Apparatus device for removing scale in a borehole installation

There is described an apparatus device for mechanically loosening scale inside a pipe arranged to convey hydrocarbon fluids from a production zone in a well, in which an actuator arranged in a housing includes an axially movable stem which extends through at least part of the housing and is provided with at least one cam, at least one cutting means is arranged radially movable in a recess in the housing, the cam bearing, by the axial movement of the actuator towards a first extreme position, against the cutting means, applying to it a push force directed radially outwards. There is also described a method of mechanically loosening scale inside a pipe arranged to convey hydrocarbon fluids from a production zone by using the apparatus.

CROSS REFERENCES TO RELATED APPLICATIONS

This is the US National Phase application of PCT Application No. NO2009/000077 filed 6 Mar. 2009 which claims priority to Norwegian Patent Application No. 20081279 filed 11 Mar. 2008, both of which are incorporated herein by reference. The PCT Application was published in English on 17 Sep. 2009 under No. WO 2009/113863A1.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable

THE NAMES OF THE PARTIES TO A JOINT SPONSORED RESEARCH

Not Applicable

REFERENCE TO A SEQUENCE LISTING

Not Applicable

BACKGROUND OF THE INVENTION

1) Field of the Invention

The invention relates to an apparatus device for loosening scale in a borehole installation, more particularly an actuator provided with one or more cams arranged, by axial movement in the longitudinal direction of the apparatus, to move one or more cutting elements from a retracted passive state into a working position, the cutting element(s) projecting from an apparatus housing as the cutting element(s) is/are pressed against a surrounding tubular body from which scale is to be removed. The actuator is actuated mechanically by the tensioning of a line on which the apparatus is hanging or hydrostatically, for example, through coiled tubing to which the apparatus is connected.

In the recovery of hydrocarbon fluids from the underground, it is a known problem that substances carried in the fluid flow from the hydrocarbon-containing underground structure are deposited in the tubing by precipitation and deposition. The source of this problem may be substances existing in the structure, for example, substances dissolved in water accompanying the hydrocarbons, or it is substances which have been carried into the structure during production, for example salts in injection water pumped into the structure to increase the reservoir pressure. Common to the substances, which are the source of scale in the tubing, is usually that they are precipitated and deposited because of altered physical or chemical conditions as the fluid enters the tubing. Such a deposit may have ceramic properties, that is to say, it is hard and brittle—in the field also called “scale”—often in the form of calcium carbonate or calcium sulphate, or it may be in the form of paraffin wax which has a softer and tougher consistency. Common to such deposited products is that, over time, they reduce the flow from the hydrocarbon reservoir through the tubing to the surface.

2) Description of Related Art

Attempts have been made to solve the problem in different ways. One method includes the use of chemicals which are pumped down into the well to dissolve the scale so that it can be carried in the fluid flow out of the well.

Another method is mechanical cutting of the scale by means of a cutting tool which is passed through the tubing down to the production zone in question, where it is activated to work the scale inside the tubing. The pieces of scale material detached are carried in the fluid flow out of the well.

From U.S. Pat. No. 4,452,307 is known a reamer for removing paraffin, mineral scale, ice and other deposits from the inside of tubing or similar. A tapered housing provided with external cutting blades is set into limited rotation by gliding movement of the housing along a steep threaded connection between a central shaft and the housing. The rotational movement is achieved by repeated blows against the projecting end of the central shaft. The cutting blades thereby cut the deposits loose.

From U.S. Pat. No. 3,176,772 is known an arrangement of steel brushes which work a surrounding surface. U.S. Pat. Nos. 2,667,930 and 2,836,251 disclose spring-loaded scraping elements which work a surrounding surface by the rotating movement of an apparatus.

EP 516989 B1 discloses a pipe-cleaning device in which a cylindrical housing is provided with rotatable cutting elements disposed in recesses in the housing, the device being activated by a fluid flow through the pipe which is to be cleaned.

Further examples of the prior art in the field are FR 2543855 A1 and also U.S. Pat. Nos. 2,641,010, 4,920,600, 2,664,930 and 5,474,097.

BRIEF SUMMARY OF THE INVENTION

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art.

In a first aspect, the invention relates to an apparatus device for mechanically loosening scale internally in a pipe arranged to convey hydrocarbon fluids from a production zone in a well, characterized by an actuator, arranged in a housing, including an axially movable stem which extends through at least part of the housing and is provided with at least one cam, at least one cutting means being arranged radially movable in a recess in the housing. The cam bearing, by the axial movement of the actuator towards a first extreme position, against the cutting means, applying a radial outward push force to it. The cam relieving, by the axial movement of the actuator towards a second extreme position, the cutting means and having the effect of the cutting means being radially movable into the recess in the housing.

The cutting means may be a rotatable cutting disc.

The cutting means may be rotatably supported in a first end portion of an arm which is pivotal supported, at its other end portion, in the housing.

The apparatus may include several cutting means spaced on the periphery of the housing.

The cutting means may be divided into several groups, the groups being staggered in the axial direction of the apparatus.

Each group may comprise two, three or more cutting means.

The rotational axis of the cutting means may lie in a plane perpendicular to the longitudinal axis of the apparatus.

The rotational axis of the cutting means may lie in a plane deviating from the perpendicular to the longitudinal axis of the apparatus.

The actuator may include a spring which is arranged to move the actuator towards its first extreme position. Alternatively, the actuator may include a spring which is arranged to move the actuator towards the second extreme position.

In one embodiment, the actuator may be connected to a wire line.

In this embodiment the actuator may project through a first end portion of the housing and be provided with a fishing neck.

In another embodiment the first end portion of the housing may be connected in a fluid-sealing manner to coiled tubing.

In this embodiment the actuator may be provided with a through centre bore connected in a fluid-communicating manner to the coiled tubing.

In this embodiment, the actuator may further include a differential piston surface which is arranged to be subjected to a fluid pressure from a fluid contained in the coiled tubing. The actuator may be arranged to be movable towards the first extreme position by the application of a prescribed fluid pressure to the differential piston surface.

The differential piston surface may be formed of first and second stem end faces, the first stem end face being larger than the second stem end face.

In a second end portion, the housing may be provided with at least one nozzle which is in fluid communication with the coiled tubing and is arranged to carry fluid into the pipe.

The actuator may include an adjustable end stop which is arranged to reduce, when hitting a portion of the housing, the axial movement of the stem towards the first extreme position to reduce, thereby, the radial movement of the cutting means out of the recess of the housing.

In a second aspect, the invention relates to a method of mechanically loosening scale internally in a pipe arranged to convey hydrocarbon fluids from a production zone, characterized by the method comprising the following steps inserting an apparatus according to the invention to the immediate vicinity of a portion of the pipe which is to be cleaned of scale, —moving at least one cutting means radially out from a housing by moving an actuator axially towards a first extreme position in order, thereby, to push the at least one cutting means towards the scale, moving the apparatus further in the axial direction in the pipe, the at least one cutting means penetrating the scale, and carrying the loosened scale out of the pipe by means of a fluid flow.

In one embodiment, the method may further include the steps of inserting the apparatus into the pipe by means of a wire line, and moving the actuator axially towards the first extreme position by applying a spring pressure to the actuator, which exceeds the pull force of the wire line.

In this embodiment, the method may include the further step of sliding the apparatus in the direction of the pipe portion which is to be cleaned of scale by applying a push force to the wire line from a wire-line-feeding apparatus.

In an alternative embodiment, the method may include the further steps of inserting the apparatus into the pipe by means of coiled tubing, and moving the actuator axially towards the first extreme position by applying, to a differential piston surface on the actuator, a fluid pressure which overcomes the push force from a spring against the actuator.

In this embodiment the method may include the further step of carrying fluid from the coiled tubing through one or more nozzles of the apparatus into the pipe.

DETAILED DESCRIPTION OF THE INVENTION

In the Figures the reference numeral1indicates an apparatus according to the invention arranged in a pipe2, for example tubing, extending through a production zone3in an underground structure. InFIGS. 1 and 2is shown an exemplary embodiment of the apparatus connected to and operated by means of a wire line4of a design known per se. InFIGS. 3 and 4is shown an exemplary embodiment of the apparatus connected to and operated by means of coiled tubing5of a design known per se.

Scale6is schematically indicated on the inside of the pipe2inFIGS. 2 and 4.

The apparatus1is constituted by a cylinder-shaped housing11provided with a centric bore114(seeFIG. 5) accommodating an actuator12. In recesses111extending radially out from the centric bore114to the outer surface of the housing11are several pivotally arranged cutting means13.

InFIGS. 1 and 2a fishing neck15(known per se) is shown forming the attachment of the wire line4to a stem121of the actuator12, the actuator stem121projecting, in the wire-line embodiment, through a first end portion112of the housing11. The fishing neck15is formed with an attachment portion for a fishing device (not shown) of a type known per se, for use in the retrieving of the apparatus1in the case of a wire-line rupture.

In the embodiment according toFIGS. 1 and 2, an adjustable end stop17is shown arranged on the actuator12and arranged to abut against the housing11.

In the coiled-tubing embodiment, according toFIGS. 3 and 4, the stem121is provided with a center bore124which is connected in a fluid-communicating manner to the coiled tubing5via an extension of the centric bore114through the first end portion112of the housing11, and to a plug16including several nozzles161in the second end portion113of the housing11.

The stem121of the actuator12is provided with several tapered cams122arranged concentrically and spaced over a portion of the stem121. During the axial movement of the stem121in the housing11, the surface of the tapered cam122is arranged to bear against a portion of the cutting means13projecting partially into the centre bore114of the housing11.

The cutting means13includes a rotatable cutting disc131supported in the first end portion132aof an arm132. A second end portion132bof the arm132is pivotally supported in the housing11. The second end portion132bof the arm132is formed to abut the cam122, the abutment surface being smoothly rounded to be able to glide along the sloping surface of the cam122as the actuator12is moved. The cutting disc131is provided with a cutting edge.

In the wire-line embodiment according toFIGS. 1 and 2, the actuator12is provided with a spring123arranged to apply a load to the stem121so that the actuator12is moved towards the cutting means13. As the apparatus1is lowered into the pipe2, the weight of the apparatus1will lead to compression of the spring123so that the actuator12is pulled up towards its one extreme position, in which the cutting means13are not loaded and may therefore be retracted into the recesses111. A spring abutment126is secured to the housing11by means of several shear pins127(shown only inFIG. 1). The spring abutment126is arranged with a clearance to the end face of the centric bore114. In a situation in which the spring123is not sufficiently compressible for the actuator12to give the cutting means13free movement into the housing11, increased tension on the wire line4will cause the shear pins127to shear with the result that the actuator12together with the spring123and the spring abutment126may be moved until the spring abutment126hits the end face of the centric bore114.

When the apparatus1according to the embodiment ofFIGS. 1 and 2has been moved up to an area with scale6, the clearance between the apparatus1and pipe2decreases, and the apparatus1must be pushed forwards by the wire-line-feeding apparatus (not shown) being operated into forcedly running the wire line4down the pipe by applying a push force to the wire line4. Thereby, the actuator12is moved into abutment against the cutting devices13which are thereby pivoted out of the recesses111of the housing11until hitting the internal wall surface of the pipe2or the scale6.

In the coiled-tubing embodiment according toFIGS. 3 and 4, the actuator12is provided with a spring123arranged to apply a load to the stem121so that the cams122of the actuator12are moved away from their adjacent cutting means13. In this embodiment, the stem121is provided with first and second stem end faces125a,125b, together forming a differential piston surface having a surface area AΔ=A1−A2, A1being the area of the first stem end face125a, and A2being the area of the second stem end face125b. A fluid pressure in the coiled tubing5will thereby apply a load to the actuator12counteracting the load applied by the spring123, so that the cutting means13are pivoted out of the recesses111of the housing11until hitting the internal wall surface of the pipe2or the scale6.

As long as a certain fluid pressure is not applied to the actuator12, the actuator12will be moved towards its one extreme position, in which the cutting means13are not loaded and may thereby be withdrawn into the recesses111.

In the exemplary embodiments are shown four cutting means13arranged in a group evenly spaced around the apparatus1. It is obvious that each group may comprise a different number of cutting means13. The apparatus1may include more or fewer groups of cutting means13than what is shown here in the exemplary embodiments, in whichFIGS. 1 and 2show two groups, whereasFIGS. 3 and 4show three groups.

In the coiled-tubing embodiment, it is obvious to a person skilled in the art that fluid-sealing means (not shown) known per se will have to be used to prevent fluid leakage from the center bore124to the outside of the apparatus1through joining surfaces and interfaces between the stem121of the actuator12and the centric bore114.

In the coiled-tubing embodiment, it is appropriate to supply washing and conveying fluid through the nozzles161by fluid jets which are directed against the internal wall surface of the pipe2and the scale6.

Here, the cutting discs131are shown to lie in a plane coinciding with the center axis of the apparatus1. It is within the scope of the invention to arrange the cutting discs131in a plane deviating from this.