US20160160848A1 - Pumps and methods of pumping fluids into a well bore - Google Patents

Abstract

A pump for pumping fluid down a well bore in a rock formation comprises: intake and discharge passages; a pumping chamber with a plunger therein; intake and discharge valve assemblies in the intake passage and the discharge passages. At least one valve assembly has a valve body movable into sealing contact with the valve seat by fluid pressure in the pumping chamber. The valve seat may have a cylindrical outer surface for mating reception in said intake passage, and a shoulder with a radially-projecting surface biased against a wall for sealing. A cushioning member may be interposed between the valve body and the valve seat. A seal may be interposed between said valve body and said valve seat, and configured so that between 35% and 60% of a sealing surface of said valve seat contacts the valve body.

Description

RELATED APPLICATIONS
• This application claims priority to U.S. Provisional Application Nos. 62/087,018, 62/113,782 and 62/193,933, the entire contents of which are incorporated herein by reference.
FIELD
• This relates to pumps for pumping pressurized fluids down well bores, and in particular, to fluid ends of such pumps.
BACKGROUND
• Many well operations require pumping of fluids at very high pressures. For example, some wells are formed in rock formations. Completion of such wells may involve pumping of a fluid into the formation through a well bore at high pressure. Such pumping may cause cracking or expansion of cracks in the formation, which may release hydrocarbons for later extraction. Moreover, pumps may be used to pump cement down a well bore to complete the well bore casing, or to pump other fluids, such as acids, down the well bore.
• In such pumps, the term “fluid end” is typically used to refer to the components that are in direct contact with fluid being pumped. A fluid end may be driven by a power end, such as a diesel or electric motor.
• Down-hole pumping operations may require very high pumping pressures. For example, hydraulic fracturing may require pressures of many thousands of pounds per square inch (psi). High pumping pressures subject fluid end components to enormous stresses. Such stresses may cause fatigue and failure of components, requiring costly and time-consuming maintenance.
SUMMARY
• An example pump for pumping fluid down a well bore in a rock formation comprises: an intake passage in communication with a fluid reservoir; a discharge passage in communication with the well bore in the rock formation; a pumping chamber with a plunger received therein for pumping fluid from the reservoir to the well bore by reciprocation of the plunger; intake and discharge valve assemblies in the intake passage and the discharge passage, respectively, for selectively sealing the intake and discharge passages, at least one of the intake and discharge valve assemblies comprising a valve body and a valve seat, the valve body movable into sealing contact with the valve seat by fluid pressure; a cushioning member interposed between the valve body and the valve seat.
• Another example pump for pumping fluid down a well bore in a rock formation, comprises: an intake passage in communication with a fluid reservoir; a discharge passage in communication with the well bore in the rock formation; a pumping chamber with a plunger received therein for pumping fluid from the reservoir to the well bore by reciprocation of the plunger; intake and discharge valve assemblies in the intake passage and the discharge passage, respectively, for selectively sealing the intake and discharge passages, at least one of the intake and discharge valve assemblies comprising a valve body and a valve seat; the valve body movable by fluid pressure into sealing contact with the valve seat; the valve seat having a cylindrical outer surface for mating reception in the intake passage, and a shoulder with a radially-projecting surface biased against a wall of the intake passage by pressure in the pumping chamber, for sealing therewith.
• Another example pump for pumping fluid down a well bore in a rock formation, comprises: an intake passage in communication with a fluid reservoir; a discharge passage in communication with the well bore in the rock formation; a pumping chamber with a plunger received therein for pumping fluid from the reservoir to the well bore by reciprocation of the plunger; intake and discharge valve assemblies in the intake passage and the discharge passage, respectively, for selectively sealing the intake and discharge passages, at least one of the intake and discharge valve assemblies comprising a valve body and a valve seat; the valve body movable by fluid pressure into sealing contact with the valve seat; a compressible seal positioned about the perimeter of the valve body and interposed between the valve body and the valve seat, the compressible seal configured so that, with the valve body in sealing contact with the valve seat, between 35% and 60% of a sealing surface of the valve seat is in contact with the valve body.
• An example method of pumping fluid into a wellbore comprises, using a pump as disclosed herein: drawing a fluid through an intake valve of the pump by moving said plunger through an intake stroke; moving said plunger through a discharge stroke, thereby pressurizing fluid in said chamber, closing said intake valve and opening said discharge valve and forcing said fluid through said discharge valve into said wellbore.
BRIEF DESCRIPTION OF DRAWINGS
• In the drawings which illustrate, by way of example only, embodiments of the invention:
• FIG. 1 is a schematic view of a well bore in a rock formation;
• FIG. 2 is a perspective view of a pump fluid end, with a housing thereof partially cut away;
• FIG. 3 is a cross-sectional view of the pump fluid end ofFIG. 2;
• FIG. 4 is a cross-sectional view of a valve assembly;
• FIG. 5 is a cross-sectional view of another valve assembly;
• FIG. 6 is a cross-sectional view of another valve assembly;
• FIG. 7 is a cross-sectional view of another valve assembly;
• FIG. 8 is a cross-sectional view of another valve assembly;
• FIG. 9 is a cross-sectional view of another valve assembly;
• FIG. 10 is a cross-sectional view of another valve assembly; and
• FIG. 11 is a cross-sectional view of another valve assembly.
DETAILED DESCRIPTION
• FIG. 1 shows a schematic view of a wellbore100 drilled through arock formation102.Rock formation102 may be a shale formation, or another suitable formation for creation of an oil well by hydraulic fracturing.
• Apump104 may be provided for pumping a pressurized fluid down the well bore100. For example, as depicted,pump104 may be used for hydraulic fracturing. In other embodiments,pump104 may be used for other down-hole pumping, such as cement pumping for completing a well bore casing or acid pumping for cleaning components.
• Down-hole pumping may require high-pressure fluids. Accordinglypump104 may be intended to operate at very high pressures. For example,pump104 may drive a fluid into well bore100 at pressures up to many thousands of pounds per square inch (psi), forcing the fluid to create or widencracks108 information102. Typically,pump104 may operate at discharge pressures of 5,000-15,000 psi.
• The fluid pumped into wellbore100 may be a suitable liquid, such as water, mixed with a proppant such as sand. The proppant may be forced intocracks108 along with pressurized water and remain in the cracks after water is withdrawn, to maintain widening of the cracks. As used herein, the combination of injected liquid and proppant may be referred to as the fracturing fluid.
• Pump104 may comprise afluid end110 and a power end, namely,motor112. Motor112 may drive a plunger withinfluid end110 in a reciprocating motion to pump fracturing mixture. Motor112 may be, for example, an internal-combustion engine, such as a diesel-fuelled engine, or an electric motor. Other suitable types of motor will be apparent to skilled persons.Motor112 may drivefluid end110 by acrankshaft111. Motor112 may be connected with a geartrain, for example, to provide for operation ofmotor112 andfluid end110 at different rotational speeds or to convert rotary motion to linear reciprocating motion.
• FIG. 2 showsfluid end110 in greater detail.Fluid end110 has ahousing114, which may be a cast metal block with a machined plunger bore116,intake passage118 anddischarge passage120.Housing114 may be formed from carbon steel, stainless steel or another material suitable to withstand high pressures.
• Intake passage118 communicates with afracturing fluid reservoir117, and discharge passage communicates through an outlet119 (FIG. 3) with a pipe121 (FIG. 1) leading to well bore100. A blending pump (not shown) may be positioned upstream ofintake passage118. The blending pump may mix liquid and proppant in the fracturing fluid and may pressurize the fracturing fluid. As depicted inFIG. 2,housing114 is partially cut away for the sake of illustration ofbores116,118,120 and components housed therein.
• Aplunger122 is received inplunger bore116.Plunger122 may be formed from steel and may be mounted to a crankshaft (not shown) driven bymotor112 to moveplunger122 in a reciprocating back-and-forth motion withinplunger bore116. Reciprocating motion ofplunger122 draws fracturing fluid throughintake bore118 and intochamber124 and then expels fracturing fluid throughdischarge passage120 and into well bore100. In other embodiments,plunger122 may be replaced with a steel piston, which may be of reinforced construction suitable to withstand high pressures experienced influid end110.
• FIG. 2 depicts one plunger bore116, oneintake passage118 and onedischarge passage120. However,fluid end110 may have a plurality of plunger bores116, each with an associatedintake passage118 anddischarge passage120. In an example, afluid end110 may have five sets of plunger bores116,intake passages118 and dischargepassages120, which may be aligned side-by-side with one another within acommon housing114.
• FIG. 3 depicts a cross-sectional view offluid end100. As noted,plunger122 is slidably received withinplunger bore116.Plunger122 and plunger bore116 engage one another to form a fluid-tight seal.Plunger122 is slidable withinplunger bore116. Thus,plunger122 and plunger bore116 form a positive-displacement pump. Movement ofplunger122 in a first direction, indicated by arrow I inFIG. 3 (herein referred to as an intake stroke of plunger122), draws fluid throughintake passage118 into apumping chamber124 at the end of plunger bore116. Movement ofplunger122 in a second direction, indicated by arrow D inFIG. 3 (herein referred to as a discharge stroke of plunger122), forces fluid out of pumpingchamber124 and through anoutlet119 ofdischarge passage120 and out offluid end110. Plunger bore116 andoutlet passage120 may havestoppers123 sealing one end thereof.Stoppers123 may be metal (e.g. steel) and may be threaded tohousing114. Optionally,stoppers123 may include one or more elastomeric sealing member (e.g. o-rings or gaskets).
• Anintake valve assembly126 is received inintake passage118 and a discharge valve assembly128 (FIG. 2) is received indischarge passage120.
• Each ofintake valve assembly126 and dischargevalve assembly128 has avalve body130, avalve seat132 and aperimeter seal134.
• Valve seat132 has aninner bore136 and afrustoconical sealing surface138.Valve body130 is received ininner bore136 and has a plurality ofarms140 extending into contact withvalve seat132 to centervalve body130 withininner bore136.
• Perimeter seal134 is received in anannular channel142 extending around the underside ofvalve body130. As used herein, references to the “upper” or “top” side or surface ofvalve body130 refer to the surface ofvalve body130 facing away fromvalve seat132. References to the “lower”, “bottom” or “under” side or surface ofvalve body130 refer to the surface facing towardsvalve body130.
• Valve body130 andperimeter seal134 define frustoconical sealing surfaces142,144, respectively, facing sealingsurface138 ofvalve seat132. Sealingsurface138 and sealingsurfaces142 and144 have complementary shapes for cooperatively forming a fluid-tight seal.
• Valve body130 is movable away from valve seat132 (direction θ inFIG. 3) to an open position, and towards valve seat132 (direction C inFIG. 3) to a closed position. As depicted inFIG. 3,valve body130 ofdischarge valve assembly128 is in its open position andvalve body130 ofintake valve assembly126 is in its closed position.
• Valve body130 andvalve seat132 may, for example, be formed from steel or another suitably strong metallic or non-metallic material.Perimeter seal134 may, for example, be formed from elastomeric polyurethane or another resilient and durable elastomer capable of withstanding abrasion and stress due to high pressure flow.
• In the open position, apassage146 is formed betweenvalve seat132 andvalve body130 to permit fluid flow. In the closed position, sealingsurfaces142,144 ofvalve body130 andperimeter seal132 are urged against sealingsurface138 ofvalve seat132.
• Each valve body may be biased towards its closed position by a spring such as a helical spring mounted in compression between a top surface ofvalve body130 and aninternal shoulder148 defined inbore118,120.
• Intake valve assembly126 and dischargevalve assembly128 are pressure actuated. That is, high pressure in pumpingchamber124 relative to pressure outsidefluid end110 acts against the underside ofvalve body130 ofdischarge valve assembly128, causing it to open. Meanwhile, high pressure in pumpingchamber124 acts against the top surface ofvalve body130 ofintake valve assembly126, forcing it closed.
• Conversely, low pressure in pumpingchamber124 relative to the pressure outsidefluid end110 causes opening ofvalve body130 ofintake valve assembly126 and closing of valve body139 ofdischarge valve assembly128.
• In order to prevent fracturing fluid from leakingpast valve assemblies126,128, each valve assembly may form a seal with the wall ofintake passage118 ordischarge passage120. As will be apparent, the seal must be robust in order to prevent leakage despite the high pressures experienced byfluid end110.
• Accordingly, with avalve seat132 installed inintake passage118 ordischarge passage120,outer wall150 of thevalve seat132 matingly engages aninner wall152 of therespective passage118,120.Outer wall150 may be tapered in the closing direction of the valve assembly.Inner wall152 may have a complementary taper. Thus, pressure on the top surface ofvalve body130 urges taperedouter wall150 into tight sealing engagement with taperedinner wall152.Valve seat132 may thus form a fluid-tight seal withpassage118/120, which may tend to be reinforced by application of pressure to close the valve assembly.
• In operation,plunger122 is driven bymotor112 through an alternating sequence of intake and discharge strokes. Each intake stroke causes a drop in pressure in pumpingchamber124 and each discharge stroke causes an increase in pressure in pumpingchamber124. During the intake stroke, pressure upstream ofintake valve assembly126 may be greater than the pressure in pumpingchamber124, causingintake valve assembly126 to open. Fracturing fluid is drawn from reservoir113 throughintake passage118 and into pumpingchamber124. At the end of an intake stroke,plunger122 reverses direction to begin a discharge stroke. The discharge stroke causes an increase in pressure within pumpingchamber124. Elevated pressure inchamber124 acts on the bottom surface ofvalve body130 ofdischarge valve assembly128, causing it to open so that fracturing fluid is forced out offluid end110 through pumpingchamber124 anddischarge passage120. At the same time, pressure in pumpingchamber124 acts on the top surface ofvalve body130 ofintake valve assembly126, causing it to close.
• As noted, the fracturing fluid may include a liquid, such as water, and a particulate proppant, such as sand or ceramic particles, suspended in the liquid. Accordingly,valve assemblies126,128 are configured to form seals even in the presence of particulates. As best shown inFIG. 3, sealingsurface144 ofperimeter seal134 extends downwardly past sealingsurface142 ofvalve body130. Accordingly, whenvalve body130 moves to its closed position, sealingsurface144perimeter seal134contacts sealing surface138 ofvalve seat132 prior to sealingsurface142 ofvalve body130 contacting sealingsurface138.
• Perimeter seal134 andvalve seat132 may therefore form an initial seal. When subjected to closing pressure,perimeter seal134 may conform to any particulates present between sealingsurfaces144,138. That is,perimeter seal134 may deform to form a seal around such particulates.
• After forming of an initial seal betweenperimeter seal134 andvalve seat132, valve body may continue moving towards the closed position until itssealing surface142 abuts and forms a seal with sealingsurface138.
• In order for metal-to-metal contact betweenvalve body130 andvalve seat132 to occur,perimeter seal134 may be compressed and deformed.
• In order to widencracks108 in rock formation102 (FIG. 1),plunger122 may develop very high pressure. In an example,fluid end110 may be rated for pressures of up to 15,000 psi within pumpingchamber124. At such pressure, during the discharge stroke ofplunger122,valve body130 andvalve seat132 ofintake valve assembly126 may be subjected to forces of up to hundreds of thousands of pounds in the closing direction. Such forces may be borne by the interface between sealingsurface138 ofvalve seat132 and each of sealingsurface142 ofvalve body130 and sealingsurface144 ofvalve body130.Valve seat132 may in turn transfer forces tohousing114 offluid end110. In particular, the tapered sealing interface betweenouter wall150 ofvalve seat132 andinner wall152 ofintake passage118 ordischarge passage120 may act as a wedge. That is, the tapered interface may convert stress exerted onvalve body130 into hoop and radial stresses around each of theintake passage118 anddischarge passage120. Such hoop and radial stresses may be particularly high aroundintake passage118 during the discharge stroke ofplunger122 and may frequently cause cracking or failure ofhousing114 offluid end110.
• As will be apparent, the fracturing fluid may be substantially incompressible. Accordingly, pressure in pumpingchamber124 may change rapidly whenplunger122 transitions from an intake stroke to a discharge stroke or vice-versa. Rapid increase of pressure in pumpingchamber124 at the beginning of a discharge stroke may causevalve body130 ofintake valve assembly126 to rapidly move to its closed position. Due to the high pressure generated byplunger122, along with the weight of the valve assembly and closing force imparted by the bias spring, acceleration ofvalve body130 towards its closed position may be sufficient to cause significant impact betweenvalve body130 andvalve seat132. Such impact may impose further stress on one or both ofvalve body130 andvalve seat132, which may cause deterioration or failure of either or both parts.
• Accordingly, in some embodiments,valve assemblies126,128 may be provided with features for mitigating stress or wear.
• FIG. 4 shows a cross-sectional view of anexample valve assembly160, which can be substituted for either ofvalve assemblies126,128.Valve assembly160 has certain parts similar to those ofvalve assemblies126,128, and like parts are indicated with like reference characters. For example,valve body130 andperimeter seal134 ofvalve assembly160 may be substantially identical tovalve body130 andperimeter seal134 ofvalve assemblies126,128.
• Valve assembly160 has avalve seat132′.Valve seat132′ has aninner bore136 and a generallyfrustoconical sealing surface138′. Anannular channel162 may be formed in sealingsurface138′, and a cushioningmember164 may be received inchannel162.
• Cushioningmember162 is interposed betweenvalve body130 andvalve seat132′ and is configured to deceleratevalve body130 as it approaches its closed position. Specifically, when pressure acts on the upper surface ofvalve body130, pushingvalve body130 towardsvalve seat132′, sealingsurface142 ofvalve body130contacts cushioning member164 prior to contactingsealing surface138 ofvalve seat132′.
• Cushioningmember164 may deform upon being contacted byvalve body130, absorbing energy from the valve body and decelerating the movement of the valve body. Such cushioning may mitigate stresses due to impact ofvalve body130 onvalve seat132.
• As depicted,cushioning member164 is an elastomeric ring. Cushioningmember164 may be formed from a resilient elastomer. In some embodiments, the material of cushioningmember164 may be resistant to fatigue, such that cushioning member can be repeatedly compressed to absorb shock and return to its original shape. However, other suitable types of cushioning members may be used. For example, cushioningmember164 could be a helical spring seated inchannel162.Channel162 may be configured so that cushioningmember164 can be compressed such that it is entirely received withinchannel162. That is, when compressed,cushioning member164 may not protrude fromchannel162. When fully received withinchannel162, cushioningmember164 may not interfere with sealing betweenmetal sealing surface142 of valve body, andmetal sealing surface138 of valve seat.
• As depicted inFIG. 4,cushioning member164 is received in achannel162 formed invalve seat132′. In other embodiments, achannel162 may be formed in the underside ofvalve body130 and cushioningmember164 received therein. For example,FIG. 5 depicts avalve assembly160′ with avalve body130 that has achannel162 formed in its underside and a cushioningmember164 received therein.
• In still other embodiments, channels may be formed in both ofvalve body130 andvalve seat132 and cushioning members received in both channels. For example,FIG. 6 depicts avalve assembly160″ includingvalve body130′ with a first channel162aand cushioning member162b; andvalve seat132′ with a second channel162band cushioning member164b. As depicted, cushioning members164a,164bare aligned so that they abut whenvalve body130′ is in the closed position. However, in other embodiments, channels162a,162band cushioning members164a,164bmay be offset.
• In some embodiments, cushioningmember164 may be a helical spring, for example, a metal spring.FIG. 7 depicts one such embodiment, in whichvalve assembly160′″ has a helicalspring cushioning member164. Helicalspring cushioning member164 has alower coil163 received in a channel162aformed in the underside ofvalve body130′, and an upper coil165 received in a channel162bformed invalve seat132′. Whenvalve body130′ is in its closed position, channels162a,162babut one another and helicalspring cushioning member164 is compressed so that it is received entirely within channels162a,162band sealingsurfaces138,142 can engage and seal with one another.
• In other embodiments, cushioningmember164 may be formed from other types of springs. For example, cushioningmember164 may be a Belleville washer.
• FIG. 8 shows a cross-sectional view of anotherexample valve assembly170, which can be substituted for either ofvalve assemblies126,128.Valve assembly170 has certain parts similar to those ofvalve assemblies126,128, and like parts are indicated with like reference characters. For example,valve body130 andperimeter seal134 ofvalve assembly170 may be substantially identical tovalve body130 and perimeter seal ofvalve assemblies126,128.
• Valve assembly170 has a valve seat172. Valve seat172 has aninner bore136 and a generallyfrustoconical sealing surface138. Valve seat172 further has anouter surface174 and an outwardly (e.g. radially) projectingshoulder176 with a radially-extending surface177.
• Unlikeouter surface150 ofvalve seat132,outer surface174 of valve seat172 is cylindrical. That is,outer surface174 does not taper. Valve seat172 may be received in a bore defined inhousing114 with asurface178 that is likewise cylindrical. The bore may have a shoulder with a radially-extendingsurface179 opposing surface177 of valve seat172.
• The cylindrical shape ofsurfaces174,178 may avoid the wedge effect and consequent hoop and radial stress associated with the tapered interface ofsurfaces150,152 (FIG. 3). Whenvalve body130 is forced into its closed position by pressure acting on the top surface ofvalve body130, valve seat172 with its cylindricalouter surface174 may not transfer any radial or hoop stress to the housing in which it is received. Instead, force exerted onvalve body130 may be borne by radially-projectingshoulder176. Force transferred tohousing114 may be along the length of the valve assembly, i.e. in the open-close direction, rather than in the radial direction.Housing114 may be stronger in this direction, and force transferred fromshoulder176 tohousing114 may be less likely to cause cracking or failure ofhousing114.
• Sincesurfaces174,178 are cylindrical, rather than tapered, they may not engage one another as tightly assurfaces150,152 (FIG. 3) and therefore, may not form a metal-to-metal seal with one another. Rather,shoulder176 may have anannular channel180 facinghousing114, and aseal182 may be received therein for sealing with the housing surface. As depicted,seal182 may be an elastomeric ring. However, other configurations are possible.
• As will be apparent, pressure exerted on the top surface ofvalve body130 may result in valve seat172 and thus,shoulder176, being urged againsthousing114. This may likewise biasseal182 against the housing. Thus, high pressure acting onvalve body130 may tend to increase the integrity of the seal formed byseal182.
• In addition, valve seat172 may have a secondannular channel184 formed in its circumferential face, opposingsurface178. Asecond seal186 may be received withinchannel184.
• As noted above, when valve assemblies are subjected to pressure in their closed positions,perimeter seal134 may be squeezed between the valve body and valve seat. In particular,perimeter seal134 may be compressed.Perimeter seal134 may also be subjected to shear stress. Such shear stress may tend to urge theperimeter seal134 out of its channel invalve body130,130′.
• Accordingly, as shown inFIG. 3,perimeter seal134 may have a body183 and an inwardly-projectingflange186 received inchannel142.Flange186 extends at an angle approximately perpendicular to sealingsurface144 ofperimeter seal134. Whenvalve body130,130′ is in its sealing position, with sealingsurface144 urged against the sealing surface of the valve seat,flange186 is pressed intochannel142. Pressing offlange186 intochannel142 may resist deformation or displacement of perimeter seal.
• As depicted inFIG. 3,valve body130,perimeter seal134 andannular channel142 are configured such that sealingsurface138 partly seals with sealingsurface142 and partly seals with sealingsurface144. Regions in which sealingsurface142 directlycontacts sealing surface138 may be referred to as metal-elastomer regions. Regions in which sealingsurface144 directlycontacts sealing surface138 may be referred to as metal-metal regions. As depicted inFIG. 3, the area of sealingsurface142 may be approximately 0.9 times the area of sealingsurface144 and the area of sealingsurface142 may be approximately 0.34 times the area of sealingsurface138. Thus, metal-metal contact regions may occupy 34% of the area of sealingsurface138 and metal-elastomer contact regions may occupy approximately 40% of the area of sealingsurface138.
• During sealing,perimeter seal134 may be compressed untilmetal sealing surface142contacts sealing surface138 ofvalve seat132. Force associated with sealing may be borne entirely or in substantial part by the metal-metal interface betweenvalve body130 andvalve seat132.Perimeter seal134 may experience stress, such as compressive or shear stress, which may be proportional to the amount of deformation of the metal-elastomer region. Stress onperimeter seal134 may cause deterioration ofperimeter seal134, which may in turn lead to failure (e.g. leaking) of the valve assembly. In addition,valve body130 andvalve seat132 may experience stress. Stress and or wearing ofvalve body130,valve seat132 orperimeter seal134 may be inversely related to the area of the metal-metal interface betweenvalve body130 andvalve seat132 during sealing. In other words, increasing the area of metal-metal contact may limit stress on or wearing ofvalve body130,valve seat132 orperimeter seal134.
• Thus, in some embodiments, the valve body and perimeter seal may be configured to limit the size of the metal-elastomer contact area between the perimeter seal and the sealing surface of the valve seat (and correspondingly, to increase the size of the metal-metal contact area betweenvalve body130 and valve seat132).
• FIG. 9 shows one suchexample valve assembly190.Valve assembly190 has avalve body192 andperimeter seal194 configured to provide large metal-metal contact area, but is otherwise generally similar tovalve assemblies126,128 and like components are identified with like reference characters.
• Valve body190 has anannular channel196 extending around the periphery of its underside.Perimeter seal194 has abody198 and aflange200 and is received inchannel196.Body198 defines a sealingsurface202 for sealing against sealingsurface138 ofvalve seat132.Body198 is relatively smaller than body183 (FIG. 3) and sealingsurface202 is likewise smaller than sealingsurface144. In the depicted example, the metal area of valvebody sealing surface142, may be approximately 8 square inches. The area ofelastomer sealing surface202 may be approximately 4.5 square inches. The area of valveseat sealing surface138 may be approximately 16 square inches. Thus, the area of valve body sealing surface may be approximately half of the area of valveseat sealing surface138. Accordingly, when the valve assembly is sealed, about half of the area of valveseat seating surface138 may contactvalve body130. The area ofelastomer sealing surface202 may be approximately 28% of the area of valveseat sealing surface138. Accordingly, when the valve assembly is sealed, about half of the area of valveseat seating surface138 may contactperimeter seal194.
• In some embodiments, these sizes and ratios may vary. Typically, the area of sealingsurface142 ofvalve body130 is between 35% and 60% of the area of sealingsurface138 ofvalve seat132. Typically, the area of metal-to-metal contact is approximately 1.5 to 2.0 times the area of metal-to-elastomer sealing contact.
• Flange200 may have one ormore retention notches204 formed along its length. Whenperimeter seal194 is installed tovalve body190,retention notches204 may receive correspondingtabs206 extending from a wall ofchannel196. The shapes ofnotches204 andtabs206 may be such that reception oftabs206 innotches204locks perimeter seal194 inchannel196. Thus,tabs206 andnotches204 may prevent egress of perimeter seal fromchannel196 whenvalve body190 is pressed againstvalve seat132.
• In other embodiments,notches204 andtabs206 may be omitted, in whichcase perimeter seal194 may be retained inchannel196 by urging offlange200 intochannel196 whenperimeter seal194 is compressed.FIG. 10 depicts such an embodiment, in whichvalve body190 has achannel196′ that is identical to channel196 except that it lackstabs206. Aperimeter seal194′ is received inchannel196 and is identical toperimeter seal194 except that it lacksnotches204.
• In some embodiments,perimeter seal194 may be bonded inchannel196 using an adhesive bonding agent. For example, a bonding agent may be applied tochannel196, and molten elastomer may be poured intochannel196. The molten elastomer may harden to formperimeter seal194.
• Perimeter seal194 may be sized to deform between the valve and valve seat under pressure without allowing by-pass of fluid. For example,perimeter seal194 may be sufficiently large to deform and form a seal around particulates suspended in the fluid pumped byfluid end110.
• In some embodiments, valve assemblies may include some or all of the features disclosed herein for mitigating stress and wear effects. For example,FIG. 11 depicts onesuch valve assembly300.Valve assembly300 includes avalve body302 and avalve seat304, the latter received in an intake or discharge passage inhousing114 offluid end110.
• Valve body302 has an inner bore306 and anouter surface308, and a sealingsurface310.Outer surface308 is cylindrical and the passage ofhousing114 in which it is received is likewise cylindrical.Valve seat304 also has a radially-projectingflange310 which bears against a radial shoulder defined byhousing114. Aseal member312 is disposed betweenflange310 and the housing shoulder, to define a seal that is reinforced by pressure exerted on the top ofvalve body302.
• Sealingsurface308 ofvalve seat304 has anannular channel310, in which acushioning member312 is received to absorb energy from closing ofvalve assembly300 and thereby limit impact stress onvalve body302 andvalve seat304. As depicted,cushioning member312 is an elastomeric ring. However, cushioningmember312 may be any type of cushioning member as described above.
• Valve seat304 also has anannular channel314 extending around the periphery of its underside, in which aperimeter seal316 is received.Perimeter seal316 andchannel314 are configured similarly toperimeter seal194 andchannel196 discussed above. In particular,perimeter seal316 has a body318 and a flange320 extending intochannel314 and is configured so that, whenvalve assembly300 is closed, the area of metal-to-metal sealing contact betweenvalve body302 andvalve seat304 is approximately half of the area of sealingsurface310. Likeperimeter seal194 andchannel196,perimeter seal316 andannular channel314 haveretention notches322 andtabs324 to lockperimeter seal316 inannular channel314.
• Methods of pumping fluids down a well bore may be performed using pumps with valve assemblies as disclosed herein. For example, a fluid end may be provided, with onevalve assembly300 acting as an intake valve and one valve assembly acting as a discharge valve. Plunger122 (FIG. 3) may be moved through an intake stroke to draw fluid from a reservoir through anintake valve assembly300 and into pumpingchamber124. During the intake stroke, pressure differential acrossintake valve assembly300 causes theintake valve assembly300 to open anddischarge valve assembly300 to close.
• Plunger122 may be moved through a discharge stroke, which may pressurize fluid in pumpingchamber124. Positive pressure inchamber124 may causeintake valve assembly300 to close anddischarge valve assembly300 to open. Movement ofplunger122 likewise causes fluid to be forced throughdischarge valve assembly300 and into well bore100.
• Just after the beginning of the intake stroke, pressure inchamber124 drops such that pressure upstream ofintake valve assembly300 is greater than pressure downstream ofintake valve assembly300, which causesintake valve assembly300 to open. Just after the beginning of the discharge stroke, pressure inchamber124 rises, causingdischarge valve assembly300 to close. The pressures may change quickly, resulting in rapid movement ofvalve bodies302.Valve bodies302 may contact and compresscushioning members312 andflange310 may be urged againsthousing114 to seal therewith.
• The preceding discussion provides many example embodiments. Although each embodiment represents a single combination of inventive elements, other examples may include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, other remaining combinations of A, B, C, or D, may also be used.
• Although the embodiments have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope as defined by the appended claims.
• Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps
• As can be understood, the examples described above and illustrated are intended to be exemplary only. The invention is defined by the claims.

Claims (25)

What is claimed is:

1. A pump for pumping fluid down a well bore in a rock formation, comprising:

an intake passage in communication with a fluid reservoir;

a discharge passage in communication with said well bore in said rock formation;

a pumping chamber with a plunger received therein for pumping fluid from said reservoir to said well bore by reciprocation of said plunger;

intake and discharge valve assemblies in said intake passage and said discharge passage, respectively, for selectively sealing said intake and discharge passages, at least one of said intake and discharge valve assemblies comprising a valve body and a valve seat, said valve body movable into sealing contact with said valve seat by fluid pressure;

a cushioning member interposed between said valve body and said valve seat.

2. The pump ofclaim 1, wherein said valve body contacts said cushioning member prior to contacting said valve seat, thereby decelerating said valve body.

3. The pump ofclaim 1, wherein said cushioning member comprises an elastomeric ring.

4. The pump ofclaim 1, wherein said cushioning member comprises a spring.

5. The pump ofclaim 1, wherein said cushioning member is received in a channel in said valve seat.

6. The pump ofclaim 1, wherein said cushioning member is received in a channel in said valve body.

7. The pump ofclaim 4, wherein, during sealing contact of said valve body and said valve seat, said cushioning member is compressed such that it does not protrude from said channel.

8. The pump ofclaim 5, further comprising a second cushioning member received in a channel in said valve body.

9. The pump ofclaim 1, wherein said valve seat has a cylindrical outer surface for mating reception in said intake passage, and a shoulder with a radially-projecting surface biased against a wall of said intake passage by pressure in said pumping chamber, for sealing therewith.

10. The pump ofclaim 9, further comprising a compressible seal positioned about the perimeter of said valve body and interposed between said valve body and said valve seat, said compressible seal configured so that, with said valve body in sealing contact with said valve seat, between 35% and 60% of a sealing surface of said valve seat is in contact with said valve body.

11. A pump for pumping fluid down a well bore in a rock formation, comprising:

an intake passage in communication with a fluid reservoir;

a discharge passage in communication with said well bore in said rock formation;

a pumping chamber with a plunger received therein for pumping fluid from said reservoir to said well bore by reciprocation of said plunger;

intake and discharge valve assemblies in said intake passage and said discharge passage, respectively, for selectively sealing said intake and discharge passages, at least one of said intake and discharge valve assemblies comprising a valve body and a valve seat;

said valve body movable by fluid pressure into sealing contact with said valve seat;

said valve seat having a cylindrical outer surface for mating reception in said intake passage or said discharge passage, and a shoulder with a radially-projecting surface biased against a wall of said passage by pressure in said pumping chamber, for sealing therewith.

12. The pump ofclaim 11, further comprising a resilient seal member interposed between said radially-projecting shoulder and said wall of said intake or discharge passage.

13. The pump ofclaim 12, further comprising a resilient seal member interposed between said cylindrical outer surface of said valve seat and a wall of said intake or discharge passage.

14. The pump ofclaim 12, wherein said resilient seal member is received in a channel in said shoulder.

15. The pump ofclaim 11, further comprising a compressible seal positioned about the perimeter of said valve body and interposed between said valve body and said valve seat, said compressible seal configured so that, with said valve body in sealing contact with said valve seat, between 35% and 60% of a sealing surface of said valve seat is in contact with said valve body.

16. A pump for pumping fluid down a well bore in a rock formation, comprising:

an intake passage in communication with a fluid reservoir;

a discharge passage in communication with said well bore in said rock formation;

a pumping chamber with a plunger received therein for pumping fluid from said reservoir to said well bore by reciprocation of said plunger;

intake and discharge valve assemblies in said intake passage and said discharge passage, respectively, for selectively sealing said intake and discharge passages, said intake valve assembly comprising a valve body and a valve seat;

said valve body movable by fluid pressure into sealing contact with said valve seat;

a compressible seal positioned about the perimeter of said valve body and interposed between said valve body and said valve seat, said compressible seal configured so that, with said valve body in sealing contact with said valve seat, between 35% and 60% of a sealing surface of said valve seat is in contact with said valve body.

17. The pump ofclaim 16, wherein said compressible seal is received in a channel defined in said valve body.

18. The pump ofclaim 17, wherein said compressible seal has a notch for receiving a corresponding tab projecting from said valve body to lock said compressible seal in said channel.

19. The pump ofclaim 16, further comprising a cushioning member interposed between said valve body and said valve seat.

20. The pump ofclaim 1, wherein said pump is for hydraulic fracturing in said reservoir.

21. The pump ofclaim 11, wherein said pump is for hydraulic fracturing in said reservoir.

22. The pump ofclaim 16, wherein said pump is for hydraulic fracturing in said reservoir.

23. A method of pumping fluid into a wellbore, comprising:

drawing a fluid through an intake valve of the pump ofclaim 1 by moving said plunger through an intake stroke;

moving said plunger through a discharge stroke, thereby pressurizing fluid in said chamber, closing said intake valve and opening said discharge valve and forcing said fluid through said discharge valve into said wellbore.

24. A method of pumping fluid into a wellbore, comprising:

drawing a fluid through an intake valve of the pump ofclaim 11 by moving said plunger through an intake stroke;

moving said plunger through a discharge stroke, thereby pressurizing fluid in said chamber, closing said intake valve and opening said discharge valve and forcing said fluid through said discharge valve into said wellbore.

25. A method of pumping fluid into a wellbore, comprising:

drawing a fluid through an intake valve of the pump ofclaim 16 by moving said plunger through an intake stroke;

moving said plunger through a discharge stroke, thereby pressurizing fluid in said chamber, closing said intake valve and opening said discharge valve and forcing said fluid through said discharge valve into said wellbore.

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