the second hydraulic reservoir (or, optionally, a tertiary second hydraulic reservoir and an exterior of the tool).

28. The method according to any of claims 23 to 11, further characterized in that the movement of the sleeve assembly between the first and second positions opens and closes one or more circulation ports.

29. The method according to any of claims 23 to 28; further characterized in that the sleeve assembly is operatively coupled to one or more additional downhole appliances, and the method comprises changing the condition of one or more additional downhole appliances between an off condition and an on condition by moving the sleeve assembly between the first and second positions.

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