CA2928704A1 - System for reducing vibrations in a pressure pumping fleet - Google Patents

Abstract

An electrically powered hydraulic fracturing system having pumps for pressurizing fracturing fluid, piping for carrying fracturing fluid, and vibration reducing equipment for use with the piping. The vibration reducing equipment includes helical coils that support the piping. The coils are made of a wire rope made of strands of steel cable twisted together. Grooved fittings are provided on some piping connections, and which allow pivoting between adjacent fluid conveyance members. Swivel joints are strategically located in the piping which allow rotational flexing between adjacent sections of the piping; thereby attenuating vibration in the piping but without stressing the piping.

Description

, SYSTEM FOR REDUCING VIBRATIONS IN A PRESSURE PUMPING FLEET
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of, and claims priority to and the benefit of, co-pending U.S. Provisional Application Serial No. 62/156,306, filed May 3, 2015 and is a continuation-in-part of, and claims priority to and the benefit of co-pending U.S. Patent Application Serial No.
13/679,689, filed November 16, 2012, the full description and drawings of which are appended hereto.
BACKGROUND OF THE INVENTION
1. Field of Invention

[0002] The present disclosure relates to hydraulic fracturing of subterranean formations. In particular, the present disclosure relates to methods and devices for reducing vibration during hydraulic fracturing of a subterranean formation.
2. Description of Prior Art

[0003] Hydraulic fracturing is a technique used to stimulate production from some hydrocarbon producing wells. The technique usually involves injecting fluid into a wellbore at a pressure sufficient to generate fissures in the formation surrounding the wellbore.
Typically the pressurized fluid is injected into a portion of the wellbore that is pressure isolated from the remaining length of the wellbore so that fracturing is limited to a designated portion of the formation. The fracturing fluid slurry, whose primary component is usually water, includes proppant (such as sand or ceramic) that migrate into the fractures with the fracturing fluid slurry , and remain to prop open the fractures after pressure is no longer applied to the wellbore.
Sometimes, nitrogen, carbon dioxide, foam, diesel, or other fluids are used as the primary component instead of water. A typical hydraulic fracturing fleet may include a data van unit, blender unit, hydration unit, chemical additive unit, hydraulic fracturing pump unit, sand equipment, wireline, and other equipment.
100041 Traditionally, the fracturing fluid slurry has been pressurized on surface by high pressure pumps powered by diesel engines. To produce the pressures required for hydraulic fracturing, the pumps and associated engines have substantial volume and mass. Heavy duty trailers, skids, or trucks are required for transporting the large and heavy pumps and engines to sites where wellbores are being fractured. Each hydraulic fracturing pump usually includes power and fluid ends, seats, valves, springs, and keepers internally. These parts allow the pump to draw in low pressure fluid (approximately 100 psi) and discharge the same fluid at high pressures (up to 15,000 psi or more). The diesel engines and transmission which power hydraulic fracturing units typically generate large amounts of vibrations of both high and low frequencies. These vibrations are generated by the diesel engine, the transmission, the hydraulic fracturing pump as well as the large cooling fan and radiator needed to cool the engine and transmission. Low frequency vibrations and harshness are greatly increased by the large cooling fans and radiator required to cool the diesel engine and transmission. In addition, the diesel engine and transmission are coupled to the hydraulic fracturing pump through a u-joint drive shaft, which requires a three degree offset from the horizontal output of the transmission to the horizontal input of the hydraulic fracturing pump. Diesel powered hydraulic fracturing units are known to jack and jump while operating in the field from the large amounts of vibrations. The vibrations may contribute to fatigue failures of many differed parts of a hydraulic fracturing unit. Recently electrical motors have been introduced to replace the diesel motors, which greatly reduces the noise generated by the equipment during operation. Because of the high pressures generated by the pumps, and that the pumps used for pressurizing the fracturing fluid are reciprocating pumps, a significant amount of vibration is created when pressurizing the fracturing fluid. The vibration transmits to the piping that carries the fracturing fluid and its associated equipment, thereby increasing probabilities of mechanical failure for the piping and equipment, and also shortening their useful operational time.

SUMMARY OF THE INVENTION
100051 Disclosed herein is an example of a hydraulic fracturing system for fracturing a subterranean formation, and which includes an electrically powered fracturing pump having a suction side and a discharge side, a suction branch of piping having fracturing fluid therein, a discharge branch of piping having therein pressurized fracturing fluid supplied from the fracturing pump, a tubular suction lead having an end mounted to the suction side and an opposite end coupled to an end of the suction branch by a grooved connection, and which is pivotal with respect to the suction branch, swivel connections strategically located in the discharge branch of piping, so that when pressurized fracturing fluid flows through the discharge branch of piping, a section of the discharge branch of piping is axially rotatable with an adjacent section of the discharge branch of piping, and helical coils supporting suction and discharge branches of piping at strategically located positions. In one embodiment;
engines, transmissions, large cooling fans, and u-joint drive shafts are intentionally not included to minimize both high and low frequency vibrations. At least one of the helical coils can have an axis that is disposed oblique with an axis of an adjacent amount of piping. Optionally included is a pulsation dampener in fluid communication with the suction branch and adjacent the suction lead. In one example the fracturing pump is a first fracturing pump, wherein the suction and discharge branches respectively intersect with suction and discharge piping that are in fluid communication with a second fracturing pump, and wherein the suction and discharge branch intersections are at locations that are each spaced away from a surface on which the first fracturing pump is supported. The surface on which the first fracturing pump is supported can be a trailer, truck, skid, or other platform. In one example, the hydraulic fracturing pump unit has two fracturing pumps where the suction piping for the first pump and the suction piping for the second pump are separate and distinct. This allows for a much simpler fluid dynamic flow that reduces turbulence and vibrations. In another example, the discharge piping for the first pump and the discharge piping for the second pump are separate and distinct from the pump to the edge of the unit. This allows for a simpler fluid dynamic flow that reduces turbulence and vibrations. The hydraulic fracturing system can further include a turbo-generator or other power source and power distribution equipment for generating and distributing electricity used for powering the fracturing pump.

[0006] Also disclosed herein is an example of a method of hydraulically fracturing a subterranean formation, and which includes pressurizing fracturing fluid with a hydraulic fracturing system that comprises an electrically powered fracturing pump, a tubular suction branch, and a tubular discharge branch, drawing the fracturing fluid into the fracturing pump through the suction branch, discharging the fracturing fluid from the fracturing pump through the discharge branch, introducing the fracturing fluid to the formation to create a fracture in the formation, and reducing vibration in the hydraulic fracturing system by, strategically locating swivel joints in the suction and discharge branches, so that designated sections of the suction and discharge branches are moveable with respect to other sections of the suction and discharge branches, providing a grooved connection in the suction branch, so that piping supplying fracturing fluid to the fracturing pump is pivotable with respect to the fracturing pump, maintaining portions of the suction and discharge branches that are supported on a surface that supports the fracturing pump from other suction and discharge branches, and resting the suction and discharge branches on helical coils. The method can further include providing an elastomeric yoke with the helical coils. Optionally, some of the fluid in the suction branch can be routed to an accumulator. The method can further include powering the fracturing pump with electricity generated by a turbo-generator or other power supply.
[0007] An alternate example of a method of hydraulically fracturing a subterranean formation includes pressurizing fracturing fluid with a hydraulic fracturing system that includes an electrically powered fracturing pump and piping coupled with the fracturing pump, discharging pressurized fracturing fluid for delivery to a wellbore that intersects the formation so that the pressurized fracturing fluid fractures the formation, and reducing vibration in the hydraulic fracturing system by providing joints in the piping at strategic locations so that adjacent sections of the piping pivot and/or swivel. The joints can include a swiveling joint that allows relative rotational movement between adjacent sections of the piping. The joints are made up of a grooved connection joint that allows pivoting between adjacent sections of the piping. The method can further include maintaining the piping separate from piping that is in fluid communication with another fracturing pump. In one example, the traditional engine and transmission are replaced by a variable frequency drive ("VFD") and an electric motor. Then the traditional u-joint drive line, which requires at least a three degree offset from the horizontal output of the transmission with the horizontal input of the hydraulic fracturing pump, is replaced

- 4 -, by a direct coupling to reduce or eliminate the vibrations caused by the required misalignment that the traditional u-joint drive shaft requires.

- 5 -, , BRIEF DESCRIPTION OF DRAWINGS
[0008] Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:
[0009] FIG. 1 is a schematic of an example of a hydraulic fracturing system.
[0010] FIG. 2 is schematic of an example of piping of the hydraulic fracturing system of Figure 1 having vibration reducing equipment.
[0011] FIG. 3 is a schematic of an example of a pipe coupling for use with the hydraulic fracturing system of Figure 1.
[0012] FIG. 4 is a side perspective view of an example of a cable coil assembly for use with the hydraulic fracturing system of Figure 1.
[0013] FIG. 5 is a side view of an example of a swivel assembly for use with piping in the hydraulic fracturing system of Figure I.
[0014] FIG. 6 is a side perspective view of an example of pump suction and discharge piping having vibration reducing equipment.
[0015] FIG. 7 is a side perspective view of an alternate example of a cable coil assembly.
[0016] FIG. 8 is a graph having plots representing measured values of vibration of hydraulic fracturing units with and without vibration reducing equipment.
[0017] While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.

- 6 -, , DETAILED DESCRIPTION OF INVENTION
[0018] The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term "about" includes +/- 5% of the cited magnitude.
In an embodiment, usage of the term "substantially" includes +/- 5% of the cited magnitude.
[0019] It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.
[0020] Figure 1 is a schematic example of a hydraulic fracturing system 10 that is used for pressurizing a wellbore 12 to create fractures 14 in a subterranean formation 16 that surrounds the wellbore 12. Included with the system 10 is a hydration unit 18 that receives fluid from a fluid source 20 via line 22, and also selectively receives additives from an additive source 24 via line 26. Additive source 24 can be separate from the hydration unit 18 as a stand-alone unit, or can be included as part of the same unit as the hydration unit 18. The fluid, which in one example is water, is mixed inside of the hydration unit 18 with the additives.
In an embodiment, the fluid and additives are mixed over a period of time to allow for uniform distribution of the additives within the fluid. In the example of Figure 1, the fluid and additive mixture is transferred to a blender 28 via line 30. A proppant source 32 contains proppant, which is delivered to the blender 28 as represented by line 34, where line 34 can be a conveyer. Inside the blender 28, the proppant and fluid/additive mixture are combined to form a fracturing slurry, which is then transferred to a fracturing pump 36 via line 38; thus fluid in line 38 includes the discharge of blender unit 28 which is the suction (or boost) for the fracturing pump system 36.
Blender 28 can have an onboard chemical additive system, such as with chemical pumps and

- 7 -, augers. Optionally, additive source 24 can provide chemicals to blender 28; or a separate and standalone chemical additive system (not shown) can be provided for delivering chemicals to the blender 28. In an example, the pressure of the slurry in line 38 ranges from around 80 psi to around 100 psi. The pressure of the slurry can be increased up to around 15,000 psi by pump 36.
A motor 39, which connects to pump 36 via connection 40, drives pump 36 so that it can pressurize the slurry. In one example, the connection 40 is a direct coupling between an electric motor 39 and a hydraulic fracturing pump 36. In another example, the connection 40 is more than one direct coupling (one on each end of the motor) (not shown) and two hydraulic fracturing pumps. Each of these hydraulic fracturing pumps 36 may be decoupled independently from the main electric motor 39. In one example, the motor 39 is controlled by a variable frequency drive ("VFD"). After being discharged from pump 36, slurry is injected into a wellhead assembly 41;
discharge piping 42 connects discharge of pump 36 with wellhead assembly 41 and provides a conduit for the slurry between the pump 36 and the wellhead assembly 41. In an alternative, hoses or other connections can be used to provide a conduit for the slurry between the pump 36 and the wellhead assembly 41. Optionally, any type of fluid can be pressurized by the fracturing pump 36 to form a fracturing fluid that is then pumped into the wellbore 12 for fracturing the formation 14, and is not limited to fluids having chemicals or proppant.
Examples also exist wherein the system 10 includes the ability to pump down equipment, instrumentation, or other retrievable items through the slurry into the wellbore.
[0021] An example of a turbine 44 is provided in the example of Figure 1 and which receives a combustible fuel from a fuel source 46 via a feed line 48. In one example, the combustible fuel is natural gas, and the fuel source 46 can be a container of natural gas or a well (not shown) proximate the turbine 44. Combustion of the fuel in the turbine 44 in turn powers a generator 50 that produces electricity. Shaft 52 connects generator 50 to turbine 44. The combination of the turbine 44, generator 50, and shaft 52 define a turbine generator 53. In another example, gearing can also be used to connect the turbine 44 and generator 50. An example of a micro-grid 54 is further illustrated in Figure 1, and which distributes electricity generated by the turbine generator 53. Included with the micro-grid 54 is a transformer 56 for stepping down voltage of the electricity generated by the generator 50 to a voltage more compatible for use by electrical powered devices in the hydraulic fracturing system 10. In another example, the power generated by the turbine generator and the power utilized by the electrical powered devices in the hydraulic

- 8 -fracturing system 10 are of the same voltage, such as 4160 V so that main power transformers are not needed. In one embodiment, multiple 3500 kVA dry cast coil transformers are utilized.
Electricity generated in generator 50 is conveyed to transformer 56 via line 58. In one example, transformer 56 steps the voltage down from 13.8 kV to around 600 V. Other step down voltages can include 4,160 V, 480 V, or other voltages. The output or low voltage side of the transformer 56 connects to a power bus 60, lines 62, 64, 66, 68, 70, and 72 connect to power bus 60 and deliver electricity to electrically powered end users in the system 10. More specifically, line 62 connects fluid source 20 to bus 60, line 64 connects additive source 24 to bus 60, line 66 connects hydration unit 18 to bus 60, line 68 connects proppant source 32 to bus 60, line 70 connects blender 28 to bus 60, and line 72 connects motor 39 to bus 60. In an example, additive source 24 contains ten or more chemical pumps for supplementing the existing chemical pumps on the hydration unit 18 and blender 28. Chemicals from the additive source 24 can be delivered via lines 26 to either the hydration unit 18 and/or the blender 28.
[0022] Figure 2 shows in a schematic form an embodiment where multiple pumps 361õ, are used in the system 10 of Figure 1 for pressurizing fracturing fluid. In this example, fracturing fluid flows to pump 361 via suction branch 74; where an end of suction branch 74 distal from pump 361 connects to a suction manifold 76. Fracturing fluid is fed to the manifold 76 via line 38, and fracturing fluid can be delivered to the remaining pumps in 362õ via the suction manifold 76. A
discharge end of pump 361 connects to a discharge branch 78, which carries fracturing fluid pressurized by pump 361, from pump 361, and for delivery into the wellbore 12 (Figure 1). An end of discharge branch 78 distal from pump 361 connects to a discharge manifold 80, that provides fluid communication between discharge branch 78 and discharge piping 42 (Figure 1).
Discharge manifold 80 is also shown providing fluid communication to discharge piping 42 from pumps 362_g. It should be pointed out that the suction and discharge branches 74, 78 each respectively connect to suction and discharge manifolds 76, 80 outside of a support platform 81 (schematically illustrated by the dashed line). Thus the suction and discharge branches 74, 78 are kept separate from other piping while on the support platform 81. In one example, more than one pump 36 may be installed on the same platform. The suction piping 74 for each pump 36 can be separate while on the unit to minimize vibrations caused by turbulent flow. In another example, more than one pump 36 may be installed on the same platform. The discharge piping 78 in this example is separate for each pump 36 while on the unit to minimize vibrations caused

- 9 -, by turbulent flow. Examples of support surfaces 81 include skids, trailers, and any other frame or structure used for mounting the pump 361 and its associated hardware during operation.
Keeping the suction and discharge branches 74, 78 separate from one another helps reduce vibration in the system 10. An example of a pulsation dampener 82 is shown connected to suction branch 74, and which can account for pressure or flow surges within suction branch 74 to help reduce vibration within the hydraulic fracturing system 10 (Figure 1).
[0023] An additional vibration reducing component includes a groove to connection joint 84, which provides a fluid type connection between the suction branch 74 and suction lead 86 on the suction side of pump 361. In one example, the suction lead 86 includes a suction manifold to help ensure sufficient flow to the hydraulic fracturing pump and eliminate cavitation, which causes violent vibrations. Referring now to Figure 3, a schematic example of one embodiment of a grooved connection joint 84 is provided in an exploded view. Here, the connection joint 84 includes a pair of semi-circular clamp members 88, 90 that are joined to one another by a nut 92 and bolt 94. Flange portions 96, 98 on respective clamp members 88, 90 include openings through which bolt 94 can be inserted and for attachment with nut 92 to hold together the clamp members 88, 90. Opposing ends of the clamp members 88, 90 may also include flange members that can be attached by a nut bolt arrangement as shown. The inner surfaces of clamp members 88, 90 are complementarily formed to engage grooves 100, 102 shown formed respectively along the outer circumferences of the suction branch 74 and suction lead 86. An advantage of the grooved connection joint 84 is that the suction branch 74 and suction lead 86 are pivotable with respect to one another, while still maintaining a fluid type communication across the connection joint 84. One example of a pivotable motion is where the suction branch 74 and/or suction lead 86 are reoriented so that they are no longer coaxial with one another.
Facilitating relative pivoting movement between the suction branch 74 and suction lead 86 across the grooved connection joint 84 provides another way of reducing vibration within the system 10 (Figure 1).
One non-limiting example of a grooved connection joint 84 is referred to as a rigid coupling and may be obtained from Victaulic, 1833 North Promenade Boulevard, Stafford, Texas 77477, 1-800-PICK-VIC.
[0024] Referring back to Figure 2, additional means for reducing vibration in the system 10 (Figure 1) includes strategically locating cable coil assemblies 104 along the suction and discharge branches 74, 78. As its name implies, the cable coil assembly 104 is made up of

-10-strands of elastic material wound into a generally helical configuration. One example of a cable coil assembly 104 shown in a side perspective view in Figure 4 and which includes a coil 106, shown formed from a wire rope coiled into a helix, and lower and upper mounting bars 108, 104 anchoring each half turn of the coil 106. The bars 108, 110 are elongate members with rectangular cross sections that respectively couple with lower and upper plates 112, 114. The elements of the coil assembly 104 of Figure 4 provide an example of a cohesive mounting arrangement for supporting the associated suction branch 74. In this example, a U-bolt 116 is shown affixing the upper plate 114 to suction branch 74; and a semi-circular grommet 118 is provided between the U-bolt 116 and the suction branch 74. An alternate embodiment of the cable coil assembly 104A is also illustrated in Figure 4 and which is coupled with discharge branch 78. Cable coil assembly 104A includes a yoke 120 mounted to upper plate 114A. In one example, yoke 120 is formed from an elastomeric material.
[0025] Referring back to Figure 2, swivel assemblies 1221_3 are shown included at strategic locations within the discharge branch 78. The swivel assemblies 1221_3 allow adjacent sections of the piping to swivel, i.e. rotate with respect to one another. By strategically locating swivel assemblies 1221_3 in portions of a piping run that includes turns or elbows, entire segments of the piping run can be moveable with respect to other pipe segments. Moreover, as the adjacent sections of piping are coupled by a swivel assembly, the relative motion can take place without introducing stress or strain into the pipe itself. Thus implementation of the swivel assemblies can absorb vibrational motion through stress free flexing thereby further reducing and attenuating vibration in the system 10. It should be pointed out that the number of swivel assemblies 1221_3 shown is merely illustrative, and that any number of swivel assemblies can be included. Figure 5 shows one example of a swivel assembly 122 and which includes sections of pipe 124, 126 that are joined to one another by a swivel joint 128. Swivel joint 128 sealingly couples together the sections of pipe 124, 126 and yet allows relative rotation of the pipes 124, 126 as illustrated by arrows A1, A2. In one embodiment, strategically locating assemblies 122 within the discharge branch 78 (Figure 2) for entire sections of discharge branch 78 to move along an arc with respect to other sections of the discharge branch 78.
Further included in this example of the swivel assembly of Figure 5 are fittings 130, 132 shown on the ends of pipes 124, 126 that are distal from the swivel joint 128. The fittings 130, 132 allow for connection to lines 134, 136 where lines make up piping within the discharge branch 78 of Figure 2. In one

-11-, embodiment, fittings 130, 132 are hammer unions, which are female threaded wings with three large lugs on the outside which are struck with sledge hammers to ensure that they are tight. An example of a hammer wing is visible in Figure 6 where pipe 122A connects with pump 36. An example swivel assembly 122 for use herein may be acquired from FMC
Technologies, 187 North Sam Houston Parkway West, Houston, Texas 77086, 281.591.4000.
[0026] Figure 6 shows in a perspective view examples of portions of a suction branch 74 and discharge branch 78 coupled with a pump 36. Included in the example of the discharge branch 78 is an alternate example of a swivel assembly 122A which includes sections of piping, and more than one swivel joint 128A, accordingly, multiple examples of the swivel joint 122 can be incorporated in the disclosure herein. Further illustrated is an example of the pulsation dampener 82 and which couples with the suction branch 74 via grooved connection joints 84. Moreover, the downstream end of the "T" fitting connects to the actual intake of pump 36 with the grooved connection joint 84.
[0027] Figure 7 shows a side perspective view and an alternate example of the cable coil assembly in 104B, wherein multiple coils 106B are included with the coil assembly 104B.
Further, it should be pointed out that examples of the cable coil assembly 104 exists wherein an axis of the helix of the coil 106 is oriented at angles that vary from an axis of the associated piping supported by the cable coil assembly 104. Changing the direction of the axis of the helix of the coil 106 can provide for different frame constant values thereby effecting continuation of vibration in different manners.
[0028] Figure 8 includes a graph 138 whose ordinate represents gravitational forces and abscissa represents values of time. In one example, gravitational forces were measured in three coordinate axes from a hydraulic fracturing system during its operation. Plots 140, 142, 144 represent gravitational forces measure along those axes over time. Similarly, graph 146 includes plots 148, 150, 152, which represent measured gravitational forces along those same axes over time, and were obtained from a hydraulic fracturing system having the vibrational reducing elements described herein. As can be seen from comparing graph 138 and graph 146, the gravitational forces were significantly and unexpectedly reduced by implementation by the vibration reducing forces. Sensors 154 (Figure 1) are shown mounted to the wellhead, and which can be used to measure the gravitational forces. In another example, multiple sensors 154

- 12-, , may be mounted to multiple parts of the hydraulic fracturing fleet. In one example one or more sensors are mounted on each hydraulic fracturing fluid end as well as the power end. In another example a sensor is mounted near the blender discharge pump. Optionally, information sensed by sensors 154 is transmitted to an information handling system ("IHS") 156.
The IHS 156 may also be used to store recorded data as well as processing the data into a readable format. The IHS 156 may include a processor, memory accessible by the processor, nonvolatile storage area accessible by the processor, and logic algorithms for performing each of the steps above described. Information is transmitted to IHS 156 from sensor 154 via communication means 158, which can be hardwired, wireless, pneumatic, or any other way of transmitting information.
Further, IHS 156 communicates to a controller 160 via communication means 162, which can be similar to communication means 158. In an example of operation, controller 160 can be used for sending control commands for operation of the system 10, and thus can utilize vibration information from sensors 154 to adjust control commands. In one example, the communicates with the World Wide Web to allow for remote reviewing of the information. In one example, the IHS 156 system also receives information from a VFD. In another example, the IHS 156 system receives information such as fluid rate, boost pressure, discharge pressure, and other information to coordinate with the vibration data.
[0029] The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.

- 13 -APPENDIX
SYSTEM FOR PUMPING HYDRAULIC FRACTURING FLUID USING ELECTRIC
PUMPS
BACKGROUND OF THE INVENTION
1. Field of the Invention [0001] This technology relates to hydraulic fracturing in oil and gas wells.
In particular, this technology relates to pumping fracturing fluid into an oil or gas well using pumps powered by electric motors.
2. Brief Description of Related Art [0002] Hydraulic fracturing has been used for decades to stimulate production from conventional oil and gas wells. The practice consists of pumping fluid into a wellbore at high pressure. Inside the wellbore, the fluid is forced into the formation being produced. When the fluid enters the formation, it fractures, or creates fissures, in the formation. Water, as well as other fluids, and some solid proppants, are then pumped into the fissures to stimulate the release of oil and gas from the formation.
[0003] Fracturing rock in a formation requires that the fracture fluid be pumped into the wellbore at very high pressure. This pumping is typically performed by large diesel-powered pumps.
Such pumps are able to pump fracturing fluid into a wellbore at a high enough pressure to crack the formation, but they also have drawbacks. For example, the diesel pumps are very heavy, and thus must be moved on heavy duty trailers, making transport of the pumps between oilfield sites expensive and inefficient. In addition, the diesel engines required to drive the pumps require a relatively high level of expensive maintenance. Furthermore, the cost of diesel fuel is much higher than in the past, meaning that the cost of running the pumps has increased.

- 14 -, APPENDIX
[0004] What is needed therefore, is a pump system for hydraulic fracturing fluid that overcomes the problems associated with diesel pumps.

- 15-, APPENDIX
SUMMARY OF THE INVENTION
[0005] Disclosed herein is a system for hydraulically fracturing an underground formation in an oil or gas well to extract oil or gas from the formation, the oil or gas well having a wellbore that permits passage of fluid from the wellbore into the formation. The system includes a plurality of electric pumps fluidly connected to the well, and configured to pump fluid into the wellbore at high pressure so that the fluid passes from the wellbore into the formation, and fractures the formation. The system also includes a plurality of generators electrically connected to the plurality of electric pumps to provide electrical power to the pumps. At least some of the plurality of generators can be powered by natural gas. In addition, at least some of the plurality of generators can be turbine generators.
[0006] In one embodiment, the system further includes an A/C console and a variable frequency drive that controls the speed of the pumps. Furthermore, the electric pumps, as well as the electric generators, can be mounted on vehicles, and can be ported from one well to another. The vehicles can be trucks and can have at least five axles.
[0007] Further disclosed herein is a system for fracturing a rock formation in an oil or gas well by pumping hydraulic fracturing fluid into the well that includes a pump, an electric motor, a variable frequency drive, and a natural gas powered electric generator. The pump is configured for pumping the hydraulic fracturing fluid into the well, and then from the well into the formation, and is capable of pumping the hydraulic fracturing fluid at high pressure to crack the formation. The electric motor can have a high-strength steel or steel alloy shaft attached to the pump and configured to drive the pump. The variable frequency drive can be connected to the electric motor to control the speed of the motor. In addition, the natural gas powered generator,

- 16-, APPENDIX
which can be a turbine generator, can be connected to the electric motor and provide electric power to the electric motor.
[0008] In one embodiment, the pump can be a triplex or a quinteplex pump, optionally rated at about 2250 hydraulic horsepower or more. In addition, the pump can also have 4.5 inch diameter plungers with an eight inch stroke. In another embodiment, the electric motor can have a maximum continuous power output of about 1500 brake horsepower, 1750 brake horsepower, or more, and a maximum continuous torque of about 8750 lb-ft or more.
Furthermore, the electric motor can have a high temperature rating of about 1100 degrees C or more, and a shaft composed of 4340 alloy steel.
[0009] In another embodiment, variable frequency drive can frequently perform electric motor diagnostics to prevent damage to the electric motor if it becomes grounded or shorted. In addition, the variable frequency drive can include power semiconductor heat sinks having one or more thermal sensors monitored by a microprocessor to prevent semiconductor damage caused by excessive heat.
100101 Also disclosed herein is a system for hydraulically fracturing an underground formation in an oil or gas well to extract oil or gas from the formation, the oil or gas well having a wellbore that permits passage of fluid from the wellbore into the formation. The system includes a trailer for attachment to a truck. Two or more electric pumps can be attached to the trailer and are fluidly connected to the well, the electric pumps configured to pump fluid into the wellbore at high pressure so that the fluid passes from the wellbore into the formation, and fractures the formation. One or more electric motors are attached to the electric pumps to drive the pumps.
The electric motors can also be attached to the trailer. A natural gas powered generator is provided for connection to the electric motor to provide electric power to the electric motor. The

- 17-=
APPENDIX
system of claim can further include a variable frequency drive attached to the trailer and connected to the electric motor to control the speed of the motor. In addition, the system can include a skid to which at least one of the electric pumps, the one or more electric motors, and the variable frequency drives are attached.
[0011] Also disclosed herein is a process for stimulating an oil or gas well by hydraulically fracturing a formation in the well. The process includes the steps of pumping fracturing fluid into the well with an electrically powered pump at a high pressure so that the fracturing fluid enters and cracks the formation, the fracturing fluid having at least a liquid component and a solid proppant, and inserting the solid proppant into the cracks to maintain the cracks open, thereby allowing passage of oil and gas through the cracks. The process can further include powering the electrically powered pump with a natural gas generator, such as, for example, a turbine generator.

-18-, , APPENDIX
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present technology will be better understood on reading the following detailed description of nonlimiting embodiments thereof, and on examining the accompanying drawing, in which:
[0013] Fig. 1 is a schematic plan view of equipment used in a hydraulic fracturing operation, according to an embodiment of the present technology; and [0014] Fig. 2 is a schematic plan view of equipment used in a hydraulic fracturing operation, according to an alternate embodiment of the present technology.

- 19-APPENDIX
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] The foregoing aspects, features, and advantages of the present technology will be further appreciated when considered with reference to the following description of preferred embodiments and accompanying drawing, wherein like reference numerals represent like elements. In describing the preferred embodiments of the technology illustrated in the appended drawing, specific terminology will be used for the sake of clarity. However, the technology is not intended to be limited to the specific terms used, and it is to be understood that each specific term includes equivalents that operate in a similar manner to accomplish a similar purpose.
[0016] Fig. 1 shows a plan view of equipment used in a hydraulic fracturing operation.
Specifically, there is shown a plurality of pumps 10 mounted to pump vehicles 12. The pump vehicles 12 can be trucks having at least five axles. In the embodiment shown, the pumps 10 are powered by electric motors 14, which can also be mounted to the pump vehicles 12. The pumps are fluidly connected to the wellhead 16 via the missile 18. As shown, the pump vehicles 12 can be positioned near enough to the missile 18 to connect fracturing fluid lines 20 between the pumps 10 and the missile 18. The missile 18 is then connected to the wellhead 16 and configured to deliver fracturing fluid provided by the pumps 10 to the wellhead 16.
[0017] In some embodiments, each electric motor 14 can be capable of delivering about 1500 brake horsepower (BHP), 1750 BHP, or more, and each pump 10 can optionally be rated for about 2250 hydraulic horsepower (HHP) or more. In addition, the components of the system, including the pumps 10 and the electric motors 14, can be capable of operating during prolonged pumping operations, and in temperature in a range of about 0 degrees C or less to about 55 degrees C or more. In addition, each electric motor 14 can be equipped with a variable

- 20 -APPENDIX
frequency drive (VFD), and an A/C console, that controls the speed of the electric motor 14, and hence the speed of the pump 10.
[0018] The electric motors 14 of the present technology can be designed to withstand an oilfield environment. Specifically, some pumps 10 can have a maximum continuous power output of about 1500 BHP, 1750 BHP, or more, and a maximum continuous torque of about 8750 lb-ft or more. Furthermore, electric motors 14 of the present technology can include class H insulation and high temperature ratings, such as about 1100 degrees C or more. In some embodiments, the electric motor 14 can include a single shaft extension and hub for high tension radial loads, and a high strength 4340 alloy steel shaft, although other suitable materials can also be used.
[0019] The VFD can be designed to maximize the flexibility, robustness, serviceability, and reliability required by oilfield applications, such as hydraulic fracturing.
For example, as far as hardware is concerned, the VFD can include packaging receiving a high rating by the National Electrical Manufacturers Association (such as nema 1 packaging), and power semiconductor heat sinks having one or more thermal sensors monitored by a microprocessor to prevent semiconductor damage caused by excessive heat. Furthermore, with respect to control capabilities, the VFD can provide complete monitoring and protection of drive internal operations while communicating with an operator via one or more user interfaces. For example, motor diagnostics can be performed frequently (e.g., on the application of power, or with each start), to prevent damage to a grounded or shorted electric motor 14. The electric motor diagnostics can be disabled, if desired, when using, for example, a low impedance or high-speed electric motor.
[0020] In some embodiments, the pump 10 can optionally be a 2250 HHP triplex or quinteplex pump. The pump 10 can optionally be equipped with 4.5 inch diameter plungers that have an

-21-, APPENDIX
eight (8) inch stroke, although other size plungers can be used, depending on the preference of the operator. The pump 10 can further include additional features to increase its capacity, durability, and robustness, including, for example, a 6.353 to 1 gear reduction, autuofrettaged steel or steel alloy fluid end, wing guided slush type valves, and rubber spring loaded packing.
[0021] In addition to the above, certain embodiments of the present technology can include a skid (not shown) for supporting some or all of the above-described equipment.
For example, the skid can support the electric motor 14 and the pump 10. In addition, the skid can support the VFD. Structurally, the skid can be constructed of heavy-duty longitudinal beams and cross-members made of an appropriate material, such as, for example, steel. The skid can further include heavy-duty lifting lugs, or eyes, that can optionally be of sufficient strength to allow the skid to be lifted at a single lift point.

[0022] Referring back to Fig. 1, also included in the equipment is a plurality of electric generators 22 that are connected to, and provide power to, the electric motors 14 on the pump vehicles 12. To accomplish this, the electric generators 22 can be connected to the electric motors 14 by power lines (not shown). The electric generators 22 can be connected to the electric motors 14 via power distribution panels (not shown). In certain embodiments, the electric generators 22 can be powered by natural gas. For example, the generators can be powered by liquefied natural gas. The liquefied natural gas can be converted into a gaseous form in a vaporizer prior to use in the generators. The use of natural gas to power the electric generators 22 can be advantageous because, where the well is a natural gas well, above ground natural gas vessels 24 can already be placed on site to collect natural gas produced from the well.
Thus, a portion of this natural gas can be used to power the electric generators 22, thereby reducing or eliminating the need to import fuel from offsite. If desired by an operator, the , APPENDIX
electric generators 22 can optionally be natural gas turbine generators, such as those shown in Fig. 2.

[0023] Fig. 1 also shows equipment for transporting and combining the components of the hydraulic fracturing fluid used in the system of the present technology. In many wells, the fracturing fluid contains a mixture of water, sand or other proppant, acid, and other chemicals.
Examples of fracturing fluid components include acid, anti-bacterial agents, clay stabilizers, corrosion inhibitors, friction reducers, gelling agents, iron control agents, pH adjusting agents, scale inhibitors, and surfactants. Historically, diesel has at times been used as a substitute for water in cold environments, or where a formation to be fractured is water sensitive, such as, for example, clay. The use of diesel, however, has been phased out over time because of price, and the development of newer, better technologies.

[0024] In Fig. 1, there are specifically shown sand transporting vehicles 26, an acid transporting vehicle 28, vehicles for transporting other chemicals 30, and a vehicle carrying a hydration unit 32, such as, for example, a water pump. Also shown are fracturing fluid blenders 34, which can be configured to mix and blend the components of the hydraulic fracturing fluid, and to supply the hydraulic fracturing fluid to the pumps 10. In the case of liquid components, such as water, acids, and at least some chemicals, the components can be supplied to the blenders 34 via fluid lines (not shown) from the respective component vehicles, or from the hydration unit 32. In the case of solid components, such as sand, the component can be delivered to the blender 34 by a conveyor belt 38. The water can be supplied to the hydraulic unit 32 from, for example, water tanks 36 onsite. Alternately, the water can be provided by water trucks.
Furthermore, water can be provided directly from the water tanks 36 or water trucks to the blender 34, without first passing through the hydration unit 32.

APPENDIX

[0025] Pump control and data monitoring equipment 40 can be mounted on a control vehicle 42, and connected to the pumps 10, electric motors 14, blenders 34, and other downhole sensors and tools (not shown) to provide information to an operator, and to allow the operator to control different parameters of the fracturing operation. For example, the pump control and data monitoring equipment 40 can include an A/C console that controls the VFD, and thus the speed of the electric motor 14 and the pump 10. Other pump control and data monitoring equipment can include pump throttles, a pump VFD fault indicator with a reset, a general fault indicator with a reset, a main estop, a programmable logic controller for local control, and a graphics panel. The graphics panel can include, for example, a touchscreen interface.

[0026] Referring now to Fig. 2, there is shown an alternate embodiment of the present technology. Specifically, there is shown a plurality of pumps 110 which, in this embodiment, are mounted to pump trailers 112. As shown, the pumps 110 can optionally be loaded two to a trailer 112, thereby minimizing the number of trailers needed to place the requisite number of pumps at a site. The ability to load two pumps 110 on one trailer 112 is possible because of the relatively light weight of the electric pumps 110 compared to other known pumps, such as diesel pumps. In the embodiment shown, the pumps 110 are powered by electric motors 114, which can also be mounted to the pump trailers 112. Furthermore, each electric motor 114 can be equipped with a VFD, and an A/C console, that controls the speed of the motor 114, and hence the speed of the pumps 110.

[0027] In addition to the above, the embodiment of Fig. 2 can include a skid (not shown) for supporting some or all of the above-described equipment. For example, the skid can support the electric motors 114 and the pumps 110. In addition, the skid can support the VFD. Structurally, the skid can be constructed of heavy-duty longitudinal beams and cross-members made of an µ
APPENDIX
appropriate material, such as, for example, steel. The skid can further include heavy-duty lifting lugs, or eyes, that can optionally be of sufficient strength to allow the skid to be lifted at a single lift point.

[0028] The pumps 110 are fluidly connected to a wellhead 116 via a missile 118. As shown, the pump trailers 112 can be positioned near enough to the missile 118 to connect fracturing fluid lines 120 between the pumps 110 and the missile 118. The missile 118 is then connected to the wellhead 116 and configured to deliver fracturing fluid provided by the pumps 110 to the wellhead 116.

[0029] Still referring to Fig. 2, this embodiment also includes a plurality of turbine generators 122 that are connected to, and provide power to, the electric motors 114 on the pump trailers 112. To accomplish this, the turbine generators 122 can be connected to the electric motors 114 by power lines (not shown). The turbine generators 122 can be connected to the electric motors 114 via power distribution panels (not shown). In certain embodiments, the turbine generators 122 can be powered by natural gas, similar to the electric generators 22 discussed above in reference to the embodiment of Fig. 1. Also included are control units 144 for the turbine generators 122.

[0030] The embodiment of Fig. 2 can include other equipment similar to that discussed above.
For example, Fig. 2 shows sand transporting vehicles 126, acid transporting vehicles 128, other chemical transporting vehicles 130, hydration units 132, blenders 134, water tanks 136, conveyor belts 138, and pump control and data monitoring equipment 140 mounted on a control vehicle 142. The function and specifications of each of these is similar to corresponding elements shown in Fig. 1.

, APPENDIX

[0031] Use of pumps 10, 110 powered by electric motors 14, 114 and natural gas powered electric generators 22 (or turbine generators 122) to pump fracturing fluid into a well is advantageous over known systems for many different reasons. For example, the equipment (e.g.
pumps, electric motors, and generators) is lighter than the diesel pumps commonly used in the industry. The lighter weight of the equipment allows loading of the equipment directly onto a truck body. In fact, where the equipment is attached to a skid, as described above, the skid itself can be lifted on the truck body, along with all the equipment attached to the skid, in one simple action. Alternatively, and as shown in Fig. 2, trailers 112 can be used to transport the pumps 110 and electric motors 114, with two or more pumps 110 carried on a single trailer 112. Thus, the same number of pumps 110 can be transported on fewer trailers 112. Known diesel pumps, in contrast, cannot be transported directly on a truck body or two on a trailer, but must be transported individually on trailers because of the great weight of the pumps.

[0032] The ability to transfer the equipment of the present technology directly on a truck body or two to a trailer increases efficiency and lowers cost. In addition, by eliminating or reducing the number of trailers to carry the equipment, the equipment can be delivered to sites having a restricted amount of space, and can be carried to and away from worksites with less damage to the surrounding environment. Another reason that the electric pump system of the present technology is advantageous is that it runs on natural gas. Thus, the fuel is lower cost, the components of the system require less maintenance, and emissions are lower, so that potentially negative impacts on the environment are reduced.

[0033] In practice, a hydraulic fracturing operation can be carried out according to the following process. First, the water, sand, and other components are blended to form a fracturing fluid, which is pumped down the well by the electric-powered pumps. Typically, the well is designed APPENDIX
so that the fracturing fluid can exit the wellbore at a desired location and pass into the surrounding formation. For example, in some embodiments the wellbore can have perforations that allow the fluid to pass from the wellbore into the formation. In other embodiments, the wellbore can include an openable sleeve, or the well can be open hole. The fracturing fluid can be pumped into the wellbore at a high enough pressure that the fracturing fluid cracks the formation, and enters into the cracks. Once inside the cracks, the sand, or other proppants in the mixture, wedges in the cracks, and holds the cracks open.

[0034] Using the pump control and data monitoring equipment 40, the operator can monitor, gauge, and manipulate parameters of the operation, such as pressures, and volumes of fluids and proppants entering and exiting the well. For example, the operator can increase or decrease the ratio of sand to water as the fracturing process progresses and circumstances change.

[0035] This process of injecting fracturing fluid into the wellbore can be carried out continuously, or repeated multiple times in stages, until the fracturing of the formation is optimized. Optionally, the wellbore can be temporarily plugged between each stage to maintain pressure, and increase fracturing in the formation. Generally, the proppant is inserted into the cracks formed in the formation by the fracturing, and left in place in the formation to prop open the cracks and allow oil or gas to flow into the wellbore.

[0036] While the technology has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the technology. Furthermore, it is to be understood that the above disclosed embodiments are merely illustrative of the principles and applications of the present technology. Accordingly, numerous modifications can be made to the illustrative APPENDIX
embodiments and other arrangements can be devised without departing from the spirit and scope of the present technology as defined by the appended claims.

Claims (19)

What is claimed is:

1. A hydraulic fracturing system for fracturing a subterranean formation comprising:
an electrically powered fracturing pump having a suction side and a discharge side;
a suction branch of piping having fracturing fluid therein;
a discharge branch of piping having therein pressurized fracturing fluid supplied from the fracturing pump;
a tubular suction lead having an end mounted to the suction side and an opposite end coupled to an end of the suction branch by a grooved connection, and which is pivotal with respect to the suction branch; and swivel connections strategically located in the discharge branch of piping, so that when pressurized fracturing fluid flows through the discharge branch of piping, a section of the discharge branch of piping is axially rotatable with an adjacent section of the discharge branch of piping.

2. The hydraulic fracturing system of Claim 1, further comprising helical coils supporting suction and discharge branches of piping at strategically located positions.

3. The hydraulic fracturing system of Claim 1, wherein a one of the helical coils has an axis that is disposed oblique with an axis of an adjacent amount of piping.

4. The hydraulic fracturing system of Claim 1, further comprising a pulsation dampener in fluid communication with the suction branch and adjacent the suction lead.

5. The hydraulic fracturing system of Claim 1, wherein the fracturing pump is a first fracturing pump, wherein the suction and discharge branches respectively intersect with suction and discharge piping that are in fluid communication with a second fracturing pump, and wherein the suction and discharge branch intersections are at locations that are each spaced away from a surface on which the first fracturing pump is supported.

6. The hydraulic fracturing system of Claim 5, wherein the surface on which the first fracturing pump is supported comprises a trailer, truck, or skid.

7. The hydraulic fracturing system of Claim 1, further comprising a turbine generator for generating electricity used for powering the fracturing pump.

8. The hydraulic fracturing system of Claim 1, further comprising a controller that uses vibration data to monitor and/or adjust control commands of the system.

9. A method of hydraulically fracturing a subterranean formation comprising:
pressurizing fracturing fluid with a hydraulic fracturing system that comprises an electrically powered fracturing pump, a tubular suction branch, and a tubular discharge branch;
drawing the fracturing fluid into the fracturing pump through the suction branch;
discharging the fracturing fluid from the fracturing pump through the discharge branch;
introducing the fracturing fluid to the formation to create a fracture in the formation; and reducing vibration in the hydraulic fracturing system by, strategically locating swivel joints in the suction and discharge branches, so that designated sections of the suction and discharge branches are moveable with respect to other sections of the suction and discharge branches, providing a grooved connection in the suction branch, so that piping supplying fracturing fluid to the fracturing pump is pivotable with respect to the fracturing pump, and maintaining portions of the suction and discharge branches that are supported on a surface that supports the fracturing pump from other suction and discharge branches.

10. The method of Claim 9, further comprising resting the suction and discharge branches on helical coils.

11. The method of Claim 9, further comprising including an elastomeric yoke with the helical coils.

12. The method of Claim 9, diverting some of the fluid in the suction branch to an accumulator or pulsation dampener.

13. The method of Claim 9, further comprising powering the fracturing pump with electricity generated by a turbine generator or other electrical power supply.

14. The method of Claim 9, further comprising using vibration data to monitor and/or adjust control commands of the system.

15. A method of hydraulically fracturing a subterranean formation comprising:
pressurizing fracturing fluid with a hydraulic fracturing system that includes an electrically powered fracturing pump and piping coupled with the fracturing pump;
discharging pressurized fracturing fluid for delivery to a wellbore that intersects the formation so that the pressurized fracturing fluid fractures the formation;
and reducing vibration in the hydraulic fracturing system by providing joints in the piping at strategic locations so that adjacent sections of the piping pivot and/or swivel.

16. The method of Claim 15, wherein the joints comprise a swiveling joint that allows relative rotational movement between adjacent sections of the piping.

17. The method of Claim 15, wherein the joints comprise a grooved connection joint that allows pivoting between adjacent sections of the piping.

18. The method of Claim 15, further comprising maintaining the piping separate from piping that is in fluid communication with another fracturing pump while on the unit.

19. The method of Claim 15, further comprising using vibration data to monitor and/or adjust control commands of the system.