Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2000-12-21
2004-03-09
Rivell, John (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S902000
Reexamination Certificate
active
06701955
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to fluid delivery systems and more particularly to valve assemblies that must handle particulate-containing fluids.
It is common to pump fluids that contain particulates into oil and gas wells. For example, fracturing fluids typically contain proppant particles, such as sand or small beads,(sizes typically from U.S. Standard Sieve sizes 10 through 60). Reciprocating plunger pumps are frequently used to create the high-pressure fluid flow needed to inject fluids, such as fracturing fluids, into oil and gas formations. These pumps typically include valve assemblies that are biased toward the closed position. When the motion of the plunger creates a differential pressure across the valve, the differential pressure forces the valve open, allowing the fluid to flow through the valve. However, solid particles in the fluid can become trapped within the valve assembly upon valve closure, creating damage to valve assembly components and reducing the useful life of the valve assembly.
The valve assembly will typically contain an area where two metal surfaces contact each other when the valve is closed. The solid particles from the fluid can become trapped between the two metal contact surfaces in specific locations rather than evenly distributed across those surfaces, creating concentrated stress forces at these locations. These concentrated stress forces can lead to localized pitting. Once pitting has occurred, the solid particles tend to concentrate at the location of the pitting, which in turn accelerates the damage at these locations.
Valves used for slurry service typically have a resilient sealing insert around the outer perimeter of the valve closure member to provide effective valve sealing. Pressure applied to a closed valve forces the resilient sealing insert to become a hydraulic seal, extruded into the gap between the valve closure member and the valve seat member. For the insert to effect a hydraulic seal upon valve closure, the insert must protrude from the valve closure member toward the valve seat member when the valve is open. When the valve is nearly closed, the resilient sealing insert contacts the valve seat member. When the valve is closed, the resilient sealing insert is deformed against the seat member to form the hydraulic seal, and metal-to-metal contact occurs between the valve closure member and the valve seat member. Proppant trapped under the resilient sealing insert can become temporarily or permanently embedded in the resilient insert material, so that the insert can effect a hydraulic seal in the presence of proppant. In the presence of proppant, the metal surfaces of the valve closure member and valve seat member do not form a hydraulic seal.
The resilient sealing insert of current valves is on the outer perimeter of the valve closure member or valve seat member, so that applied pressure will deform the resilient sealing insert to seal between the valve closure member and the valve seat member. If the resilient sealing insert were on the inner perimeter of the valve closure member or valve seat member, then applied pressure would force the resilient sealing insert away from the contact area between the valve closure member and the valve seat member, and the valve would not seal.
The resilient sealing insert of current valves contacts the valve seat member before the valve closure member contacts the valve seat member. The gap between the sealing insert and the seat of an open valve is smaller than the gap between the valve closure member and the valve seat. When the valve is closing, the gap between the sealing insert and the valve seat member becomes too small to pass particles in the fluid, while the gap between the valve closure member and the valve seat member is still large enough to pass particles into the region between them. Thus a standard valve sealing insert can act as a forward screening element that concentrates proppant particles in the region between the valve closure member and the valve seat member. Such concentrations of proppant particles cause damage to the contacting surfaces of the valve closure member and the valve seat member.
If the pump is operated in such a way as to have significant valve lag, i.e. a discharge valve does not close until well after the plunger starts its suction stroke, there will be reverse flow through the valve before it closes. The standard sealing insert will screen out proppant particles from the reverse fluid flow, preventing the particles from entering the region between the valve closure member and the valve seat member. However, the volume of fluid which flows through current valves during the short time interval between the onset of such reverse particle screening and the closure of the valve typically is insufficient to displace the proppant-laden fluid from the valve before closure. Particles are still trapped between the valve closure member and the valve seat member.
Conventional liquid end valve assemblies may also experience failures due to foreign objects becoming lodged within the valve assembly (e.g., bolts or gravel can accidentally enter the fluid flow path). These foreign objects can become wedged between the contact surfaces of the valve, and thus prevent the valve from closing.
There is a need for improved valve assemblies that reduce the incidence of damage caused by particulates or foreign objects in well treating fluids.
SUMMARY OF THE INVENTION
The present invention relates to valve assemblies that can reduce the problem of solid particle damage within the valve, and can also help reduce or avoid the problems associated with foreign objects becoming lodged within the valve. This invention is well suited for use with pumps that inject particle-laden fluid during the treatment of oil and gas wells, but could be used for other purposes as well.
One aspect of the invention is a valve apparatus that can screen particles from fluid flowing forward through the valve. This valve apparatus has a longitudinal axis therethrough and comprises a valve seat member, a valve closure member, a fluid flow path, and a forward screening member. The valve seat member is usually stationary, and comprises a hollow bore and a first frustoconical contact surface. The valve closure member comprises a body and a second frustoconical contact surface that is adapted to seal against the first frustoconical contact surface. The valve closure member is movable along the longitudinal axis of the valve apparatus (i.e., toward and away from the valve seat member). The fluid flow path extends through the bore of the valve seat member and between the valve seat member and the valve closure member. This fluid flow path is closed when the second frustoconical contact surface is sealed against the first frustoconical contact surface. The forward screening member is attached to at least one of the valve closure member or the valve seat member. This forward screening member screens particles from fluid passing through the fluid flow path in a forward direction when the valve closure member approaches the valve seat member. This results in preventing the screened particles from entering the region between the valve closure member and the valve seat member. To perform such forward flow screening, the forward screening member may be located around the inner perimeter of the region between the valve closure member and the valve seat member.
In one embodiment the forward screening member comprises a cylindrical plug that is near the inner perimeter of the second frustoconical contact surface and can extend into the bore of the valve seat member. The valve seat member comprises a cylindrical inner wall, and a screening gap exists between the cylindrical inner wall and the cylindrical plug when the valve closure member is near to the valve seat member. This screening gap is small enough to prevent passage of particles of a selected size from passing through the fluid flow path. The particles to be screened out will generally consist of proppant particles having a genera
Hubenschmidt Joseph M.
McIntire William R.
Pham Hau N.
Upton Mark E.
Jeffery Brigitte
Mitchell Thomas O.
Rivell John
Ryberg John
Schlumberger Technology Corporation
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