Patent Application
20130340873
Not applicable.
The disclosure relates generally to apparatus for reducing turbulence in a fluid stream and damping pressure pulsations propagated by the fluid. More particularly, the disclosure relates to a flow straightening device that reduces turbulence in moving fluid. Still more particularly, it relates to a flow straightener that reduces turbulence of drilling fluid passing through a mud pump and that dampens pressure pulsations propagated by the drilling fluid.
To form an oil or gas well, a bottom hole assembly (BHA), including a drill bit, is coupled to a length of drill pipe to form a drill string. Instrumentation for performing various downhole measurements and communication devices are commonly mounted within the drill string. The drill string is then inserted downhole, where drilling commences. During drilling, fluid, or “drilling mud,” is circulated down through the drill string to lubricate and cool the drill bit as well as to provide a vehicle for removal of drill cuttings from the borehole.
Mud pumps are commonly used to deliver drilling mud to the drill string during drilling operations. Many conventional mud pumps include a piston-cylinder assembly hydraulically coupled to a compression chamber disposed between a suction module and a discharge module. The suction module is coupled to a suction manifold through which drilling mud is supplied to the mud pump, and the discharge module is coupled to a discharge manifold into which pressurized drilling mud is exhausted from the mud pump. The suction module includes a valve which is operable to allow or prevent the flow of drilling mud from the suction manifold into the compression chamber. Similarly, the discharge module includes a valve which is operable to allow or prevent the flow of pressurized drilling mud from the compression chamber into the discharge manifold. Each valve has a closure member or poppet that is urged into sealing engagement with a sealing member or seat by a biasing member, such as a spring.
During operation of the mud pump, the piston reciprocates within its associated cylinder. As the piston moves to expand the volume within the cylinder, the discharge valve closes, and suction valve opens. Drilling mud is drawn from the suction manifold through the suction valve into the compression chamber. When the piston reverses direction, decreasing the volume within the cylinder and increasing the pressure of drilling mud contained with the compression chamber, the suction valve closes, and the discharge valve opens to allow pressurized drilling mud from the compression chamber into the discharge manifold. While the mud pump is operational, this cycle repeats, often at a high cyclic rate, and pressurized drilling mud is continuously fed to the drill string.
Due to the reciprocating motion of the mud pump piston, cyclic loads are transferred to the suction module by virtue of its coupling to the mud pump. The transferred loads cause cyclic deformation of the suction module. Consequently, pressure pulsations are created within and propagated by the drilling mud passing therethrough.
Additionally, because the suction module typically includes piping elbows, bends, and “Ts,” drilling mud flowing from the suction manifold into the suction module, upstream of the suction valve, is often highly turbulent. When the suction valve opens, the turbulent drilling mud flows rapidly into the compression chamber. Due to the turbulent nature of the drilling fluid, bubbles form within the compression chamber as the drilling fluid flows rapidly around the suction valve poppet. When the piston subsequently compresses the drilling mud within the compression chamber, these bubbles burst, creating additional pressure pulsations within the drilling mud.
The formation of bubbles within the compression chamber due to the turbulent nature of drilling mud passing around the suction valve poppet reduces the efficiency of the mud pump. Moreover, pressure pulsations created within and carried by the drilling mud disturb downhole communication devices and instrumentation, and potentially degrade the accuracy of measurements taken by the instrumentation. Over time, the pressure pulsations may also cause fatigue damage to the drill string pipe.
Accordingly, there is a need for apparatus that reduces turbulence within drilling mud systems and that dampens pressure pulsations caused by the reciprocating motion of mud pumps coupled thereto.
A flow straightener includes a conduit segment and a plurality of elongate vanes. The conduit segment has an inner surface and an interior volume for conveying the fluid in a predetermined direction of flow. The elongate vanes are disposed within the interior volume. Each of the vanes has a radially innermost edge and a radially outermost edge. The innermost edges of the vanes are spaced apart from one another so as to provide a core portion of the interior volume that is generally free of obstruction.
In some embodiments, the flow straightener includes the conduit section and a plurality of pins that support the vanes within the interior volume. The pins are flexibly coupled to the inner surface of the conduit segment. Likewise, in certain embodiments, the flexible coupling includes an elastomeric insert having tapered sides that engage correspondingly tapered sides of a recess formed in the conduit section. The cross-sectional shape of the pins may be noncircular in various embodiments.
Thus, embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with certain prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, and by referring to the accompanying drawings.
For a detailed description of the disclosed embodiments, reference will now be made to the accompanying drawings in which:
The following description is directed to an exemplary embodiment of a drilling fluid system including a fluid flow straightener. The embodiment disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. One skilled in the art will understand that the following description has broad application, and that the discussion is meant only to be exemplary of the described embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment. For example, the apparatus described herein may be employed in any fluid conveyance system where it is desirable to reduce the turbulence of fluid contained within or moving through the system.
Certain terms are used throughout the following description and the claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. Moreover, the drawing figures are not necessarily to scale. Certain features and components described herein may be shown exaggerated in scale or in somewhat schematic form, and some details of conventional elements may not be shown in interest of clarity and conciseness.
In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections. Further, the terms “axial” and “axially” generally mean along or parallel to a central or longitudinal axis. The terms “radial” and “radially” generally mean perpendicular to the central or longitudinal axis, while the terms “azimuth” and “azimuthally” generally mean perpendicular to both the central or longitudinal axis and a radial axis normal to the central longitudinal axis. As used herein, these terms are consistent with their commonly understood meanings with regard to a cylindrical coordinate system.
Referring now to
Pump assembly 105 includes a pump 125 and a valve assembly 120. Pump 125 is a reciprocating pump, having a piston 185 slidingly disposed within a cylinder 190. Valve assembly 120 includes a suction module 130, a discharge module 135, and a fluid conduit or compression chamber 140 disposed therebetween. Pump 125, suction manifold 110, and discharge manifold 115 are each hydraulically or fluidicly coupled to compression chamber 140. Suction module 130 includes a valve 145 that is operable to allow or prevent the flow of fluid from suction manifold 110 into compression chamber 140. Suction valve 145 has a closure member or poppet 155 that is urged into sealing engagement with a sealing member or seat 160 by a biasing member 165, such as a spring. Similarly, discharge module 135 includes a valve 150 that is operable to allow or prevent the flow of pressurized fluid from compression chamber 140 into discharge manifold 115. Discharge valve 150 also has a closure member or poppet 170 that is urged into sealing engagement with a sealing member or seat 175 by a biasing member 180, such as a spring.
Flexible connection 195 is configured to reduce the transfer of cyclic loads produced by the reciprocating motion of pump 125 from pump assembly 105 to suction manifold 110. Such loads cause cyclic deformation of suction manifold 110, which, in turn, produces pressure pulsations within fluid passing through suction manifold 110. As previously described, pressure pulsations may disturb downstream instrumentation and communication devices, and/or cause fatigue damage to downstream piping.
In the embodiment shown in
Turning now to
Conduit segment 205 further includes a plurality of axially extending throughbores 215 circumferentially spaced about segment 205 near its perhiphery. Throughbores 215 enable coupling of flow straightener 200 between flexible connection 195 and suction manifold 110. To couple flow straightener 200 between flexible connection 195 and suction manifold 110, as shown in
Conduit segment 205 further includes a plurality of throughbores 230, each throughbore 230 extending radially between a generally cylindrical outer surface 235 of segment 205 and flowbore 210. As shown in
Each flexible insert 265 is generally cup-shaped and is insertable within an inner portion 240 of one throughbore 230. In this embodiment, flexible inserts 265 are formed of elastomeric material. As best viewed in
Referring still to
Each pin 260 is configured to be insertable within a recess 290 of an insert 265. Pin 260 is preferably made from stainless steel for its ability to resist corrosion when exposed to the drilling fluid, but may also be made of other steel alloys or reinforced composite materials. As best viewed in
Base 305 of pin 260 is configured to be received within recess 290 of insert 265, as shown in
Turning now to
Each vane 270 further includes a tapered nose portion 330 and tail portion 335 extending therefrom. In this embodiment, nose portion 330 has a linear, leading surface 340, and tail portion 335 that is rectangular in shape. In other embodiments, leading surface 340 may be nonlinear or curved. The taper of nose portion 330 is characterized by a nose angle 365 formed between leading surface 340 and a longitudinally extending outer surface 360 of vane 270. In the embodiment shown, nose angle 365 is approximately equal to 45 degrees. In other embodiments, however, nose angle 365 may be greater or less than 45 degrees. Nose angle 365 is generally within the range of 30 to 60 degrees, and preferable within the range 30 to 45 degrees. Further, in some embodiments, a leading edge of nose portion 330 is hammed, meaning a small width of the leading edge is folded over itself such that it forms a rigid and slightly rounded leading edge. This results in increased stiffness of the leading edge, and thus nose portion 330.
Further, vane 270 has a length 350, measured from a tip 355 of nose portion 330 along outer surface 360, and a width 345, measured from an end 370 of tail portion 335 along an outer surface 375 normal to surface 360. In some embodiments, the ratio of length 350 to a diameter 212 (
Second, because vanes 270 extend longitudinally along flowbore 210, vanes 270 provide some resistance to fluid flow through drilling fluid system 100. The capacity of pump 125 must be sufficient to overcome the flow resistance through drilling fluid system 100, including that resistance created by vanes 270, in order to deliver pressurized fluid to discharge manifold 115 at a desired rate. Increasing width 345 of vanes 270 beyond that which is needed to reduce fluid turbulence, including by extending vanes 270 fully across flowbore 210, for example, would further obstruct fluid flow through system 100 and increase the flow resistance which pump 125 must overcome. A consequence of obstructing fluid flow through flowbore 210 too much is that insufficient fluid is provided to pump 125, which may result in cavitation.
Each vane 270 is not entirely rigid, but may flex and elastically bend to some degree as it resists turbulent fluid flow and provides a fluid-straightening effect. This flexure is a result both of the vane's dimensions, including its substantial length relative to its width, and the substantial narrowness of its thickness in relation to length and width. Such flexure is also provided by attaching vane 270 to pin 260 relatively close to one end, for instance nose 330, and relatively far from the second end, for instance tail 335. Still further flexure is provided by employing the resilient insert 265 used in securing pin 260 to conduit segment 205.
Notwithstanding the description above regarding the capabilities of vanes 270 to flex when used in the embodiment described with reference to
Referring next to
Although each vane 270 extends longitudinally in direction 390 generally parallel to the flow direction 380, direction 390 need not be perfectly parallel to the flow direction 380. Rather, in some embodiments, illustrated by
Furthermore, the width 345 (
Referring again to
Drilling fluid system 100 includes flow straightener 200 which is configured to reduce the turbulence of fluid passing from suction manifold 110. Vanes 270 of flow straightener 200 subdivide turbulent fluid from suction manifold 110 between channels 425 through which the fluid passes. In doing so, vanes 270 redirect or straighten the fluid flow such that it is more uniform, and therefore less turbulent.
Further, vanes 270 are configured to minimize the disruption to the fluid flow caused by the initial contact of the fluid with vanes 270. Fluid passing from suction manifold 110 into flow straightener 200 initially contacts vanes 270 over leading surfaces 340 of nose portions 330. Due to the taper of nose portions 330, meaning the angular orientation of leading surfaces 340 relative to the fluid flow direction 380, contact between the fluid and vanes 270 gradually increases over the length of leading surfaces 340. Were nose portions 330 not tapered and leading surfaces 340 normal to the fluid flow direction 380, contact between the fluid and vanes 270 would not be a gradual, but a blunt interaction that creates additional turbulence in the fluid. Thus, the taper of nose portion 330 reduces this undesirable effect.
Moreover, vanes 270 are oriented to further minimize the disruption to the fluid flow. Fluid passing from suction manifold 110 into flow straightener 200 is typically more turbulent in a near-wall region 435 (
Still further, the shape of pins 260 may be selected to minimize the resistance of pins 260 to, and therefore the pressure decrease of, fluid flow passing through flowbore 210 of flow straightener 200. Fluid passing from suction manifold 110 into flow straightener 200 initially contacts each tapered nose 330 of vanes 270 and is divided or separated into two fluid streams. Each stream then flows along opposite sides of vane 270 toward cylindrical portion 300 of pin 260 supporting vane 270. When each stream contacts portion 300, it flows around portion 300. Because portion 300 is cylindrical in shape, a low pressure region is created proximate the apex zone 262 of pin 260. Fluid is drawn into this low pressure region, and assumes the velocity of fluid near the surface of pin 260. After flowing around pin 260, each fluid stream continues along length 350 of vane 270 toward tail 335 where both streams reunite. Length 350 of vane 270 may be selected such that both streams have substantially the same velocity when they reunite at tail 335 of vane 270. The effect of cylindrically-shaped portion 300 of pin 260 enables a lower pressure drop across pin 260 than would otherwise be obtained with a pin having a different shape.
As fluid passes through flow straightener 200, the size of the radial cross-section of each outer portion 245 of throughbores 230 in conduit segment 205 relative to that of the radial cross-section of each inner portion 240 in which inserts 265 are disposed enable pins 260 to maintain the position of vanes 270. Fluid passing through flowbore 210 of flow straightener 200 exerts pressure loads on tops 280 of inserts 265. Because the diameter of outer portions 245 of throughbores 230 is smaller than that of inner portions 240 at their bases 255, inserts 265 are prevented from disengaging throughbores 230 by extruding through outer portions 245 in response to the pressure load. Instead, flexible inserts 265 are simply compressed by the pressure loads within inner portions 240 of throughbores 230, and the pre-selected positions of vanes 270 are maintained.
Also, as fluid passes through flow straightener 200, the cross-sectional shapes of recesses 290 of inserts 265 and bases 305 of pins 260 disposed therein enable pins 260 to maintain the orientation of vanes 270. Fluid passing through flowbore 210 of flow straightener 200 contacts vanes 270 and imparts loads thereto. Even so, vanes 270 are prevented from rotating in response to the loads due to the interaction between recesses 290 of inserts 265 and bases 305 of pins 260. As described above, the shape of surfaces 295, which bound recesses 290 in which bases 305 of pins 260 are disposed, and the shape of surfaces 320 of bases 305 are configured to prevent rotation of pins 260 relative to inserts 265.
As described, flow straightener 200 includes a number of features, each of which enables the reduction of the turbulence within fluid passing from suction manifold 110. Consequently, fluid entering valve assembly 120 contacts poppet 155 of suction valve 145 more uniformly, reducing the tendency for poppet 155 to flutter, or act unstably. Moreover, fewer bubbles are created as the comparatively less turbulent fluid passes around poppet 155 into compression chamber 145. Reduced fluttering of poppet 155 and fewer bubbles within compression chamber 145 enable increased efficiency of pump 125. Also, fewer pressure pulsations are created within the fluid during the compression cycle of pump 125.
Furthermore, flow straightener 200 is configured to dampen pressure pulsations created within fluid upstream of flow straightener 200, such as those created by cyclic deformation of suction manifold 110. Pressure pulsations created in fluid upstream of flow straightener 200 are carried by the fluid as the fluid flows toward and into flow straightener 200. When the fluid contacts vanes 270 of flow straightener 200, pressure forces, or loads, are imparted to vanes 270 by the fluid. The imparted loads are then transferred through vanes 270 and pins 260 coupled thereto to flexible inserts 265, where the pressure loads are absorbed.
The above-described embodiment is directed to a drilling fluid system 100 for pressurizing drilling mud. Drilling fluid system 100 includes a flow straightener 200 in accordance with the principles disclosed herein. Flow straightener 200 is positioned downstream of suction manifold 110, and is configured to reduce the turbulence of and pressure pulsations propagated by drilling fluid passing therethrough. Reductions in flow turbulence enable increased efficiency of pump 125. Moreover, reductions in pressure pulsations propagated by the drilling fluid decrease disturbances to downhole instrumentation and lessen the likelihood of fatigue damage to downstream piping.
One of ordinary skill in the art will readily appreciate the applicability of the flow straightener in other positions within drilling fluid system 100. For example, a flow straightener may be positioned on the discharge side of pump assembly 105. In such embodiments, it is sometimes desirable for fluid flow on the discharge side to have a higher level of turbulence, as compared to that of fluid entering the suction side of pump assembly 105. Consequently, angle 395 and/or angle 410 may be selectably adjusted to increase the turbulence of fluid passing through the flow straightener.
Also, one of ordinary skill in the art will readily appreciate the applicability of a flow straightener in accordance with the principles disclosed herein within other types of fluid conveyance systems wherein it is desired to reduce fluid turbulence and/or dampen pressure pulsations propagated by a fluid. Thus, the flow straightener disclosed herein is not limited to the context of a drilling fluid system.
While various embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings herein. The embodiments herein are exemplary only, and are not limiting. Many variations and modifications of the apparatus disclosed herein are possible and within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.
The present application is a continuation of U.S. patent application Ser. No. 12/478,015, filed on Jun. 4, 2009, entitled “Apparatus For Reducing Turbulence In A Fluid Stream”, the disclosure of which is incorporated herein by reference.
