Boring or penetrating the earth – With above-ground means for handling drilling fluid or cutting – With valve
Reexamination Certificate
2001-04-01
2003-12-16
Bagnell, David (Department: 3672)
Boring or penetrating the earth
With above-ground means for handling drilling fluid or cutting
With valve
C166S237000, C166S321000, C166S332300, C166S373000
Reexamination Certificate
active
06662886
ABSTRACT:
BRIEF DESCRIPTION OF THE INVENTION
The present invention relates in general to a mudsaver valve and particularly to a mudsaver having a rotating ball valve with snap-action for both opening and closing the valve.
BACKGROUND OF THE INVENTION
Mudsaver valves, mounted on the bottom of the drilling rig kelly or top drive, serve to automatically retain drilling mud within the kelly or top drive and its supply hoses and tubing whenever the kelly or top drive is disconnected from the drillstring. The kelly or top drive is routinely disconnected to add or remove pipe from the drillstring.
Retention of drilling mud is desirable in order to avoid the loss of expensive mud, as well as the creation of slick and hazardous working conditions and the resultant loss of time due to rig floor cleanup. The mudsaver functions as a type of relief valve. Whenever the mudsaver is closed, it must support the hydrostatic head of the noncirculating fluid trapped above the mudsaver when the drillstring is separated from the mudsaver. However, when the mudsaver is reconnected in the drillstring, the valve must readily open when the mudpumps are started.
Several previous designs of mudsaver have been created and used, as is discussed below. However, most such designs have had significant drawbacks and are not widely used in the oilfield. Two very significant drawbacks to all of the designs reviewed below is their susceptibility to wear from abrasive fluids and their complex assembly. Partially open valves, particularly ball valves, experience significantly worsened fluid-induced wear rates. This is especially true when used with drilling mud, which is highly loaded with abrasive particles.
In fact, current mudsaver designs are so unsatisfactory that typical operations will retain the mud within the kelly or top drive by manual closure of a valve at the lower end of the kelly, called the kellycock. This situation is highly undesirable because the lower kellycock is a critical drilling safety component intended for occasional or emergency use. In addition, an actuator and its controls must be provided and maintained for the operator to close and open the lower kellycock. Thus, the provision of a suitable autonomous mudsaver would preserve the lower kellycock for its intended safety purposes.
The mudsaver described in U.S. Pat. No. 3,965,980 is one attempt to solve the problems set forth above. The valve described is basically a poppet relief valve. The poppet is spring-biased closed and is opened when drilling mud pressure acting on one side of the piston on the upper end of the sealed spring chamber exceeds the combined resistance of the biasing spring and the counter pressure within the sealed spring chamber. The poppet valve has a check valve mounted concentrically within its head to permit communication of mud pressure from below through the closed poppet for measurement above the mudsaver. Flaws in the design of the valve are its length, multiple-part outer body, difficult assembly and disassembly, and that its sealing plug and seat are subject to high erosion and attendant leakage due to mud circulation impinging both components. Drilco Inc. (a division of Smith International, Inc.) of Houston, Tex. markets the patented valve and SMF International of France markets a similar valve.
U.S. Pat. No. 3,743,015 describes another approach. This mudsaver has a rotatable, translatable ball sealing plug with a through hole. The valve is actuated by differential pressure across an annular piston. On the upper side of the piston, pump pressure acts, while on the other side, a biasing chamber provides a reference pressure (typically atmospheric). The ball is further urged toward its closed position by biasing springs. A means of locking the ball open by means of an externally operated wrench permits wireline operations through the valve. Drawbacks of the valve are the potential leakage paths through the side of its body, high operating forces on the valve with rapid increases in pump pressure or water-hammer, and an involved assembly and disassembly of the large number of parts positioned in crossbores.
A further approach is found in U.S. Pat. No. 4,262,693 which discloses a mudsaver based upon a rotatable, nontranslatory ball sealing plug with a through hole. This valve appears to be substantially similar to the mudsaver marketed by Arrowhead Continental, San Bernardino, Calif. An actuation piston is exposed to pump pressure on one side and a second bias pressure in a sealed spring chamber plus a biasing spring force on the second piston face. A net differential pressure causes axial movement of the actuation piston. The actuation piston is coupled to a rotator sleeve by means of one or more piston-mounted camming pins acting in one or more helical grooves in the rotator. Accordingly, axial movement of the piston imparts rotary motion to the rotator, which in turn rotates the ball by means of bevel gears. This mudsaver has relatively high frictional loads and multiple interacting parts.
Yet another approach is seen in the mudsaver valves offered by American International Tool Company, Inc. and A-Z International Tool Company. Their mudsavers retain the mud above the valve by comating annular flat sealing faces transverse to the mudsaver axis dividing an upper annular fluid path from a lower central fluid path. The flat faces are spring-biased together to remain in a closed position under non-flowing mud when the drillstring is separated. The lower flat sealing face constitutes a piston head which is exposed to the pressure above the sealing face on its upper side and the pressure downstream of the annular orifice between the sealing faces on the other side. Pump pressure is sufficient to overcome the spring bias and then the pressure drop across the annular orifice will maintain the valve open. This mudsaver has a coaxial poppet check valve to permit communication of pressure below the valve past the primary valve seal. The primary disadvantage of this valve is the tendency of the sealing faces to wear under direct flow impingement.
U.S. Pat. No. 5,509,442 discloses another mudsaver based upon a rotatable, nontranslatory ball sealing plug with a through hole. An actuation piston is exposed to pump pressure on one side and atmospheric bias pressure in a spring chamber plus a biasing spring force on the second piston face. A net differential pressure causes axial movement of the actuation piston, which in turn can cause valve shifting if permitted by an interlock system controlled by the presence of the abutting end of the drillstring below the valve. The tool is relatively long and has a jointed body which makes assembly and disassembly difficult.
U.S. Pat. No. 4,248,264 discloses a flapper valve-based mudsaver. The flapper is normally biased closed both by gravity and by a torsion spring. The flapper is mounted on an upwardly spring-biased piston ring concentric with the flow passage. Atmospheric pressure is retained within the spring chamber below the piston. When pump pressure forces the annular piston carrying the flapper valve and its seat downwardly, the flapper encounters a fixed annular tube concentric within the valve seat and passing through the annular piston. This unseats the flapper, permitting flow. Pressure from below will either unseat the flapper or, if it is already open, not permit the piston to travel to a position where the flapper will seat. If there is no pressure overcoming the spring bias, the piston moves up against the pressure of the retained mud and closes. This valve gradually opens and closes and is susceptible to wear. Furthermore, pressure surges produce high loadings on the flapper hinges.
U.S. Pat. No. 4,889,837 discloses a poppet-type mudsaver in which the poppet is restrained against downward movement by an integral spider which abuts a stop shoulder. The poppet seat is a spring-loaded annular piston which translates away from the poppet when the pump pressure exceeds the atmospheric pressure acting on the piston area and the spring preload. The poppet is free to reciprocate up
Bagnell David
Gay Jennifer H
Hall Elizabeth R.
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