Fail-Safe Safety Cut-Off Valve for a Fluid Well

This invention relates to a sub-surface safety cut-off valve, and more particularly to a fail-safe safety cut-off valve utilizing electromagnetic actuating means controllable from the surface.

It is critically essential that petroleum wells have suitable provision for protecting the well against certain hazards commonly encountered in the operation of such wells. Abnormal conditions can be encountered suddenly and without advance notice. Thus there may be a sudden release of undergrounding pressure causing the well to go wild and out of control. Even under normal operating conditions it is often desirable to interrupt flow at sub-surface depths.

To meet the foregoing and the like contingencies numerous cut-off valve constructions have been proposed heretofore incorporating the capability of responding to emergency conditions to interrupt flow. These various types are in widespread daily use but are subject to certain disadvantages and shortcomings avoided by this invention. One common type employs a flapper valve pivotally supported along the interior sidewall of the flow passage and held open by a protector tube so long as normal operating conditions prevail. Some safety valves of this type respond to an abnormal increase in the flow velocity to close automatically whereas others are held in open position hydraulically by static pressure means controlled from the ground surface. Another type of safety cut-off valve in use employs a rotary ball valve held in open position by hydraulic pressure controlled at the well head. Among the serious shortcomings of certain of these valves is the fact that one or more springs is relied upon to close the valve operating mechanism and these springs are required to operate in opposition to the static hydraulic head in the line employed to open the valve. For this reason it has been found impractical to utilize such valves at a depth in excess of about 500 feet. This is a highly objectionable and serious limitation on land based wells, and particularly as respects wells beneath the sea bed. Moreover prior safety cut-off valves lack the capability of control at will from ground level as well as the ability to close automatically in response to abnormally rapid flow.

To avoid the foregoing and other limitations and shortcomings of prior safety cut-off valve constructions, there is provided by this invention an improved safety cut-off valve having an electromagnetic operating mechanism controllable from the surface by power leads extending along the tubing annulus. The operating mechanism functions equally well to open either a flapper or ball-type valve. The cut-off valve assembly functions in a highly satisfactory manner at any desired depth, the valve-opening operation being facilitated at greater depths by equalizing the pressure on the upper side of the valve in accordance with well known technique. The valve assembly, with the exception of the solenoid coil sub-assembly, is installable and retrievable by wire line operating techniques. The solenoid coil must be energized to open the flow control member and to hold it open. If power fails for any reason or is deliberately cut off, spring means, acting alone or in cooperation with flow past the valve quickly closes the valve and positively prevents further flow. Additionally, both illustrative species of our improved safety cut-off valve close automatically if flow increases abnormally for any reason.

Accordingly, it is a primary object of the present invention to provide a sub-surface safety cut-off valve of the normally closed type having electro-mechanical means for opening and retaining the valve in open position so long as energized.

Another object of the invention is the provision of a fail-safe sub-surface safety cut-off valve for a petroleum well having electrically powered means for opening and retaining the same in open position.

Another object of the invention is the provision of a fail-safe cut-off valve for installation at substantially any selected depth and provided with surface-controlled electrically powered means for controlling operation of the valve rather than hydraulic pressure.

Another object of the invention is the provision of a sub-surface petroleum well safety cut-off valve embodying self-contained means for normally holding the same closed and having electrically powered means for retaining the valve open.

Another object of the invention is the provision of an oil well safety cut-off valve normally held open by surface-controlled electromagnetic means and which closes automatically in response to an abnormal increase in fluid flow past the valve.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawing to which they relate.

Referring now to the drawing in which a preferred embodiment of the invention is illustrated:

FIG. 1 is a diagrammatic view, partly in cross-section, showing a petroleum well extending beneath the sea bed and equipped with an illustrative embodiment of the invention safety cut-off valve;

FIG. 2 is a longitudinal cross-sectional view on an enlarged scale showing a flapper valve embodiment of the invention in closed position;

FIG. 3 is a view similar to FIG. 2 taken along the right-hand half of FIG. 2 but showing the valve open;

FIG. 4 is a view similar to FIG. 2 but showing a second embodiment utilizing a ball valve shown in closed position; and

FIG. 5 is a fragmentary cross-sectional view similar to FIG. 4 but showing the position of the parts with the ball valve in open position.

Referring initially more particularly to FIG. 1, there is shown a typical petroleum well having one embodiment of the invention safety cut-off valve designated generally 10 installed in a landing nipple 11 forming part of a tubing string 12 inside casing 13 extending through sea bed 14 from an operating platform 15 supported in any suitable manner at the water surface. The top of the wall casing is provided with the customary Christmas tree 16. Located on platform 15 is a d.c. power source 18 and suitable controls not shown and described more fully presently.

Referring now to FIGS. 2 and 3, the constructional details of the safety cut-off valve 10 will be described. The retrievable portion of the cut-off valve assembly comprises a tubular housing formed in several coaxial sections threaded to one another including an upper section 20, to midsections 21, 22, and an inlet section 23. Slidably supported in this housing is a tubular armature 24 normally urged upwardly by a compression spring 25 thereby permitting flapper valve 26 to close against seat 27. Valve 26 is pivotally supported on housing member 22 by a pivot pin 28 and is biased to closed position by a suitable spring, not shown.

The tubular housing of the cut-off valve is detachably supported within landing nipple 11 of the tubing string by a fluid-tight seal and coupling assembly 30 of well known construction. For example, this coupling may be of the type in which the portion fixed to the upper end of the tubular housing can be securely locked assembled to the landing nipple by a bayonet type connector which is readily engaged and disengaged by a conventional wire line tool lowered through tubing string 12.

Surrounding the lower end of landing nipple 11 is a solenoid coil 33 enclosed in a casing 34 of excellent magnetic material having high permeability. Extending from the top of this solenoid is a cable 35 enclosing electrical conductors 36 connected at the well head to the d.c. power supply 18. As is clearly evident from the drawings, the solenoid and its casing are sealed to the exterior of the landing nipple in the annulus between the tubing string 12 and the well casing 13.

Certain components of the assembly embraced by the solenoid coil such as tubular members 11, 21, and 22, are of suitable non-magnetic material whereas the armature or plunger 24 and the tubular fitting 23 forming the inlet end of the valve housing and the solenoid coil casing 34 are formed of magnetic material and cooperate with the solenoid coil to provide an excellent low reluctance flux path for the flux generated by coil 33 when energized. The upper end 39 of inlet fitting 23 forms a stationary pole piece against which the lower end of armature 24 is firmly held so long as the solenoid coil 33 is energized. When this coil is not energized the compression spring 25 cooperates with flange 40 of the housing section 20 and with the flanged upper end 41 of the armature to elevate this armature until its lower end is withdrawn vertically above the valve seat 27 allowing the flapper cut-off valve 26 to close. This flapper valve 26 may be lightly biased toward closed position by a torsion spring not shown. It will be noted that the lower end of the armature, when seated against surface 39 of the pole piece, not only acts to hold valve 26 fully open but provides a protective barrier isolating the valve from contact with the well flow. Of equal importance is the fact that the armature prevents any portion of the well flow coming in contact with the valve and tending to pivot the valve toward closed position.

Normally and with the solenoid coil de-energized spring 25 holds the tubular armature 24 elevated against stop flange 40 wherein valve 26 is closed against seat 27. Before opening the valve it is necessary to equalize the pressure above to that below the valve which is accomplished from the operating platform 15 in well known manner by operating valves and equipment to pressurize the tubing string until pressure equalization is obtained. Thereupon the operator restores the power supply to solenoid coil 33 via cable 35 and leads 36. The resulting flux generated by this coil is confined to casing 34, armature 24, and the tubular pole piece 23 at the lower end of the valve housing. This highly concentrated flux is effective in shifting the armature 24 axially downwardly unitl its lower end contacts the upper end of pole piece 39. As the armature moves downwardly, spring 25 is compressed and valve 26 is pivoted counterclockwise to the open position through contact with the lower end of the armature and is held fully open until the solenoid is de-energized. Oil seals 44 embracing the opposite ends of armature 24 prevent fluid and foreign matter from entering the chamber housing spring 25 and the chamber above the valve seat. These seals prevent the well fluid from entering these two chambers which contain only air. Each is sufficiently large relative to the axial movement of the armature to permit the latter to operate without need for increasing the air pressure in an amount interfering with operation of the valve. As soon as the valve is fully open, the operator may discontinue pressurizing the upper end of the tubing string and open the valves controlling production flow from the well. Flow takes place in the normal manner through the production flow passage which includes the tubular armature and the inlet and outlet passages at the opposite ends of the tubular valve housing members 20-23.

The safety cut-off valve may be closed either by cutting off the power to the solenoid coil or by an abnormal increase in the flow through the valve. If the power is cut off, spring 25 closes the valve. However, the valve will also close if the pressure differential at the opposite ends of the armature 24 exceeds a predetermined value. For example, flow at a rate above that for which a particular cut-off valve is designed will increase the friction flow forces along the length of armature member 24. These forces plus the energy stored in spring 25 will exceed the holding power of the solenoid coil on armature 24 with the result that the armature will move automatically to its elevated position thereby allowing valve 26 to close. The pressure differential effective to cause the valve to close may be adjusted at will from ground level by varying the direct current voltage applied to the solenoid coil by any suitable means such as a voltage divider, potentiometer or the like, not shown.

Referring now to FIGS. 4 and 5, there is shown a second preferred embodiment of the invention utilizing a ball-type cut-off valve element arranged to be operated between its closed and open positions electromagnetically. The same or similar parts of the second embodiment are designated by the same reference characters employed above in connection with FIGS. 1-3 but distinguished therefrom by the addition of a prime. In all major respects these two embodiments are constructed in the same general manner and operate similarly with the exception that the ball valve element 26' is constructed and mounted quite differently from the flapper valve 26. Also in the interests of brevity the construction details of the valve cage supporting ball valve 26' have not been shown in full since these components are well known and fully disclosed in Reissue Pat. No. 28,131 granted to Leutwyler on Aug. 20, 1974. Valve 26' is supported in a two-part cylindrical valve cage 50 embracing this ball valve and having a pair of trunnions 51 projecting toward one another and into V-shaped notches 52 formed in the diametrically opposed sides of valve 26'. The axes of trunnions 51 are offset below the center of ball valve 26' and so arranged as to rotate valve 26' through 90.degree. about a horizontal axis as the tubular armature 24' of the valve operating mechanism reciprocates between its fully retracted and extended positions by solenoid coil 33'. It will be understood that this operating range of movement of the armature 24' is similar to the range of movement of the armature 24 in FIGS. 2 and 3. The valve seat 27' is located at the lower end of armature 24' and bears directly against the upper surface of the ball. The ball is urged to rotate upwardly toward seat 27' by an underlying tube 54 having a loose sliding fit with the lower half of the valve cage 50 and biased against the underside of the ball by the coil compression spring 25'. The upper end of this spring bears against a radial flange 41' surrounding tube 54 whereas its lower end rests on flanges 40' projecting inwardly from housing member 23'. The lower end of tube 54 is provided with a downwardly and outwardly flaring inlet tube 57 having a sliding fit with the interior sidewall of housing member 23'.

Cooperating with valve seat 27' and the upper side of ball 26' is a sealing ring 58 of any suitable material.

Of importance is the fact that certain components are formed of excellent magnetic material whereas other parts are made of non-magnetic material. Those parts made of good magnetic material comprise the solenoid casing 34', the tubular armature 24', and preferably ball valve 26'. The other components 11', 20', 21', 50, 54 embraced by the solenoid coil are preferably made of non-magnetic material.

Normally, with the solenoid coil 33' de-energized spring 25' urges the tubular inlet members 54, 57, ball 26' and armature 24' upwardly along the interior of the tubular housing 20', 21', 22' and 23'. Valve cage 50 will be understoood as held stationary between shoulder components of 21' and 22'. When the parts are positioned as illustrated in FIG. 4, ball 26' is held firmly seated in closed position against seat 27' and the seat sealing ring assembly 58.

To open the valve, the operator proceeds much in the same manner described above for the first embodiment. Usually there is a pressure differential across the valve when closed and this differential should be equalized by pressuring the upper end of the tubing string 12' in well known manner. This having been done, the operator energizes the solenoid coil to provide a powerful circuit of flux through the solenoid casing 34', tubular armature 24', ball valve 26' and the adjacent lower end of the solenoid casing. When first energized, valve 26' is at an elevation appreciably above the lower end of solenoid casing 34'. The magnetic force provided by this flux tends to centralize the magnetic armature and ball valve between the opposite ends of the solenoid coil and to close the gap between the lower end of the solenoid casing and the lower portion of the ball 26'. Accordingly, the armature and ball along with the non-magnetic inlet tube 54 are moved axially downwardly compressing spring 25'. During the downward movement the trunnions 51 cooperate with V-shaped notches 52 in the sides of ball 26' to rotate this ball 90.degree. to its open position wherein its diametric bore 59 is axially aligned with the flow passages through inlet tube 54 and armature 24'.

Oil seals 44' prevent fluid and foreign matter from entering the air-filled chamber housing spring 25' and the annular air chamber above valve seat 27'.

The valve assembly now remains open to provide unobstructed flow so long as the solenoid coil remains energized or until the pressure drop or differential across the cut-off valve exceeds a predetermined value in which event the valve closes automatically as explained in detail above in connection with the valve illustrated in FIGS. 1 to 3.

While the particular fail-safe safety cut-off valve for a fluid well herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiment of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.