Single acting subterranean well valve assembly with conduit fluid stripping means

A formation protection valve is normally held in an open position relative to an annular elastomeric valve seat by an inserted wash pipe during performance of a gravel packing operation in a subterranean well. Upon removal of the wash pipe, a valve head swings downwardly to a sealing position on an annular elastomeric valve seat. A valve seat support structure is mounted below the annular valve seat to provide support of the inner periphery of the annular valve seat against downward fluid pressure forces exerted on the valve head. The elastomeric valve seat is shearable by a subsequently inserted tubing string, which also effects the displacement of the valve seat support structure to a radially outwardly disposed position wherein it no longer interferes with the passage of the tubing string therethrough.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a formation protection valve that may be inserted 
in the casing of a subterranean well at a position above a production 
formation and operated to a closed position upon the withdrawal of the 
mandrel and wash tube commonly employed for effecting the gravel packing 
of the screen and production formation, to protect the underlying 
formation from fluids remaining in the well upon withdrawal of the gravel 
packing equipment. 
2. Description of the Prior Art 
A number of operations are performed in the completion and maintenance of 
subterranean wells that require the introduction of fluids into the well 
and the production formation for specific purposes. For example, 
subsequent to gravel packing, completion fluids are introduced to the well 
to displace the fluid used during the gravel packing procedure. When the 
gravel packing and completion fluid introduction operations are completed, 
it is, of course, necessary to remove the mandrel and associated wash tube 
of the gravel packing apparatus and, in particular, the tubular work 
string carrying such apparatus, and substantial quantities of completion 
fluid are normally contained in the removed apparatus. It is, therefore, 
desirable to prevent the loss of such costly fluid by flow into the 
formation upon the removal of the tubular work string and the associated 
gravel packing apparatus from the well. 
There is, therefore, a distinct need for a valve which may be conveniently 
inserted into the well casing in an open position above a production 
formation so that a wash tube of a gravel packing apparatus may be readily 
inserted through the open valve to extend to a position adjacent the 
production formation. Such valve should be automatically closeable by the 
withdrawal of the wash string from the well and it is further desirable 
that the external surface of the wash pipe be wiped of any adhering fluid 
during such withdrawal movement. Of equal importance is the need for the 
reliable reopening of the valve upon the insertion of the production 
tubing or another work string into the well, and particularly the removal 
of the valve elements from the path of the production string, permitting 
the bottom of such string to be moved to a position adjacent the 
production formation. 
SUMMARY OF THE INVENTION 
The invention provides a shiftable valve mounted in a valve housing which, 
in turn, is appropriately secured within the casing of the subterranean 
well at a position above a production formation. The valve comprises a 
valve head mounted on a horizontally pivoted arm of a torsion spring and 
the valve head is normally held in an inoperative position with respect to 
an annular elastomeric valve seat by a wash pipe inserted in the housing 
prior to the initial run-in of the equipment into the well. The torsion 
forces in the spring urges the valve head supporting arm downwardly to a 
closed position in sealing engagement with an annular elastomeric seal 
element which also snugly engages the periphery of the inserted wash pipe. 
The outer periphery of the annular valve is sealingly engaged with the 
housing bore and retained by a support sleeve shouldered in the housing. 
Upon removal of the wash pipe, the lower exterior surface portions of the 
wash pipe are stripped of any adhering fluid by the frictional engagement 
therewith of the annular elastomeric seal element. When the end of the 
wash pipe clears the valve head, the valve head swings downwardly under 
the bias of its torsion spring support to effect a sealing engagement with 
the annular elastomeric seal. 
To effect the convenient opening of the closed formation protection valve, 
the valve head is secured to the free end of the torsion spring support 
arm by a shearable bolt. Thus, a substantial increase in internal pressure 
in the valve housing will have the effect of shearing such bolt and 
forcing the valve head downwardly through the annular elastomeric seal 
element. More commonly, the bottom end of a subsequently inserted 
production string, or another work string, engages the support arm and 
exerts a downward force upon such arm sufficient to force the valve head 
through the annular elastomeric seal element. During such forceable 
movement, the retaining bolt is sheared through sliding contact with the 
end face of the inserted tubing string. 
In order to ensure that the formation protection valve would not 
inadvertently open under a modest increase in internal fluid pressure in 
the valve housing, a seat support sleeve is provided having its upper 
portion formed as radially outwardly biased collet arms, the upper ends of 
which are compressed inwardly by a retaining sleeve to form a vertical 
support for the inner periphery of the annular elastomeric valve seat. 
This vertical support prevents any modest fluid pressure existing above 
the valve head from forcing the valve head through the opening in the 
annular elastomeric valve seat. However, when any subsequently inserted 
production string contacts the valve head, it can impose sufficient 
downward force on the collet support sleeve to effect the shearing of 
shear pins which hold the collet support sleeve in the valve supporting 
position in the valve housing. The collet support sleeve is thus moved 
downwardly, permitting the valve head to be forced downwardly through the 
annular elastomeric seat, producing radial tears in the inner periphery of 
the elastomeric seat. After a limited downward movement of the collet 
support sleeve, the head portions of the collet arms of such sleeve ride 
off the retaining sleeve and spring outwardly into an appropriate annular 
recess provided in the housing wall, thus permitting unimpeded passage of 
the subsequently inserted production string downwardly through the entire 
valve housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, the numeral 1 designates a well bore having a 
production formation 1a. A casing 2 is inserted into well bore 1 and 
provided with perforations 2a in conventional fashion. Within the casing 
2, a formation protection valve housing 10 is mounted by any conventional 
form of packer 12 which is expanded to achieve a rigid sealed engagement 
with the internal bore 2b of the casing 2. 
Valve housing 10 may comprise one of a plurality of threadably 
interconnected tubular elements, such as a conventional perforated 
extension sleeve 13, a conventional shear out safety joint 14, and a 
conventional screen assemblage 15, all of which are suspended from the 
internal threads 12a provided in the packer 12. 
Valve housing 10 is preferably located just above the shear out safety 
joint 14. Valve housing 10 includes a central elongated sleeve portion 10a 
having internal threads 10b and 10c respectively connecting to an upper 
connector sub 10d and a lower connector sub 10e. 
As shown in FIG. 1, a conventional gravel packing mandrel 18, including a 
crossover portion 19 and a wash pipe 20, is inserted through the bore 
defined by packer 12 and the tubular elements depending therefrom, 
including the protector valve housing 10. The wash pipe 20 extends to a 
position within the bore 15a of the screen 15. 
The gravel packing apparatus thus assembled may comprise any one of several 
well known types, such for example, the gravel packing assemblage 
described and illustrated on Pages 6 and 7 of the Baker Sand Control 
Catalog, 1980-1981, published by Baker International Corporation. As is 
well known to those skilled in the art, such gravel packing apparatus is 
suspended from a tubular work string 21 and includes expansible slips 12e 
and an expansible seal 12f for secure sealing engagement with the bore 2b 
of casing 2. Such apparatus further includes serially connected sleeves 
defining seal bores 12b and 12c for cooperation with axially spaced 
sealing elements 18a provided on the inserted crossover mandrel 18. 
The operation of such gravel packing apparatus is entirely conventional and 
forms no particular part of this invention. Its function is to provide a 
packing of gravel 1b around the annulus defined between the screen 15 and 
the casing bore 2b and also in the casing perforations 2a and the 
surrounding perforations in the production formation 1a. When the tubular 
work string 21 is elevated out of the well casing, all of the residual 
completion fluid contained therein would drain into the production 
formation and would thus not only entail an economic loss of relatively 
expensive fluid, but additionally, such fluid could very well adversely 
affect the production efficiency of the well. 
To prevent such adverse effects, this invention provides a shiftable 
formation protection valve 30 which is appropriately mounted on a valve 
mounting ring 31 (FIG. 2) which is secured by a set screw 31a to the 
interior of the mounting ring 31. 
The formation protection valve 30 preferably comprises a flapper valve 
construction including a torsion spring 32 which is mounted on a suitable 
horizontal pin 31b traversing the wall of the mounting ring 31 and having 
an elongated arm portion 32a which normally tends to occupy a downwardly 
inclined position, as shown in dotted lines in FIG. 2. A semi-spherical 
valve element 33 is secured to the underside of the spring arm 32a by a 
shear bolt 34 having a head portion 34a which projects above the plane of 
the spring arm 32a for a purpose to be hereinafter described. The wash 
pipe 20, which is inserted within the valve housing 10 prior to run-in of 
the gravel packing apparatus into the well, is provided with a radially 
enlarged portion 20a, which may comprise a joint in the pipe sections 
making up the wash pipe. Enlarged portion 20a engages the semi-spherical 
valve head 33 and holds it in its fully open position, illustrated in FIG. 
2, wherein it is biased to swing downwardly by the torsion spring 32 upon 
removal of the wash pipe 20 from the valve housing 10. 
The semi-spherical valve head 33 cooperates in sealing relationship with an 
annular elastomeric valve seat 40 which is mounted within housing portion 
10a at a position below the mounting pin 31b for the flapper valve 
assemblage 30. The outer peripheral portion 40a of the annular valve seat 
40 maintains a sealing engagement with the inner bore 10f of the housing 
sleeve portion 10a and is secured against vertical displacement by a 
sleeve 41. Sleeve 41 has a downwardly facing shoulder 41a cooperating with 
an upwardly facing shoulder 10g formed in the interior bore of the housing 
sleeve portion 10a. 
An annular metallic valve shearing element 42 is provided having a 
horizontal flange portion 42a mounted between the top surface of the 
periphery of the annular elastomeric valve seat 40 and the bottom surface 
of the support ring 31. Annular shearing element 42 is further provided 
with an integral depending vertical sleeve portion 42b which terminates in 
a plurality of radially inwardly and downwardly projecting finger portions 
42c which overlie the central portions of the annular elastomeric valve 
seat 40 for a purpose to be hereinafter described. The finger portions 42c 
do not project inwardly so far as to prevent the sealing engagement of the 
semi-spherical valve head 33 with the inner extremities of the annular 
elastomeric valve seat 40. 
Hence, whenever the wash pipe 20 is removed from the housing 10, the valve 
head 33 automatically swings downwardly and achieves a sealing engagement 
with the inner periphery of the annular elastomeric valve seat 40, as 
shown in FIG. 3. This action thus provides protection for the underlying 
formation from any fluids carried in the wash pipe 20 and the associated 
tubing string. Moreover, as the wash pipe 20 moves upwardly through the 
inner periphery 40b of the annular elastomeric valve seat 40 it is 
subjected to a wiping action to strip any remaining fluid from the surface 
of the wash pipe 20. 
To ensure that the flapper valve assembly 30 will maintain its sealing 
engagement with the annular valve seat 40 even though the pressure above 
such valve seat may be significantly increased, a valve seat supporting 
mechanism is provided. Such mechanism includes a collet sleeve 50 having a 
solid ring portion 50a at its bottom and a plurality of axially extending 
collet arm portions 50b defining its upper portions. The ring portion 50a 
is secured by a plurality of radially disposed set screws 51a to a support 
ring 51 which is mounted in an appropriate recess 10k formed in the 
housing sleeve portion 10a. The upper ends of collet arm portions 50b are 
radially enlarged as indicated at 50c and are clamped in an inward 
position, against their inherent spring bias, by a ring element 54 which 
is engaged with some of the collet arm head portions 50c by shear screws 
54a. In their internally compressed clamped positions, the top surfaces 
50d of the enlarged head portions 50c define a conical surface supporting 
the correspondingly shaped bottom surface 40e of the annular elastomeric 
valve seat 40. Thus substantial fluid pressure may be applied to the bore 
of the housing 10 without disturbing the sealed relationship between the 
semi-spherical valve head 33 and the annular valve seat 40. 
It is, however, necessary that the aforedescribed sealed relationship 
between the flapper valve assemblage 30 and the annular elastomeric valve 
seat 40 be opened to permit the bottom portions of a production string to 
be inserted through the housing 10 so that the bottom end of the 
production string may be positioned adjacent the production formation 1a. 
This may be accomplished solely by the forceable insertion of the bottom 
end 22a of a production string 22 in the manner illustrated in FIGS. 4 
through 6. 
Referring first to FIG. 4, the bottom end 22a of a production string 22 is 
shown in engagement with the top surface of the spring arm 32a of the 
flapper valve assembly 30 and sufficient downward force has been applied 
by the production string 21 to cause the semi-spherical valve seat to 
depress the shearing fingers 42c of the seal shearing ring 42 downwardly. 
Such further downward movement produces a downward force on the collet 
support sleeve 50 and first effects a shearing of the shear screws 51a 
which hold such sleeve in its original vertical position in the housing 
10. Continued downward movement of the production string 22 will effect a 
radial splitting of the inner peripheral portions of the annular 
elastomeric valve seat 40, by radially expanding the valve splitting 
fingers 42c. 
Referring next to FIG. 5, it will be observed that the semi-spherical valve 
head 33 has been moved downwardly an additional distance by the inserted 
end 22a of the production string 22 so as to bring the radially split 
portions 40d of the annular valve seat 40 into engagement with the side 
wall of the valve seat support ring 41. At this point, the end 22a of the 
downwardly moving production string 22 engages the upwardly projecting 
head portion 34a of the shear bolt 34 and effects the shearing of the 
bolt, thus freeing the semi-spherical valve head portion 33 from the 
spring arm 32 and permitting it to move downwardly with the further 
downward movement of the production string 22. It will be noted that the 
valve splitting fingers 42c cause a splitting of the annular elastomeric 
valve seat 40 only back to the enlarged peripheral portion 40a. It is thus 
assured that no pieces of the elastomeric material will be torn from the 
valve seat 40 by the splitting thereof, and this prevents interference of 
such pieces, which would be generally readily movable with any well fluid, 
with any other components of the well, either above or below the original 
location of the elastomeric valve seat 40. 
Following such initial downward movement of the collet sleeve 50, a 
downwardly facing shoulder 54b provided on the perimeter of the collet 
compression sleeve 54 engages an upwardly facing shoulder 41b (FIG. 6) 
provided on the valve seat support sleeve 41 and prevents any further 
downward movement of the compression ring 54. This then causes the shear 
screws 54a between the compression ring 54 and the individual collet arm 
head portions 50c to be severed and the collet 50 moves freely downwardly 
with further downward movement of the inserted production string 22. 
The limit of downward movement of the collet sleeve 50 is determined by an 
upwardly facing shoulder 10n formed in the lower housing connector sub 
10e. When the bottom surface of collet 50 reaches the shoulder 10n, 
however, the enlarged collet head portions 50c are aligned with an annular 
recess 10p provided in the internal bore of the housing sleeve portion 10a 
and such collet arms spring outwardly to position the enlarged head 
portions in the recess 10p, as illustrated in FIG. 6. 
In this position, the inner ends of the enlarged collet head portions 50c 
are disposed outside of the path of the inserted production tubing 22 and 
are also large enough to permit the sheared hemispherical ball head 33 to 
pass freely therethrough and drop into the lower portions of the well. It 
will therefore be apparent that further downward movement of the 
production string 22 is completely unimpaired by the various elements of 
the formation protection valve 30 and the production string 22 may be 
subsequently removed and reinserted without incurring any interference 
with the elements of the protection valve 30. 
In the event that it is desired to effect an opening of the protector valve 
assemblage 30, without passing the end of a production string through the 
valving elements, such can be accomplished by providing a sufficiently 
high pressure differential across the valve to cause the semi-spherical 
valve head 33 to be forced downwardly to cause the splitting of the 
annular valve seat member 40, and thus permit fluid flow around the valve 
head. Normally, however, the valve is opened by the insertion movement of 
the production string. 
Although the invention has been described in terms of specified embodiments 
which are set forth in detail, it should be understood that this is by 
illustration only and that the invention is not necessarily limited 
thereto, since alternative embodiments and operating techniques will 
become apparent to those skilled in the art in view of the disclosure. 
Accordingly, modifications are contemplated which can be made without 
departing from the spirit of the described invention.