Apparatus for clearing a plugged control line

Abstract

The present invention relates to an apparatus (20) for clearing a plugged control line (12), in particular for clearing a plugged surface controlled sub-surface safety valve (11) control line (12), the apparatus (20) comprising a connecting means (27) configured to connect the apparatus (20) to an upstream end of the plugged control line (12); and a pumping means (21, 22) configured to pump a dissolvent (30) through the connecting means (27) into the control line (12) to build up dissolvent pressure in the control line (12). The invention further comprises a bore system and a method for clearing a plugged control line (12).

Claims

1. An apparatus for clearing a plugged control line, in particular for clearing a plugged surface controlled sub-surface safety valve control line, the apparatus comprising: a. a connecting means configured to connect the apparatus to an upstream end of the plugged control line; and b. a pumping means configured to pump a dissolvent through the connecting means into the control line to build up dissolvent pressure in the control line.

2. The apparatus of claim 1, wherein the dissolvent comprises a corrosive substance.

3. The apparatus of claim 1, wherein the connecting means comprises an autoclave fitting.

4. The apparatus of claim 1, wherein the connecting means comprises a valve configured to control the flow of the dissolvent between the apparatus and the control line.

5. The apparatus of claim 1, wherein the pumping means is configured to build up dissolvent pressure in the control line in the range of 3.4-34.5 MPa.

6. The apparatus of claim 1, wherein the pumping means comprises a dissolvent pump.

7. The apparatus of claim 6, wherein the pumping means comprises a hand operated hydraulic pump connected to the dissolvent pump and configured to operate the dissolvent pump via a hydraulic fluid.

8. The apparatus of claim 6, wherein the dissolvent-contacting components of the dissolvent pump comprises or essentially consists of a. steel; or b. a Carbone steel base material cladded with Inconel 625; or c. a nickel base alloy; or d. all components of the dissolvent pump are manufactured of Inconel 718.

9. The apparatus of claim 6, wherein the dissolvent pump comprises a cylinder and a piston, movable within the cylinder, for separating dissolvent from hydraulic fluid.

10. The apparatus of claim 1, wherein the pumping means provides for dual stroke pumping functionality.

11. A bore system, comprising: a. a tubing; b. a safety valve, in particular a surface controlled sub-surface safety valve, located in the tubing; c. a control line connected to the safety valve for controlling the safety valve; and d. an apparatus according to claim 1 connected to an upstream end of the control line.

12. The apparatus of claim 1, wherein the dissolvent comprises an acid.

13. The apparatus of claim 1, wherein the dissolvent comprises a mineral acid.

14. The apparatus of claim 1, wherein the dissolvent comprises a hydrofluoric acid.

15. The apparatus of claim 1, wherein the pumping means is configured to build up dissolvent pressure in the control line in the range of 3.4-27.6 MPa.

16. The apparatus of claim 1, wherein the pumping means is configured to build up dissolvent pressure in the control line in the range of 3.4-20.7 MPa.

17. The apparatus of claim 1, wherein the pumping means is configured to build up dissolvent pressure in the control line in the range of 6.9-20.7 MPa.

18. The apparatus of claim 1, wherein the pumping means is configured to build up dissolvent pressure in the control line in the range of 6.9-13.8 MPa.

19. The apparatus of claim 1, wherein the pumping means comprises an acid pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, a preferred embodiment of the invention is described with reference to the enclosed FIGURE. In which shows:

(2) FIG. 1 a schematic illustration of a system including an apparatus for clearing a plugged control line according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) According to the embodiment illustrated in FIG. 1, a tubing 10 of a well or wellhead is provided, which may extend from the surface level into the ground. The tubing 10 can be part of a petrochemical well for the production of oil and gas. The tubing 10 is provided with a surface-controlled sub-surface safety valve (SCSSSV) ii that can stop fluid flow in case of emergency. The SCSSSV 11 is hydraulically controlled by means of a control line 12. As will be appreciated by the person skilled in the art, the control line 12 at operating pressure holds the SCSSSV 11 in the open position, and when hydraulic pressure in the control line 12 drops, the SCSSSV 11 closes. The control line 11 may become plugged, as indicated with reference sign 13. This plugging 13 may compromise the overall functionality of the SCSSSV 11 and needs to be cleared.

(4) In order to clear the plugging 13, an apparatus 20 is connected to the control line 12 via a connecting means 27. The connecting means 27 comprises some flexible high pressure and acid-resistant pipes and fittings for the connection to the upstream end of the control line 12, preferably a piece of Inconel control line may be used. The upstream end of the control line 12 is upstream to the plugging 13 and at surface level.

(5) The apparatus 20 further comprises a pumping means 21, 22 for pumping a dissolvent 30 through the connecting means 27 into the control line 12 to build up dissolvent pressure within the plugged control line. The pumping means 21, 22 comprises an acid pump 21 which is configured to pump an acid into the control line 12 to build up acid pressure in the control line 12. The acid pump 21 is operated by hydraulic fluid 31 provided by a manually operated hydraulic pump 22.

(6) The acid pump 21 comprises a cylinder 28 and a piston 29, which is movable within the piston and separates dissolvent 30, shown in FIG. 1 on the left side of the piston 29, from hydraulic fluid 31, shown in FIG. 1 on the right side of the piston 29.

(7) The cylinder 28 of the acid pump 21 are preferably made of 4130 Carbone steel base material with Inconel 625 cladded inner diameter. The cylindrical piston 29 of the acid pump 21 is made of Inconel 718 base material and 2 hydrogenated nitrile butadiene rubber elastomeric seals at the outer diameter. The acid pump 21 further comprises a cap 35 for opening the acid pump 21 preferably at the hydraulic fluid side of the acid pump 21. The cap 35 is preferably screwed to cylinder 28 and allows for re-filling dissolvent 30 into the acid pump 21. The cap 35 is preferably made of 4130 Carbone steel base material with an internal ACME thread.

(8) The acid pump 21 is connected to the control line 12 by means of the connecting means 27. The connecting means 27 further comprises an autoclave fitting 23, which allows for an easy and safe connection to the cylinder 28, a manifold 24, which includes a pressure relief needle valve 25 and control valves 26 and 37. A pressure gauge 39 may be also provided on the manifold 24 and a pressure gauge 28 may be provided between the control valve 37 and the control line 12. By the pressure relief needle valve 25 dissolvent 30 can be released from the apparatus 20. By the control valve 26 or 37 the dissolvent end of the acid pump 21 can be separated or isolated from the tube of the connecting means 27.

(9) The apparatus 20 further comprises a hand operated hydraulic pump 22, which is connected to the acid pump 21 by a flexible high-pressure tubing 34 and by means of an autoclave fitting and a manifold 36 with a pressure relief needle valve 32 and a control valve 33. By actuating the hydraulic hand pump 22, hydraulic fluid 31 is pumped into the cylinder 28 of the acid pump 21 and the piston 29 of the acid pump 21 is moved, in order to inject acid 30, or another dissolvent 30, from the acid pump 21 into the control line 12. Due to this separation of hydraulic pressure generation by the hydraulic pump 22 and high-pressure dissolvent provision by the acid pump 21 security is increased for the operator and the costs for the apparatus 20 can be decreased as a commonly available hydraulic pump 22 can be used, which does not need to be acid resistant.

(10) The acid pump 21 is configured to inject a high concentration acid 30, e.g. 28% HCl, at low flow rates and with a small volume into the control line 12, in order to dissolve the plugging 13 in the control line 12. The acid pump 21 is thereby filled with the acid 30. All connections between the acid pump 21 and the control line 12 are rated to a working pressure of 34,5 MPa or higher. By injecting the acid 30 into the control line 12 at elevated pressure, the fluid present in the control line 12 is flushed and direct contact between the acid 30 and the plugging material 13 can be established. Then, a chemical reaction between acid 30 and plugging material can take place in order to dissolve the plugging 13. Depending on the amount of plugging material, a soaking step may be performed.

(11) All connections between the acid pump 21 and the control line 12 are made of corrosion resistant alloys, as are the components of the acid pump 21 coming in contact with the acid. This further improves safe operation.

(12) The apparatus 20 also provide for a dual stroke pump functionality, capable of sucking plugging material from the control line 12, in addition to pumping acid 30 into the control line 12. Thereby, the acid 30 may be pumped into the control line 12, and after reacting with the plugging 13, the acid 30 and dissolved plugging material may be completely extracted in the case of the plugging material occurred at near point from surface (control line 12 outlet) but may be at least turnover, mixed or preferably replaced by the injected acid to be in contact with remaining plugging material.

(13) According to a preferred embodiment, the following method is carried out to clear a plugged control line. In the first step, pressure in the control line 12 is released. Next, the acid pump 21 of the apparatus 20 is connected to the control line 12 via the connecting means 27. In a further step, the acid pump 21 is filled with the acid 30, and the hydraulic hand pump 22 is connected to the acid pump 21 via the hydraulic line 34. Afterwards, the control valve 26 between the control line 12 and the acid pump 21 is opened, as well as any further valves, e.g. control valve 33, between the hydraulic hand pump 22 and the acid pump 21.

(14) Next, the hydraulic hand pump 22 is actuated by an operator. Thereby, the acid pump 21 is operated to build up acid pressure in the control line 12 by pumping hydraulic fluid 31 into the acid pump 21 and then acid 30 into the control line 12. In an initial pumping step, an acid pressure of 6,89 MPa may be built up, before the control valve 26 is closed. To reduce wear of the apparatus 20, hydraulic and acid pressure in the pumps 21, 22 may be released, for example by opening the pressure relief needle valve 25 or pressure relieve needle valve 32. After waiting for 5-10 minutes, the dissolvent pressure in the control line 12 may is released, for example by means of the control valve 26 and pressure relief needle valve 25. These steps are then repeated 3-5 times or more depends on the plugging material response to the chemical reaction.

(15) Afterwards, the steps of pumping acid 30 into the control line 12 and keeping the control line 12 pressurized with the acid are repeated, wherein the pressure built up in the control line 12 is increased to 10.3 MPa and the waiting period before releasing pressure is extended to 20 minutes. With these adjusted parameters, 3-5 repetitions are performed.

(16) Afterwards, the pressure and waiting period may again be increased, as will be appreciated by the person skilled in the art. The operator may measure and analyze the return from the control line 12 when releasing pressure, to check whether the plugging 13 is dissolving.

(17) Once all plugging material inside the control line 12 is dissolved, the hand pump 22 may be operated reverse for pumping hydraulic fluid 31 out of the acid pump 21 and for pumping acid out of the control line 12 or may be flushed out to the other bottom end point of the control line 12 at the SSSCV landing nipple.

(18) Preferably, the SSSCV 11 can be pulled out or removed from place in the landing nipple while performing the above steps in order to allow pushing plugging material outside the control line 12 end after it is released. Alternatively, the SSSCV limn be removed and reset during performing of the above-mentioned steps in order to allow attempting to flush control line 12 and check or confirm the release status of the plugging material.

(19) Finally, the control line 12 is connected to an oil pump and flushed with new hydraulic oil. Preferably, the hydraulic hand pump 22 can directly connected to the control line 12 via the connecting means 27 for flushing the control line 12 with oil.

(20) In this manner, the plugging 13 and the control line 12 can be cleared in a short time taking from only minutes or hours up to only several days, depending on the plugging material volume and dissolvent suitability and concentration.