Patent Application
20090050333
The subject matter of the present disclosure generally relates to a surface controlled sub-surface safety valve for a well and, more particularly, to a dual control line system for communicating control fluid to a sub-surface safety valve that is remotely controlled from the surface and that has a single line input for the control fluid.
In an oil and gas well, a sub-surface safety valve is a downhole valve normally maintained in an open position to allow fluid to flow through the valve. The safety valve is closed to prevent blowout of the well, for example, if an excessive pressure drop or flow occurs across the safety valve. One type of sub-surface safety valve uses a spring and choke mechanism to close the valve if the well flow rate exceeds a predetermined level. Another type uses a pre-charged chamber to close the valve if the pressure caused by increased flow falls below a predetermined value.
Yet another type of sub-surface safety valve is remotely controlled and is commonly referred to as a Surface Controlled Sub-surface Safety Valve (SCSSSV).
The control line 20, which may be ¼-inch diameter tubing, can fail due to various reasons, which may make the valve 10 inoperable. For example, the control line 20 over time may become contaminated or blocked due to debris in the control fluid. Typical debris, contamination, or particles that can develop and become suspended in the control fluid can come from reservoirs, physical wear of system components, chemical degradation, and other sources. Therefore, it is known in the art to use a filtering system with the control line 20 due to the importance of the safety valve 10.
Accordingly, what is needed is a system that can improve the collection of debris and filtering of debris in control fluid communicated to a surface controlled sub-surface safety valve and that can increase the reliability of the safety valve's operation. The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
A dual control line system is used for a surface controlled sub-surface safety valve. In the dual control line system, first and second control lines communicate control fluid to the same control port of the sub-surface safety valve. The first control line preferably has a sump component to collect debris from the control fluid and has one or more in-line filters to filter debris from the control fluid. Preferably, the second control line also has a sump component to collect debris but may not have any in-line filters in one embodiment. A connecting valve is connected between the first and second control lines. The connecting valve allows control fluid to communicate from the first control line to the safety valve but prevents fluid communication from the second control line to the first control line. To open the valve, a well control panel applies hydraulic pressure to the safety valve via the first control line. To close the valve, the well control panel exhausts the hydraulic pressure to a reservoir via the second control line. Use of the dual control lines, sumps, and filters allows control fluid to migrate through the system and can reduce the debris and contamination in the control fluid. In addition, the dual control line system can be cycled to remove debris from the system. Furthermore, the dual control lines provide redundant control of the safety valve if one of the control lines becomes blocked or damage.
In particular, the first control line 52A is the main line used to power the safety valve 10 hydraulically to the open position. To open the valve, for example, a wellhead control panel (not shown) at the surface applies hydraulic pressure to the control port 12 via control fluid in the first control line 52A. The well control panel can include any conventional device at the surface used to operate a sub-surface safety valve or the like via control lines and fluids. The hydraulic pressure moves the internal sleeve 14 against the spring force 16. When sufficiently moved, the internal sleeve 14 opens the flap 18 that normally blocks the internal bore 11 of the safety valve 10. To close the safety valve 10, the wellhead control panel exhausts the second control line 52B to a fluid reservoir (not shown), allowing the release of hydraulic pressure of the control fluid. The release allows the spring force 16 to move the internal sleeve 14 and permits the flap 18 to close the bore 11.
The dual control line system 50 offers a number of advantages for operating the safety valve 10. For example, the dual control lines 52A-B provide redundant control of the safety valve 10. If the first control line 52A breaks or becomes blocked due to debris, then the second control line 52B can be used as a redundant line to open and close the safety valve 10. In such a situation, the wellhead control panel can apply hydraulic pressure to the control port 12 via the second control line 52B. The one-way connecting valve 58 prevents the control fluid in the second control line 52B from entering into the first control line 52A. Thus, even if the first control line 52A becomes clogged or broken, the second control line 52B can still be used to operate the valve 10 because the connecting valve 58 can block off communication with the first control line 52A.
In another advantage, the dual control line system 50 can aid in keeping the control fluid substantially clean of debris and can reduce the potential for blockage. For example, the first control line 52A preferably has a sump 54A to collect debris and has one or more in-line filters 56B to filter debris from the control fluid. The second control line 52B can also have a sump and one or more in-line filters 56B. During use, control fluid and associated debris is allowed to migrate through the system 50 so that the potential for blockage can be reduced. In addition, operators can cycle the safety valve 10 open and closed by applying control fluid with the first control line 52A and exhausting the control fluid with the second line 52B. This cycling can act to flush the system 50 of debris and contaminants. For example, the second sump 54B used to collect debris in the second control line 52B can be flushed of debris so that potential blockage of the filter 56B can be minimized and the filter 56B can remain cleaner for longer periods of time.
During operation, the well control panel 90 is operable to communicate control fluid to the sub-surface safety valve 10 via the first control line 62A to open the safety valve 10. During this procedure, the well control panel 90 maintains the second line 62B closed at the wellhead to prevent exhausting of control fluid through it. Using techniques known in the art, the well control panel 90 monitors flowline pressure sensors and automatically closes the safety valve 10 in response to an alarm condition requiring shut-in. To close the safety valve 10, the well control panel 90 removes the hydraulic pressure applied to the safety valve 10 by exhausting the control fluid from the valve 10 via the second control line 62B, recalling that the connecting valve 78 prevents control fluid from migrating back up through the first control line 62A. Likewise, the well control panel 90 is operable to communicate control fluid to the safety valve 10 via the second control line 62B to open the safety valve 10 in the event the first control line 62A is blocked or damaged.
As before, the assemblies 70A-B can keep the control fluid substantially free of debris and contamination. In addition, the well control panel 90 can cycle control fluid through the system 60 by repeatedly opening and closing the safety valve 10 as discussed previously so that the cycling can substantially flush debris from at least the second control line 62B. If the system 60 is intended to be flushed of debris by cycling the safety valve 10, then not including any in-line filter components 74 on the second line 62B may be preferred because including an in-line filter on the second control line 62B may prevent sufficient flushing of debris.
The sump-filter assemblies 70A-B can be positioned in various places along the control lines 62A-B as they run from the surface along the tubing to the sub-surface safety valve 10. In general, they can be positioned anywhere between the wellhead and the safety valve 10.
The system 60 can use any suitable in-line filter components 74 known in the art. For example, the filter component 74 can be a high pressure filter capable of providing anywhere from 2 to 20 micron filtration of hydraulic fluids and that can use a wire mesh media, sintered metal, or the like as the filter media. The in-line filter components 74 can also be connected in series along the control line before, after, or both before and after the sump component 72. Furthermore, any multiple in-line filter components 74 can have different degrees of micron filtration as desired. One example of a suitable filter component 74 is 50 micron available from Nova Technology. The one-way connecting valve 78 used for the system 60 can include any suitable one-way valve known in the art for downhole hydraulic control lines. One example of a suitable connecting valve 78 is Parker C-Series Check Valve part no. 2F-C2L-* available from Parker Hannifin Corporation.
Because the sumps-filter assemblies 70A-B can be positioned near the safety valve 10 at the bottom of the tubing string 15, the sump components 72 are preferably capable of operating at a grade or tilt, for example, when the wellbore is horizontal or non-vertical.
The sump component 100 has a tubular housing 102. Port members 104 and 106 are attached (i.e., welded) to the opposing ends of the tubular housing 102 to create a chamber 105 within the component 100. These port members 104 and 106 have ports for communicating control fluid with other components of the system, such as in-line filters and control lines. A filter tube 110 is disposed within the chamber 105 and has its proximate end connected to the bottom port member 106. The distal end of the tube 110 extends approximately halfway into the chamber 105, creating an annulus 150 at the lower half of the housing 102 in which to collect potential debris in the control fluid.
A diverter body 120 is attached to the distal end of the tube 110. To divert control fluid communicated from the top port member 104, the body 120 has a cone-shaped diverter head 130 and a sleeve 140. The diverter head 130 is attached to the distal end of the filter tube 110 and has openings 132 on its underside that communicate with the tube 110 to allow control fluid to communicate between the annulus 150 and the tube 110. The sleeve 140 is substantially tubular and has a proximate end connected to the diverter head 130 by a spring pin 134. The tubular body of the sleeve 140 extends over the openings 132 and along a portion of the tube 110, dividing part of the annulus 150 into an inner annulus portion 152 and an outer annulus portion 154. Preferably, the opening 142 at the distal end of the sleeve 140 has a smaller diameter than a central diameter of the rest of the sleeve 140.
In use, control lines or filter components may be coupled to the port members 104 and 106. Control fluid to the top port member 104 may come from the well control panel, while control fluid may communicate to the safety valve from the bottom port member 106. When hydraulic pressure is applied at the top port member 104, the control fluid migrates into the chamber 105 and down around the filter diverter head 130. Passing the diverter head 130, the control fluid is driven along the sleeve 140 in the outer annulus portion 152 until it migrates to the bottom annulus 150 of the chamber 105. Making the control fluid travel outside of the diverter body 120 may tend to force debris and contamination out of the control fluid and to accumulate at the bottom of the chamber 105. As it further migrates, the control fluid is allowed to travel through the smaller diameter opening 142 of the sleeve 140 and into the inner annulus portion 154. Eventually, the control fluid can enter the openings 132, then travel through the filter tube 110, and then pass out the bottom port member 106 to reach the safety valve.
With the above arrangement in the sump component 100, the debris will tend to settle to the bottom annulus 150 of the chamber 105. If the component 100 is at a grade (i.e., is non-vertical), the diverter body 120 will tend to keep the collected debris from inadvertently migrating out of the sump component 100 via the top port member 102 and will tend to keep the debris from entering through the opening 142 of the sleeve 140 to the openings 132 and tube 110. For example, as shown in the partial view of
In one embodiment, the sump component 100 is approximately 22-inches long and has a diameter of about 1-inch. These dimensions can make it well suited for being strapped outside tubing, a sub-assembly housing, and/or part of a safety valve. Because the sump component 100 is used in a well, the housing 102 and port members 104 and 106 are preferably composed of a nickel-chromium alloy. The filter tube 110, diverter head 130, and sleeve 140 are preferably made of nickel-based alloy. Other suitable materials could also be used.
The sump component 100 can be used for both control lines 62A-B of the disclosed dual control line system 60 (See
Not only is the sump component 100 useful for a sub-surface safety valve, but the inventive sump component 100 can be used in other control line applications in a well and especially when the wellbore has a grade. In just one example, the inventive sump component 100 can be used on control lines for packers or other subsurface tools that are hydraulically controlled from the surface.
The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.
