Blender for Frac Fluids

Abstract

The density of slurries produced by mobile blender for injection into oil and gas wells is controlled using a microwave flow meter. Liquid having a known density is provided to the blender. The liquid is flowed through a conduit and discharged into a blending tub on the mobile blender. The amount of liquid introduced into the tub is measured with a liquid flow meter. Solid particulates having a known density are provided to the blender. The particulates are discharged into the tub by allowing them to fall into the tub from a conveyor on the mobile blender. The amount of the particulates falling into the tub are measured with a microwave flow meter. The flow of the liquid and the particulates are controlled in response to the measurements to blend a slurry having a predetermined density. The slurry is provided for injection into the well.

Claims

1. A method of controlling the density of a slurry for injection into a well as said slurry is blended by a mobile blending apparatus, said slurry comprising particulates suspended in liquid; said method comprising: (a) providing liquid having a known density to said blender; (b) flowing said liquid through a conduit and discharging said liquid into a blending tub on said mobile blender; (c) measuring the amount of liquid introduced into said tub with a liquid flow meter; (d) providing solid particulates having a known density to said blender; (e) discharging said particulates into said tub by allowing them to fall into said tub from a conveyor on said mobile blender; and (f) measuring the amount of said particulates falling into said tub with a microwave flow meter; (g) controlling the flow of said liquid and said particulates in response to said measurements to blend a slurry having a predetermined density; and (h) providing said slurry for injection into said well.

2. The method of claim 1, wherein said liquid is measured using a magnetic resonance or turbine flow meter.

3. The method of claim 1, wherein said conveyor is a screw auger and the flow of said particulates is controlled by varying the speed of said auger.

4. The method of claim 1, wherein said conveyor discharges said particulates through a gravity flow metering device and the flow of said particulates is controlled by adjusting said device.

5. The method of claim 1, wherein said mobile blender comprises a centrifugal pump in said conduit and the flow of said liquid is controlled by varying the speed of said pump.

6. The method of claim 1, wherein said conduit comprises a flow control valve and the flow of said liquid is controlled by adjusting said valve.

7. A mobile apparatus for blending liquid and particulates into a slurry, said blender comprising: (a) a chassis; (b) a blending tub mounted on said chassis; (c) a suction system adapted to discharge liquid into said tub, said suction system comprising a flow meter adapted to measure the flow of liquid through said suction system; (d) a solids system adapted to discharge solid particulates into said tub, said solids system comprising a conveyor and a microwave flow meter adapted to measure the flow of said particulates discharged by said conveyor as said particulates fall into said tub; and (e) a controller operatively connected to said suction system, said flow meter, said solids system, and said microwave flow meter and adapted to control the rate of liquid and solids discharged into said tub by, respectively, said suction system and said solids system in response to input from said liquid flow meter and said microwave flow meter to produce a slurry having a predetermined density.

8. The mobile blending apparatus of claim 7, wherein: (a) said suction system comprises: i) a suction line adapted to convey fluid into said tub; and ii) a pump adapted to pump fluid through said suction line; iii) wherein said flow meter is provided in said suction line; and (b) wherein said controller is operatively connected to said pump and is adapted to control the rate of liquid discharged into said tub by controlling the speed of said pump.

9. The mobile blending apparatus of claim 7, wherein: (a) said suction system comprises: i) a suction line adapted to convey fluid into said tub; ii) a pump adapted to pump fluid through said suction line; and iii) a flow control valve; iv) wherein said flow meter and said flow control valve are provided in said suction line; and (b) wherein said controller is operatively connected to said flow control valve and is adapted to control the rate of liquid discharged into said tub by adjusting said flow control valve.

10. The mobile blending apparatus of claim 7, wherein said controller is operatively connected to said conveyor and is adapted to control the rate of solids discharged into said tub by controlling the speed of said conveyor.

11. The mobile blending apparatus of claim 7, wherein: (a) said solids system comprises a gravity flow metering device adapted to receive the discharge from said conveyor; and (b) said controller is operatively connected to said metering device and is adapted to control the rate of solids discharged into said tub by adjusting said metering device.

12. The blender of claim 7, wherein said solids system comprises a discharge chute having surfaces adapted to guide the flow of said particulates proximate to said microwave flow meter.

13. The blender of claim 12, wherein said chute is mounted below the discharge end of said conveyor and above said tub such that particulates discharged from said conveyor fall through said chute and into said tub.

14. The blender of claim 13, wherein said solids system comprises a plurality of said conveyors, said chute comprises an open receiving portion adapted to receive said particulates discharged by said plurality of conveyors and guide said particulates into a plurality of outlet ducts, and a said microwave flow meter is mounted in each said outlet duct.

15. (canceled)

16. (canceled)

17. A system for introducing solid particulates into a mixing tub on a mobile apparatus for blending liquid and particulates into a slurry, said solids system comprising: (a) a supply bin; (b) a conveyor mounted on said mobile blender and adapted to transport said particulates from a receiving end communicating with said supply bin to a discharge end elevated above said tub; (c) a baffle mounted below said discharge end of said conveyor and above said tub such that particulates discharged from said conveyor fall on said baffle and then into said tub; (d) said baffle adapted to divide said particulates into a plurality of streams.

18. The solids system of claim 17, wherein said baffle is a plate having a plurality of openings.

19. The solids system of claim 18, wherein said openings are obround.

20. The solids system of claim 18, wherein said openings are arranged in offset, linear arrays.

21. The solids system of claim 18, wherein said baffle comprises a plate mounted at an angle such that said openings are situated at a plurality of elevations and said particulates discharged onto said baffle plate are directed downward across said plate.

22. The solids system of claim 17, wherein said baffle comprises a chute mounted under said conveyor discharge end and having surfaces adapted to guide the flow of said particulates onto said baffle plate.

23. The solids system of claim 17, wherein said conveyor is a screw auger.

24. (canceled)

25. (canceled)

26. (canceled)

27. (canceled)

28. (canceled)

29. (canceled)

30. (canceled)

31. (canceled)

32. (canceled)

33. (canceled)

34. (canceled)

35. (canceled)

36. (canceled)

37. (canceled)

38. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] FIG. 1 (prior art) is a schematic view of a system for fracturing a well and receiving flow back from the well, which system includes a conventional blender 6.

[0066] FIG. 2 is an isometric view, taken generally from one side and above, of a preferred embodiment 100 of the novel blender units of the subject invention which shows the suction side of blender 100.

[0067] FIG. 3 is an isometric view, similar to the view of FIG. 1 except that it is taken from the other side, of blender 100 showing its discharge side.

[0068] FIG. 4 is an enlarged isometric view taken from the suction side of blender 100 showing suction system 34 of blender 100.

[0069] FIG. 5 is an enlarged view of the suction side of blender 100 having suction system 34 removed to show suction bracket system 25 for mounting suction system 34.

[0070] FIG. 6 is an enlarged isometric view taken from the discharge side of blender 100 showing discharge system 60 of blender 100 and portions of mixing system 40 and power system 70.

[0071] FIG. 7 is another enlarged isometric view, similar to the isometric view of FIG. 6 except that it is taken somewhat below blender 100, showing portions of discharge system 60 and power system 70.

[0072] FIG. 8 is another enlarged isometric view from the discharge side of blender 100 having discharge system 60 removed, which view shows portions of power system 70 and discharge bracket system 26 for mounting discharge system 60.

[0073] FIG. 9 is an isometric view showing, in isolation, solids system 50 used in blender 100.

[0074] FIG. 10 is an isometric view showing, in isolation, another preferred solids system 150 that may be used in blender 100.

[0075] FIG. 11 is another isometric view, taken from in front and below, of solids system 150.

[0076] FIG. 12A is an axial cross-sectional view of a first novel vortex breaker 80 which may be incorporated into blender 100.

[0077] FIG. 12B is a lateral cross-sectional view of vortex breaker 80 shown in FIG. 12A.

[0078] FIG. 13A is an axial cross-sectional view of a second novel vortex breaker 85 which may be incorporated into blender 100.

[0079] FIG. 13B is a lateral cross-sectional view of vortex breaker 85 shown in FIG. 13A.

[0080] FIG. 14 is a schematic view of portions of power system 70 illustrating a novel cooling system 90 for engines 71 of power system 70.

[0081] In the drawings and description that follows, like parts are identified by the same reference numerals. The drawing figures are not necessarily to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional design and construction may not be shown in the interest of clarity and conciseness.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0082] The invention, in various aspects and embodiments, is directed generally to blender units used in fluid transportation systems, and especially to systems that are used to prepare and convey abrasive, corrosive fluids as are employed in temporary systems for oil and gas well fracturing operations. Various specific embodiments will be described below. For the sake of conciseness, all features of an actual implementation may not be described or illustrated. In developing any actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve a developers' specific goals. Decisions usually will be made consistent within system-related and business-related constraints, and specific goals may vary from one implementation to another. Development efforts might be complex and time consuming and may involve many aspects of design, fabrication, and manufacture. Nevertheless, it should be appreciated that such development projects would be a routine effort for those of ordinary skill having the benefit of this disclosure.

[0083] The novel blender units typically will be used in temporary fluid transportation systems. They are particularly useful for temporary installations that must be assembled and disassembled on site and which may be installed at one site and then another. Such systems are common in chemical and other industrial plants, on marine dredging vessels, strip mines, and especially in the oil and gas industry. Frac systems, such as those shown in FIG. 1, are a very common application where temporary fluid transportation systems are routinely assembled and disassembled at various sites to fracture different wells.

[0084] A preferred embodiment 100 of the novel blenders is shown generally in FIGS. 2-3. Blender 100 is particularly suited for use in frac systems such as the system shown in FIG. 1. Blender 100 is mounted on a trailer 20. Trailer 20 is a conventional trailer and generally comprises a frame 23 upon which the various components of blender 100 will be mounted, either directly or indirectly. It also comprises wheels, axels, and a suspensions system, and a hook up mechanism allowing it to be hitched to a truck or other vehicle. Typical safety systems and accessories also will be provided on trailer 20. The interface for various conventional control systems will largely be provided in a cabin 21 mounted on trailer 20. Ladders and platforms also will be provided to allow access to various operational components.

[0085] Such features and others are well known in trailers of this type and may be employed as required or desirable. Likewise, while blender 100 is mounted on a rolling chassis such as trailer 20, the novel blenders may be carried on the chassis of a truck. They also may be mounted on a non-rolling chassis such as a skid which may be transported to and from a well site.

[0086] Blender 100, as best appreciated from FIGS. 1-2, generally comprises a suction system 34, a mixing system 40, a solids system 50, a discharge system 60, and a power system 70. The primary function of suction system 34 is to receive the liquid phase of frac fluids, such as gelled water, from a hydration unit, such as hydration unit 3 shown in FIG. 1, and deliver it to mixing system 40.

[0087] Suction system 34, as seen best in FIGS. 4-5, generally comprises a suction bank 31, a suction pump 32, and a main suction line 33. Fluid from hydration unit 3 (or from multiple hydration units) will be fed into blender 100 via a number of hoses. Thus, suction bank 31 comprises a plurality of hose connections 34 feeding into a combining manifold 35.

[0088] Connections 34 preferably are hammer union subs which allow a union to be made up quickly and easily with a hose carrying a mating union sub. They are connected to manifold 35 via flanged butterfly valves 36 that allow each connection to be opened and closed. For transport, as shown in FIG. 4, connections 34 will be provided with a cover to prevent damage to the hammer union sub. It also will be noted that manifold 35 comprises modular units 35a, 35b, and 35c. Manifold units 35a-35c may be joined, for example, by flange unions 37.

[0089] Suction bank 31 and manifold 35 preferably, as exemplified, run generally laterally along trailer 20. Manifold 35 feeds into and is connected to suction pump 32. Suction pump 32 typically will be a centrifugal pump. It preferably will be connected to a conventional automatic motor controller to control the speed of the pump. Liquid introduced though suction bank 31 will be pumped by suction pump 32 through a short vertical section into main suction line 33. Main suction line 33 runs generally laterally along trailer 20 above and generally parallel to manifold 35. As exemplified, main suction line 33 may be made up of several shorter pipes joined, for example, by flange or threaded unions. It is connected to and discharges into mixing system 40 and, more particularly, into a tub 41.

[0090] The suction systems of the novel blenders may be mounted to a chassis in any conventional manner, such as by bolting or welding it to components of frame 23 of trailer 20. Preferably, however, they will be mounted such that they may be quickly and easily installed and removed as needed. More preferably, they will be supported by a mounting system that allows some translation relative to the chassis while the components are loosely assembled to the chassis.

[0091] For example, in FIG. 5 suction system 34 has been removed in large part to show a mounting system 25 for suction manifold 35 of suction system 34. As appreciated therefrom, manifold 35 is supported on brackets, such as saddle mounts or cradles 27, that are affixed to frame 23 of trailer 20. Manifold 35 may be secured in cradles 27 with retainers, such as straps 28 that are connected to cradles 27 with conventional connectors, such as threaded connectors. It will be appreciated that main suction line 33 preferably is mounted on a similar mounting system having cradles and straps.

[0092] It will be appreciated, therefore, that when straps 28 are loose, manifold 35 and main suction line 33 may slid laterally within cradles 27 along trailer 20. Moreover, suction bank 31 and main suction line 33 run substantially parallel to each other. That arrangement makes installation and service much easier than, for example, many bolt-on systems. For example, once disconnected from tub 41 the entire suction system 34 may be shifted as a unit laterally along trailer 20. If a particular component needs repair or replacement, the rest of the system may be shifted laterally. Moreover, because they and their components may be shifted laterally as a whole or individually, the components of suction line 31 and manifold 35 may be assembled with flange unions. Flange unions provide a robust seal and connection between components, but require the components to be backed off first so that threaded studs on one component may be inserted through corresponding openings in a flange of the other component.

[0093] Moreover, in the event repairs are needed, such systems are better able to accommodate imprecision. For example, if a repair is needed to a portion of suction line 33, it will not be critical that a replacement section match exactly the length of the portion that has been removed. Any differences between the worn portion and its replacement may be made up by moving the rest of discharge system 34 laterally within mounts 25.

[0094] The primary function of solids system 50 is to receive solids, such as sand or other proppants, supplied, for example, via sand conveyers 4 from sand tanks 5, and feed the solids into mixing system 40. Thus, as seen best in FIGS. 2-3, solids system 50 comprises a bin 51 and a conveyor, such as screw-type augers 52. Solids from conveyers 4 are dumped into bin 51. The lower or receiving ends of augers 52 extend toward the bottom of bin 51 and the upper or discharge ends extend over and beyond the lip of tub 41. As augers 52 rotate, solids will be carried up from bin 41 and will fall into tub 41. Augers 52, as is typical in the art, preferably will be connected to automatic motor controllers to control the speed at which they rotate. As seen best in FIG. 9, augers 52 preferably will discharge solids into a discharge chute 53 that will guide the solids into tub 41.

[0095] Conventional solid particulate conveyors other than augers, however, may be used if desired. It also will be appreciated that solids system 50 preferably will be mounted on a carriage or similar sub-frame that will allow it to be moved, for example, by hydraulic pistons. Solids system 50 thus may be moved into an operational position, in which it is positioned to discharge into tub 41, or into a transport position, where it is moved forward and tucked into trailer 20 to provide a more compact unit. Solids system 50 is illustrated in FIGS. 2-3 in its transport position.

[0096] Mixing system 40 primarily serves to ensure that the liquid phase supplied through suction system 34 and the particulates supplied through solids system 50 are thoroughly blended into a homogeneous slurry. Tub 41, therefore, is provided with various paddles and mixing blades (not shown). Various designs for such mixers are known and may be used as desired. Tub 41 preferably is mounted to frame 23 with bolt-on slides having oval through-holes to allow some flexibility in positioning tub 41 on trailer 20. Many conventional designs for slide mounts are known and may be used.

[0097] Discharge system 60 primarily serves to accept slurry from tub 41 and convey the slurry into hoses leading to, for example, frac manifold 9. Thus, as seen best in FIGS. 6-7, discharge system 60 generally comprises a drain line 61, a pump 62, a main discharge line 63, and a discharge bank 64. Slurry draining from tub 41 flows through drain line 61 leading to pump 62. Discharge pump 62, like suction pump 32, preferably is a centrifugal pump and will be connected an automatic controller. Pump 62 pumps the slurry through a short vertical section of discharge line 63. The major portion of discharge line 63 runs laterally along trailer 20 before turning down and trailer 20. It then connects with discharge bank 64 which also runs laterally along trailer 20 and generally parallel to discharge line 63.

[0098] It will be appreciated by workers in the art that fluids used in a fracturing operation are carefully designed for a particular formation and for the pattern of fractures that will be created. Among many others, one of the more important factors is the density of the frac fluid. The fluid's density will determine the weight of the fluid column in the well and will provide a component of the hydraulic pressure used to fracture the formation. Particulates added in the blender, in turn, greatly affect the density of the slurry and, in fact, are the primary way of adjusting the slurry's density. Thus, it is essential that the density of the slurry being produced in the blender he carefully monitored to ensure that it is within specifications.

[0099] As noted, conventional blenders typically rely on radioactive densitometers because they are capable of measuring the density of liquids having entrained solids. In contrast, novel blender 100 preferably uses a liquid flow meter to infer the amount, that is the mass of liquid introduced into the slurry in combination with a microwave flow meter to infer the amount of solids introduced into the slurry. Measurements from those meters, along with known or measured separate densities of the liquid and solid phases, will allow determination of the density of the slurry delivered by blender 100. Readings will be made, and density determined, at predetermined time intervals via programmable logic controllers or other conventional digital computer systems to provide essentially real-time density data.

[0100] Conventional flow meters for liquids may be used, such as magnetic resonance and turbine flow meters, to provide a measurement of liquid flow into tub 41. Such meters measure the velocity of fluid flowing in the conduit from which, the dimensions of the conduit being known, the quantity of fluid flowing into tub 41 may be inferred. They are available commercially from a number of sources, such as NW-Lake Company, Oak Creek, Wis. (turbine flow meters), Badger Meter, Milwaukee, Wis. (turbine flow meters), Keyence Corporation of America, Itasca, Ill. (magnetic resonance flow meters), and Ludwig Krohne GmbH & Co. (Krohne Group), Duisburg, Germany (magnetic resonance flow meters). They will be installed in main suction line 33 between suction manifold 35 and tub 41. For example, as may be seen best in FIG. 4, a magnetic resonance flow meter 38 is mounted in main suction line 33.

[0101] Conventional microwave flow meters may be used to measure the amount of solids flowing into tub 41. The meters incorporate a microwave generator. Sensors in the meter detect microwaves reflected by moving particles. The quantity of moving particles then may be inferred by measuring the change in frequency and amplitude of the reflected microwaves. Typically, they will be calibrated by using a reference sample and flow rate. They are available commercially from a number of sources, such as Monitor Technologies LLC, DYNA Instruments GmbH, Hamburg, Germany, and Matsushima. Measure Tech Co., Ltd., Kitakyushu, Japan.

[0102] Microwave flow meters may be used to measure the flow rate of particles falling through air, carried in pneumatic lines or on conveyors, or flowing along chutes. Thus, they may be installed in a suitable housing proximate to the point where augers 52 drop solids into tub 41. In order to improve the accuracy of measurements, particulates should flow as uniformly as possible past the meter. Thus, the housing for the meter preferably will include guides designed to direct particulates in a predictable stream past the meter.

[0103] For example, solids system 50 incorporates discharge chute 53. As seen best in FIG. 9, chute 53 is mounted below augers 52 such that solids discharged from their ends will fall through the open top of chute 53. Opposing parallel walls 54a and tapered side walls 54b allow chute 53 to receive the solids and guide them as they continue their fall toward one of two outlet ducts 55. Chute 53 therefore, will encourage the solids to exit ducts 55 in two uniform flows. Microwave flow meters 56 (illustrated schematically) may be mounted on ducts 55. Flow meters 56, thus, are able to measure the amount of solids delivered into tub 41. It will be appreciated, of course, that the meter housing may be of any conventional design that is effective in creating a substantially uniform flow of particles across flow meters 56. Chutes having many different geometries and designs are known and may be used.

[0104] Solids system 50 also preferably includes vibrators to shake the particulates being conveyed into tub 41. For example, conventional vibrators may be mounted on the housing of augers 52 more or less at location 59 shown in FIGS. 2-3 or another suitable location. Alternately, vibrating guides may be employed to both shape and provide uniformity to the particulate flow. In any event, it will be appreciated that by using a combination of a flow meter to measure liquid flowing into tub 41 and a microwave flow meter to measure solids flowing into tub 41, the density of the slurry produced by blender 100 may be monitored and controlled without the need for a radioactive densitometer.

[0105] Flow rates of liquid and solids into tub 41 may be adjusted automatically by conventional control systems in response to density data. For example, the flow rate of liquid delivered to tub 41 may be controlled by varying the speed of suction pump 32. Alternately, a conventional automatically controlled flow control valve, such as butterfly valve 39 in main suction line 33, may be opened to varying degrees to adjust liquid flow. The flow rate of solids may be controlled, for example, by varying the speed of augers 52 pulling sand up from bin 51. Augers 52 also may discharge into a conventional automatic gravity flow metering device, such as a slide or roller gate valve, that can be opened to varying degrees. Suitable gravity flow metering devices are available commercially from a number of sources, such as Salina Vortex Corporation, Salina, Kans., and Kemutec Group, Inc., Bristol, Pa. Such components may be connected to the controller and operated automatically in response to density data through conventional motor controls to maintain a targeted density or to adjust the density on the fly.

[0106] As noted, solids flowing into mixing tub 41 can drag air along with it. The fluid will contain suspension agents to keep solids from settling, but the suspension agents also may cause air pulled into the slurry to become entrained for longer periods of time. Entrained air can damage centrifugal pumps, such as discharge pump 62, and can significantly affect the density of the slurry that will be pumped into the well. Thus, preferred embodiments of the novel blenders may comprise novel discharge chute 153.

[0107] As may be seen in FIGS. 10-11, discharge chute 153 may be mounted below augers 52 such that solids discharged from their ends will fall through the open top of chute 153. In the absence of chute 153, it will be appreciated that the solids would fall from augers 52 into tub 41 in three relatively heavy streams, each of which could tend to drag significant quantities of air into the slurry. In contrast, opposing parallel wall 154a and baffle plate 155 and tapered side walls 154b of chute 153 will guide the discharge from augers 52 over baffle plate 155.

[0108] Baffle plate 155 is adapted to divide particulates discharged from augers 52 into a plurality of smaller streams. For example, baffle plate 155 may have a large number of relatively small openings. Baffle plate 155 as illustrated has 36 openings, but a suitable number can vary according to the expected discharge rates from the conveyor. By relatively small it will be appreciated that cumulatively the openings have the same or even greater flow capacity than the conveyor. Each individual opening, however, has a much smaller flow capacity, preferably at least an order of magnitude less, and more preferably at least 20 or 34 times less.

[0109] Preferably, as shown, the openings have an obround shape and are arranged in offset, linear arrays. The openings, however, may be circular, oval, rectangular, or any of many different shapes, and they may be arranged in many different patterns. Baffle plate 155 also preferably is mounted at an angle between vertical and horizontal, such as at approximately 45. Particles falling on the upper portion of baffle plate 155 will fall downward across the face of plate 155 toward the openings. The arrays of openings will be situated at different elevations and will be offset in the horizontal plane. Thus, particulates sliding down baffle 155 will fall through the openings and be divided into much smaller, lighter streams that are far less likely to drag air into the slurry. Preferably, the particulates will be encouraged to divide into at least about 15, at least about 25, or at least about 35 smaller streams.

[0110] It will be appreciated, of course, that dividing discharge chute 153 may be modified in various ways. For example, baffle plate 155 may be oriented more or less horizontally and form a bottom of a tapered chute guiding particles onto baffle plate 155. More complicated baffles for dividing the stream are known and may be used. Baffle plate 155, however, is relatively easy to fabricate and effectively divides a much larger stream into many smaller streams.

[0111] Returning to discharge system 60, it will be noted that like suction bank 31, discharge bank 64 preferably comprises a dividing manifold 65 and numerous connections 66. Discharge connections 66, like suction connections 34, are hammer union subs which are assembled to manifold 65 by flanged butterfly valves 67. Also, like suction manifold 35, discharge manifold 65 comprises modular units 65a, 65b, and 65c which are joined by flange unions 68.

[0112] The discharge systems of the novel blenders, like the suction systems, may be mounted to a chassis in any conventional manner. Preferably, however, they also will be mounted and supported to allow some translation relative to the chassis. For example, blender 100 is provided with a mounting system 26 for discharge manifold 65 of discharge system 60. As seen best in FIG. 8, in which discharge system 60 has been removed, mounting system 26 is similar to mounting system 25 for suction manifold 35. Discharge manifold 65 is supported on cradles 27 like those in mounting system 25. Discharge manifold also may be secured by in cradles 27 by straps 28. It will be appreciated that main discharge line 63 preferably is mounted on a similar mounting system. Thus, similar tolerances may be provided in installing and repairing components of the discharge system 60 as are provided in suction system 34.

[0113] In addition, by using modular units, replacement of manifolds 35 and 65 is greatly facilitated, especially in the field. For example, it may be desirable to provide different banks 31 and 64 for different types of slurries. Banks 31 and 64 may be quickly and easily switched out for banks better suited for other slurries. There is no need to return to the shop for service or to bring an additional blender to the well.

[0114] It also will be appreciated that flow through both manifolds 35 and 65 is quite turbulent and is subject to sharp changes in direction. Unlike suction system 34, however, which handles essentially solid-free liquids, discharge system 60 handles large volumes of high-solids, highly abrasive slurry. Manifold 65, therefore, is subject to much greater erosion, especially in the upstream portion of manifold 65. Other factors being equal, module 65a of manifold 65 likely will be the first manifold component to suffer unacceptable erosion. Preferably, at least some of the manifold modules are identical, for example, modules 35a and 35b of manifold 35 and modules 65a and 65b of manifold 65 all are identical. Thus, modules from manifold 35 and modules from manifold 65 may be switched out to distribute wear more evenly throughout the system and to allow blender 100 to remain operational on site for longer periods of time.

[0115] It also will be appreciated that as the slurry drains from tub 41 into drain line 61, it will tend to form a vortex. Entrained air, and especially the formation of a vortex in liquid being pumped through a centrifugal pump, such as discharge pump 62, can significantly diminish its pump rates and damage the pump. Conventional blenders, therefore, typically incorporate one or more bars extending normally, that is, perpendicularly to the central axis of the drain line leading from the mixing tub. While such bars can reduce the tendency for a vortex to form in the drain line, they are subject to relatively rapid erosion, particularly at their junction with the inner walls of the drain line.

[0116] Thus, blender 100 preferably incorporates improved vortex breakers in drain line 61, such as vortex breakers 80 and 85 as shown in FIGS, 12-13. Breaker 80, as will be appreciated from FIG. 12, comprises what may be viewed as four fin members 81. Each fin member 81 is shaped like an isosceles trapezoid. Fin members 81 abut each other at their bases and project radially outward from the center of drain line 61. They are angularly arrayed at 90 intervals about an axis defined by their abutting bases. The tops of fins 81 are joined to the inner wall of drain line 61. Fin members 81 thus come to a point at each end 82, with one end 82 pointing upstream against the direction of flow of slurry through drain line 61. The other end 82 points downstream along the flow.

[0117] Breaker 80 preferably is mounted in a relatively short section of pipe 61a which may be assembled into drain line 61, for example, by flanges 83 provided at each end thereof. It is believed that breaker 80 will be subject to less erosion, particularly at the junction between fins 81 and the inner walls of drain line 61, than conventional breakers. It also will be appreciated that greater or fewer fins 81 may be provided in breaker 80, although typically three to six fins 81 will suffice. Likewise, the precise geometry of fins 81 may be varied. For example, the forward and rearward sweep of fins 81 may be varied and need not necessarily be linear. Likewise, ends 82 of tins 81 may be somewhat truncated.

[0118] Breaker 85, as will be appreciated from FIG. 13, has a rectilinear portion 86 disposed between cylindrical portions 87. Cylindrical portions 87 may be provided with, for example, flanges 88 on their ends to allow them to be assembled into drain line 61. Breaker 85, it is believed, will provide effective protection against the formation of vortexes in discharge pump 62, yet does not incorporated any cross-members that might be particularly susceptible to erosion.

[0119] It will be appreciated, of course, that breaker 85 may have other geometries and configurations and is not limited to the specific, illustrated design. For example, the length of rectilinear portion 86 may be varied, as may be the length and shape of the transition area between rectilinear portion 86 and cylindrical portions 87. The cross-section of rectilinear portion 86 also need not be square as illustrated. It may have other rectangular cross-sections, or even other polygonal cross-sections. Higher-order polygons, however, will tend to be less effective as they more closely approximate a circle.

[0120] Power system 70 serves primarily to power pumps 32, the mixing apparatus in tub 41, and the various control systems provided in blender 100. Power system 70 also typically drives electrical generators and includes alternators and storage batteries to power various control devices and systems. Otherwise, as best appreciated from FIGS. 3 and 6-8 showing the discharge side of blender 100, power system 70 generally includes a pair of diesel engines 71. One engine 71 drives a hydraulic pump (not shown) which in turn hydraulically drives suction pump 32 and the mixing apparatus in tub 41. The other engine 71 powers a drive train 72 which drives discharge pump 62. Drive train 72 includes a transmission 73 which is coupled to a first drive shaft 74. First drive shaft 74 is coupled to a gear box 75. Gear box 75 incorporates a plurality of mating gears which allow the rotation of drive shaft 74 to be increased as is typical of such gear boxes. A second drive shaft 76 is coupled to gear box 75 and ultimately drives discharge pump 62. (It will be appreciated that what are indicated in the figures as drive shafts 74 and 76 are actually the housings through which they pass.)

[0121] It will be appreciated that the gearbox of drive trains in conventional blenders typically is incorporated into, or otherwise coupled directly and rigidly to the transmission. That typically places severe space constraints on the gear box which can reduce its efficiency and decrease its service life. Moreover, when the clutch is released, and the engine operatively engages the drive train, conventional gear boxes can be subject to high mechanical shock created in overcoming inertia in the drive shaft and pump. The engine is operating at high rpms, the rotation of the engine is stepped up by the gear box, and there is a large, and essentially incompressible head of fluid in and above the pump. An elastomeric drive coupler typically is assembled between the gear box and drive shaft, but such couplers wear rapidly, must be changed often, and do not entirely absorb shock transmitted to the gear box.

[0122] In contrast, gear box 75 of blender 100 preferably, as seen best in FIGS. 7-8, is not coupled directly to transmission 73. It is connected to transmission 73 via first drive shaft 74, and then to discharge pump 62 via second drive shaft 76. Being removed from transmission 73, gear box 75 may be enlarged to accommodate a better gear design. Moreover, gear box 75 may be, and preferably is mounted to trailer 20 by shock absorbing mounts (not shown). The gear box mounts typically will incorporate hard rubber elastomer shock absorbers, and there are many conventional designs for engine mounts that may be used to mount gear box 75. In any event, the mounts will enable the entire gear box 75 to rotate in resistance as drive train 72 is engaged. The mounts will be able to absorb a large proportion of the torque created at engagement instead of having that force absorbed by the gears within gear box 75. It also is expected that they will be more durable than the elastomeric drive couplers used in conventional drive trains for blenders.

[0123] As generally shown in FIGS. 2-3, power system 70 of blender 100 comprises a conventional cooling system 90 for engines 71. More particularly, each engine 71 is provided with its own conventional radiator 91 and fan 93. Preferably, however, blender 100 will incorporate an improved cooling system 190 for engines 71. As shown schematically in FIG. 14, cooling system 190 comprises a pair of radiators 191 and a single air mover 192. Radiators 191 are of conventional design as are commonly employed in systems for circulating liquid coolant fluids through internal combustion engines. Heated coolant from each engine 71 is circulated into its associated radiator 191 by a pump driven by engine 71 where it is cooled prior to flowing back into engine 71. Air mover 192 includes one or more fans 193 mounted within various conventional shrouds and is designed to create and direct air flow across radiators 191. Air movers 192 also may be of conventional design. It will be noted in FIG. 14, however, that each engine 71 is connected via coolant lines 194 to its own radiator 191. A single air mover 192, however, directs air flow over both radiators 191. Air mover 192 may be mounted to either trailer 20, to radiators 191, to both, or in other conventional ways.

[0124] Thus, each engine 71 and its associated radiator 191 preferably, as shown schematically in FIG. 14, may be mounted on a common base or skid 22. In the event engine 71 requires service, therefore, air mover 192 first will be removed. Engine 71 and its associated radiator 191 then may be removed from trailer 20 as a unit. Conventional blenders typically include separate radiators and air movers for each engine, or they have a single air mover and a single radiator for both engines.

[0125] During a frac job, blender 100 will provide slurry for injection into a well. For example, as will be appreciated from FIG. 1, blender 100 may supply slurry to frac pumps 10 through low-pressure hoses 7 connected to low-pressure lines 8 in frac manifold 9, which in turn feed pumps 10 through suction hoses 11. Frac manifold 9 typically is not provided with a pump. Discharge pump 62 on blender 100 provides the pumping power to feed frac pumps 10.

[0126] Preferably, discharge pump 62 will be controlled to maintain a specified hydraulic pressure in hoses 7, low-pressure lines 8, and suction hoses 11, that is, between discharge pump 62 and the intakes of frac pumps 10. The specified pressure will correspond to the pressure head required by the frac pumps, that is, the hydraulic pressure that must be present at the intakes of the pumps to ensure that they operate properly. The pressure head is a more accurate way of measuring the fluid requirements of a pump. Flow rates are less reliable, as the pressure head at a specified flow rate will depend on the density of the fluid being pumped.

[0127] Accordingly, blender 100 may be provided with a pressure sensor (not shown), such as a pressure transducer. The pressure sensor is mounted downstream of discharge pump 62 in, for example, discharge line 63. Pressure readings will be made, and the speed of pump 62 will be adjusted to pump enough slurry to maintain the specified pressure. The sensor will be connected to a programmable logic controller or another conventional digital computer system which then will control the speed of discharge pump 62 by conventional control systems in response to the pressure data. It is expected that slurry will be delivered reliably to frac pumps 10, avoiding cavitation in frac pumps 10 while at the same time avoiding unnecessary wear on discharge pump 62.

[0128] The discharge pumps on conventional blender units typically are controlled to pump slurry at a specified flow rate. That is, an array of frac pumps will be determined to require a certain amount of a fluid over a certain amount of time, for example, 100 bbl/min. A meter in the discharge line of the blender unit will measure the flow rate from the discharge pump. The speed of the discharge pump then will be controlled to provide the specified flow rate.

[0129] If the frac pumps are speeded up during a fracturing operation, either intentionally or by accident, they will need more fluid to provide the required pressure head. The increased fluid requirements may exceed the specified flow rate. The blender, however, will continue to provide the specified flow rate, creating a risk that the frac pumps will not receive enough fluid and will cavitate. Cavitation can seriously damage the frac pumps. Consequently, operators of conventional blenders tend to set and keep the flow rate high, sometimes higher than specified, in an effort to ensure that the frac pumps always receive the required amount of slurry.

[0130] A problem arises, however, if frac pumps 10 are slowed down, either intentionally to reduce the pump rate into a well, or by inadvertence. An individual pump also may fail. The array of frac pumps then will require less slurry, causing pressure within the blender discharge lines to build, and flow rates to decrease. The discharge pump, however, will respond to decreased fluid flow by operating at high speed in an attempt to deliver the specified flow. Operating the discharge pump under such conditions can create considerable stress and wear on the pump.

[0131] It is expected that the novel blenders will be able to deliver slurry to frac pumps 10 at rates more accurately reflecting their requirements, and will reduce the risk of cavitation in frac pumps 10 while at the same time avoiding unnecessary wear on discharge pump 62. In the situations described above, if the fluid requirements of frac pumps 10 increase, novel blender 100 will detect a pressure drop. The speed of discharge pump 62 will be increased, thereby increasing the amount of slurry fed into frac pumps 10 and bringing the pressure head at pumps 10 back in line with their requirements. Conversely, if frac pumps 10 slow down, if their fluid requirements drop, blender 100 will detect a pressure increase and slow the speed of pump 62. Less fluid will be discharged, and discharge pump 62 will not be forced to operate at high speeds against an excessively high pressure head.

[0132] It also will be appreciated that conventional blenders where the discharge pump is controlled in response to flow rates cannot easily be adjusted to accommodate changes, expected or otherwise, in the density of slurry pumped from the blender. The pumps will be operated at the same speed regardless of the slurry density. In contrast, the novel blenders will be able to respond to changes in density. More dense slurries will increase the hydraulic pressure in the discharge line. Discharge pump 62 will be slowed accordingly to bring the pressure head at pumps 10 back in line with requirements. Likewise, discharge pump 62 will be sped up if slurry density decreases. Thus, the proper pressure head is maintained at frac pumps 10.

[0133] Blender 100 and its components, as well as other embodiments of the subject invention, may be manufactured by methods and from materials commonly used in manufacturing blenders. Many components are available commercially. Given the extreme stress and the corrosive and abrasive fluids to which the flowline components are exposed, suitable materials will be hard, strong, and durable, and typically will be steel, such as 4130 and 4140 chromoly steel or from somewhat harder, stronger steel such as 4130M7, high end nickel alloys, and stainless steel. The components may be made by any number of conventional techniques, but typically and in large part will be made by forging, extruding, or mold casting a blank part and then machining the required features into the part. Similarly, the engine and drive train components of the blenders will be manufactured or sourced for heavy duty service.

[0134] It also will be appreciated that blender 100 and other embodiments of the novel blenders, incorporate many different improvements in the systems conventionally incorporated into such equipment. Preferably, the novel blenders will incorporate all such improvements. At the same time, however, the invention encompasses embodiments where only one, or fewer than all such improvements are incorporated.

[0135] Similarly, the novel blenders have been described in the context of frac systems. While frac systems in particular and the oil and gas industry in general rely on blenders for mixing liquid and solid components, the novel blenders are not limited to such applications or industries. Suffice it to say that the novel blenders have wide applicability wherever there is a need to blend such components, and especially in the context of temporary fluid transportation systems.

[0136] While this invention has been disclosed and discussed primarily in terms of specific embodiments thereof, it is not intended to be limited thereto. Other modifications and embodiments will be apparent to the worker in the art.