Patent Application
20120012202
Surface-controlled, subsurface safety valves (SCSSVs) are commonly used to shut-in oil and gas wells. The SCSSV fits onto production tubing in a well and operates to block flow of formation fluid upwardly through the tubing should a failure or hazardous condition occur at the well surface. The SCSSV can be tubing retrievable and rigidly connected to the production tubing (tubing retrievable), or it can be wireline retrievable and installed and retrieved by wireline without disturbing the production tubing.
Most SCSSVs are “normally closed” and use a flapper type closure mechanism biased to a closed position. A hydraulic actuator can be moved longitudinally in the SCSSV to overcome the flapper's bias and open the valve. Typically, the actuator uses a piston and a flow tube.
During normal production, hydraulic pressure transmitted to the piston moves the flow tube longitudinally in the valve to keep the flapper open. The hydraulic pressure is commonly supplied by a control line run along the annulus between the production tubing and casing. When a hazardous condition occurs, the SCSSV provides automatic shutoff of the production flow. The hazardous condition can be sensed and/or indicated at the surface or elsewhere and can include a fire on the platform, a high/low flow line pressure condition, a high/low flow line temperature condition, operator override, or the like.
Once the condition is sensed or indicated, the hydraulic pressure is removed from the control line, and the loss of hydraulic pressure causes the flapper to close and block the flow of production fluids up the tubing. When the flapper closes (as well as opens), the flapper's mating surface engages with the flow tube. In fact, the conventional flapper has a concentrated area on its inside surface that engages with the flow tube as they both moving during closing (or opening). This area and even the flapper's sealing surface can be damaged or deformed during harsh opening and closing operations.
The direct solution to address the problem of damage to the flapper simply involves limiting the flow level for which the flapper mechanism is rated. Alternatively, the flapper's thickness can be increased to make it more robust, but this reduces the cross-sectional flow area that can pass through the valve. In any event, operators strive for valves providing as much flow area as possible when open and capable of operating in high working pressures. When operators need a valve with a very slim diameter, such as 7-in., addressing problems with damage to the flapper becomes even more problematic.
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 flapper valve for a downhole tool, such as a surface controlled sub-surface safety valve, has a seat and a flapper. The seat has a seating rim and can be dispose in a housing's tubular bore. The flapper can pivot at a proximal end relative to the seat. The flapper has a sealing rim that corresponds in shape to the seating rim so that the two rims seal when mated together.
In particular, the seating rim defines a first perimeter conforming to a circular profile, but the seating rim has an irregular shape having first lobes disposed outside the first perimeter. The flapper's sealing rim defines a second perimeter conforming to the first perimeter of the seating rim. The sealing rim also has second lobes disposed outside the second perimeter and disposed on either side of the flapper's proximal end about which it pivots.
A flow tube of the downhole tool can move relative to the seat and the flapper. A biasing member biases this flow tube away from the flapper so that the flapper can close. However, a hydraulically actuated piston pushes the flow tube toward the flapper to open it when the piston is activated.
When the flow tube moves away from the flapper, the flapper closes transverse to the tubular bore and engages the seat. When the flow tube moves towards the flapper, the flapper fits in a space between the flow tube and the tubular bore of the housing. In either case, the second lobes protect the flapper's sealing rim as the flapper's inside surface engages the moving flow tube.
The flapper can be a curved flapper, a flat flapper, or a combination thereof, and the teachings of the present disclosure can apply to a flapper of any shape flapper, whether flat or curved. For example, when the flapper is curved or flat, the lobes on the flapper can help protect its sealing rim when engaged by the moving flow tube. When the flapper has a curved body, both the sealing and seating rims have an irregular contour in addition to the irregular perimeters with lobes. In this instance, the seat's rim defines a first edge undulating transversely about the first perimeter. Similarly, the flapper's rim defines a second edge undulating transversely about the second perimeter. At the first lobes, the seating rim defines outcroppings that deviate outwardly from the transverse undulation of the first edge. The flapper's sealing rim defines incroppings at the second lobes that deviate inwardly from the transverse undulation of the second edge.
As an alternative or in addition to the irregular perimeter and contour, the sealing and seating rims of the flapper valve can have a groove and a ridge disposed at least partially thereabout. For example, the seating rim can have the groove disposed at least partially thereabout, while the sealing rim can have the ridge disposed at least partially thereabout. The groove and ridge can define triangular cross-sections, rectilinear cross-sections, or a combination of these. When the sealing rim engages the seating rim as the flapper closes on the seat, the ridge engages or fits in the groove to hold the flapper's rim in place. Use of the grooves and ridges can be beneficial to any shaped flapper, whether flat, curved, or combination thereof.
The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure.
The tool 10 has a through-bore 12 for passage of production fluid. A control line 14 from the surface supplies hydraulic fluid to a chamber 16 in the tool 10, and hydraulic pressure in the chamber 16 moves a piston 20 against the bias of a spring 35. Coupled to this piston 20, a flow tube 30 moves in the tool's through-bore 12. When moved downward in the tool 10 as shown in
During well production, the flapper 100 is maintained open by hydraulic pressure applied to the piston 20, which moves the flow tube 30 against the bias of the spring 35 to open the flapper 100. Any loss of hydraulic pressure at the control line 14 causes the piston 20 and actuated flow tube 30 to retract. This causes the flapper 100 to return to its normally closed position. When hydraulic pressure is released from the line 14, for example, the spring 35 biases the piston 20 and flow tube 30 upward in the through-bore 12. Freed, the flapper 100 pivots on a hinged connection to the seat 150 by a torsion spring (64;
For reference,
Depending on the reasons for closing, the movement of the flow tube 30 and pivoting of the flapper 100 can be quite sudden and hard. Therefore, the components are made to withstand hard closings. Yet, as the flow tube 30 moves and frees the flapper 100 to pivot, the flow tube 30 tends to rub along the top or inside surface of the flapper 100. Because the flapper 100 is curved, the flow tube 30 can damage various areas of the inside surface and even jeopardize the resultant seal that can be achieved with the flapper 100, especially when the flapper valve 50 undergoes several hard closures. The same problems can occur when opening the flapper 100. As the flow tube 30 forces the flapper 100 open, it tends to ride along the inside surface, which can cause damage.
The flapper valve 50 of the present disclosure addresses this type of damage. As detailed below, the flapper 100 and seat 150 have irregular shapes that are different than what is conventionally used in the art. At the same time, the flapper valve 50 can maintain the flow area through the tool 10. In this way, the flapper valve 50 can address damage to the flapper 100 while accounting for the scarcity of space in the downhole tool 10 and not decreasing the flow area through the tool 10.
As shown in
The flapper's body 102 has a bottom or outside surface 104 (shown in
As best shown in
Yet, the contour of the flapper's edge and the profile of its perimeter are irregular to protect the inside surface 106 from damage by the flow tube (30) during hard openings and closings. As best seen in
As best seen in the diagram of
In one implementation, the angle β can be about 23-degrees, while the angle α can be about 95-degrees. Yet, the various dimensions (especially large radius R and length of the sections of the perimeter) for the flapper can vary depending on the implementation.
As shown in
Because the perimeter 120 of the flapper's rim 110 is irregularly shaped with the lobes 126a-b, the perimeter 170 of the seat's rim 160 is complementarily shaped. Likewise, to accommodate the irregular perimeter's 120/170, the edge contours of the seating rim 160 deviate from the typically smooth transverse undulating contour that is generally sinusoidal.
As shown in
In fact, as seen in
As visible in
As with the flapper 100, the perimeter 170 of the seat's rim 160 is generally circular. In fact, as best seen in the diagram of
By making the perimeters 120/170 of the rims 110 and 160 irregular in shape, the area on the flapper's inside surface 106 can be increased, and the sealing rim 110 can be moved away from potential contact with the flow tube (30). For example,
Protecting the flapper's rim 110 can be done without sacrificing the cross-sectional area in the tool 10. Therefore, the irregular shaped flapper 100 and seat 150 allows the components to be slimmer and take up less space in the downhole tool 10. All the same, the arrangement can operate under greater working pressure and can resist damage during harsh operations. As is known, a typical flapper used with a smaller tubing size may be restricted to lower working pressures due to potential collapse or failure of the flapper. For example, a downhole valve with a 7-in. diameter having a typical curved flapper seal may be restricted to operating in working pressures below 10-ksi. Because the irregular shape of the flapper 100 and seat 150 disclosed herein permit the flapper 100 to be slimmer, use of the flapper valve 50 with smaller tubing sizes may also be restricted to lower working pressures than desired.
To alleviate this issue, however, the flapper valve 50 uses a groove and ridge arrangement to improve the engagement between the sealing rim 110 and seating rim 160 of the flapper 100 and seat 150. The sealing rim 110 of the flapper 100 shown in detail in
The ridge 130 and groove 180 are preferably defined all the way around the rims 110, 160, but in other implementations they may only be partially defined around portions of the rims 110/160. Having the ridge 130 on the flapper's rim 110 may be preferred so it can be protected from flow when the flapper 100 is pivoted to an opened condition and concealed by the flow tube (30). However, the reverse arrangement can also be used. Thus, the flapper 100 can have a groove, and the seat 150 can have a ridge.
The shape of the ridge 130 and groove 180 can vary. Generally, they can be “V”-shaped, can be symmetrical or not, and can angle from 1° to 90° or more.
For its part, the groove 180 can be complimentary to the shape of the ridge 130.
The various ridges 130 in
When the flapper 100 closes against the seat 150, the ridge 130 engages in the groove 180. This helps keep the rims 110/160 in place when sealing and enhances the seal produced between them. Moreover, the curved flapper 100 can experience forces at higher working pressures that may attempt to deform (flatten or fold) the flapper 100. Engagement between the ridge 130 and groove 180 can help reinforce the flapper 100 so it can keep its shape and resist flattening or folding. Consequently, the minimum yield strength of the flapper 100's material can be decreased while still permitting higher working pressures. Likewise, the thickness of the flapper 100 can be decreased due to the ridge and groove 130/180.
As shown in present examples, the flapper 100 is a curved type flapper rather than a flat type flapper. As such, the flapper 100 has a curved body 102 with its inside and outsides surfaces 104/106 conforming to a cylindrical contour so the flapper 100 can fit into an annular space 18 between the flow tube 30 and tool's housing when open. Yet, the teachings of the present disclosure can apply to a flapper of any shape, whether curved, flat, or a combination thereof. Therefore, the flapper 100 disclosed herein can have flat inside and outside surfaces 104/106, curved inside and outside surfaces 104/106, or a curved inside surface 106 with a flat outside surface 104 or vice versa.
For example, the flapper 100 can have a curved or flat body 102 with its inside surface 106 and its outside surface 104 being either curved or flat. In either case, the lobes 126a-b on the flapper 100 can help protect its sealing rim 110 when engaged by the moving flow tube 30. Likewise, the features of the ridges 130 and grooves 180 can be beneficial in either instance.
As another example, when the flapper 100 has a curved body 102 with its inside surface 106 curved and its outside surface 104 being either curved or flat, the irregular contour of the sealing and seating rims 110/160 including the transversely undulating edges and outcroppings/incroppings that deviate from the transverse undulation of the edge can be beneficial in addition to the irregular perimeter having the lobes 126a-b/176a-b and the ridges 130 and grooves 180.
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.
