US20200011165A1

US20200011165A1 - System and method for the use of pressure exchange in hydraulic fracturing

Info

Publication number: US20200011165A1
Application number: US16/503,147
Authority: US
Inventors: Paul George; Kyle Pierskalla
Original assignee: Nextier Completion Solutions Inc
Current assignee: Nextier Completion Solutions Inc
Priority date: 2018-07-05
Filing date: 2019-07-03
Publication date: 2020-01-09
Also published as: WO2020010278A1

Abstract

A pressure exchange system for use in hydraulic fracturing includes a closed-loop clean fluid circuit; an energizing system comprising a first pump; a high-pressure clean manifold system; a pressure exchange system; a low-pressure supply system; and a high-pressure dirty manifold system. The closed-loop clean fluid circuit delivers clean fluid to the energizing system, and the energizing system energizes the clean fluid to supply pressurized clean fluid. The high-pressure clean manifold system delivers the pressurized clean fluid to the pressure exchange system. Meanwhile, the low-pressure supply system delivers a low-pressure dirty stream to the pressure exchange system. The pressure exchange system transfers the energy from the pressurized clean fluid to the low-pressure dirty stream thereby supplying a pressurized dirty-stream, whereby the high-pressure dirty manifold system delivers the pressurized dirty-stream to a well-head.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/694,183, filed Jul. 5, 2018, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

Hydraulic fracturing well sites, setups, and equipment have not changed for many years in fundamental form and function. The hydraulic fracturing fluids primarily containing sand, water and chemicals that are erosive and corrosive are combined in a blender, are energized to high pressures and rates using reciprocating pumps, and then injected down hole. There are, generally speaking, several pumps, manifolds, pipework, valves, and safety systems required to combine, pressurize, and reach the injection rates required to perform hydraulic fracturing.
One significant problem with such systems is that the reciprocating high-pressure pumps are continuously subjected to the hydraulic fracturing fluids. The materials that make up this fluid, such as sand and proppants, decrease the component life of the pump by corroding the valves and seals. As a result, maintenance must occur more frequently, which necessarily increases the cost of the pump. Additionally, the equipment generally has a lower run life, thereby decreasing the life of the overall system.

SUMMARY

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented elsewhere herein.
According to one embodiment, a pressure exchange system for use in hydraulic fracturing includes a closed-loop clean fluid circuit; an energizing system comprising a first pump; a high-pressure clean manifold system; a pressure exchange system; a low-pressure supply system; and a high-pressure dirty manifold system. The closed-loop clean fluid circuit delivers clean fluid to the energizing system, and the energizing system energizes the clean fluid to supply pressurized clean fluid. The high-pressure clean manifold system delivers the pressurized clean fluid to the pressure exchange system. Meanwhile, the low-pressure supply system delivers a low-pressure dirty stream to the pressure exchange system. The pressure exchange system transfers the energy from the pressurized clean fluid to the low-pressure dirty stream thereby supplying a pressurized dirty-stream, whereby the high-pressure dirty manifold system delivers the pressurized dirty-stream to a well-head.
In another embodiment, a method for pressurizing a fluid for delivery to a well bore begins with pumping a low-pressure clean fluid from a clean fluid reservoir to an energizing system, where the low-pressure clean fluid is energized resulting in a high-pressure clean fluid. The high-pressure clean fluid is delivered from the energizing system to a pressure exchange system. A low-pressure fracking fluid is further delivered to the pressure exchange system. The pressure exchange system transfers energy from the high-pressure clean fluid to the low-pressure fracking fluid resulting in a high-pressure fracking fluid and a reduced-pressure clean fluid. The high-pressure fracking fluid is subsequently delivered to the well bore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram of a PRIOR ART fluid pressurization system for a hydraulic fracturing application.

FIG. 2 is a system diagram of a pressure exchange system for hydraulic fracturing applications.

FIG. 3 is a system diagram of the pressure exchange system of FIG. 1 showing pressure relief valves according to an embodiment of the invention.

WRITTEN DESCRIPTION

Referring first to FIG. 1, typical hydraulic fracturing sites 10 include (1) a low pressure blending system 15; (2) an energizing system 20 configured to pressurize combined fluids and materials; and (3) a high-pressure manifold system 25 for delivering the fluids to the well head 30 and down hole.
The low pressure blending system utilizes one or more blenders 16 to combine streams or flows of dry and/or solid materials and wet and/or liquid materials. The materials may be delivered to the blender 16 in different ratios and concentrations as may be appropriate for the particular application. Exemplary materials which may be blended in the low-pressure blending system 15 include but are not limited to proppants (e.g., sand, ceramic materials, etc.) and chemicals (e.g., guar, pH balancing agents, etc.). Wet or liquid materials may additionally be added to the blender. Exemplary liquid materials include but are not limited to water, oils, and chemicals (e.g., thickening agents, surfactants, emulsifiers, friction reducers, breakers, and oxidizers). It shall be understood that liquid materials may be pre-blended, preprocessed, and/or premixed in various concentrations and form.
As is well-known in the art, the materials may be delivered to the blender 16 using any transportation mechanism, including common transportation means such as pneumatics, conveyors, augers, containers, gates, and hoppers, and the controls and systems necessary to operate such apparatus. Liquid materials may be delivered via various configurations of pumps, tanks, conduits, pipes, hoses, valves, and gates, and the sensors, controls, and metering mechanisms necessary to move the materials through the system.
Once in the blender 16, the materials are blended into a consistent liquid slurry. It may be preferable to control and regulate the make-up of the slurry, including characteristics such as quality, quantity, makeup, density, and consistency of the liquid slurry. Once the slurry reaches the desired consistency, the slurry may be pressurized, e.g., to about 0-100 PSI, depending on the configurations and requirements of the system. The slurry may then be delivered through low pressure slurry delivery systems 17.
The low-pressure slurry delivery system 17 is an equipment network which connects the blender 16 (or blenders, as the case may be) to the high-pressure fracturing pump 21 (or pumps, as the case may be). The slurry delivery system 17 contains a configuration of pipes, valves, controls, connections, sensors, adapters, etc., which are connected in various combinations to deliver, transport, supply, contain, control and distribute the liquid slurries to the high-pressure fracturing pumps 21, as is known to those of skill in the art.
In general, the slurries coming out of the blender 16 are referred to as “dirty streams” due to the mixtures and concentrations of sand, and/or proppants, and/or chemicals contained within these streams. As is described in greater detail herein, these dirty streams can be harmful to the hydraulic fracturing system 10 and cause premature failure of the system components.
The high-pressure fracturing pumps 21 form the primary function of the energizing system 20. The pumps 21 accept the low-pressure liquid slurries from the blenders 16, via the low-pressure liquid slurry delivery systems 17, described above. The pumps 21 energize and increase the pressures, rates, and volumes of the liquid slurries. Typically, the pumps 21 are connected and operated in parallel, with each contributing some percentage to the total rate and pressures required to hydraulically fracture the formations. For example, if a rate of 80 BPM is required, and each pump 21 is capable of 8 BPM, then 10 or more hydraulic fracturing pumps would be operating at any point of time when 80 BPM is required.
Several hydraulic pumps 21 are typically rigged up and available to operate at any time due to load requirements, dependability, wear, backup capabilities in case of failure, et cetera. The individual fracturing pumps 21 may range in power between 2000-3000 Horsepower, although other sizes may be accommodated as well. The pumps 21 are generally configured to deliver up to 10,000 PSI and 8 BPM depending on combinations of horsepower, piston sizes, stroke lengths, operational speeds, and slurry characteristics; however, the pumps 21 are not limited to such configurations and examples of systems designed with smaller, or greater capabilities can be found. As noted above, several pumps 21 may be combined, and in combination, the horsepower is such that the pumps 21 can deliver liquid slurries at 10,000 PSI and 100 BPM to the well, for example. 15,000 PSI systems are also available.
Each high-pressure fracturing pump 21 is generally configured as a combination of a power source (such as diesel-, electric-, or turbine-powered engines), connecting mechanisms such as transmissions, gear boxes, power ends, and reciprocating pressure pumps (known as fluid ends), valves, and low pressure and high-pressure pipe work. The fluid ends used in the hydraulic fracturing pumps 21 are powered typically via the engine transmission and the power ends, although other embodiments are possible.
Typically, the pumps 21 are reciprocating in nature, although this is not required. The use of centrifugal pumps as high-pressure fracturing pumps is generally limited because of the combinations of solid materials and fluids that are pumped; the pressures the centrifugal pumps are practically capable of generating in current design states; and the structural configurations, weight, and size needed to achieve the required pressures and rates. However, any type of pump 21 is contemplated within the scope of the invention.
As is known in the industry, the pumps 21 deliver highly pressurized fluid streams and aggregate the fluids into high pressure slurry systems or manifold systems 25 consisting of high pressure conduits, valves, and additional control systems for delivery into the well head 30. The high-pressure slurries are provided to the well head 30, causing the down hole formations to hydraulically fracture, and stimulating the well to produce hydrocarbons.
The high-pressure manifold system 25 aggregates and delivers the liquid slurries from the high-pressure fracturing pumps 21, at high rates and pressures, to the wellhead 30 and into the well bore, causing the down hole formations to hydraulically fracture. The equipment forming the high-pressure manifold system 25 includes conduits, manifolds, and sub configurations of high pressure pipework (conduits), valves, controls, and assemblies. The manifold system must be generally capable of safely and reliably handling pressures up to at least 10,000 PSI, and flow rates up to at least 100 barrels per minute (BPM).
There are several issues with the high-pressure pumps 21 used in the systems today. First, high pressure fluid ends are prone to failure because of the operating pressures, rates, and dirty fluids they are pumping. Moreover, the conduits, pipework, and valves which make up the low-pressure 17 and high-pressure fluid delivery systems 25 are subject to failures due to the dirty fluid, rates, and pressures that is conveyed there through.
The “missile” is a unitized, and modularly mounted high-pressure manifold consisting of pipes, valves, connections, controls, sensors, etc., which forms a part of the high-pressure slurry delivery system 25. Generally, the missile is located between an assembly of hydraulic fracturing pumps 21 and the well head 30. The missile aggregates the high-pressure fluids from the high-pressure pumps 21 into a consolidated liquid slurry system for pumping into the well head 30 and down the well bore. The missile can be a skid mounted, or trailer mounted package. The missile operates at high pressures and rates up to at least 10,000 PSI and 100 BPM. However, it does not energize, or change the pressure, type, consistency, makeup, or physical characteristics of the slurry.
One hydraulic fracturing system commonly used in the industry to reduce the wear on pumps is a “split stream” system. Due to the increased likelihood of failures as a result of the harsh environment, split stream systems are designed to minimize the number of hydraulic fracturing pumps exposed to the liquid slurries containing sand and/or proppants and/or chemicals (i.e., the dirty stream). In a split stream system, the total number of required pumps (based on Horsepower) is divided into two sub sets of hydraulic fracturing pumps.
A first subset includes hydraulic fracturing pumps having the necessary horsepower to receive the fully combined liquid slurry from the blender (i.e., the dirty stream). These pumps are generally exposed to, and energize, the dirty stream through the low-pressure slurry delivery system. Typically, there are fewer pumps exposed to the dirty fluids than traditional set ups. The pumps are connected to the traditional high-pressure slurry delivery systems as described herein. The streams of energized fluids from this set of hydraulic fracturing pumps deliver a portion of the total rate and pressures into the high-pressure slurry system and are comingled with the streams and flows from the second subset of hydraulic fracturing pumps, described below. The pumps in the first subset are fully burdened, and are subject to maximum wear and tear due to the erosive and corrosive characteristics of the slurries. Accordingly, the performance, life, reliability, and operational characteristics of the pumps in the first subset are less than optimal because the pumps are still fully exposed to the corrosive slurries.
The second subset of hydraulic fracturing pumps receives low pressure fluids from a secondary blender or blending system through a secondary low-pressure slurry delivery system. These low-pressure fluids have little (or significantly less) solid material, sand, proppants and/or chemicals than the dirty stream. Accordingly, this stream is considered the “clean stream.” The pumps in the second subset are also connected to the high-pressure slurry delivery systems. However, because the pumps in the second subset only receive the clean stream of liquids, they are subject to less wear and tear. Accordingly, the performance, life, reliability, and operational characteristics of these pumps are generally more optimal.
The streams from the first and second subsets of hydraulic fracturing pumps are delivered at the required rates and pressures into the high-pressure slurry system. The flows from the two sets may be joined, or comingled in the missile (as described above), or elsewhere in the high-pressure slurry delivery system based on the most optimal configuration of piping, valves, and connections required. The sum of the comingled fluid from the two subsets of pumps equals the required rate to be pumped into the well, and has the correct characteristics for being pumped into the well. While split stream systems have benefits over non-split stream systems, there is still significant downside with having pumps that are exposed to the dirty stream.
Embodiments of the invention described herein include systems and methods for fluid pressure exchange in hydraulic fracturing applications which has considerable benefits over prior art systems. Referring now to FIG. 2, according to embodiments of the invention, a pressure exchange system 100 includes a closed-loop clean fluid supply system 115, an energizing system 120, a first high-pressure manifold 122, a pressure exchange system 125, and a second high-pressure manifold system 127. The closed-loop clean fluid supply system 115 delivers clean fluid, represented by stream 116, that does not contain any solid materials, to the pumps 121 in the energizing system 120 for pressurization, and then returns depressurized clean fluid, represented by stream 116 a, for reuse after processing in the pressure exchange system 125.
The energizing system 120 takes the low-pressure clean fluids 116 and pressurizes or energizes this to a high-pressure condition. In FIG. 2, the energizing system 120 includes several pumps 121. Each pump 121 contributes a portion of the required flow rate and pressure. A first high-pressure manifold 122 aggregates the “clean” high pressure fluids from the energizing pumps 121 and delivers high pressured clean fluid, represented by stream 117, to the pressure exchange system 125. The pressure exchange system 125 accepts the high-pressure energized clean fluid 117, and low pressure dirty fluid, represented by stream 118, and functions to transfer the energy from the clean fluid 117 to the dirty fluid 118, resulting in a high-pressure dirty fluid, represented by streams 119. The dirty fluid streams 119 may be aggregated in a second high-pressure manifold system 127 for delivery to the well head 130 and down hole. The various system components are described in greater detail below.
The closed-loop clean fluid supply system 115 incorporates one or more fluid reservoirs 140, a charge pump 142 (or pumps), and a low-pressure manifold system 143. The clean fluid 116 from the reservoir 140 is delivered to the energizing system 120, and once energized and processed through the pressure exchange system 125, is recirculated within the closed-loop to the reservoir 140. Because the clean fluids in the reservoir 140 are isolated from the rest of the system, the fluid can be relatively easily cooled, conditioned, supplemented, filtered, etc. Additionally, many different types of fluid may be used according the specific needs of the system, and to optimize pump life.
The energizing system 120 utilizes a plurality of hydraulic fracturing pumps 121 to energize the clean fluids 116 up to the required operating pressure, which, in embodiments, may be greater than 10,000 PSI, and to energize the dirty stream 118 to the required operating pressure, generally greater than 10,000 PSI and greater than 100 BPM. Significantly, hydraulic fracturing pumps 121 that were traditionally subjected to dirty fluid streams are now completely isolated from the dirty fluid stream 118 and are instead connected to the closed-loop high pressure clean fluid system via the pressure exchange system 125. Because the pumps 121 are exposed now only to “clean fluids,” different pumps types and combinations that are more efficient can be considered.
In one embodiment, for example, a centrifugal pump can be designed which can deliver fluid at up to 10,000 PSI or more. In another embodiment, a staged system using different pump types or styles can be developed. For example, in a first stage a centrifugal boost pump can deliver 0-5,000 PSI, and in a second stage, one or more reciprocating pumps can stage pressurization from 5,000-10,000 PSI.
The first high pressure clean manifold system 120 aggregates the high pressure clean fluids 117 and delivers them to the pressure exchange system 125. The system 120 includes an assembly of conduits valves, connections, etc. configured to join together multiple fluid streams from the pumps 121 and aggregating or consolidating the streams into one or two manifold outputs 122. Typically, the number of input ports into the manifold system 122 will be greater than the number of output ports. Optionally, the manifold system 122 may include a missile or missiles.
The pressure exchange system 125 is configured to utilize clean high pressure energized fluids 117 to transfer energy to the dirty fluid 118 in the exchange mechanism. There are different types of exchange systems that may be appropriate to provide the fluid-to-fluid energy transfer. For example, Dweer by Flowserve and Vortek by EMI are two examples of pressure exchange mechanisms used in other industries. By reconfiguring such systems to operate at high pressures required for hydraulic fracturing, they may be utilized as part of the hydraulic fracturing system. The pressure exchange unit 125 can include multiple pressure exchange mechanisms, and have varying lengths and varying diameters and sizes to deliver the rates, volumes, and pressure to be exchanged in order to meet required hydraulic fracturing pressures and rates.
In embodiments, combinations of fluids with advantageous properties may be utilized on the clean high pressure energizing side. Properties such as better cooling or freezing, added viscosity, improved lubricity, or improved friction characteristics can be used as needed. Examples might be a glycol based fluid, with friction reducers added, or oil based fluids with improved lubricity.
The blending and delivery system 128 for dirty fluids 118 is similar in design and configuration to historical systems. Here, however, the dirty fluids 118 are delivered to the pressure exchange system 125. The dirty stream provided by the low-pressure material blending system 128 is delivered via a low pressure dirty manifold system 129 to the pressure exchange system 125 where it is energized to high-pressure within the exchange system 125 for delivery to the well head 130 via the second high-pressure manifold 127.
The second high-pressure manifold 127 may be substantially similar to the first high-pressure manifold 122. Its purpose is to deliver energized or pressurized dirty fluid streams 119 via an assembly of conduits, manifolds, valves, and controls to the well head 130. The high-pressure manifold 127 is required between the output of the fluid exchange unit 125 and the well head 130 to deliver the pressurized dirty stream 119, though possibly to a smaller degree when compared to conventional systems. This is because the multiples of high pressure pumps 121, and their outputs of high pressure clean fluids 117 used as an energizing source are aggregated before the energy exchange system 125.
In use, a small area of contamination may occur at an interface of the clean fluid 117 and the dirty fluid 118. To avoid further contamination of the clean system 120, the clean system 120 can be “over pumped” or displaced by a small percentage or volume that is sufficient to ensure all dirty fluid 118, plus the small contaminated interface is sent to the well head 130 and down hole. The clean high-pressure system 120 can be over flushed to eliminate the dirty fluid interface and send this interface down hole. Optionally, a shuttle can be added to separate or cause the interface to remain clean. This ensures that there is no contamination back into the clean system.
Referring now to FIG. 3, the pressure exchange system 100 may include one or more pressure relief valves 150, 151. The pressure relief valves 150, 151 may allow pressure to release from the high- pressure manifolds 122 and 127. When the pressure relief valve 150 relieves pressure from the high-pressure clean fluid 117, reduced-pressure clean fluid 116 a can return to the fluid reservoir 140. Likewise, when the pressure relief valve 151 relieves pressure from the high-pressure dirty fluid 118, reduced-pressure dirty fluid 118 can be delivered to a storage pit or tank, if necessary. Of course, additional, or fewer, relief valves may be dispersed throughout the system 100.
One significant advantage to the pressure exchange system 100 described herein is that the fluid cycle rates within the pressure exchange system 125 are significantly lower. In other words, the valves and seats and seals exposed to the dirty fluids 118 are subject to less stress, wear, erosion, corrosion, et cetera. Therefore, the life of the system 100 can be dramatically increased. Additional benefits include minimizing the equipment required for the system 100, for example, a blender 145 (such as those used in typical hydraulic fracturing systems) is not required in series with the high-pressure pumps 121. Additionally, if over pressure occurs, only the clean fluids 116 need to be dumped. This prevents, or can considerably limit, the environmental concerns associated with dumping the dirty stream 118. Also, it is notable that the high-pressure side never has to be dumped except in the event of a malfunction. Still further, the system 100 can be vented back to the high-pressure charge reservoir 140.
Many different arrangements of the described invention are possible without departing from the spirit and scope of the present invention. Embodiments of the present invention are described herein with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the disclosed improvements without departing from the scope of the present invention.
Further, it will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. Not all steps listed in the various figures and description need to be carried out in the specific order described. The description should not be restricted to the specific described embodiments.

Claims

1. A pressure exchange system for use in hydraulic fracturing, comprising:

a closed-loop clean fluid circuit;

an energizing system comprising a first pump;

a high-pressure clean manifold system;

a pressure exchange system;

a low-pressure supply system; and

a high-pressure dirty manifold system;

wherein:

the closed-loop clean fluid circuit delivers clean fluid to the energizing system;

the energizing system energizes the clean fluid to supply pressurized clean fluid;

the high-pressure clean manifold system delivers the pressurized clean fluid to the pressure exchange system;

the low-pressure supply system delivers a low-pressure dirty stream to the pressure exchange system;

the pressure exchange system transfers the energy from the pressurized clean fluid to the low-pressure dirty stream thereby supplying a pressurized dirty-stream; and

the high-pressure dirty manifold system delivers the pressurized dirty-stream to a well-head.

2. The system of claim 1, wherein the clean fluid is stored in one or more reservoirs, and is pumped from the reservoir to the energizing system.

3. The system of claim 2, wherein the pressurized clean fluid being delivered to the pressure exchange system is optionally instantly depressurized and redirected into the reservoir, thereby stopping the process while remaining contained within the closed loop clean fluid circuit.

4. The system of claim 2, wherein the pressurized clean fluid is returned to the reservoir subsequent to processing by the pressure exchange system.

5. The system of claim 1, wherein the clean fluid is glycol-based.

6. The system of claim 1, wherein the clean fluid is oil-based.

7. The system of claim 1, wherein the pump is configured to pressurize the clean fluid to an operating pressure of at least 10,000 PSI.

8. The system of claim 1, wherein the pressure exchange system comprises a pressure exchange unit configured to operate at clean fluid operating pressures of at least 10,000 PSI.

9. The system of claim 1, wherein the pressure exchange system comprises a plurality of pressure exchange units configured to transfer energy from the clean fluid to the low-pressure dirty stream at an operating pressure of at least 10,000 PSI.

10. The system of claim 1, wherein the energizing system comprises a first stage comprising the first pump, the first pump being configured to partially pressurize the clean fluid; and a second stage comprising a second pump configured to partially pressure the clean fluid, wherein the first and second pumps are together configured to pressurize the clean fluid to an operating pressure of at least 10,000 PSI.

11. The system of claim 10, wherein the first pump and the second pump are not the same.

12. The system of claim 11, wherein the first pump is a centrifugal pump, and the second pump is a reciprocating pump.

13. The system of claim 1, wherein the pump of the energizing system comprises two pumps, and wherein the high-pressure manifold system aggregates the pressurized clean fluid from the pumps and delivers the pressurized clean fluid to the pressure exchange system.

14. A method for pressurizing a fluid for delivery to a well bore, comprising:

pumping a low-pressure clean fluid from a clean fluid reservoir to an energizing system;

energizing the low-pressure clean fluid resulting in a high-pressure clean fluid;

delivering the high-pressure clean fluid from the energizing system to a pressure exchange system;

delivering a low-pressure fracking fluid to the pressure exchange system;

transferring, via the pressure exchange system, energy from the high-pressure clean fluid to the low-pressure fracking fluid resulting in a high-pressure fracking fluid and a reduced-pressure clean fluid; and

delivering the high-pressure fracking fluid to the well bore.

15. The method of claim 14, wherein the high-pressure clean fluid interfaces with the low-pressure fracking fluid in the pressure exchange system creating a volume of contaminated clean fluid; and wherein a volume of the high-pressure clean fluid delivered to the pressure exchange system is greater than a volume of the low-pressure fracking fluid delivered to the pressure exchange system such that the volume of contaminated clean fluid is delivered to the well bore with the high-pressure fracking fluid.

16. The method of claim 14, further comprising delivering at least a portion of the reduced-pressure clean fluid back to the clean fluid reservoir for reuse.

17. The method of claim 14, wherein the pressure exchange system comprises an energy recovery device.

18. The method of claim 17, wherein the pressure exchange unit comprises a plurality of energy recovery devices.

19. The method of claim 17, wherein the pressure exchange unit is a dual work exchange energy recovery device.

20. The method of claim 17, wherein the pressure exchange unit is configured to transfer energy from the clean fluid to the low-pressure dirty stream at an operating pressure of at least 10,000 PSI.