WO2016176531A1

WO2016176531A1 - Optimized pressure exchanger fracturing

Info

Publication number: WO2016176531A1
Application number: PCT/US2016/029961
Authority: WO
Inventors: Rod William Shampine; Jijo Oommen JOSEPH
Original assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp
Current assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp
Priority date: 2015-04-30
Filing date: 2016-04-29
Publication date: 2016-11-03
Anticipated expiration: 2017-10-30

Abstract

Apparatus and methods for forming and pressurizing well operations fluids, utilizing a stream of dirty fluid at a first pressure and a stream of clean fluid at a second pressure that is substantially greater than the first pressure. A pressure exchanger receives the streams of dirty and clean fluids to pressurize the stream of dirty fluid. A portion of the clean fluid is communicated into the dirty fluid within the pressure exchanger. A stream of the pressurized dirty fluid is discharged from the pressure exchanger, as well as another stream comprising clean and perhaps dirty fluid.

Description

Optimized Pressure Exchanger Fracturing

Cross-Reference to Related Applications

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 62/155,077, titled "OPTIMIZED PRESSURE EXCHANGER FRACTURING," filed April 30, 2015, the entire disclosure of which is hereby incorporated herein by reference.

Background of the Disclosure

[0002] A variety of fluids are used in oil and gas operations. Fluids may be pumped into the subterranean formation through the use of one or more high-pressure pumps. Abrasive fluids, such as solids-laden fluids containing insoluble solid particles, can reduce functional life and increase maintenance of the high-pressure pumps.

Summary of the Disclosure

[0003] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify

indispensable features of the claimed subject matter, nor is it intended for use as an aid in limiting the scope of the claimed subject matter.

[0004] The present disclosure introduces an apparatus that includes a pressure exchanger and a fluid control device. The pressure exchanger includes a rotor, and at least one chamber extends through the rotor. The pressure exchanger is operable to receive dirty fluid at a first pressure into the at least one chamber via a dirty fluid inlet, and to receive clean fluid at a second pressure into the at least one chamber via a clean fluid inlet to pressurize the dirty fluid to a third pressure, the second and third pressures being substantially greater than the first pressure. The pressure exchanger is also operable to discharge the dirty fluid at the third pressure from the at least one chamber via a dirty fluid outlet, and to discharge the clean fluid from the at least one chamber via a clean fluid outlet. The fluid control device is fluidly connected with at least one of the clean fluid inlet, the clean fluid outlet, the dirty fluid inlet, and the dirty fluid outlet, and is operable to maintain a first flow rate of the clean fluid discharged via the clean fluid outlet at less than a second flow rate of the clean fluid received via the clean fluid inlet. [0005] The present disclosure also introduces a method that includes operating a pressure exchanger to receive a stream of dirty fluid at a first pressure into at least one chamber of the pressure exchanger, and to receive a stream of clean fluid at a second pressure into the at least one chamber to pressurize the dirty fluid within the at least one chamber, the second pressure being substantially greater than the first pressure. The pressure exchanger then discharges a stream of the pressurized dirty fluid from the at least one chamber, and discharges a stream of the clean fluid from the at least one chamber. The method also includes controlling a first flow rate of the received stream of clean fluid or a second flow rate of the discharged stream of clean fluid such that the second flow rate is less than the first flow rate.

[0006] The present disclosure also introduces a method that includes forming a stream of dirty fluid at a first pressure and forming a stream of clean fluid at a second pressure, the second pressure being substantially greater than the first pressure. The method also includes

pressurizing the stream of dirty fluid utilizing a pressure exchanger. The pressure exchanger includes a rotor disposed within a housing and having a pressure chamber. Pressurizing the stream of dirty fluid utilizing the pressure exchanger may includes directing a portion of the stream of dirty fluid into the pressure chamber, directing a first portion of the stream of clean fluid into the pressure chamber to pressurize the dirty fluid within the pressure chamber as the rotor rotates within the housing, thereby depressurizing the clean fluid within the pressure chamber. The method also includes directing a second portion of the stream of clean fluid into a gap defined between the rotor and the housing, discharging a stream including the pressurized dirty fluid from the pressure exchanger, and discharging a stream including the depressurized clean fluid from the pressure exchanger.

[0007] These and additional aspects of the present disclosure are set forth in the description that follows, and/or may be learned by a person having ordinary skill in the art by reading the materials herein and/or practicing the principles described herein. At least some aspects of the present disclosure may be achieved via means recited in the attached claims.

Brief Description of the Drawings

[0008] The present disclosure is understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0009] FIG. 1 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0010] FIG. 2 is a schematic view of the apparatus shown in FIG. 1 in an operational stage according to one or more aspects of the present disclosure.

[0011] FIG. 3 is a schematic view of the apparatus shown in FIG. 2 in another operational stage according to one or more aspects of the present disclosure.

[0012] FIG. 4 is a schematic view of the apparatus shown in FIGS. 2 and 3 in another operational stage according to one or more aspects of the present disclosure.

[0013] FIG. 5 is a partially exploded view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0014] FIG. 6 is a sectional view of an example implementation of the apparatus shown in

FIG. 5 according to one or more aspects of the present disclosure.

[0015] FIG. 7 is another view of the apparatus shown in FIG. 6 in a different stage of operation.

[0016] FIG. 8 is an enlarged view of the apparatus shown in FIG. 7 according to one or more aspects of the present disclosure.

[0017] FIG. 9 is an enlarged view of the apparatus shown in FIG. 6 according to one or more aspects of the present disclosure.

[0018] FIG. 10 is a sectional view of another example implementation of the apparatus shown in FIG. 5 according to one or more aspects of the present disclosure.

[0019] FIG. 11 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0020] FIG. 12 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0021] FIG. 13 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0022] FIG. 14 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure. [0023] FIG. 15 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0024] FIG. 16 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0025] FIG. 17 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0026] FIG. 18 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0027] FIG. 19 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0028] FIG. 20 is a schematic view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0029] FIG. 21 is a flow-chart diagram of at least a portion of an example implementation of a method according to one or more aspects of the present disclosure.

[0030] FIG. 22 is a flow-chart diagram of at least a portion of an example implementation of another method according to one or more aspects of the present disclosure.

Detailed Description

[0031] It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments.

Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for simplicity and clarity, and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. It should also be understood that the terms "first," "second," "third," etc., are arbitrarily assigned, are merely intended to differentiate between two or more parts, fluids, etc., and do not indicate a particular orientation or sequence.

[0032] The present disclosure introduces one or more aspects related to utilizing one or more pressure exchangers to divert abrasive fluids away from high-pressure pumps, instead of pumping solids-laden fluid with the high-pressure pumps. A non-abrasive solids-free fluid may be pressurized by the high-pressure pumps, while the pressure exchangers, located downstream from the high-pressure pumps, transfer the pressure from the pressurized solids-free fluid to a low-pressure solids-laden fluid. Such use of pressure exchangers may facilitate improved fluid control during well treatment operations and/or increase functional life of the high-pressure pumps and other wellsite equipment fluidly coupled between the high-pressure pumps and the pressure exchangers.

[0033] As used herein, a "fluid" is a substance that can flow and conform to the outline of its container when the substance is tested at a temperature of 71 °F (22 °C) and a pressure of one atmosphere (atm) (0.1 megapascals (MPa)). A fluid may be liquid, gas, or both. A fluid may be water based or oil based. A fluid may have just one phase or more than one distinct phase. A fluid may be a heterogeneous fluid having more than one distinct phase. Example heterogeneous fluids within the scope of the present disclosure include a solids-laden fluid or slurry (such as may comprise a continuous liquid phase and undissolved solid particles as a dispersed phase), an emulsion (such as may comprise a continuous liquid phase and at least one dispersed phase of immiscible liquid droplets), a foam (such as may comprise a continuous liquid phase and a dispersed gas phase), and mist (such as may comprise a continuous gas phase and a dispersed liquid droplet phase), among other examples also within the scope of the present disclosure. A heterogeneous fluid may comprise more than one dispersed phase. Moreover, one or more of the phases of a heterogeneous fluid may be or comprise a mixture having multiple components, such as fluids containing dissolved materials and/or undissolved solids.

[0034] Plunger pumps may be employed in high-pressure oilfield pumping applications, such as for hydraulic fracturing applications. Plunger pumps are often referred to as positive displacement pumps, intermittent duty pumps, triplex pumps, quintuplex pumps, or frac pumps. Multiple plunger pumps may be employed simultaneously in large-scale operations where tens of thousands of gallons of fluid are pumped into a wellbore. These pumps are linked to each other with a manifold, which is plumbed to collect the output of the multiple pumps and direct it to the wellbore.

[0035] As described above, some fluids (e.g., fracturing fluid) may contain ingredients that are abrasive to the internal components of a pump. For example, a fracturing fluid generally contains proppant or other solid particulate material, which is insoluble in a base fluid. To create fractures, the fracturing fluid may be pumped at high pressures ranging, for example, between about 5,000 to about 15,000 pounds force per square inch (psi) or more. The proppant may initiate the fractures and/or keep the fractures propped open. The propped fractures provide highly permeably flow paths for oil and gas to flow from the subterranean formation, thereby enhancing the production of a well. However, the abrasive fracturing fluid may accelerate wear of the internal components of the pumps. Consequently, the repair, replacement, and

maintenance expenses of the pumps can be quite high, and life expectancy can be low.

[0036] Example implementations of apparatus described herein relate generally to a fluid system for forming and pressurizing a solids-laden fluid (e.g., fracturing fluid) having

predetermined concentrations of solid material for injection into a wellbore during well treatment operations. The fluid system may include a blending or mixing device for receiving and mixing a solids-free carrying fluid or gel and a solid material to form the solids-laden fluid. The fluid system may also include a fluid pressure exchanger for increasing pressure or otherwise energizing of the solids-laden fluid formed by the mixing device before being injected into the wellbore. The fluid pressure exchanger may be utilized to pressurize the solids-laden fluid by facilitating or permitting pressure from a pressurized solids-free fluid to be transferred to a low- pressure solids-laden fluid, among other uses. The fluid pressure exchanger may comprise one or more chambers into which the low-pressure solids-laden fluid and the pressurized solids-free fluid are conducted. The solids-free fluid may be conducted into the chamber at a higher pressure than the solids-laden fluid, and may thus be utilized to pressurize the solids-laden fluid. The pressurized solids-laden fluid is then conducted from the chamber to a wellhead for injection into the wellbore. By pumping just the solids-free fluid with the pumps and utilizing the pressure exchanger to increase the pressure of the solids-laden fluid, the useful life of the pumps may be increased. Example implementations of methods described herein relate generally to utilizing the fluid system to form and pressure the solids-laden fluid for injection into the wellbore during well treatment operations. For clarity and ease of understanding, the solids- laden fluid may be referred to hereinafter simply as a "dirty fluid" and the solids-free fluid may be referred to hereinafter simply as a "clean fluid."

[0037] FIG. 1 is a schematic view of an example implementation of a chamber 100 of a fluid pressure exchanger for pressurizing a dirty fluid with a clean fluid according to one or more aspects of the present disclosure. The chamber 100 includes a first end 101 and a second end 102. The chamber 100 may include a border or boundary 103 between the dirty and clean fluids defining a first volume 104 and a second volume 105 within the chamber 100. The boundary 103 may be a membrane that is impermeable or semi-permeable to a fluid, such as a gas. The membrane may be an impermeable membrane in implementations in which the dirty and clean fluids are incompatible fluids, or when mixing of the dirty and clean fluids is to be substantially prevented, such as to recycle the clean fluid absent contamination by the dirty fluid. The boundary 103 may be a semi -permeable membrane in implementations permitting some mixing of the clean fluid with the dirty fluid, such as to foam the dirty fluid when the clean fluid comprises a gas.

[0038] The boundary 103 may be a floating piston or separator slidably disposed along the chamber 100. The floating piston may physically isolate the dirty and clean fluids and be movable via pressure differential between the dirty and clean fluids. The floating piston may be retained within the chamber 100 by walls or other features of the chamber 100. The density of the floating piston may be set between that of the clean and dirty fluids, such as may cause gravity to locate the floating piston at an interface of the dirty and clean fluids when the chamber 100 is oriented vertically.

[0039] The boundary 103 may also be a diffusion or mixing zone in which the dirty and clean fluids mix or otherwise interact during pressurizing operations. The boundary 103 may also not exist, such that the first and second volumes 104 and 105 form a continuous volume within the chamber 100. A first inlet valve 106 is operable to conduct the dirty fluid into the first volume 104 of the chamber 100, and a second inlet valve 107 is operable to conduct the clean fluid into the second volume 105 of the chamber 100.

[0040] For example, FIG. 2 is a schematic view of the chamber 100 shown in FIG. 1 in an operational stage according to one or more aspects of the present disclosure, during which the dirty fluid 110 has been conducted into the chamber 100 through the first inlet valve 106 at the first end 101, such as via one or more fluid conduits 108. Consequently, the dirty fluid 110 may move the boundary 103 within the chamber 100 along a direction substantially parallel to the longitudinal axis 111 of the chamber 100, thereby increasing the first volume 104 and decreasing the second volume 105. The first inlet valve 106 may be closed after entry of the dirty fluid 110 into the chamber 100.

[0041] FIG. 3 is a schematic view of the chamber 100 shown in FIG. 2 in a subsequent operational stage according to one or more aspects of the present disclosure, during which a clean fluid 120 is being conducted into the chamber 100 through the second inlet valve 107 at the second end 102, such as via one or more fluid conduits 109. The clean fluid 120 may be conducted into the chamber 100 at a higher pressure compared to the pressure of the dirty fluid 110. Consequently, the higher-pressure clean fluid 120 may move the boundary 103 and the dirty fluid 110 within the chamber 100 back towards the first end 101, thereby reducing the volume of the first volume 104 and thereby pressurizing or otherwise energizing the dirty fluid 110. The clean fluid 120 may be a combustible or cryogenic gas that, upon combustion or heating, acts to pressurize the dirty fluid 110, whether instead of or in addition to the higher pressure of the clean fluid 120 acting to pressurize the dirty fluid 110. The boundary 103 and/or other components may include one or more burst discs to protect against overpressure from the clean fluid 120.

[0042] As shown in FIG. 4, the boundary 103 may continue to reduce the first volume 104 as the pressurized dirty fluid 110 is conducted from the chamber 100 to a wellhead (not shown) at a higher pressure than when the dirty fluid 110 entered the chamber 100, such as via a first outlet valve 112 and one or more conduits 113. The second inlet valve 107 may then be closed, for example, in response to pressure sensed by a pressure transducer within the chamber 100 and/or along one or more of the conduits and/or inlet valves.

[0043] After the pressurized dirty fluid 110 is discharged from the chamber 100, the clean fluid 120 may be drained via an outlet valve 114 at the second end 102 of the chamber 100 and one or more conduits 116. The discharged clean fluid 120 may be stored as waste fluid or reused during subsequent iterations of the fluid pressurizing process. For example, additional quantities of the dirty and clean fluids 110, 120 may then be introduced into the chamber 100 to repeat the pressurizing process to achieve a substantially continuous supply of pressurized dirty fluid 110.

[0044] A fluid pressure exchanger comprising the apparatus shown in FIGS. 1-4 and/or others within the scope of the present disclosure may also comprise more than one of the example chambers 100 described above. FIG. 5 is a schematic view of an example fluid pressure exchanger 200 comprising multiple chambers 100 shown in FIGS. 1-4 and designated in FIG. 5 by reference numeral 150. FIGS. 6 and 7 are sectional views of the pressure exchanger 200 shown in FIG. 5. The following description refers to FIGS. 5-7, collectively.

[0045] The pressure exchanger 200 may comprise a housing 210 having a bore 212 extending between opposing ends 208, 209 of the housing 210. An end cap 202 may cover the bore 212 at the end 208 of the housing 210, and another end cap 203 may cover the bore 212 at the opposing end 209 of the housing 210. The housing 210 and the end caps 202, 203 may be sealingly engaged and statically disposed with respect to each other. The housing 210 and the end caps 202, 203 may be distinct components or members, or the housing 210 and one or both of the end caps 202, 203 may be formed as a single, integral, or continuous component or member. A rotor 201 may be slidably disposed within the bore 212 of the housing 210 and between the opposing end caps 202, 203 in a manner permitting relative rotation of the rotor 201 with respect to the housing 210 and end caps 202, 203. The rotor 201 may have a plurality of bores or chambers 150 extending through the rotor 201 and circumferentially spaced around an axis of rotation 21 1 extending longitudinally through the rotor 201. The rotor 201 may be an discrete member, as depicted in FIGS. 5-7, or an assembly of discrete components, such as may permit replacing worn portions of the rotor 201 and/or utilizing different materials for different portions of the rotor 201 to account for expected or actual wear.

[0046] The rotation of the rotor 201 about the axis 21 1 is depicted in FIG. 5 by arrow 220. Rotation of the rotor 201 may be achieved by various means. For example, rotation may be induced by utilizing force of the fluids received by the pressure exchanger 200, such as in implementations in which the fluids may be directed into the chambers 150 at a diagonal angle with respect to the axis of rotation 21 1, thereby imparting a rotational force to the rotor 201 to rotate the rotor 201. Rotation may also be achieved by a longitudinal geometry or configuring of at least a portion of the chambers 150 as they extend through the rotor 201. For example, an inlet portion of the each chamber 150, or the entirety of each chamber 150, may extend in a helical manner with respect to the axis of rotation 211, such that the incoming stream of clean fluid imparts a rotational force to the rotor 201 to rotate the rotor 201.

[0047] Rotation may also be imparted via a motor (not shown) operably connected to the rotor 201. For example, the motor may be an electrical or fluid powered motor connected with the rotor 201 via a shaft, a transmission, or another intermediate driving member, such as may extend through at least one of the end caps 202, 203 and/or the housing 210, to transfer torque to the rotor 201 to rotate the rotor 201. The motor may also be connected with the rotor 201 via a magnetic shaft coupling, such as in implementations in which a driven magnet may be physically connected with the rotor 201 and a driving magnet may be located outside of the pressure exchanger 200 and magnetically connected with the driven magnet. Such implementations may permit the motor to drive the rotor 201 without a shaft extending through the end caps 202, 203 and/or housing 210.

[0048] Rotation may also be imparted into the rotor 201 via an electrical motor (not shown) disposed about and connected with the rotor 201. For example, the electrical motor may comprise an electrical stator disposed about or included as part of the housing 210 and an electrical rotor connected about or included as part of the rotor 201. The electrical stator may comprise field coils or windings that generate a magnetic field when powered by electric current from a source of electric power. The electrical rotor may comprise windings or permanent magnets fixedly disposed about or included as part of the rotor 201. The electrical stator may surround the electrical rotor in a manner permitting rotation of the rotor 201/electrical rotor assembly within the housing 210/electrical stator assembly during operation of the electrical motor. The electrical motors utilized within the scope of the present disclosure may include, for example, synchronous and asynchronous electric motors.

[0049] The pressure exchanger 200 may also comprise means for sensing or otherwise determining the rotational speed of the rotor 201. For example, the rotor speed sensing means may comprise one or more sensors 214 associated the rotor 201 and operable to convert position or presence of a rotating or otherwise moving portion of the rotor 201, feature of the rotor 201, or marker 215 disposed in association with the rotor 201, into an electrical signal or information related to or indicative of the position and/or speed of the rotor 201. Each sensor 214 may be disposed adjacent the rotor 201 or otherwise disposed in association with the rotor 201 in a manner permitting sensing of the rotor or the marker 215 during pressurizing operations.

[0050] Each sensor 214 may sense one or more magnets on the rotor 201, one or more features on the rotor 201 that can be optically detected, conductive portions or members on the rotor 201 that can be sensed with an electromagnetic sensor, and/or facets or features on the rotor 201 that can be detected with an ultrasonic sensor, among other examples. Each sensor 214 may be or comprise a linear encoder, a capacitive sensor, an inductive sensor, a magnetic sensor, a Hall effect sensor, and/or a reed switch, among other examples. The speed sensing means may also include an intentionally imbalanced rotor 201 whose vibrations may be detected with an accelerometer and utilized to determine the rotational speed of the rotor 201.

[0051] The sensors 214 may extend through the housing 210, the end caps 202, 203, or another pressure barrier fluidly isolating the internal portion of the pressure exchanger 201 in a manner permitting the detection of the presence of the rotor 201 or marker 215 at a selected or predetermined position. The sensor 214 and/or an electrical conductor connected with the sensor 214 may be sealed against the pressure barrier, such as to prevent or minimize fluid leakage. However, a non-magnetic housing 210 and/or end caps 202, 203 may be utilized, such as may permit a magnetic field to pass therethrough and, thus, permit the sensors 214 to be disposed on the outside of the housing 210 and/or end caps 202, 203. The sensor 214 may also be an ultrasonic transducer operable to send a pressure wave through the housing 210 and into the rotor 201, such as in implementations in which the housing 210 is a steel housing and the rotor 201 is a ceramic stator. The pressure wave may be reflected from varying markers or portions of the rotor 201 and sensed by the ultrasonic transducer to determine the rotational speed of the rotor 201.

[0052] The end caps 202, 203 may functionally replace the valves 106, 107, 1 12, and 114 depicted in FIGS. 1-4. For example, the first end cap 202 may be substantially disc-shaped, or may comprise a substantially disc-shaped portion, through which an inlet 204 and an outlet 205 extend. The inlet 204 may act as the first inlet valve 106 shown in FIGS. 1-4, and the outlet 205 may act as the first outlet valve 112 shown in FIGS. 1-4. Similarly, the second end cap 203 may be substantially disc-shaped, or may comprise a substantially disc-shaped portion, through which an inlet 206 and an outlet 207 extend. The inlet 206 may act as the second inlet valve 107 shown in FIGS. 1-4, and the outlet 207 may act as the second outlet valve 114 shown in FIGS. 1-4. The fluid inlets and outlets 204-207 may have a variety of dimensions and shapes. For example, as in the example implementation depicted in FIG. 5, the inlets and outlets 204-207 may have dimensions and shapes substantially corresponding to the cross-sectional dimensions and shapes of the openings of each chamber 150 at the opposing ends of the rotor 201. However, other implementations are also within the scope of the present disclosure, provided that the chambers 150 may each be sealed against the end caps 202, 203 in a manner preventing or minimizing fluid leaks. For example the surfaces of the end caps 202, 203 that mate with the corresponding ends of the rotor 201 may comprise face seals and/or other sealing means.

[0053] In the example implementation depicted in FIG. 5, the rotor 201 comprises eight chambers 150. However, other implementations within the scope of the present disclosure may comprise as few as two chambers 150, or as many as several dozen. The rotational speed of the rotor 201 may also vary and may be timed as per the velocity of the boundary 103 between the dirty and clean fluids and the length 221 of the chambers 150 so that the timing of the inlets and outlets 204-207 are adjusted in order to facilitate proper functioning as described herein. The rotational speed of the rotor 201 may be based on the intended flow rate of the pressurized dirty fluid exiting the chambers 150 collectively, the amount of pressure differential between the dirty and clean fluids, and/or the dimensions of the chambers 150. For example, larger dimensions of the chambers 150 and greater rotational speed of the rotor 201 relative to the end caps 202, 203 and housing 210 will increase the discharge volume of the pressurized dirty fluid.

[0054] The size and number of instances of the fluid pressure exchanger 200 utilized at a wellsite in oil and gas operations may depend on the location of the fluid pressure exchanger 200 within the process flow stream at the wellsite. For example, some oil and gas operations at a wellsite may utilize multiple pumps (such as the pumps 306 shown in FIG. 11) that each receive low-pressure dirty fluid from a common manifold (such as the manifold 308 shown in FIG. 11) and then pressurize the dirty fluid for return to the manifold. For such operations, an instance of the fluid pressure exchanger 200 may be utilized between each pump and the manifold, and/or one or more instances of the fluid pressure exchanger 200 may replace one or more of the pumps. In such implementations, the rotor 201 may have a length 221 ranging between about 25 centimeters (cm) and about 150 cm and a diameter 222 ranging between about 10 cm and about 30 cm, the cross-sectional area (flow area) of each chamber 150 may range between about 5 cm² and about 20 cm², and/or the volume of each chamber 150 may range between about 75 cubic cm (cc) and about 2500 cc. However, although other dimensions are also within the scope of the present disclosure. Some oil and gas operations at a wellsite may utilize multiple pumps that each receive low-pressure dirty fluid directly from a corresponding mixer (such as the mixer 304 shown in FIG. 1 1) or another source of dirty fluid and then pressurize the dirty fluid for injection directly into a well (such as the well 311 shown in FIG. 11). For such operations, an instance of the fluid pressure exchanger 200 may be utilized between each pump and the well, and/or one or more instances of the fluid pressure exchanger 200 may replace one or more of the pumps.

[0055] In some implementations, the pumps may each receive low-pressure clean fluid from the manifold (such as may be received at the manifold from a secondary fluid source) and then pressurize the clean fluid for return to the manifold. The pressurized clean fluid may then be conducted from the manifold to one or more instances of the fluid pressure exchanger 200 to be utilized to pressurize low-pressure dirty fluid received from a gel maker, proppant blender, and/or other low-pressure processing device, and the pressurized dirty fluid discharged from the fluid pressure exchanger(s) 200 may be conducted towards a well. Examples of such operations include those shown in FIGS. 12-19, among other examples within the scope of the present disclosure. In such implementations, the length 221 of the rotor 201, the diameter 222 of the rotor 201, the flow area of each chamber 150, the volume of each chamber 150, and/or the number of chambers 150 may be much larger than as described above.

[0056] FIG. 6 is a sectional view of the pressure exchanger 200 shown in FIG. 5 during an operational stage in which two of the chambers are substantially aligned with the inlet and outlet 204, 205 of the first end cap 202 but not with the inlet and outlet 206, 207 of the second end cap 203. Thus, the inlet 204 fluidly connects one of the depicted chambers 150, designated by reference number 250 in FIG. 6, with the one or more conduits 108 supplying the non- pressurized dirty fluid, such that the non-pressurized dirty fluid may be conducted into the chamber 250. At the same time, the outlet 205 fluidly connects another of the depicted chambers 150, designated by reference number 251 in FIG. 6, with the one or more conduits 113 conducting previously pressurized dirty fluid out of the chamber 251, such as for conduction into a wellbore (not shown). As the rotor 201 rotates relative to the end caps 202, 203, the chambers 250, 251 will rotate out of alignment with the inlet and outlet 204, 205, thus preventing fluid communication between the chambers 250, 251 and the respective conduits 108, 113.

[0057] FIG. 7 is another view of the apparatus shown in FIG. 6 during another operational stage in which the chambers 250, 251 are substantially aligned with the inlet and outlet 206, 207 of the second end cap 203 but not with the inlet and outlet 204, 205 of the first end cap 202. Thus, the inlet 206 fluidly connects the chamber 250 with the one or more conduits 109 supplying the pressurizing or energizing clean fluid, such that the clean fluid may be conducted into the chamber 250. At the same time, the outlet 207 fluidly connects the other chamber 251 with the one or more conduits 116 conducting previously used pressurizing clean fluid out of the chamber 251, such as for recirculation to the clean fluid source (not shown). As the rotor 201 further rotates relative to the end caps 202, 203 and the housing 210, the chambers 250, 251 will rotate out of alignment with the inlet and outlet 206, 207, thus preventing fluid communication between the chambers 250, 251 and the respective conduits 109, 116.

[0058] The pressurizing process described above with respect to FIGS. 1-4 is achieved within each chamber 150, 250, 251 with each full rotation of the rotor 201 relative to the end caps 202, 203. For example, as the rotor 201 rotates relative to the end caps 202, 203 and the housing 210, the non-pressurized dirty fluid is conducted into the chamber 250 during the portion of the rotation in which the chamber 250 is in fluid communication with inlet 204 of the first end cap 202, as indicated in FIG. 6 by arrow 231. The rotation is continuous, such that the flow rate of non-pressurized dirty fluid into the chamber 250 increases as the chamber 250 comes into alignment with the inlet 204 and then decreases as the chamber 250 rotates out of alignment with the inlet 204. Further rotation of the rotor 201 relative to the end caps 202, 203 permits the pressurizing clean fluid to be conducted into the chamber 250 during the portion of the rotation in which the chamber 250 is in fluid communication with the inlet 206 of the second end cap 203, as indicated in FIG. 7 by arrow 232. The influx of the pressurizing clean fluid into the chamber 250 pressurizes the dirty fluid, such as due to the pressure differential between the dirty and clean fluids described above with respect to FIGS. 1-4.

[0059] Further rotation of the rotor 201 relative to the end caps 202, 203 and the housing 210 permits the pressurized dirty fluid to be conducted out of the chamber 250 during the portion of the rotation in which the chamber 250 is in fluid communication with the outlet 205 of the first end cap 202, as indicated in FIG. 6 by arrow 233. The discharged fluid may substantially comprise just the (pressurized) dirty fluid or a mixture of the dirty and clean fluids (also pressurized), depending on the timing of the rotor 201 and perhaps whether the chambers include the boundary 103 shown in FIGS. 1-4. Further rotation of the rotor 201 relative to the end caps 202, 203 permits the reduced-pressure clean fluid to be conducted out of the chamber 250 during the portion of the rotation in which the chamber 250 is in fluid communication with the outlet 207 of the second end cap 203, as indicated in FIG. 7 by arrow 234. The pressurizing process then repeats as the rotor 201 further rotates and the chamber 250 again comes into alignment with the inlet 204 of the first end cap 202. [0060] Depending on the number and size of the chambers 150, the non-pressurized dirty fluid inlet 204 and the pressurizing clean fluid inlet 206 may be wholly or partially misaligned with each other about the central axis 211, such that the dirty fluid may be conducted into the chamber 150 to entirely or mostly fill the chamber 150 before the clean fluid is conducted into that chamber 150. The non-pressurized dirty fluid inlet 204 is completely closed to fluid flow from the conduit 108 before the pressurizing clean fluid inlet 206 begins opening. The pressurized dirty fluid outlet 205 and the reduced-pressure clean fluid outlet 207, however, may be partially open when the pressurizing clean fluid inlet 206 is permitting the clean fluid into the chamber 150. Similarly, the non-pressurized dirty fluid inlet 204 may be partially open when one or both of the pressurized dirty fluid outlet 205 and/or the reduced-pressure clean fluid outlet 207 is at least partially open.

[0061] The pressurized dirty fluid outlet 205 and the reduced-pressure clean fluid outlet 207 may be wholly or partially misaligned with each other about the central axis 21 1. For example, the pressurized dirty fluid (and perhaps a pressurized mixture of the dirty and clean fluids) may be substantially discharged from a chamber 150 via the pressurized dirty fluid outlet 205 before the remaining reduced-pressure clean fluid is permitted to exit through the reduced-pressure clean fluid outlet 207. As the rotor 201 continues to rotate relative to the end caps 202, 203 and the housing 210, the pressurized dirty fluid outlet 205 becomes closed to fluid flow, and the reduced-pressure clean fluid outlet 207 becomes open to discharge the remaining reduced- pressure clean fluid. Thus, the reduced-pressure clean fluid outlet 207 may be completely closed to fluid flow while the pressurized dirty fluid (or mixture of the dirty and clean fluids) is discharged from the chamber 150 to the wellhead. Complete closure of the reduced-pressure clean fluid outlet 207 may permit the pressurized fluid to maintain a higher-pressure flow to the wellhead.

[0062] The inlets and outlets 204-207 may also be configured to permit fluid flow into and out of more than one chamber 150 at a time. For example, the non-pressurized dirty fluid inlet 204 may be sized to simultaneously fill more than one chamber 150, the inlet and outlets 204- 207 may be configured to permit non-pressurized dirty fluid to be conducted into a chamber 150 while the reduced-pressure clean fluid is simultaneously being discharged from that chamber 150. Depending on the size of the rotor 201 and the chambers 150, the fluid properties of the dirty and clean fluids, and the rotational speed of the rotor 201 relative to the end caps 202, 203, the pressurizing process within each chamber 150 may also be achieved in less than one rotation of the rotor 201 relative to the end caps 202, 203 and the housing 210, such as in

implementations in which two, three, or more iterations of the pressurizing process is achieved within each chamber 150 during a single rotation of the rotor 201.

[0063] The flow of dirty fluid out of the pressure exchanger 200 via the fluid conduit 116 may be prevented or otherwise minimized by controlling the timing of the opening and closing of the fluid inlets 204, 206 and outlets 205, 207 of the pressure exchanger 200. For example, during the pressurizing operations, as the chambers 150 rotate, each chamber 150 is in turn aligned and, thus, fluidly connected with the low-pressure inlet 204 to receive the dirty fluid and the low-pressure outlet 207 to discharge the clean fluid. As the dirty fluid fills the chamber 150, the boundary 103 moves toward the low-pressure outlet 207 as the clean fluid is pushed out of the chamber 150. However, the rotation of the rotor 201 seals off the outlet 207 of the chamber 150 when or just before the boundary 103 reaches the outlet 207 to prevent or minimize the dirty fluid from entering into the fluid conduit 116. The chamber 150 then becomes aligned with the high-pressure inlet 206 and the high-pressure outlet 205 to permit the high-pressure clean fluid to enter the chamber 150 via the inlet 206 to push the dirty fluid from the chamber 150 via the outlet 205 at an increased pressure. As the clean fluid fills the chamber 150, the boundary 103 moves toward the high-pressure outlet 205 as the dirty fluid is pushed out of the chamber 150. However, the rotation of the rotor 201 seals off the outlet 205 of the chamber 150 when or just before the boundary 103 reaches the outlet 205 to prevent or minimize the clean fluid from entering into the fluid conduit 113. The clean fluid left in the chamber 150 may be pushed out through the fluid conduit 116 by the dirty fluid when the chamber 150 again becomes aligned with the low-pressure inlet 204 to receive the dirty fluid and the low-pressure outlet 207 to discharge the clean fluid. Such cycle may be continuously repeated to continuously receive and pressurize the stream of dirty fluid.

[0064] FIGS. 8 and 9 are enlarged views of portions of the pressure exchanger 200 shown in FIGS. 7 and 6, respectively, according to one or more aspects of the present disclosure. The following description refers to FIGS. 6-9, collectively.

[0065] Small gaps or spaces 261, 262, 263 may be maintained between the rotor 201 and the housing 210 and end caps 202, 203 to permit rotation of the rotor 201 within the housing 210 and the end caps 202, 203. For clarity, the housing 210 and the end caps 202, 203 may be collectively referred to hereinafter as a "housing assembly." The spaces 261, 262, 263 may permit comingling of high-pressure and low-pressure fluids within the pressure exchanger 200. For example, dirty fluid within the pressure exchanger 200 may flow through the space 261 along the end cap 202 from the high-pressure outlet 205 to the low-pressure fluid inlet 204, and through the spaces 261, 262, 263 along the housing 210 and end caps 202, 203 from the high- pressure outlet 205 to the clean fluid low-pressure outlet 207. Clean fluid within the pressure exchanger 200 may flow through the space 263 along the end cap 203 from the high-pressure inlet 206 to the low-pressure outlet 207, as indicated by arrow 265, and through the spaces 261, 262, 263 along the housing 210 and end caps 202, 203 from the high-pressure inlet 206 to the dirty fluid inlet and outlet 204, 205, as indicated by arrows 265, 266, 267.

[0066] The fluid flow through the spaces 261, 262, 263 within the pressure exchanger 200 may form a fluid film or layer operating as a hydraulic bearing or otherwise providing lubrication between the rotating rotor 201 and the static housing assembly, such as may prevent or reduce contact or friction between the rotor 201 and the housing assembly during pressurizing operations. The flow of fluids through the spaces 261, 262, 263 may be biased such that substantially just the clean fluid, and not the dirty fluid, flows through the spaces 261, 262, 263 during pressurizing operations, as indicated by arrows 265, 266, 267. Biasing the flow of clean fluid through the spaces 261, 262, 263 may also cause the clean/dirty fluid boundary 103 (shown in FIGS. 1-4) to maintain a net velocity directed toward the dirty fluid outlet 205. Accordingly, biasing the flow of clean fluid may result in substantially just the clean fluid being

communicated through the spaces 261, 262, 263, such as to prevent or minimize friction or wear caused by the dirty fluid between the rotor 201 and the housing assembly. Biasing the flow of the clean fluid may also result in substantially just the clean fluid being discharged via the clean fluid outlet 207, such as to prevent or minimize contamination of the clean fluid discharged from the pressure exchanger 200. The apparatus and method implemented to biasing the flow of clean fluid through the spaces 261, 262, 263 is further described below.

[0067] FIG. 10 is a sectional view of another example implementation of the pressure exchanger 200 shown in FIG. 5 according to one or more aspects of the present disclosure and designated in FIG. 10 by reference numeral 270. The pressure exchanger 270 is substantially similar in structure and operation to the pressure exchanger 200, including where indicated by like reference numbers, except as described below. [0068] The pressure exchanger 270 may include a rotor 272 slidably disposed within the bore of the housing 210 and between the opposing end caps 202, 203 in a manner permitting relative rotation of the rotor 272 with respect to the housing 210 and end caps 202, 203. The rotor 272 may have multiple bores or chambers 274 extending through the rotor 272 between the opposing ends 208, 209 of the housing 210 and circumferentially spaced around an axis of rotation 276 extending longitudinally along the rotor 272. For the sake of clarity, cross-hatching of the rotor 272 is removed from FIG. 10, and just four chambers 274 are depicted, it being understood that other chambers 274 may also exist.

[0069] The chambers 274 extend through the rotor 272 in a helical manner about or otherwise with respect to the axis of rotation 276. As described above, such helical chamber implementations may be utilized to impart rotation to the rotor 272 instead of with a separate motor or other rotary driving means. Such helical chamber implementations may also permit the length 278 of the chambers 274 to be greater than the axial length 280 of the rotor 272, which may permit the axial length 280 of the rotor 272 to be reduced. The increased length 278 of the chambers 274 may also permit the rotor 272 to be rotated at slower speeds than a rotor having chambers that extend substantially parallel with respect to an axis of rotation.

[0070] The pressure exchangers 200, 270 shown in FIGS. 5-10 and/or otherwise within the scope of the present disclosure may utilize various forms of the dirty and clean fluids described above. For example, the dirty fluid may be a high-density and/or high -viscosity solids-laden fluid comprising insoluble solid particulate material and/or other ingredients that may compromise the life or maintenance of pumps disposed downstream of the fluid pressure exchangers 200, 270, especially when such pumps are operated at higher pressures. Examples of the dirty fluid utilized in oil and gas operations may include treatment fluid, drilling fluid, spacer fluid, workover fluid, a cement composition, fracturing fluid, acidizing fluid, stimulation fluid, and/or combinations thereof, among other examples also within the scope of the present disclosure. The dirty fluid may be a foam, slurry, emulsion, or compressible gas. The viscosity of the dirty fluid may be sufficient to permit transport of solid additives or other solid particulate material (collectively referred to hereinafter as "solids") without appreciable settling or segregation. Chemicals, such as biopolymers (e.g. polysaccharides), synthetic polymers (e.g. polyacrylamide and its derivatives), crosslinkers, viscoelastic surfactants, oil gelling agents, low molecular weight organogel ators, and phosphate esters, may also be included in the dirty fluid, such as to control viscosity of the dirty fluid.

[0071] The composition of the clean fluid may permit the clean fluid to be pumped at higher pressures with reduced adverse effects on the downstream pumps. For example, the clean fluid may be a solids-free fluid that does not include insoluble solid particulate material or other abrasive ingredients, or a fluid that includes low concentrations of insoluble solid particulate material or other abrasive ingredients. The clean fluid may be a liquid, such as water (including freshwater, brackish water, or brine), a gas (including a cryogenic gas), or combinations thereof. The clean fluid may also include substances, such as tracers, that can be transferred to the dirty fluid upon mixing within the chambers 150, 250, 274 or upon transmission through a semipermeable implementation of the boundary 103. The viscosity of the clean fluid may also be increased, such as to minimize or reduce viscosity contrast between the dirty and clean fluids. Viscosity contrast may result in channeling of the lower viscosity fluid through the higher viscosity fluid. The clean fluid may be viscosified utilizing the same chemicals and/or techniques described above with respect to the dirty fluid.

[0072] The clean and/or dirty fluid may be chemically modified, such as via one or more fluid additives temporarily (or regularly) injected into the clean and/or dirty fluids to produce a reaction at the clean/dirty boundary 103 that acts to stabilize the boundary 103 (e.g., a membrane, mixing zone). For example, viscosity modification may be utilized to help form a substantially flat flow profile within the chambers 150, 250, 274. Also, one or repeated pulses of a cross linker applied to the clean fluid may be utilized to form cross linked gel pills in the chambers 150, 250, 274 to act as boundary stabilizers. Such stabilizers may be safely pumped into the well and replaced over time.

[0073] Furthermore, the clean and dirty fluids may be selected or formulated such that a reaction between the clean and dirty fluids creates a physical change at the clean/dirty boundary 103 that stabilizes the boundary 103. For example, the clean and dirty fluids may cross-link when interacting at the boundary 103 to produce a floating, viscous plug. The clean and dirty fluids may be formulated such that the plug or another product of such reaction may not damage downstream components when trimmed off and injected into the well by the action of the outlet 205 or another discharge valve. [0074] The following are additional examples of the dirty and clean fluids that may be utilized during oil and gas operations. However, the following are merely examples, and are not considered to be limiting to the dirty and clean fluids and that may also be utilized within the scope of the present disclosure.

[0075] For fracturing operations, the dirty fluid may be a slurry with a continuous phase comprising water and a dispersed phase comprising proppant (including foamed slurries), including implementations in which the dispersed proppant includes two or more different size ranges and/or shapes, such as may optimize the amount of packing volume within the fractures. The dirty fluid may also be a cement composition (including foamed cements), or a compressible gas. For such fracturing implementations, the clean fluid may be a liquid comprising water, a foam comprising water and gas, a gas, a mist, or a cryogenic gas.

[0076] For cementing operations, including squeeze cementing, the dirty fluid may be a cement composition comprising water as a continuous phase and cement as a dispersed phase, or a foamed cement composition. For such cementing implementations, the clean fluid may be a liquid comprising water, a foam comprising water and gas, a gas, a mist, or a cryogenic gas.

[0077] For drilling, workover, acidizing, and other wellbore operations, the dirty fluid may be a homogenous solution comprising water, soluble salts, and other soluble additives, a slurry with a continuous phase comprising water and a dispersed phase comprising additives that are insoluble in the continuous phase, an emulsion or invert emulsion comprising water and a hydrocarbon liquid, or a foam of one or more of these examples. In such implementations, the clean fluid may be a liquid comprising water, a foam comprising water and gas, a gas, a mist, or a cryogenic gas.

[0078] In the above example implementations, and/or others within the scope of the present disclosure, the dirty fluid 110 may include proppant; swellable or non-swellable fibers; a curable resin; a tackifying agent; a lost-circulation material; a suspending agent; a viscosifier; a filtration control agent; a shale stabilizer; a weighting agent; a pH buffer; an emulsifier; an emulsifier activator; a dispersion aid; a corrosion inhibitor; an emulsion thinner; an emulsion thickener; a gelling agent; a surfactant; a foaming agent; a gas; a breaker; a biocide; a chelating agent; a scale inhibitor; a gas hydrate inhibitor; a mutual solvent; an oxidizer; a reducer; a friction reducer; a clay stabilizing agent; an oxygen scavenger; cement; a strength retrogression inhibitor; a fluid loss additive; a cement set retarder; a cement set accelerator; a light-weight additive; a de- foaming agent; an elastomer; a mechanical property enhancing additive; a gas migration control additive; a thixotropic additive; and/or combinations thereof.

[0079] FIG. 11 is a schematic view of an example wellsite system 370 that may be utilized for pumping a fluid from a wellsite surface 310 to a well 311 during a well treatment operation. Water from a plurality of water tanks 301 may be substantially continuously pumped to a gel maker 302, which mixes the water with a gelling agent to form a carrying fluid or gel, which may be a clean fluid. The gel may be substantially continuously pumped into a blending/mixing device, hereinafter referred to as a mixer 304. Solids, such as proppant and/or other solid additives stored in a solids container 303, may be intermittently or substantially continuously pumped into the mixer 304 to be mixed with the gel to form a substantially continuous stream or supply of treatment fluid, which may be a dirty fluid. The treatment fluid may be pumped from the mixer 304 to a plurality of plunger, frac, and/or other pumps 306 through a system of conduits 305 and a manifold 308. Each pump 306 pressurizes the treatment fluid, which is then returned to the manifold 308 through another system of conduits 307. The stream of treatment fluid is then directed to the well 311 via a wellhead 313 through a system of conduits 309. A control unit 312 may be operable to control various portions of such processing via wired and/or wireless communications (not shown).

[0080] FIG. 12 is a schematic view of an example implementation of another wellsite system 371 according to one or more aspects of the present disclosure. The wellsite system 371 comprises one or more similar features of the wellsite system 370 shown in FIG. 1 1, including where indicated by like reference numbers, except as described below.

[0081] The wellsite system 371 includes a fluid pressure exchanger 320, which may be utilized to eliminate or reduce pumping of dirty fluid through the pumps 306. The dirty fluid may be conducted from the mixer 304 to one or more chambers 100/150/250/251/274 of the fluid pressure exchanger 320 via the conduit system 305. The fluid pressure exchanger 320 may be, comprise, and/or otherwise have one or more aspects in common with the apparatus shown in one or more of FIGS. 1-10. Thus, as similarly described above with respect to FIGS. 1-10, the fluid pressure exchanger 320 comprises a non-pressurized dirty fluid inlet 331, a pressurized clean fluid inlet 332, a pressurized fluid discharge or outlet 333, and a reduced-pressure fluid discharge or outlet 334. Consequently, the pumps 306 may conduct the clean fluid to and from the manifold 308 and then to the pressurized clean fluid inlet 332 of the fluid pressure exchanger 320, where the pressurized clean fluid may be utilized to pressurize the dirty fluid received at the non-pressurized dirty fluid inlet 331 from the mixer 304.

[0082] A centrifugal or other type of pump 314 may supply the clean fluid to the manifold 308 from a holding or firac tank 322 through a conduit system 315. An additional source of fluid to be pressurized by the manifold 308 may be flowback fluid from the well 311. The pressurized clean fluid is conducted from the manifold 308 to one or more chambers of the fluid pressure exchanger 320 via a conduit system 316. The pressurized fluid discharged from the fluid pressure exchanger 320 is then conducted to the wellhead 313 of the well 31 1 via a conduit system 309. The reduced-pressure clean fluid remaining in the fluid pressure exchanger 320 (or chamber 100/150 thereof) may then be conducted to a settling tank/pit 318 via a conduit system 317, where the fluid may be recycled back into the high-pressure stream via a centrifugal or other type of pump 321 and a conduit system 319, such as to the tank 322.

[0083] Some of the components, such as conduits, valves, and the manifold 308, may be configured to provide dampening to accommodate pressure pulsations. For example, liners that expand and contract may be employed to prevent problems associated with pumping against a closed valve due to intermittent pumping of the high-pressure fluid stream.

[0084] FIG. 13 is a schematic view of an example implementation of another wellsite system 372 according to one or more aspects of the present disclosure. The wellsite system 372 is substantially similar in structure and operation to the wellsite system 371, including where indicated by like reference numbers, except as described below.

[0085] In the wellsite system 372, the clean fluid may be conducted to the manifold 308 via a conduit system 330, the pump 314, and the conduit system 315. That is, the fluid stream leaving the gel maker 302 may be split into a low-pressure side, for utilization by the mixer 304, and a high-pressure side, for pressurization by the manifold 308. Similarly, although not depicted in FIG. 13, the fluid stream entering the gel maker 302 may be split into the low-pressure side, for utilization by the gel maker 302, and the high-pressure side, for pressurization by the manifold 308. Thus, the clean fluid stream and the dirty fluid stream may have the same source, instead of utilizing the tank 322 or other separate clean fluid source.

[0086] FIG. 13 also depicts the option for the reduced-pressure fluid discharged from the fluid pressure exchanger 320 to be recycled back into the low-pressure clean fluid stream between the gel maker 302 and the mixer 304 via a conduit system 343. In such implementations, the flow rate of the proppant and/or other ingredients from the solids container 303 into the mixer 304 may be regulated based on the concentration of the proppant and/or other ingredients entering the low-pressure stream from the conduit system 343. The flow rate from the solids container 303 may be adjusted to decrease the concentration of proppant and/or other ingredients based on the concentrations in the fluid being recycled into the low-pressure stream. Similarly, although not depicted in FIG. 13, the reduced-pressure fluid discharged from the fluid pressure exchanger 320 may be recycled back into the low-pressure flow stream before the gel maker 302, or perhaps into the low-pressure flow stream between the mixer 304 and the fluid pressure exchanger 320.

[0087] FIG. 14 is a schematic view of an example implementation of another wellsite system

373 according to one or more aspects of the present disclosure. The wellsite system 373 is substantially similar in structure and operation to the wellsite system 372, including where indicated by like reference numbers, except as described below.

[0088] In the wellsite system 373, the source of the clean fluid is the tank 322, and the reduced-pressure fluid discharged from the fluid pressure exchanger 320 is not recycled back into the high-pressure stream, but is instead directed to a tank 340 via a conduit system 341. However, in a similar implementation, the reduced-pressure fluid discharged from the fluid pressure exchanger 320 is not recycled back into the high-pressure stream, as depicted in FIG. 13. In either implementation, utilizing the tank 322 or other source of the clean fluid separate from the discharge of the gel maker 302 and the fluid pressure exchanger 320 permits a single pass clean fluid system with very low probability of proppant entering the pumps 306.

[0089] FIG. 15 is a schematic view of an example implementation of another wellsite system

374 according to one or more aspects of the present disclosure. The wellsite system 374 is substantially similar in structure and operation to the wellsite system 373, including where indicated by like reference numbers, except as described below.

[0090] Unlike the wellsite system 373, the wellsite system 374 utilizes multiple instances of the fluid pressure exchanger 320. The low-pressure discharge from the mixer 304 may be split into multiple streams each conducted to a corresponding one of the fluid pressure exchangers 320 via a conduit system 351. Similarly, the high-pressure discharge from the manifold 308 may be split into multiple streams each conducted to a corresponding one of the fluid pressure exchangers 320 via a conduit system 352. The pressurized fluid discharged from the fluid pressure exchangers 320 may be combined and conducted towards the well 311 via a conduit system 353, and the reduced-pressure discharge from the fluid pressure exchangers 320 may be combined or separately conducted to the tank 340 via a conduit system 354.

[0091] FIG. 16 is a schematic view of an example implementation of another wellsite system 375 according to one or more aspects of the present disclosure. The wellsite system 375 is substantially similar in structure and operation to the wellsite system 373, including where indicated by like reference numbers, except as described below.

[0092] Unlike the wellsite system 373, the wellsite system 375 includes multiple instances of the fluid pressure exchanger 320 between the manifold 308 and a corresponding one of the pumps 306. The low-pressure discharge from the mixer 304 may be split into multiple streams each conducted to a corresponding one of the fluid pressure exchangers 320 via a conduit system 361. The high-pressure discharge from each of the pumps 306 is conducted to a corresponding one of the fluid pressure exchangers 320 via corresponding conduits (not numbered). The pressurized fluid discharged from each fluid pressure exchanger 320 is returned to the manifold 308 for combination, via a conduit system 362, and then conducted towards the well 311 via a conduit system 363. The reduced-pressure discharge from the fluid pressure exchangers 320 may be combined or separately conducted to one or more tanks 340 via a conduit system 364.

[0093] Furthermore, one or more of the pressure exchangers 320 may be integrated or otherwise combined with the manifold 308 as a single unit or piece of wellsite equipment. For example, one or more of the pressure exchangers 320 and the manifold 308 may be combined to form a manifold assembly 390, wherein fluid pathways and connections of the manifold 308 and one or more of the pressure exchangers 320 may be hard-piped and/or otherwise integrated as a single unit. Accordingly, the mixer 304 and each pump 306 may be fluidly coupled, via the corresponding conduit systems 361, 307, with corresponding inlet ports of the manifold assembly 390, instead of with individual inlet ports 331, 332 of the pressure exchangers 320. For example, the manifold assembly 390 may comprise a plurality of clean fluid inlet ports each fluidly connected with a corresponding fluid conduit of the conduit system 307 to receive the clean fluid from the pumps 306. Each clean fluid inlet port may in turn be fluidly connected with the clean fluid inlet 332 of a corresponding pressure exchanger 320. The manifold assembly 390 may further comprise a plurality of dirty fluid inlet ports each fluidly connected with a corresponding fluid conduit of the conduit system 361 to receive the dirty fluid from the mixer 304. Each dirty fluid inlet port may in turn be fluidly connected with the dirty fluid inlet 331 of a corresponding pressure exchanger 320. The manifold assembly 390 may also comprise a plurality of clean fluid outlet ports each fluidly connected with a corresponding fluid conduit of the conduit system 364 to discharge the clean fluid from the manifold assembly 390. Each clean fluid outlet port may in turn be fluidly connected with the clean fluid outlet 334 of a

corresponding pressure exchanger 320. The manifold assembly 390 may also comprise a dirty fluid outlet port fluidly connected with the conduit system 363 to discharge the dirty fluid from the manifold assembly 390. The dirty fluid outlet port may in turn be fluidly connected with the dirty fluid outlet 333 of a corresponding pressure exchanger 320.

[0094] Combinations of various aspects of the example implementations depicted in FIGS. 12-16 are also within the scope of the present disclosure. For example, the high-pressure side may comprise a dual-stage pumping scheme that pumps a clean fluid from the pumps 306 at a medium pressure and pumps flowback fluid into the clean fluid stream to increase the pressure of the pressurized fluid entering the fluid pressure exchanger 320.

[0095] A wellsite system within the scope of the present disclosure may be further utilized to form a substantially continuous stream or supply of dirty fluid having a predetermined solids concentration before being pressurized by one or more pressure exchangers and injected into a well during a well treatment operation. For example, the solids concentration of the dirty fluid stream being formed and injected into the well may be held substantially constant during the well treatment operation. However, the solids concentration of the dirty fluid may be dynamically varied during the well treatment operation.

[0096] FIG. 17 is a schematic view of an example implementation of a wellsite system 376 according to one or more aspects of the present disclosure. The wellsite system 376 is substantially similar in structure and operation to the wellsite systems 371-375, including where indicated by like reference numbers, except as described below. Although not shown in FIGS. 12-16, the various features described below may be implemented as part of the wellsite systems 371-375 described above. The following description refers to FIGS. 5-17, collectively.

[0097] As stated above, the flow of clean fluid through the spaces 261, 262, 263 may be biased such that substantially just the clean fluid, and not the dirty fluid, flows through the spaces 261, 262, 263 during pressurizing operations. For example, the flow of clean fluid may be biased by adjusting or controlling flow rate of the stream of clean fluid flowing through the pressure exchanger such that the flow rate of the stream of clean fluid discharged via the clean fluid outlet 334 is less than the flow rate of the stream of clean fluid received via the clean fluid inlet 332. The flow rate of the clean fluid discharged from the pressure exchanger 320 may be adjusted with a fluid control device 336 fluidly connected with the clean fluid outlet 334 and operable to reduce the flow rate of the stream of clean fluid discharged via the clean fluid outlet 334 with respect to the flow rate of the stream of clean fluid received via the clean fluid inlet 332 to cause a portion of the stream of clean fluid received via the clean fluid inlet 332 to flow through the spaces 261, 262, 263 between the rotor 201 and the housing assembly, as indicated by arrows 265, 266, 267, toward the inlet and outlet ports 331, 333 to be combined with the stream of dirty fluid.

[0098] The fluid control device 336 may be or comprise a flow rate control valve, such as a needle valve, a metering valve, a butterfly valve, a globe valve, or another valve operable to progressively or gradually open and close to control rate of fluid flow. The fluid control device 336 may be or comprise a pressure control or throttling device, such as a flow restriction, a choke, or a pinch valve, operable to create a pressure drop and, thus, a resistance to fluid flow. The fluid control device 336 may also be or comprises a positive displacement device, such as a positive displacement pump or a positive displacement hydraulic motor, which may achieve flow control without throttling pressure. For example, the fluid control device 336 may be a lobe pump, a progressing cavity pump, and a gear pump, among other examples. The pump may be operated with an actuator, such as an electrical or hydraulic motor to meter a predetermined flow rate of clean fluid to be discharged via the clean fluid outlet 334. When the fluid control device 336 is or comprises a hydraulic motor, the clean fluid flow may generate shaft work, which may be controlled to meter a predetermined flow rate of clean fluid to be discharged via the clean fluid outlet 334. The shaft work may be transferred or otherwise recovered to perform work at a wellsite comprising the wellsite system 376. For example, the shaft work may be transferred to a generator (not shown) to generate electrical power to be utilized by other wellsite equipment.

[0099] The portion of the fluid flowing through the spaces 261, 262, 263 includes the difference between the received and discharged clean fluid flows forced to flow through the spaces 261, 262, 263 toward the dirty fluid inlet and outlet 331, 333 and merge with or flow into the dirty fluid stream. The clean fluid flowing through the spaces 261, 262, 263 may merge with or flow into the stream of dirty fluid being received via the dirty fluid inlet 331 at the interface of the dirty fluid inlet 331 and the chamber 250 and/or the clean fluid flowing through the spaces 261, 262, 263 may merge with or flow into the stream of dirty fluid being discharged via the dirty fluid outlet 333 at the interface of the dirty fluid outlet 333 and the chamber 250.

[00100] Another fluid control device 337 may be fluidly connected with the clean fluid inlet 332 to control the flow rate of the stream of clean fluid received via the clean fluid inlet 332. Accordingly, the fluid control devices 336, 337 may be collectively operable to control the difference between the flow rate of the stream of clean fluid received via the clean fluid inlet 332 and the stream of clean fluid discharged via the clean fluid outlet 334 and, thus, control the flow rate of the portion of the fluid flowing through the spaces 261, 262, 263 between the rotor 201 and the housing assembly and into the stream of dirty fluid. The fluid control device 337 may comprise the same or similar structure and/or operation as the fluid control device 336 described above. If the fluid control devices 336, 337 are implemented as positive displacement devices and if displacement per revolution of the fluid control device 337 is equal to or greater than the displacement per revolution of the fluid control device 336, then the resulting net clean fluid flow through the spaces 261, 262, 263 may be zero or positive.

[00101] Furthermore, the portion of the stream of clean fluid received via the clean fluid inlet 332 flowing through the spaces 261, 262, 263 and into the stream of dirty fluid may cause dilution or reduction in the solids concentration of the stream of dirty fluid flowing through the pressure exchanger 200.

[00102] Modulating excess clean fluid flow from the clean high-pressure side to the dirty high-pressure side may therefore control the density of the dirty fluid, including the solids density. The dirty fluid may be substantially denser than intended and may be selectively diluted with the clean fluid. Accordingly, one or both of the fluid control devices 336, 337 may be further operable to control the flow rate of the portion of the stream of clean fluid flowing through the spaces 261, 262, 263 and into the stream of dirty fluid to control the rate of dilution of the stream of dirty fluid discharged via the dirty fluid outlet 333. By adjusting the difference between the flow rate of the stream of clean fluid received via the clean fluid inlet 332 and the stream of clean fluid discharged via the clean fluid outlet 334, the flow rate of the clean fluid through the spaces 261, 262, 263 and into the stream of dirty fluid may be adjusted.

Accordingly, one or both of the fluid control devices 336, 337 may be operable to control the rate of dilution of the dirty fluid with the clean fluid within the pressure exchanger 200. [00103] Density measurements may be conducted on the high-pressure discharge line 309. Density measurements may also be conducted along the clean fluid supply conduit system 316 and the dirty fluid supply conduit system 305 to determine density of the dirty fluid being injected into the well 311. Accordingly, fluid analyzers 347, 348, 349 may be disposed along the conduit systems 305, 309, 316 in a manner permitting monitoring of the clean and dirty fluid flow rate and/or solids concentration of the dirty fluid supplied to and discharged from the pressure exchanger 320.

[00104] The fluid analyzers 347, 348 may be disposed along the conduit systems 305, 309 in a manner permitting monitoring of the dirty fluid flow rate and/or solids concentration or density of the dirty fluid received by the pressure exchanger 320 from the mixer 304 and the diluted dirty fluid discharged by the pressure exchanger 320 for injection into the well 311. For example, each fluid analyzer 347, 348 may comprise a density sensor operable to measure the solids concentration or the amount of particles in the dirty fluid, which may be indicative of the amount of proppant or other solids in the fluids conducted by the conduit systems 305, 309. The density sensor may emit radiation that is absorbed by different particles in the fluid. Different absorption coefficients may exist for different particles, which may then be utilized to translate the signals or information generated by the density sensor to determine the density or solids concentration. Each fluid analyzer 347, 348 may also comprise a flow rate sensor, such as a flow meter, operable to measure the volumetric and/or mass flow rate of the dirty fluid. Each fluid analyzer 347, 348 may be operable to generate signals or information indicative of the flow rate and/or solids concentration of the dirty fluid and utilized by a controller 410 (shown in FIG. 20), for example, to facilitate intended changes to the flow rate and/or solids concentration of the dirty fluid.

[00105] The fluid analyzer 349 may be disposed along the conduit system 316 in a manner permitting monitoring of the clean fluid flow rate received by the pressure exchanger 320 from the clean fluid source, such as the manifold 308. The fluid analyzer 349 may comprise a flow rate sensor, such as a flow meter, operable to measure the volumetric and/or mass flow rate of the clean fluid. The fluid analyzer 349 may be operable to generate signals or information indicative of the flow rate of the clean fluid and utilized by a controller 410, for example, to facilitate intended changes to the clean fluid flow rate, such as to adjust the solids concentration of the dirty fluid. [00106] Another fluid control device 338 may be fluidly connected with the dirty fluid inlet 331 to control flow rate of the stream of dirty fluid received via the dirty fluid inlet 331.

Accordingly, the fluid control devices 336, 337, 338 may be collectively operable to control a ratio of the flow rate of the stream of clean fluid received via the clean fluid inlet 332 and the flow rate of the stream of dirty fluid received via the dirty fluid inlet 331. The fluid control device 338 may be utilized, for example, when the clean fluid is communicated from the clean fluid source 308 to the pressure exchanger 320 via centrifugal pumps, which may not be suitable for flow rate control. The fluid control device 338 may comprise the same or similar structure and/or operation as the fluid control devices 336, 337 described above.

[00107] During pressurizing operations, various components of the wellsite system 376 may form cyclic pressure spikes, fluctuations, or pulsations that may travel through the fluid conduit systems 309, 316, 317, the pressure exchanger 320, the wellhead 313, and into the wellbore 311. Such pulsations may cause cyclic motion and stresses in the conduit systems 309, 316, 317 and other wellsite components, which may lead to fatigue failures. The pressure pulsations may be formed by the high-pressure pumps 306 at a frequency related to operating speed of the pump or frequency of pump plungers. Pressure pulsations may also be formed by the pressurizing action of the pressure exchanger 320 at a frequency related to the rotating speed of the rotor or the frequency at which the rotor chambers 150 pass the fluid outlet ports 333, 334.

[00108] The wellsite system 376 may be provided with damping means, such as may reduce the amplitude of the pressure pulsations. The damping means may be provided, for example, along the conduit system 309 downstream of the pressure exchanger 320 to decrease the amplitude of the pressure pulsations traveling between the pressure exchanger 320 and the wellbore 311. The damping means may be or comprise, for example, one or more flow restrictions 323 fluidly connected along the conduit system 309. Such flow restrictions 323 may comprise a converging/diverging configuration, such as fluid chokes, which may withstand erosion damage while reducing the pressure pulsations.

[00109] The damping means may also be or comprise a resonant fluid system configured to match one or more expected rotor speeds of the pressure exchanger 320 and reduce the associated pressure fluctuations. FIG. 18 is a schematic view of a portion of an example implementation of the wellsite system 377 comprising an example resonant fluid system 385 according to one or more aspects of the present disclosure. The wellsite system 377 is substantially similar in structure and operation to the wellsite system 376 including where indicated by like reference numbers, except as described below. Although not shown in FIGS. 12-17, the various features of the wellsite system 377 described below may be implemented as part of the wellsite systems 371-376 described above. The following description refers to FIGS. 5-18, collectively.

[00110] The resonant fluid system 385 may comprise a Helmholtz resonator chamber 380 fluidly connected along the fluid conduit system 309 or otherwise along the stream of dirty fluid discharged via the dirty fluid outlet 333 to dampen the pressure pulsations within the stream of dirty fluid discharged from the pressure exchanger 320. The chamber 380 may comprise an opening or port 381 fluidly connected with or along the conduit system 309, such as may fluidly connect the stream of dirty fluid with an internal volume 383 of the chamber 380. The chamber 380 may be oriented such that the solids or particular matter within the stream of dirty fluid flowing through the conduit system 309 may settle out of the bottom of the chamber 380 and not collect therein. The chamber 380 may be provided with venting means at the top of the chamber 380 and/or the chamber 380 may be fluidly connected with a fluid conduit 382, which may permit addition or removal of gas from the chamber 380 to adjust or tune the resonant frequency of the chamber 380 to the frequency of the pressure pulsations. The chamber 380 may also be provided with a piston 384 slidably disposed therein or other means of changing the internal volume 383 of the chamber 380 to adjust or tune the resonant frequency of the chamber 380 to the frequency of the pressure pulsations.

[00111] Vibrations of the fluid conduit systems 305, 309, 316, 317 caused by the pressure pulsations may be isolated to minimize or otherwise reduce fatigue damage. The vibration isolation may be provided, for example, in the form of wire rope isolators separating the high- pressure conduit systems 305, 309, 316, 317 from the wellsite surface 310 or frames of mobile trailers or skids. Rubber sleeves or blocks may also be utilized along the conduit systems 305, 309, 316, 317 to provide this isolation. Finally, air bags may be utilized to provide adjustable and/or high compliance vibration isolation.

[00112] Failure of the rotor 201 during pressurizing operations may cause unintended flows through the pressure exchanger 320. For example, a stuck or otherwise non-rotating rotor 201 may result in certain fluid inlets and outlets 331-334 being fluidly connected or short circuiting via the chambers 150 and/or the spaces 361, 362, 363, resulting in fluid flows in unintended directions and through unintended inlets and outlets. Accordingly, fluid control valves 326-329 may be utilized at the inlet and outlet 331-334 to selectively and independently isolate each inlet and outlet 331-334 from the corresponding fluid conduit systems 305, 309, 316, 317, such as when the rotor 201 becomes non-rotating or otherwise fails. In an example implementation, the fluid control valves 326-329 may be operated when the sensors 214 detect that the rotor 201 is not rotating while the pressurized clean fluid and/or low-pressure dirty fluid is being supplied to the pressure exchanger 200. Each fluid control valve 326-329 may be a fluid shut-off valve, which may be independently opened and closed to permit and prevent fluid flow through the corresponding fluid inlets and outlets 331-334. The fluid control valves 326-329 may be or comprise ball valves, globe valves, butterfly valves, and/or another type of fluid valves, such as may be selectively opened and closed to permit and prevent fluid flow.

[00113] The wellsite system 376 may be configured to cause rotation of the rotor 201 of the pressure exchanger 320 before introducing the stream of dirty fluid into the pressure exchanger 320. For example, during rotor start-up operations, clean fluid may be fluidly connected with the fluid inlets and outlets 331-334 to initiate rotation of the rotor 201. Once intended rotation is achieved, the dirty fluid may be permitted to flow into the pressure exchanger 320 to be pressurized.

[00114] The wellsite system 376 may comprise a fluid conduit system 366 fluidly connecting the dirty fluid inlet 331 with the clean fluid outlet 334, such as may permit clean fluid discharged via the clean fluid outlet 334 to be communicated into the dirty fluid inlet 331, thus permitting the stream of clean fluid to circulated through the pressure exchanger 320 to start rotation of the rotor 201. During such clean fluid start-up operations, the fluid control valve 326 may be operated to the closed-flow position to prevent the dirty fluid from flowing into the pressure exchanger 320. Once the rotor 201 is rotating at the intended speed, a fluid shut-off valve 367 may close the conduit system 366 and the fluid control valve 326 may be opened to permit the dirty fluid to be communicated into the pressure exchanger 320 via the dirty fluid inlet 331.

[00115] During rotor start-up, the clean fluid being discharged via the dirty fluid outlet 333 may be permitted to be injected into the well 311, the clean fluid may be circulated back into the pressure exchanger 320, and/or the clean fluid may be collected in the tank 340. For example, the wellsite system 376 may further comprise a fluid conduit system 368 fluidly connecting the dirty fluid outlet 333 with the dirty fluid inlet 331, such as may permit the stream of clean fluid discharged via the dirty fluid outlet 333 to be recirculated into the pressure exchanger 320 via the dirty fluid inlet 331. During recirculation, the fluid control valve 328 may be operated to the closed-flow position to prevent the clean fluid from being injected into the well 331. Once the rotor 201 is rotating at the intended speed, a fluid shut-off valve 369 may close the conduit system 368 and the fluid control valve 328 may be opened to permit the dirty fluid to be injected into the well 31 1 via the dirty fluid outlet 331.

[00116] The wellsite system 376, including the conduit systems 366, 368 and the

corresponding valves 367, 369, may be utilized to purge the pressure exchanger 320, including the rotor 201, with the stream of clean fluid before shut-down of the wellsite system 376.

Leaving the pressure exchanger 320 full of slurry or another dirty fluid may jam or otherwise cause the rotor 201 to become stuck. The start-up procedures described above may be utilized to purge the pressure exchanger 320 with the clean fluid before shutdown.

[00117] FIG. 19 is a schematic view of an example implementation of a wellsite system 378 according to one or more aspects of the present disclosure. The wellsite system 378 is substantially similar in structure and operation to the wellsite systems 371-377 including where indicated by like reference numbers, except as described below. Although not shown in FIGS. 12-18, the various features described below may be implemented as part of the wellsite systems 371-377 described above. The following description refers to FIGS. 5-19, collectively.

[00118] Similarly as in wellsite system 374, the wellsite system 378 includes multiple pressure exchangers 320 fluidly connected to receive pressurized clean fluid from a common source, such as the manifold 308. In such wellsite systems, flow division of the pressurized clean fluid may be actively controlled, such as to prevent one of the pressure exchangers 320 from receiving excessive, low, or otherwise unintended portions of the stream of clean fluid supplied by the common fluid source 308. For example, low flow rates of the clean fluid through the pressure exchanger 320 may lead to rotational bearing failure. Fluid flow division may be achieved by adjusting resistance of clean fluid flow through each pressure exchanger 320 by adjusting the flow rate of the clean fluid being received by each pressure exchanger 320. Accordingly, a flow rate control valve 335 may be fluidly connected at the clean fluid inlet 332 of each pressure exchanger 320. The flow rate control valves 335 may each be or comprise a needle valve, a metering valve, a butterfly valve, a globe valve, or another valve operable to progressively or gradually open and close to control rate of fluid flow. The fluid flow division may also be achieved by adjusting resistance of clean fluid flow through each pressure exchanger 320 by adjusting the flow rate of the clean fluid being discharged from the pressure exchangers 320. Such flow adjustments may be achieved by utilizing one or more of the fluid control valves 336, 337 described above, such as may be fluidly connected at the clean fluid inlet 332 and/or outlet 334 of each pressure exchanger 320. Alternatively, fluid flow division may also be achieved by fluidly connecting each pressure exchanger 320 to receive the high-pressure clean fluid from its own corresponding fluid source. An example of such configuration is shown in FIG. 16 as the wellsite system 375.

[00119] Similarly to as described above, a stuck or otherwise non-rotating rotor 201 may result in certain fluid inlets and outlets 331-334 being fluidly connected or short circuiting, resulting in fluid flows in unintended directions through the inlets and outlets 331, 333 and along the conduit systems 351, 353. Similarly as in the wellsite system 376, the wellsite system 378 may comprise the fluid shut-off valves 326, 328 to isolate the inlets and outlets 331, 333 from the corresponding conduit systems 351, 355. Instead of or in addition to the fluid shut-off valves 326, 328, the wellsite system 378 may include check valves 342, 344 fluidly connected with the dirty fluid inlets and outlets 331, 333, respectively. The check valves 342, 344 may prevent such unintended fluid flows by permitting fluid flow in one direction. For example, the check valves 344 may be fluidly connected at the dirty fluid outlets 333 to separate the dirty high-pressure discharge from a main treating line 355, such as may prevent the dirty fluid from backing up into the pressure exchangers 320 from the well 311. The check valves 344 may also prevent high- pressure dirty fluid discharged by one pressure exchanger 320 from being forced or otherwise injected into another pressure exchanger 320 fluidly coupled via the conduit system 353.

Furthermore, if the clean fluid discharge conduit system 354 is maintained above the pressure of the dirty fluid supply conduit system 351, the check valve 342 fluidly connected at the dirty fluid inlets 331 may prevent or minimize clean fluid flows into the mixer 304 or other upstream components.

[00120] Each fluid control valve 323, 326-329, 335-338, 367, 369 may be actuated remotely by a corresponding actuator (not shown) coupled with each fluid control valve 323, 326-329, 335-338, 367, 369. The actuators may be or comprise electric actuators, such as solenoids or motors, or fluid actuators, such as pneumatic or hydraulic cylinders or rotary actuators. The fluid control valves 323, 326-329, 335-338, 367, 369 may also be actuated manually, such as by a lever (not shown).

[00121] Various portions of the wellsite systems 371 -378 described above may collectively form and/or be controlled by a control system, such as may be operable to monitor and/or control operations of the wellsite systems 371-378. FIG. 20 is a schematic view of at least a portion of an example implementation of such a control system 400 according to one or more aspects of the present disclosure. The following description refers to one or more of FIGS. 1-20.

[00122] The control system 400 may comprise the above-mentioned controller 410, which may be in communication with the gel maker 302, the solids container 303, the mixers 304, the pumps 306, 314, the manifold 308, the pressure exchangers 320, the sensors 214, the fluid control valves, 323, 326-329, 335-338, 367, 369, the fluid analyzers 347, 348, 349, and/or actuators associated with one or more of these components. For clarity, these and other components in communication with the controller 410 will be collectively referred to hereinafter as "controlled equipment." The controller 410 may be operable to receive coded instructions 432 from wellsite operators and signals generated by the fluid analyzers 347, 348, 349, process the coded instructions 432 and the signals, and communicate control signals to the controlled equipment to execute the coded instructions 432 to implement at least a portion of one or more example methods and/or processes described herein, and/or to implement at least a portion of one or more of the example systems described herein. The controller 410 may be or form a portion of the control unit 312.

[00123] The controller 410 may be or comprise, for example, one or more processors, special- purpose computing devices, servers, personal computers (e.g., desktop, laptop, and/or tablet computers) personal digital assistant (PDA) devices, smartphones, internet appliances, and/or other types of computing devices. The controller 410 may comprise a processor 412, such as a general-purpose programmable processor. The processor 412 may comprise a local memory 414, and may execute coded instructions 432 present in the local memory 414 and/or another memory device. The processor 412 may execute, among other things, the machine-readable coded instructions 432 and/or other instructions and/or programs to implement the example methods and/or processes described herein. The programs stored in the local memory 414 may include program instructions or computer program code that, when executed by an associated processor, facilitate the wellsite system 371 -378 to perform the example methods and/or processes described herein. The processor 412 may be, comprise, or be implemented by one or more processors of various types suitable to the local application environment, and may include one or more of general-purpose computers, special-purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as non- limiting examples. Of course, other processors from other families are also appropriate.

[00124] The processor 412 may be in communication with a main memory 417, such as may include a volatile memory 418 and a non-volatile memory 420, perhaps via a bus 422 and/or other communication means. The volatile memory 418 may be, comprise, or be implemented by random access memory (RAM), static random access memory (SRAM), synchronous dynamic random access memory (SDRAM), dynamic random access memory (DRAM), RAMBUS dynamic random access memory (RDRAM), and/or other types of random access memory devices. The non-volatile memory 420 may be, comprise, or be implemented by read-only memory, flash memory, and/or other types of memory devices. One or more memory controllers (not shown) may control access to the volatile memory 418 and/or non-volatile memory 420.

[00125] The controller 410 may also comprise an interface circuit 424. The interface circuit 424 may be, comprise, or be implemented by various types of standard interfaces, such as an Ethernet interface, a universal serial bus (USB), a third generation input/output (3GIO) interface, a wireless interface, a cellular interface, and/or a satellite interface, among others. The interface circuit 424 may also comprise a graphics driver card. The interface circuit 424 may also comprise a communication device, such as a modem or network interface card to facilitate exchange of data with external computing devices via a network (e.g., Ethernet connection, digital subscriber line (DSL), telephone line, coaxial cable, cellular telephone system, satellite, etc.). One or more of the controlled equipment may be connected with the controller 410 via the interface circuit 424, such as may facilitate communication between the controlled equipment and the controller 410.

[00126] One or more input devices 426 may also be connected to the interface circuit 424. The input devices 426 may permit the wellsite operators to enter the coded instructions 432, including control commands, operational set-points, and/or other data for use by the processor 412. The operational set-points may include, as non-limiting examples, solids concentration set- points, time interval set-points, rotor speed set-points, and/or flow rate set-points, such as may collectively control the solids concentration levels and/or the flow rate of the dirty fluid being injected into the well 311. The input devices 426 may be, comprise, or be implemented by a keyboard, a mouse, a touchscreen, a track-pad, a trackball, an isopoint, and/or a voice recognition system, among other examples.

[00127] One or more output devices 428 may also be connected to the interface circuit 424. The output devices 428 may be, comprise, or be implemented by display devices (e.g., a liquid crystal display (LCD), a light-emitting diode (LED) display, or cathode ray tube (CRT) display), printers, and/or speakers, among other examples. The controller 410 may also communicate with one or more mass storage devices 430 and/or a removable storage medium 434, such as may be or include floppy disk drives, hard drive disks, compact disk (CD) drives, digital versatile disk (DVD) drives, and/or USB and/or other flash drives, among other examples.

[00128] The coded instructions 432 may be stored in the mass storage device 430, the main memory 417, the local memory 414, and/or the removable storage medium 434. Thus, the controller 410 may be implemented in accordance with hardware (perhaps implemented in one or more chips including an integrated circuit, such as an ASIC), or may be implemented as software or firmware for execution by the processor 412. In the case of firmware or software, the implementation may be provided as a computer program product including a non-transitory, computer-readable medium or storage structure embodying computer program code (i.e., software or firmware) thereon for execution by the processor 412.

[00129] The coded instructions 432 may include program instructions or computer program code that, when executed by the processor 412, may cause the wellsite systems 371-378 to perform methods, processes, and/or routines described herein. For example, the controller 410 may receive and process the operational set-points entered by a human operator. Based on the received operational set-points and the signals generated by the sensors 214 and/or the fluid analyzers 347, 348, 349, the controller 410 may send signals or information to the various controlled equipment to cause the gel maker 302, the solids container 303, the mixers 304, the pressure exchangers 320, the fluid control valves, 323, 326-329, 335-338, 367, 369, and/or other portions of the wellsite system 371-378 to automatically perform and/or undergo one or more operations or routines described herein or otherwise within the scope of the present disclosure.

[00130] FIG. 21 is a flow-chart diagram of at least a portion of an example implementation of a method (500) according to one or more aspects of the present disclosure. The method (500) may be performed utilizing or otherwise in conjunction with at least a portion of one or more implementations of one or more instances of the apparatus shown in one or more of FIGS. 1-20 and/or otherwise within the scope of the present disclosure. For example, the method (500) may be performed and/or caused, at least partially, by the controller 410 executing the coded instructions 432 according to one or more aspects of the present disclosure. Thus, the following description of the method (500) also refers to apparatus shown in one or more of FIGS. 1-20. However, the method (500) may also be performed in conjunction with implementations of apparatus other than those depicted in FIGS. 1-20 that are also within the scope of the present disclosure.

[00131] The method (500) comprises operating (510) a pressure exchanger as described above to pressurize low-pressure dirty fluid utilizing high-pressure clean fluid. For example, operating (510) the pressure exchanger may comprise receiving (515) a stream of dirty fluid at a first pressure into at least one chamber of the pressure exchanger, and receiving (520) a stream of clean fluid at a second pressure into the at least one chamber to pressurize (522) the dirty fluid within the at least one chamber. As described above, the second pressure is substantially greater than the first pressure. As a result, a stream of the pressurized dirty fluid is discharged (525) from the at least one chamber, and a stream of the consequently depressurized clean fluid is discharged (530) from the at least one chamber.

[00132] The method (500) may also comprise controlling (535) a first flow rate of the received (520) stream of clean fluid or a second flow rate of the discharged (530) stream of clean fluid such that the second flow rate is less than the first flow rate. Controlling (535) the first or second flow rate may comprise controlling the second flow rate, such as by reducing the second flow rate with respect to the first flow rate, such as may cause a portion of the received (520) stream of clean fluid to flow between the housing and the rotor (and perhaps combine with dirty fluid leakage) to form a fluid bearing between the housing and the rotor. The portion of the received (520) stream of clean fluid flowing between the housing and the rotor may flow into the received (515) stream of dirty fluid and/or the discharged (525) stream of dirty fluid.

[00133] Controlling (535) the second flow rate may control, or comprise controlling, a third flow rate of the portion of the received (520) stream of clean fluid flowing between the housing and the rotor, such as to control a solids density of the discharged (525) stream of dirty fluid. Controlling (535) the first or second flow rate may also or instead comprise controlling the first flow rate, and the method (500) may further comprise controlling (540) the third flow rate of the portion of the received (520) stream of clean fluid flowing between the housing and the rotor, such as to control a rate of dilution of the dirty fluid by the clean fluid. Thus, the third flow rate may be equal to the difference between the first and second flow rates.

[00134] The method (500) may also comprise controlling (545) a fourth flow rate of the received (515) stream of dirty fluid. The method (500) may also comprise controlling (550) a difference between the first flow rate and the fourth flow rate to control a ratio of the first and fourth flow rates, thereby controlling the ratio of clean and dirty fluid entering the pressure exchanger.

[00135] As described above, controlling (530) the first or second flow rate may comprise controlling a fluid control device. For example, the fluid control device may be or comprise a positive displacement device, such as a positive displacement pump or a positive displacement motor. The fluid control device may also be or comprise a pressure control device operable to control pressure and, thus, the controlled (530) first or second flow rate.

[00136] The method (500) may also comprise causing (555) a pressure drop along the discharged (525) stream of pressurized dirty fluid, such as by utilizing a flow restrictor, as described above. The method (500) may also or instead comprise dampening (560) pressure fluctuations within the discharged (525) stream of pressurized dirty fluid, such as by utilizing a resonator chamber, as also described above. The method (500) may also comprise sensing (565) a rotational speed of the rotor, as also described above.

[00137] Operating (510) the pressure exchanger may also comprise, after receiving (520) the stream of clean fluid but before receiving (515) the stream of dirty fluid, initiating (570) rotation of the rotor. For example, initiating (570) the rotor rotation may comprise temporarily directing the discharged (530) stream of clean fluid through the dirty fluid inlet into the at least one chamber.

[00138] As also described above, the dirty fluid may comprise suspended solid particles, and the clean fluid may be substantially free of suspended solid particles. The method (500) may also comprise utilizing (575) the discharged (525) stream of pressurized dirty fluid in a subterranean well treatment operation. For example, the clean fluid may comprise water, the dirty fluid may be or comprise a fracturing fluid, and the discharged (525) stream of pressurized dirty fluid may be utilized (575) in a subterranean formation fracturing operation. [00139] FIG. 22 is a flow-chart diagram of at least a portion of an example implementation of a method (600) according to one or more aspects of the present disclosure. The method (600) may be performed utilizing or otherwise in conjunction with at least a portion of one or more implementations of one or more instances of the apparatus shown in one or more of FIGS. 1-20 and/or otherwise within the scope of the present disclosure. For example, the method (600) may be performed and/or caused, at least partially, by the controller 410 executing the coded instructions 432 according to one or more aspects of the present disclosure. Thus, the following description of the method (600) also refers to apparatus shown in one or more of FIGS. 1-20. However, the method (600) may also be performed in conjunction with implementations of apparatus other than those depicted in FIGS. 1-20 that are also within the scope of the present disclosure. One or more aspects of the method (600) may also be utilized in conjunction with one or more aspects of the method (500) shown in FIG. 21 and/or other methods described above or otherwise within the scope of the present disclosure.

[00140] The method (600) may comprise forming (605) a stream of dirty fluid at a first pressure, forming (610) a stream of clean fluid at a second pressure, and pressurizing (615) the stream of dirty fluid utilizing a pressure exchanger as described above. Pressurizing (615) the stream of dirty fluid utilizing the pressure exchanger comprises: directing (620) a portion of the stream of dirty fluid into a pressure chamber of the pressure exchanger; directing (625) a first portion of the stream of clean fluid into the pressure chamber to pressurize the dirty fluid within the pressure chamber as the rotor rotates within the housing, thereby depressurizing the clean fluid within the pressure chamber; (630) directing a second portion of the stream of clean fluid into a gap defined between the rotor and the housing; discharging (635) a stream comprising the pressurized dirty fluid from the pressure exchanger; and discharging (640) a stream comprising the depressurized clean fluid from the pressure exchanger. The discharged (640) stream comprising the depressurized clean fluid may further comprise leakage of the dirty fluid from the pressure chamber.

[00141] The method (600) may also comprise injecting (645) the discharged (635) stream comprising the pressurized dirty fluid into a wellbore during a subterranean well treatment operation. For example, the clean fluid may comprise water, the dirty fluid may be or comprise a fracturing fluid, and the subterranean well treatment operation may comprise a subterranean formation fracturing operation during which the discharged (635) stream comprising the pressurized dirty fluid is injected (645) into the wellbore.

[00142] It is also noted that the example implementations shown in several of the figures depict a pressure exchanger being oriented substantially horizontally. However,

implementations in which the pressure exchanger is oriented substantially vertically or otherwise non-horizontal are also within the scope of the present disclosure.

[00143] In view of the entirety of the present disclosure, including the figures and the claims, a person having ordinary skill in the art will readily recognize that the present disclosure introduces an apparatus comprising: (A) a pressure exchanger comprising a rotor, wherein at least one chamber extends through the rotor, and wherein the pressure exchanger is operable to: (1) receive dirty fluid at a first pressure into the at least one chamber via a dirty fluid inlet; (2) receive clean fluid at a second pressure into the at least one chamber via a clean fluid inlet to pressurize the dirty fluid to a third pressure, wherein the second and third pressures are substantially greater than the first pressure; (3) discharge the dirty fluid at the third pressure from the at least one chamber via a dirty fluid outlet; and (4) discharge the clean fluid from the at least one chamber via a clean fluid outlet; and (B) a fluid control device fluidly connected with at least one of the clean fluid inlet, the clean fluid outlet, the dirty fluid inlet, and the dirty fluid outlet, and operable to maintain a first flow rate of the clean fluid discharged via the clean fluid outlet at less than a second flow rate of the clean fluid received via the clean fluid inlet.

[00144] The apparatus may further comprise a manifold assembly that includes: a manifold; and a plurality of instances of the pressure exchanger.

[00145] The pressure exchanger may further comprise: a housing having a bore extending between first and second ends of the housing; a first cap covering the bore at the first end of the housing, wherein the first cap comprises the dirty fluid inlet and the dirty fluid outlet; and a second cap covering the bore at the second end of the housing, wherein the second cap comprises the clean fluid inlet and the clean fluid outlet. The rotor may be rotatably disposed within the bore of the housing and between the first and second caps, and the at least one chamber may extend through the rotor between the first and second ends of the housing.

[00146] The fluid control device may be fluidly connected with the clean fluid outlet, and may be operable to reduce the first flow rate with respect to the second flow rate, such as to cause a portion of the clean fluid received via the clean fluid inlet to flow between the housing and the rotor, such as to form a fluid bearing between the housing and the rotor. The fluid bearing may also comprise a portion of the dirty fluid.

[00147] The fluid control device may also or instead be operable to cause the portion of the clean fluid received via the clean fluid inlet to flow between the housing and the rotor and combine with the dirty fluid received via the dirty fluid inlet. The fluid control device may also or instead be operable to cause the portion of the clean fluid received via the clean fluid inlet to flow between the housing and the rotor and combine with the dirty fluid being discharged via the dirty fluid outlet.

[00148] The fluid control device may also or instead be operable to control a third flow rate of the portion of the clean fluid flowing between the housing and the rotor and combining with the dirty fluid to control a solids density of the dirty fluid discharged via the dirty fluid outlet. The fluid control device may be a first fluid control device, and the apparatus may further comprise a second fluid control device fluidly connected with the clean fluid inlet and operable to control the second flow rate, wherein the first and second fluid control devices may be collectively operable to control the third flow rate to control dilution of the dirty fluid, and wherein the difference between the first and second flow rates may be the third flow rate.

[00149] The fluid control device may be a first fluid control device, the apparatus may further comprise a second fluid control device fluidly connected with the dirty fluid inlet and operable to control a third flow rate of the dirty fluid received via the dirty fluid inlet, and the first and second fluid control devices may be collectively operable to control a ratio of the second and third flow rates.

[00150] The fluid control device may be or comprise a positive displacement device. The positive displacement device may be or comprise a positive displacement pump or a positive displacement motor. The fluid control device may also be or comprise a pressure control device.

[00151] The at least one chamber may comprise multiple chambers circumferentially spaced around an axis of rotation of the rotor. The at least one chamber may extend through the rotor in a helical manner about an axis of rotation of the rotor. The incoming dirty and/or clean fluid may act against the at least one helical chamber to impart rotary motion to the rotor.

[00152] The apparatus may further comprise a flow restrictor fluidly connected with the dirty fluid outlet and operable to cause a pressure drop of the discharged dirty fluid. The apparatus may also or instead comprise a resonator chamber having a port fluidly connected with the dirty fluid outlet and operable to dampen pressure fluctuations within the discharged dirty fluid.

[00153] The fluid control device may be a first fluid control device, and the apparatus may further comprise at least one second fluid control device fluidly connected with at least one of the clean fluid inlet, clean fluid outlet, dirty fluid inlet, and dirty fluid outlet and operable to prevent fluid flow via the at least one of the clean fluid inlet, clean fluid outlet, dirty fluid inlet, and dirty fluid outlet. The at least one second fluid control device may be or comprise a check valve fluidly connected with the dirty fluid outlet and operable to prevent the dirty fluid from flowing into the pressure exchanger via the dirty fluid outlet. The at least one second fluid control device may be or comprise a check valve fluidly connected with the dirty fluid inlet and operable to prevent the clean fluid from flowing out of the pressure exchanger via the dirty fluid inlet. The at least one second fluid control device may be or comprise a flow shut-off valve operable to prevent fluid flow when the rotor is not rotating but the pressure exchanger is receiving the clean fluid via the clean fluid inlet.

[00154] The apparatus may further comprise: a sensor disposed in association with the pressure exchanger and operable to generate information indicative of rotational speed of the rotor; and a recording device in communication with the sensor and operable to record the information generated by the sensor.

[00155] The pressure exchanger may be a first pressure exchanger, the fluid control device may be a first fluid control device, and the apparatus may further comprise: a second pressure exchanger; a first pump fluidly connected with the clean fluid inlet of the first pressure exchanger and fluidly isolated from a clean fluid inlet of the second pressure exchanger; and a second pump fluidly connected with the clean fluid inlet of the second pressure exchanger and fluidly isolated from the clean fluid inlet of the first pressure exchanger.

[00156] The pressure exchanger may be a first pressure exchanger, the fluid control device may be a first fluid control device fluidly connected with the clean fluid outlet of the first pressure exchanger, and the apparatus may further comprise: a second pressure exchanger having a clean fluid inlet; a second fluid control device fluidly connected with a clean fluid outlet of the second pressure exchanger; and a common source of clean fluid fluidly connected with the clean fluid inlets of the first and second pressure exchangers. The first and second fluid control devices may be further operable to control flow rates of the corresponding streams of clean fluid received from the common source of clean fluid via corresponding clean fluid inlets of the first and second pressure exchangers.

[00157] The clean fluid outlet may be fluidly connected with the dirty fluid inlet, and the pressure exchanger may be further operable to receive, via the dirty fluid inlet, the clean fluid discharged via the clean fluid outlet to rotate the rotor. The fluid control device may be a first fluid control device, and the apparatus may further comprise a second fluid control device fluidly connected with the dirty fluid inlet and operable to prevent the pressure exchanger from receiving the incoming dirty fluid via the dirty fluid inlet when the stream of clean fluid is being received via the dirty fluid inlet. The dirty fluid outlet may be fluidly connected with the dirty fluid inlet, and the pressure exchanger may be further operable to receive, via the dirty fluid inlet, the clean fluid discharged via the dirty fluid outlet.

[00158] The dirty fluid may comprise suspended solid particles, and the clean fluid may be substantially free of suspended solid particles. The stream of dirty fluid discharged at the third pressure via the dirty fluid outlet may be for use in a subterranean well treatment operation. For example, the clean fluid may comprise water, the dirty fluid may be or comprise a fracturing fluid, and the subterranean well treatment operation may comprise a subterranean formation fracturing operation.

[00159] The present disclosure also introduces a method comprising: (A) operating a pressure exchanger to: (1) receive a stream of dirty fluid at a first pressure into at least one chamber of the pressure exchanger; (2) receive a stream of clean fluid at a second pressure into the at least one chamber to pressurize the dirty fluid within the at least one chamber, wherein the second pressure is substantially greater than the first pressure; (3) discharge a stream of the pressurized dirty fluid from the at least one chamber; and (4) discharge a stream of the clean fluid from the at least one chamber; and (B) controlling a first flow rate of the received stream of clean fluid or a second flow rate of the discharged stream of clean fluid such that the second flow rate is less than the first flow rate.

[00160] The dirty fluid may comprise suspended solid particles, and the clean fluid may be substantially free of suspended solid particles.

[00161] The method may further comprise utilizing the discharged stream of pressurized dirty fluid in a subterranean well treatment operation. For example, the clean fluid may comprise water, the dirty fluid may be or comprise a fracturing fluid, and the subterranean well treatment operation may comprise a subterranean formation fracturing operation.

[00162] The pressure exchanger may comprise a housing having a bore extending between first and second ends of the housing, a first cap covering the bore at the first end of the housing, and a second cap covering the bore at the second end of the housing. The first cap may comprise a dirty fluid inlet by which the stream of dirty fluid at the first pressure is received, and a dirty fluid outlet by which the stream of pressurized dirty fluid is discharged. The second cap may comprise a clean fluid inlet by which the stream of clean fluid at the second pressure is received, and a clean fluid outlet by which the stream of clean fluid is discharged. A rotor is rotatably disposed within the bore of the housing between the first and second caps, and the at least one chamber extends through the rotor between first and second ends of the housing.

[00163] The method may further comprise sensing a rotational speed of the rotor.

[00164] Controlling the first or second flow rate may comprise controlling the second flow rate, and controlling the second flow rate may comprise reducing the second flow rate with respect to the first flow rate to cause a portion of the received stream of clean fluid to flow between the housing and the rotor, such as to combine with the dirty fluid, and forming a fluid bearing between the housing and the rotor. The portion of the received stream of clean fluid flowing between the housing and the rotor may flow into the received stream of dirty fluid and/or the discharged stream of dirty fluid. Controlling the second flow rate may control a third flow rate of the portion of the received stream of clean fluid flowing between the housing and the rotor and into the received or discharged stream of dirty fluid to control a solids density of the discharged stream of dirty fluid. Controlling the first or second flow rate may comprise controlling the first flow rate, and the method may further comprise controlling the third flow rate of the portion of the received stream of clean fluid flowing between the housing and the rotor to control a rate of dilution of the dirty fluid by the clean fluid, wherein the third flow rate may be equal to the difference between the first and second flow rates. The method may further comprise controlling a fourth flow rate of the received stream of dirty fluid, and controlling a difference between the first flow rate and the fourth flow rate to control a ratio of the first and fourth flow rates.

[00165] Controlling the first or second flow rate may comprise controlling a fluid control device. The fluid control device may be or comprise a positive displacement device. The positive displacement device may be or comprise a positive displacement pump or a positive displacement motor. The fluid control device may also be or comprise a pressure control device operable to control pressure and, thus, the controlled first or second flow rate.

[00166] The method may further comprise causing a pressure drop along the discharged stream of pressurized dirty fluid, such as by utilizing a flow restrictor.

[00167] The method may further comprise dampening pressure fluctuations within the discharged stream of pressurized dirty fluid, such as by utilizing a resonator chamber.

[00168] The received stream of dirty fluid may be received via a dirty fluid inlet, the discharged stream of clean fluid may be discharged via a clean fluid outlet, the pressure exchanger may comprise a rotor, the rotor may comprise the at least one chamber, and operating the pressure exchanger may further comprise, after receiving the stream of clean fluid but before receiving the stream of dirty fluid, initiating rotation of the rotor, such as by temporarily directing the discharged stream of clean fluid through the dirty fluid inlet into the at least one chamber.

[00169] The present disclosure also introduces a method comprising: forming a stream of dirty fluid at a first pressure; forming a stream of clean fluid at a second pressure, wherein the second pressure is substantially greater than the first pressure; and pressurizing the stream of dirty fluid utilizing a pressure exchanger, wherein the pressure exchanger comprises a rotor disposed within a housing and comprising a pressure chamber. Pressurizing the stream of dirty fluid utilizing the pressure exchanger may comprise: directing a portion of the stream of dirty fluid into the pressure chamber; directing a first portion of the stream of clean fluid into the pressure chamber to pressurize the dirty fluid within the pressure chamber as the rotor rotates within the housing, thereby depressurizing the clean fluid within the pressure chamber; directing a second portion of the stream of clean fluid into a gap defined between the rotor and the housing; discharging a stream comprising the pressurized dirty fluid from the pressure exchanger; and discharging a stream comprising the depressurized clean fluid from the pressure exchanger.

[00170] The discharged stream comprising the depressurized clean fluid may further comprise leakage of the dirty fluid from the pressure chamber.

[00171] The dirty fluid may comprise suspended solid particles, and the clean fluid may be substantially free of suspended solid particles. [00172] The method may further comprise injecting the discharged stream comprising the pressurized dirty fluid into a wellbore during a subterranean well treatment operation. For example, the clean fluid may comprise water, the dirty fluid may be or comprises a fracturing fluid, and the subterranean well treatment operation may comprise a subterranean formation fracturing operation.

[00173] The foregoing outlines features of several embodiments so that a person having ordinary skill in the art may better understand the aspects of the present disclosure. A person having ordinary skill in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same functions and/or achieving the same benefits of the embodiments introduced herein. A person having ordinary skill in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

[00174] The Abstract at the end of this disclosure is provided to permit the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Claims

WHAT IS CLAIMED IS:

1. An apparatus comprising:

a pressure exchanger comprising a rotor, wherein at least one chamber extends through the rotor, and wherein the pressure exchanger is operable to:

receive dirty fluid at a first pressure into the at least one chamber via a dirty fluid inlet; receive clean fluid at a second pressure into the at least one chamber via a clean fluid inlet to pressurize the dirty fluid to a third pressure, wherein the second and third pressures are substantially greater than the first pressure;

discharge the dirty fluid at the third pressure from the at least one chamber via a dirty fluid outlet; and

discharge the clean fluid from the at least one chamber via a clean fluid outlet; and a fluid control device fluidly connected with at least one of the clean fluid inlet, the clean fluid outlet, the dirty fluid inlet, and the dirty fluid outlet, and operable to maintain a first flow rate of the clean fluid discharged via the clean fluid outlet at less than a second flow rate of the clean fluid received via the clean fluid inlet.

2. The apparatus of claim 1 further comprising a manifold assembly that includes:

a manifold; and

a plurality of instances of the pressure exchanger.

3. The apparatus of claim 1 wherein the pressure exchanger further comprises:

a housing having a bore extending between first and second ends of the housing;

a first cap covering the bore at the first end of the housing, wherein the first cap comprises the dirty fluid inlet and the dirty fluid outlet; and

a second cap covering the bore at the second end of the housing, wherein the second cap

comprises the clean fluid inlet and the clean fluid outlet;

wherein the rotor is rotatably disposed within the bore of the housing and between the first and second caps, and wherein the at least one chamber extends through the rotor between the first and second ends of the housing.

4. The apparatus of claim 3 wherein the fluid control device is fluidly connected with the clean fluid outlet and is operable to reduce the first flow rate with respect to the second flow rate to cause a portion of the clean fluid received via the clean fluid inlet to flow between the housing and the rotor to form a fluid bearing between the housing and the rotor.

5. The apparatus of claim 4 wherein the fluid bearing also comprises a portion of the dirty fluid.

6. The apparatus of claim 4 wherein the fluid control device is further operable to control a third flow rate of the portion of the clean fluid flowing between the housing and the rotor and combining with the dirty fluid to control a solids density of the dirty fluid discharged via the dirty fluid outlet.

7. The apparatus of claim 6 wherein the fluid control device is a first fluid control device, and wherein the apparatus further comprises a second fluid control device fluidly connected with the clean fluid inlet and operable to control the second flow rate, wherein the first and second fluid control devices are collectively operable to control the third flow rate to control dilution of the dirty fluid, and wherein the difference between the first and second flow rates is the third flow rate.

8. The apparatus of claim 1 wherein:

the fluid control device is a first fluid control device;

the apparatus further comprises a second fluid control device fluidly connected with the dirty fluid inlet and operable to control a third flow rate of the dirty fluid received via the dirty fluid inlet; and

the first and second fluid control devices are collectively operable to control a ratio of the second and third flow rates.

9. The apparatus of claim 1 wherein the fluid control device is or comprises a positive

displacement device.

10. The apparatus of claim 9 wherein the positive displacement device is or comprises a positive displacement pump or a positive displacement motor.

11. The apparatus of claim 1 wherein the fluid control device is or comprises a pressure control device.

12. The apparatus of claim 1 wherein the at least one chamber comprises multiple chambers circumferentially spaced around an axis of rotation of the rotor.

13. The apparatus of claim 1 wherein the at least one chamber extends through the rotor in a helical manner about an axis of rotation of the rotor.

14. The apparatus of claim 13 wherein the incoming dirty and/or clean fluid acts against the at least one helical chamber to impart rotary motion to the rotor.

15. The apparatus of claim 1 further comprising a flow restrictor fluidly connected with the dirty fluid outlet and operable to cause a pressure drop of the discharged dirty fluid.

16. The apparatus of claim 1 further comprising a resonator chamber having a port fluidly

connected with the dirty fluid outlet and operable to dampen pressure fluctuations within the discharged dirty fluid.

17. The apparatus of claim 1 wherein the fluid control device is a first fluid control device, and wherein the apparatus further comprises at least one second fluid control device fluidly connected with at least one of the clean fluid inlet, clean fluid outlet, dirty fluid inlet, and dirty fluid outlet and operable to prevent fluid flow via the at least one of the clean fluid inlet, clean fluid outlet, dirty fluid inlet, and dirty fluid outlet.

18. The apparatus of claim 17 wherein the at least one second fluid control device is or

comprises a check valve fluidly connected with the dirty fluid outlet and operable to prevent the dirty fluid from flowing into the pressure exchanger via the dirty fluid outlet.

19. The apparatus of claim 17 wherein the at least one second fluid control device is or comprises a check valve fluidly connected with the dirty fluid inlet and operable to prevent the clean fluid from flowing out of the pressure exchanger via the dirty fluid inlet.

20. The apparatus of claim 17 wherein the at least one second fluid control device is or

comprises a flow shut-off valve operable to prevent fluid flow when the rotor is not rotating but the pressure exchanger is receiving the clean fluid via the clean fluid inlet.

21. The apparatus of claim 1 further comprising:

a sensor disposed in association with the pressure exchanger and operable to generate

information indicative of rotational speed of the rotor; and

a recording device in communication with the sensor and operable to record the information generated by the sensor.

22. The apparatus of claim 1 wherein the pressure exchanger is a first pressure exchanger,

wherein the fluid control device is a first fluid control device, and wherein the apparatus further comprises:

a second pressure exchanger;

a first pump fluidly connected with the clean fluid inlet of the first pressure exchanger and

fluidly isolated from a clean fluid inlet of the second pressure exchanger; and

a second pump fluidly connected with the clean fluid inlet of the second pressure exchanger and fluidly isolated from the clean fluid inlet of the first pressure exchanger.

23. The apparatus of claim 1 wherein:

the pressure exchanger is a first pressure exchanger;

the fluid control device is a first fluid control device fluidly connected with the clean fluid outlet of the first pressure exchanger;

the apparatus further comprises:

a second pressure exchanger having a clean fluid inlet; a second fluid control device fluidly connected with a clean fluid outlet of the second pressure exchanger; and

a common source of clean fluid fluidly connected with the clean fluid inlets of the first and second pressure exchangers; and

the first and second fluid control devices are further operable to control flow rates of the

corresponding streams of clean fluid received from the common source of clean fluid via corresponding clean fluid inlets of the first and second pressure exchangers.

24. The apparatus of claim 1 wherein the clean fluid outlet is fluidly connected with the dirty fluid inlet, and wherein the pressure exchanger is further operable to receive, via the dirty fluid inlet, the clean fluid discharged via the clean fluid outlet to rotate the rotor.

25. The apparatus of claim 24 wherein the fluid control device is a first fluid control device, and wherein the apparatus further comprises a second fluid control device fluidly connected with the dirty fluid inlet and operable to prevent the pressure exchanger from receiving the incoming dirty fluid via the dirty fluid inlet when the stream of clean fluid is being received via the dirty fluid inlet.

26. The apparatus of claim 25 wherein the dirty fluid outlet is fluidly connected with the dirty fluid inlet, and wherein the pressure exchanger is further operable to receive, via the dirty fluid inlet, the clean fluid discharged via the dirty fluid outlet.

27. The apparatus of claim 1 wherein the dirty fluid comprises suspended solid particles, and wherein the clean fluid is substantially free of suspended solid particles.

28. The apparatus of claim 1 wherein the stream of dirty fluid discharged at the third pressure via the dirty fluid outlet is for use in a subterranean well treatment operation.

29. The apparatus of claim 28 wherein the clean fluid comprises water, wherein the dirty fluid is or comprises a fracturing fluid, and wherein the subterranean well treatment operation comprises a subterranean formation fracturing operation.

30. A method comprising:

operating a pressure exchanger to:

receive a stream of dirty fluid at a first pressure into at least one chamber of the pressure exchanger;

receive a stream of clean fluid at a second pressure into the at least one chamber to

pressurize the dirty fluid within the at least one chamber, wherein the second pressure is substantially greater than the first pressure;

discharge a stream of the pressurized dirty fluid from the at least one chamber; and discharge a stream of the clean fluid from the at least one chamber; and

controlling a first flow rate of the received stream of clean fluid or a second flow rate of the discharged stream of clean fluid such that the second flow rate is less than the first flow rate.

31. The method of claim 30 wherein the dirty fluid comprises suspended solid particles, and wherein the clean fluid is substantially free of suspended solid particles.

32. The method of claim 30 further comprising utilizing the discharged stream of pressurized dirty fluid in a subterranean well treatment operation.

33. The method of claim 32 wherein the clean fluid comprises water, wherein the dirty fluid is or comprises a fracturing fluid, and wherein the subterranean well treatment operation comprises a subterranean formation fracturing operation.

34. The method of claim 30 wherein the pressure exchanger comprises:

a housing having a bore extending between first and second ends of the housing;

a first cap covering the bore at the first end of the housing, wherein the first cap comprises: a dirty fluid inlet by which the stream of dirty fluid at the first pressure is received; and a dirty fluid outlet by which the stream of pressurized dirty fluid is discharged;

comprises:

a clean fluid inlet by which the stream of clean fluid at the second pressure is received; and

a clean fluid outlet by which the stream of clean fluid is discharged; and

a rotor rotatably disposed within the bore of the housing and between the first and second caps, wherein the at least one chamber extends through the rotor between first and second ends of the housing.

35. The method of claim 34 further comprising sensing a rotational speed of the rotor.

36. The method of claim 34 wherein controlling the first or second flow rate comprises

controlling the second flow rate, and wherein controlling the second flow rate comprises reducing the second flow rate with respect to the first flow rate to cause a portion of the received stream of clean fluid to flow between the housing and the rotor toward the first end of the housing and combine with the dirty fluid to form a fluid bearing between the housing and the rotor.

37. The method of claim 36 wherein the portion of the received stream of clean fluid flowing between the housing and the rotor flows into the received stream of dirty fluid.

38. The method of claim 36 wherein the portion of the received stream of clean fluid flowing between the housing and the rotor flows into the discharged stream of dirty fluid.

39. The method of claim 36 wherein controlling the second flow rate controls a third flow rate of the portion of the received stream of clean fluid flowing between the housing and the rotor and into the received or discharged stream of dirty fluid to control a solids density of the discharged stream of dirty fluid.

40. The method of claim 36 wherein controlling the first or second flow rate comprises

controlling the first flow rate, and wherein the method further comprises:

controlling a third flow rate of the portion of the received stream of clean fluid flowing between the housing and the rotor to control a rate of dilution of the dirty fluid by the clean fluid, wherein the third flow rate is equal to the difference between the first and second flow rates.

41. The method of claim 36 further comprising:

controlling a third flow rate of the received stream of dirty fluid; and

controlling a difference between the first flow rate and the third flow rate to control a ratio of the first and third flow rates.

42. The method of claim 30 wherein controlling the first or second flow rate comprises

controlling a fluid control device.

43. The method of claim 42 wherein the fluid control device is or comprises a positive

displacement device.

44. The method of claim 42 wherein the positive displacement device is or comprises a positive displacement pump or a positive displacement motor.

45. The method of claim 42 wherein the fluid control device is or comprises a pressure control device operable to control pressure and, thus, the controlled first or second flow rate.

46. The method of claim 30 further comprising causing a pressure drop along the discharged stream of pressurized dirty fluid utilizing a flow restrictor.

47. The method of claim 30 further comprising dampening pressure fluctuations within the discharged stream of pressurized dirty fluid utilizing a resonator chamber.

48. The method of claim 30 wherein

the received stream of dirty fluid is received via a dirty fluid inlet;

the discharged stream of clean fluid is discharged via a clean fluid outlet;

the pressure exchanger comprises a rotor;

the rotor comprises the at least one chamber; and

operating the pressure exchanger further comprises, after receiving the stream of clean fluid but before receiving the stream of dirty fluid, initiating rotation of the rotor by temporarily directing the discharged stream of clean fluid through the dirty fluid inlet into the at least one chamber.

49. A method comprising:

forming a stream of dirty fluid at a first pressure;

forming a stream of clean fluid at a second pressure, wherein the second pressure is substantially greater than the first pressure; and

pressurizing the stream of dirty fluid utilizing a pressure exchanger, wherein the pressure

exchanger comprises a rotor disposed within a housing and comprising a pressure chamber, and wherein pressurizing the stream of dirty fluid utilizing the pressure exchanger comprises: directing a portion of the stream of dirty fluid into the pressure chamber;

directing a first portion of the stream of clean fluid into the pressure chamber to

pressurize the dirty fluid within the pressure chamber as the rotor rotates within the housing, thereby depressurizing the clean fluid within the pressure chamber; directing a second portion of the stream of clean fluid into a gap defined between the rotor and the housing;

discharging a stream comprising the pressurized dirty fluid from the pressure exchanger; and

discharging a stream comprising the depressurized clean fluid from the pressure

exchanger.

50. The method of claim 49 wherein the discharged stream comprising the depressurized clean fluid further comprises leakage of the dirty fluid from the pressure chamber.

51. The method of claim 49 wherein the dirty fluid comprises suspended solid particles, and wherein the clean fluid is substantially free of suspended solid particles.

52. The method of claim 49 further comprising injecting the discharged stream comprising the pressurized dirty fluid into a wellbore during a subterranean well treatment operation.

53. The method of claim 52 wherein the clean fluid comprises water, wherein the dirty fluid is or comprises a fracturing fluid, and wherein the subterranean well treatment operation comprises a subterranean formation fracturing operation.