What is claimed is
1. Valve apparatus for controlling flow and backflow of a fluid through a pipe string in a well during run-in and cementing operations, comprising:
2. The apparatus of claim 1 wherein said resilient second valve member means further comprises a thin rigid retainer member adapted to transmit compressive forces to said elastomeric sleeve; and said elastomeric sleeve is further adapted to compress enough under a predetermined differential pressure to move said annular exterior shoulders a sufficient distance to expose said port means to said lower bore passage.
3. The apparatus of claim 1 wherein said tubular body means further comprises a tough metallic outer housing, a drillable inner housing located concentrically and centrally within said outer housing and spaced a predetermined distance therefrom and a drillable composite material between said inner housing and said outer housing.
4. The apparatus of claim 3 wherein said outer housing is made of steel; said inner housing is comprised of an upper body removably connected to a lower body, both made of high strength drillable plastic; and said composite material comprises drillable concrete which was flowed in wet slurry form into the space between said inner housing and said outer housing and allowed to harden.
5. The apparatus of claim 1 wherein said first valve members means comprises a plunger head having a conical surface adapted to seat in said valve seat means in sealing engagement and said valve stem further comprises an upper stem and a lower stem assembly, said upper stem being connected to said plunger head and said lower stem assembly being fixedly attached by removable connector means to said upper stem, said lower stem assembly further comprising an inner rod member attached to said removable connector means and having an enlarged lower end defining an annular perpendicular shoulder, and a tubular case telescopically mounted over said rod member and attached thereto by said frangible means, said case having an inner annular shoulder projecting inward arranged to abut said annular perpendicular shoulder upon shearing of said frangible means.
6. The apparatus of claim 5 wherein said first valve means further comprises an elastomeric cover located on said plunger head and adapted to contact said valve seat means and provide sealing engagement between said plunger head and said valve seat means, and said elastomeric cover further comprises an annular lip extending past said plunger head periphery and adapted to receive fluid back-flow and provide further sealing arrangements with said valve seat means.
7. The apparatus of claim 1 wherein said valve guide means is connected to said tubular body means by one or more vane members attached to said valve guide means and said tubular body means; said vane members serving to define said port means by their passage through the space between said valve guide means and said tubular body means.
8. The apparatus of claim 7 wherein said valve guide means further comprises a generally cylindrical collar arranged to encircle said valve stem in slidable relationship and having an upper portion extending above said vane members, said upper portion adapted to receive said spring means in abutting relationship.
BACKGROUND OF THE INVENTION
In preparing an oil well bore hole for production, it is desirable to run in a string of casing and cement the space between the casing and the bore hole. Usually, the bore hole contains some fluid which must be partially displaced by the casing when running-in. If the fluid is not allowed to flow into the casing as it goes into the hole, the casing will become completely buoyant after reaching a certain depth and further insertion of the casing becomes increasingly difficult and dangerous. If the casing is inserted into the fluid far enough the hydrostatic pressure on it could cause collapse of the casing.
To prevent this buoyancy effect and possible casing collapse, it has long been the practice to place at or near the bottom of the casing string a valved collar or shoe which allows the fluid to flow into the casing as it is being run-in.
The difficulties encountered in this type of tool have been to develop a valve that would allow the fluid to flow into the casing at a precontrolled rate during running-in, then allow the fluid to be pumped out of the casing after it is in place and also allow cement slurry to be pumped down the casing and back up the annulus between the casing and the bore hole, with the valve then being capable of sealing off the casing so that none of the cement slurry can backflow out of the annulus and back into the casing.
After the cementing operation the float collar must act as a back pressure valve while during the running-in of the casing it must act just the opposite and serve as a self-fill valve, allowing fluid to flow into the casing. Thus, several valves whch are seemingly incompatible are required in carrying out casing placement, cementing and related operations. One conventional method of controlling the flow in a well casing is to use plug members or balls which are dropped through the casing string to trip a valve or seat in a valve to open or close it. It is clear that if such valves are used, it would be necessary to have a clear passage through the entire casing string to permit the plug members or balls to pass down through the casing to the valves near the bottom. If intermediate tools are inserted in the casing string, such as multiple stage cementing tools or packers, then the use of plugs or balls to operate valves below these tools may be awkward, or even impossible.
An obvious disadvantage of other prior art devices is their tendency to allow an inrush of fluid through the casing, which fluid usually shoots to the surface causing a dangerous, slippery situation in the drilling area, contaminating the rig floor and everyone in the general area of the well.
Devices which are able to perform these functions are disclosed in U. S. Pat. No. 3,385,370 and 3,385,372. Although these tools offer specific advancements in the art, the present invention is an improvement thereover, providing a differential fill feature and more dependable operation.
The present invention, unlike the prior art devices, allows fluid to flow into the casing regardless of how high the pressure differential may be between the annulus and the casing bore. This obviates the necessity of filling the casing with fluid from the top in order to open the self-fill valve when the casing has been run-in too quickly and built up too high a differential pressure between the casing and the annulus.
The prior art devices also lack a satisfactory means of circulating downward through the self-fill valve without causing the self-fill valve to transform into the back-flow valve until desired.
The disadvantages of the prior art devices are overcome by the present invention which provides in a casing string a valve assembly having a flow rate valve element which can be selectively converted into a check valve. The assembly provides an upwardly opening differential fill valve arrangement for allowing the fluid in the annulus to flow into the casing as the casing is being run-in the hole. Another feature is that fluid can be flowed in both directions through the valve assembly to circulate and reverse circulate fluid through the valve until it is desirable to transform the valve assembly into a check valve allowing flow in one direction only, and preventing back-flow therethrough.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of the float collar as it is placed into the casing string prior to run-in of the casing.
FIG. 2 illustrates the position of the valve assembly as the casing is being run-in.
FIG. 3 illustrates the valve assembly during a limited flow rate circulation through the valve assembly into the bore hole.
FIG. 4 illustrates the valve assembly during cementing after it has been transformed into a check-valve type assembly.
FIG. 5 is a view of the float collar after cementing is completed.
FIG. 6 is a top view of the float collar taken at line 6--6 in FIG. 1.
FIG. 7 is an alternative embodiment of the float collar having an alternate lower valve arrangement.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1 the float collar 1 comprises an outer cylindrical housing 2 made of a durable material such as steel. Centered within the housing 2 by concrete fill 3 is the lower valve body 4 and upper valve body 5 joined together by a releasable connection such as matching threads 6.
Lower valve body 4 has an integral valve guide 7 with a bore passage extending vertically therethrough located centrally therein and one or more vanes 8 passing from valve guide 7 to the outer wall 9 of the lower valve body and further defining flow parts 10 through the lower valve body. Valve body 4 also contains a lower central recessed opening 11 communicating with the flow ports 10.
Passing through valve guide 7 and in slidable relationship therewith is valve member 12 having plunger head 13, valve stem 14, and threaded rod 15. Plunger head 13 has conical valve surface 16 which matches upper valve seat 17 formed in upper valve body 5. Elastomeric covering 18 sufficiently encases plunger head 13 to provide better sealing engagement between head 13 and valve seat 17.
Plunger head 13 has an integral collar 19 formed at the bottom thereof, around stem 14, and of substantially the same diameter as the upper part of valve guide 7. Also formed in the plunger head 13 at the junction of collar 19 and the plunger head is spring recess 20 arranged to receive coil spring 21 which passes in fitting arrangement over collar 19 and the upper shoulder 22 of valve guide 7.
Valve stem 14 passes through valve guide 7 and extends into recess 11 and out past the bottom 23 of lower body 4. Elastomeric valve ring 24 is located about valve stem 14 within recess 11 and has upper sleeve 25, intermediate shoulder 26, and sealing shoulder 27. Valve ring 24 is retained on valve stem 14 by retainer washer 37 located below ring 24 and slidably mounted on a lower bolt 28 which is threaded onto threaded rod 15. Encasing lower bolt 28 is bolt housing 29 which is a cylindrical tubular housing having an upper bore passage 30 and an enlarged lower passage 31 which lower passage defines an annular recess 32 between bolt 28 and housing 29.
Bolt 28 has a lower enlarged portion 33 which is formed by an annular shoulder 34 passing circumferentially around the lower portion of the bolt. The annular shoulder 34 is just large enough to leave a small annular gap 35 between the shoulder and the enlarged lower bore 31 in housing 29.
Passing transversely through housing 29 and bolt 28 through shoulder 34 is shear pin 36 which serves to attach housing 29 to bolt 28 in the uppermost position of housing 29. In this uppermost position as shown in FIGS. 1 through 3, housing 29 abuts retainer washer 37 and maintains valve ring 24 substantially within recessed opening 11 in lower valve body 4.
Coil spring 21 which is in a compressed position in FIGS. 1 through 3 and pushes down against valve body 4 and upward against plunger head 13, works through valve stem 14, threaded rod 15, lower bolt 28, shear pin 36 and housing 29 to maintain washer 37 and valve ring 24 in their upper initial position as shown in FIG. 1.
Spring 21 also biases plunger head 13 toward valve seat 17 and has sufficient travel to seat head 13 in valve seat 17 when bolt 28 has been freed from housing 29 allowing the plunger head to move upward.
In operation, the float collar as shown in FIG. 1 is inserted in the casing string either at the bottom or at one or two joints up from the bottom. After the casing string is made up, it is run in the well and the float collar assumes the position as shown in FIG. 2. In FIG. 2 the elastomeric valve ring 24 has been pressed into the opening 11. This occurs because the sealing shoulder 27 of ring 24 sealingly engages the wall of opening 11 and, due to the fluid in the bore hole and the unfilled area in the casing, a differential pressure arises across valve ring 24 immediately upon entering the bore hole fluid with the casing. As the casing progresses deeper into the bore hole fluid, the differential pressure across shoulder 27 increases, compressing the valve ring, causing sleeve 25 to bulge and take up the compression forced on it by pressure on shoulder 27. As the sleeve 25 bulges and is compressed as shown in FIG. 2, shoulder 27 moves upward into the opening 11. At a predetermined differential pressure, preset by adjusting the length and stiffness of valve ring 24, shoulder 27 moves past the lowermost tip 38 of ports 10 and allows fluid communication from the open bore area 39 in housing 2 through ports 10 and out through upper bore 40 into the casing string. Any time the differential pressure across valve ring 24 drops below the preset opening pressure, the valve ring expands to close ports 10. Referring now to FIG. 3, if at any time during or after the descent of the casing into the bore hole fluid it is desired to flow down the casing and into the bore hole and still retain the reverse circulation feature, this can be done at a relatively low flow rate as long as the flow rate used does not exceed that which is predetermined to shear pin 36 and convert to a check-valve type operation. This conversion flow rate can be preset at any desirable level; for instance, it is desirable in some circumstances to set this at three barrels per minute. Thus, downward flow can occur through the collar at any rate below three barrels per minute without shearing pin 36 and preventing any further reverse circulation.
When it is desirable to convert to check-valve type of operation (for instance, when cementing is to begin), this is achieved as shown in FIG. 4 by pumping down the casing at a rate in excess of the predetermined conversion rate, which excessive rate places sufficient downward shearing force on valve ring 24, which force is transmitted through washer 37 to housing 29 thereby shearing pin 36 which passes through the housing. The downward force on pin 36 is resisted by upward force of spring 21 pushing upward on plunger 13, valve stem 14, threaded rod 15 and through lower bolt 28, thus shearing the shear pin 36 and releasing housing 29 from bolt 28.
The release of bolt 28 from housing 29 allows valve ring 24 to move out of opening 11 thereby fully opening ports 10 into open bore 39. Housing 29 drops down until shoulder 41 of the housing abuts shoulder 34 of the bolt, thereby preventing the housing from dropping off of the float collar and possibly interfering with any tools which may be located below the float collar.
After the valve ring 24 moves out of the opening 11 in response to hydraulic forces above it pushing it downward, the downward force on bolt 28 drops to a negligible amount allowing spring 21 to expand forcing plunger head 13 upward. Cement flowing through upper bore 40 is sufficient to maintain spring 21 compressed and plunger head 13 in an open valve position. When cement flow is stopped, spring 21 pushes plunger head 13 into valve seat 17, thereby closing the tool against reverse flow of cement. Hydrostatic pressure now being higher in the annulus than in the casing, cement will attempt to flow back into the casing through the valve but will act on the backside of plunger head 13 and in conjunction with lip 42 on the lower periphery of elastomeric covering 18 to form a tighter better seal of the valve assembly by forcing plunger head 13 tighter into seat 17 and by further acting upward against the back side of lip 42 forcing it into sealing arrangement with the lower part 43 of seat 17.
The advantages achieved by the use of this invention are partly a result of the ability of the valve ring 24 to compress sufficiently to allow the casing string to fill up as it enters the bore hole. Due to the limited ability of the valve ring to compress, a flow restrictive orifice is always present during back-flow between the valve ring and the lower end 23 of the lower valve body 4, thereby tending to prevent the casing from filling too quickly and overflowing at the surface.
Whereas the prior art devices utilize a resilient washer to limit back-flow, the present device utilizes a rather lengthy valve ring 24. The valve ring is advantageous over the washer due to the tendency of the washer to extrude out of position in high pressure hot wells and also due to the lateral movement of the valve stem which can occur within the rather loose-fitting valve guide.
The present invention also allows the casing to be filled at a controlled rate regardless of how high the pressure differential is between the bore hole and the casing bore, whereas if too high a pressure differential occurs across the prior art devices, the casing string must be pulled upward in the hole or filled from the surface to reduce the pressure differential and allow further back-flowing.
The present invention allows the fluid to be forward-flowed or back-flowed as many times as desired as long as the conversion flow rate is not reached. As soon as the operator desires to convert to check-valve type operation (for instance, to begin cementing), this is easily and simply achieved from the surface without having to drop mechanical devices through the casing or run a stinger into the casing. The conversion is easily accomplished by increasing flow rates through the casing to above the present conversion flow rate.
All the parts of the present invention within the housing 2 can be made of easily drilled materials such as concrete, plastic, rubber, aluminum and brass, to allow the collar to be drilled out after the cementing operation has been completed and the cement set up. The drilling out leaves a full-open passage through the collar to pass other tools down the casing for further work, production or testing.
Although a specific preferred embodiment of the present invention has been described in the detailed description above, the description is not intended to limit the invention to the particular forms or embodiments disclosed herein, since they are to be recognized as illustrative rather than restrictive and it will be obvious to those skilled in the art that the invention is not so limited. For instance, it is contemplated that different numbers of vanes could be used between the valve guide and the lower body to vary the number and size of ports through the collar. It would also be possible to use other spring means to replace the sleeve portion of the valve ring and still maintain the differential fill feature. The invention is declared to cover all changes and modifications of the specific example of the invention herein disclosed for purposes of illustration, which do not constitute departures from the spirit and scope of the invention.