WO2017048740A1

WO2017048740A1 - Linear electric motor pump for well treatment

Info

Publication number: WO2017048740A1
Application number: PCT/US2016/051570
Authority: WO
Inventors: Jonathan Wun Shiung Chong; Alhad Phatak
Original assignee: Schlumberger Technology Corporation; Schlumberger Canada Limited; Services Petroliers Schlumberger; Schlumberger Technology B.V.
Priority date: 2015-09-15
Filing date: 2016-09-14
Publication date: 2017-03-23

Abstract

Apparatus and methods for pressurizing well treatment fluids. Communication is established between a plurality of pumps and a controller operable to control operation of the pumps. Each pump includes a chamber, a plunger slidably disposed within the chamber, a stator disposed about at least a portion of the chamber, and a sensor operable to generate information indicative of the plunger position within the chamber. Based on the information generated by the sensors, the controller controls magnetic fields generated by the stators to move the plungers within the corresponding chambers, thereby controlling the pumps so that fluid is collectively discharged by the pumps to a common conduit at a substantially constant flow rate.

Description

Linear Electric Motor Pump for Well Treatment

Cross-Reference to Related Applications

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 62/218,907, titled "LINEAR ELECTRIC MOTOR PUMP FOR WELL TREATMENT," filed September 15, 2015, the entire disclosure of which is hereby incorporated herein by reference.

Background of the Disclosure

[0002] In oilfield operations, reciprocating pumps are utilized at wellsites for large scale, high-pressure operations. Such operations may include drilling, cementing, acidizing, water jet cutting, and hydraulic fracturing of subterranean formations. In some applications, several pumps may be connected in parallel to a single manifold, flow line, or well. Some reciprocating pumps include reciprocating members driven by a crankshaft toward and away from a fluid chamber to alternatingly receive, pressurize, and discharge fluid from the fluid chamber.

Hydraulic fracturing of a subterranean formation, for example, may utilize fluid at a pressure exceeding 10,000 PSI. The success of pumping operations can be affected by many factors, including physical size of the pumps, weight of the pumps, energy efficiency of the pumps, and ability to collectively control individual pumps operating at the wellsite.

[0003] Reciprocating pumps may have a large physical size and weight to satisfy intended fluid pressures and flow rates during oilfield operations. Accordingly, one or more pumps may be mounted on a mobile carrier or skid for transportation to the wellsite. However, due to their size and/or weight, a limited number of pumps may be mounted on a single carrier or skid. The pumps may also include a diesel engine or an asynchronous AC electric motor as part of a power section of the pump driving a fluid section of the pump. However, diesel engines and some asynchronous AC electric motors operate at high speeds, such as 1500 to 2000 revolutions per minute (RPM), and the fluid section of the pump operates at low speeds, such as 300 to 400 RPM. Accordingly, a gear box, chain case, or other transmission may be included in the power section to operatively couple the engine/motor with the crankshaft. This further increases the size, weight, and cost of the pumps. Moreover, each engine is individually fueled and controlled, which limits flexibility and control over a collective pumping system when multiple pumps are being operated simultaneously. [0004] Although the reciprocating pumps may operate well at high pressures, the pressurized fluid is discharged in an oscillating manner forming pressure spikes at the pump outlet. These pressure spikes may be transmitted through a piping system and/or other portions of the pumping system connected downstream from the pumps. Piping, hose, and equipment failures have been linked to high-pressure spikes formed by the reciprocating pumps. Pressure failures may be reduced by over-designing portions of the pumping systems downstream from the reciprocating pumps with large safety factors and by introducing dampening systems. Such solutions, however, increase the size, weight, and cost of the pumping systems.

Summary of the Disclosure

[0005] 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.

[0006] The present disclosure introduces a method that includes establishing communication between a controller and a plurality of pumps. The controller includes a processor and a memory storing computer program code that, when executed, is operable to control operation of the pumps. The pumps collectively discharge a fluid into a common conduit. Each pump includes a chamber, a plunger slidably disposed within the chamber, a stator disposed about at least a portion of the chamber, and a sensor operable to generate information indicative of the plunger position within the chamber. The method also includes operating the controller, based on the information generated by the sensors, to control magnetic fields generated by the stators that move the plungers within the corresponding chambers, thereby controlling the pumps so that the fluid collectively discharged by the pumps to the common conduit is at a substantially constant flow rate.

[0007] The present disclosure also introduces an apparatus that includes a pump assembly. The pump assembly includes a chamber, a plunger having a plunger length and slidably disposed within the chamber, and a stator having a stator length and disposed about at least a portion of the chamber. The stator length is substantially greater than the plunger length. The stator is operable to generate magnetic fields operable to reciprocatingly move the plunger within the chamber and thereby draw and discharge a fluid into and from the chamber. [0008] The present disclosure also introduces an apparatus that includes a pump assembly. The pump assembly includes a chamber, a plunger having a plunger length and slidably disposed within the chamber, and a stator having a stator length and disposed about at least a portion of the chamber. The plunger length is substantially greater than the stator length. The stator is operable to generate magnetic fields operable to reciprocatingly move the plunger a stroke distance within the chamber and thereby draw and discharge a fluid into and from the chamber. The stroke distance is not less than the stator length.

[0009] 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

[0010] 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.

[0011] 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.

[0012] FIG. 2 is a perspective view of at least a portion of an example implementation of apparatus according to one or more aspects of the present disclosure.

[0013] FIG. 3 is a sectional schematic view of the apparatus shown in FIG. 2 according to one or more aspects of the present disclosure.

[0014] FIG. 4 is an enlarged view of a portion of the apparatus shown in FIG. 3 according to one or more aspects of the present disclosure.

[0015] FIG. 5 is a sectional schematic view of at least a portion of an example

implementation of apparatus according to one or more aspects of the present disclosure.

[0016] FIG. 6 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.

[0017] FIG. 7 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. [0018] FIG. 8 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.

[0019] FIG. 9 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. 10 is a graph related to one or more aspects of the present disclosure.

[0021] 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.

Detailed Description

[0022] 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.

[0023] Example implementations of apparatus described within the scope of the present disclosure relate generally to pumps and pumping units comprising linear electric motors (LEM) and operable to generate pressurized fluid flow in well treatment operations. Example implementations of methods described within the scope of the present disclosure relate generally to utilizing such pumps and pumping units to generate the pressurized fluid flow in the well treatment operations. Example implementations of an apparatus related to one or more aspects of the present disclosure are described in a commonly assigned and co-pending U.S. Patent Application No. 1 1/740,750, the entire disclosure of which is hereby incorporated herein by reference.

[0024] FIG. 1 is a schematic view of at least a portion of an example environment in which an apparatus according to one or more aspects of the present disclosure may be utilized. The figure shows a wellsite 102, a wellbore 104 extending from the terrain surface of the wellsite 102, a partial sectional view of a subterranean formation 106 penetrated by the wellbore 104, and a wellhead 105, as well as a wellsite system 100 comprising various pieces of equipment or components located at the wellsite 102. The wellsite system 100 may be operable to transfer various materials and additives from corresponding sources to a destination location for blending or mixing and eventual injection into the wellbore 104 during fracturing operations.

[0025] The wellsite system 100 may comprise a mixing unit 108 (referred to hereinafter as a "mixer") fluidly connected with one or more tanks 110 and a container 112. The container 112 may contain a first material and the tanks 110 may contain a liquid. The first material may be or comprise a hydratable material or gelling agent, such as guar, polymers, synthetic polymers, galactomannan, polysaccharides, cellulose, and/or clay, among other examples. The liquid may be or comprise an aqueous fluid, such as water or an aqueous solution comprising water, among other examples. The mixer 108 may be operable to receive the first material and the liquid, via two or more conduits or other material transfer means 114, 1 16 (referred to hereafter as

"conduits"), and mix or otherwise combine the first material and the liquid to form a base fluid, which may be or comprise that which is known in the art as a gel. The mixer 108 may then discharge the base fluid via one or more fluid conduits 118. Depending on the subterranean well treatment operation, the base fluid may also be oil-based, an emulsion, or a foam.

[0026] The wellsite system 100 may further comprise a mixer 124 fluidly connected with the mixer 108 and a container 126. The container 126 may contain a second material that may be substantially different than the first material. For example, the second material may be or comprise a proppant material, such as sand, sand-like particles, silica, quartz, and/or propping agents, among other examples. The mixer 124 may be operable to receive the base fluid from the mixer 108 via one or more fluid conduits 118, and the second material from the container 126 via one or more fluid conduits 128, and mix or otherwise combine the base fluid and the second material to form a mixture. The mixture may be or comprise that which is known in the art as a fracturing fluid. The mixer 124 may then discharge the mixture via one or more fluid conduits 130.

[0027] The mixture may be communicated from the mixer 124 to a common manifold 136 via the one or more fluid conduits 130. The common manifold 136 may comprise various valves and diverters, as well as a suction line 138 and a discharge line 140, such as may be collectively operable to direct the flow of the mixture in a selected or predetermined manner. The common manifold 136, which may be known in the art as a missile or a missile trailer, may distribute the mixture to a fleet of pumping units 150. Although the fleet is shown comprising six pumping units 150, the fleet may comprise other quantities of pumping units 150 within the scope of the present disclosure.

[0028] Each pumping unit 150 may comprise one or more pumps. Each pumping unit 150 may receive the mixture from the suction line 138 of the common manifold 136, via one or more fluid conduits 142, and discharge the mixture under pressure to the discharge line 140 of the common manifold 136, via one or more fluid conduits 144. The mixture may then be discharged from the common manifold 136 into the wellbore 104 via one or more fluid conduits 146, the wellhead 105, and perhaps various additional valves, conduits, and/or other hydraulic circuitry fluidly connected between the common manifold 136 and the wellbore 104.

[0029] The pumping system 100 may also comprise a source of electrical power 170 operable to provide electrical power to one or more portions of the wellsite system 100, including the pumping units 150. The source of electrical power 170 may be or comprise an engine-generator set, such as a gas turbine generator or an internal combustion engine generator. The electrical power may be communicated between the source of electrical power 170 and other wellsite equipment via an electrical conductor system 174. Electrical power may also be supplied from a location external of the wellsite 102. For example, the electrical power may be supplied from an external power station (not shown) via an electrical power grid or network.

[0030] The wellsite system 100 may also comprise a control center 160, which may be operable to provide control to one or more portions of the wellsite system 100. The control center 160 may be further operable to monitor health and functionality of one or more portions of the wellsite system 100. For example, the control center 160 may be operable to monitor and control one or more portions of the mixers 108, 124, the pumping units 150, the common manifold 136, and various other pumps, conveyers, and/or other equipment (not shown) disposed along the conduits 114, 116, 118, 128, 130, such as may be operable to move, mix, separate, or measure the fluids, materials, and/or mixtures described above. The control center 160 may also be operable to control power distribution between the source of electrical power 170 and the wellsite equipment. Control signals may be communicated between the control center 160 and the wellsite equipment wirelessly and/or via the electrical conductor system 174.

[0031] One or more of the containers 1 12, 126, the mixers 108, 124, the pumping units 150, the control center 160, and the source of electrical power 170 may each be disposed on corresponding trucks, trailers, and/or other mobile carriers 122, 134, 120, 132, 152, 162, 172, respectively, such as may permit their transportation to the wellsite surface 102. However, one or more of the containers 112, 126, the mixers 108, 124, the pumping units 150, the control center 160, and the source of electrical power 170 may each be skidded or otherwise stationary, and/or may be temporarily or permanently installed at the wellsite surface 102.

[0032] Although FIG. 1 shows the wellsite system 100 operable for mixing and/or producing fluids and mixtures that may be pressurized and injected into the wellbore during fracturing operations, it is to be understood that the apparatus within the scope of the present disclosure may be implemented or otherwise utilized with other wellsite systems. For example, the apparatus within the scope of present disclosure may be utilized with other wellsite systems operable to perform other wellsite operations, such as drilling, cementing, dosing, acidizing, chemical injecting, gravel packing, and water jet cutting, among other fluid delivery operations. Depending on the subterranean well treatment operation, the fluid may also be oil -based, an emulsion, or a foam. Accordingly, except when referring to a specific fluid, the various fluids or mixtures communicated between the various components of the wellsite system 100 described above may be referred to hereinafter simply as "a fluid."

[0033] FIG. 2 is a perspective view of at least a portion of an example implementation of a pump 200 according to one or more aspects of the present disclosure. FIG. 3 is a sectional schematic view of the pump 200 shown in FIG. 2. The pump 200 may be utilized in various implementations of a wellsite system. However, for the sake of clarity and ease of

understanding, the pump 200 is described below in the context of the wellsite system 100 shown in FIG. 1. Thus, the following description refers to FIGS. 1-3, collectively.

[0034] The pump 200 may comprise a power section 202 and one or more fluid sections 204, 205 connected with the power section 202. A chamber 206 may extend through the power section 202 and at least partially into the fluid sections 204, 205. A plunger assembly 210 may be slidably disposed within the chamber 206 and movable through the chamber 206 between the fluid sections 204, 205. The power section 202 may be operable to actuate the plunger assembly 210 to move along the chamber 206 to discharge and/or receive a fluid from and/or into the fluid chamber 206.

[0035] The plunger assembly 210 may comprise opposing pistons or other sealing portions 212, 213 connected together with a shaft 214. The shaft 214 may be solid or uniform

throughout, or the shaft 214 may comprise a bore or hollow space 216 extending at least partially through the shaft 214, such as to decrease the weight of the plunger assembly 210. The sealing portions 212, 213 may comprise fluid seals 218 sealingly engaging an inner surface or wall 207 of the chamber 206. The plunger assembly 210 may divide the chamber 206 into a volume 221 on one side of the plunger assembly 210 and a volume 222 on an opposing side of the plunger assembly 210.

[0036] Each volume 221, 222 of the chamber 206 may be fluidly connected with a corresponding fluid inlet 229, 230 of the fluid section 204, 205 via a fluid inlet channel 225, 226 extending between a corresponding volume 221, 222 and fluid inlet 229, 230. The fluid inlets 229, 230 may be in fluid communication with a corresponding fluid conduit 142. Each fluid section 204, 205 may further comprise an inlet valve 231, 232 operable to control fluid flow between a corresponding fluid inlet 229, 230 and volume 221, 222 via the fluid inlet channel 225, 226. Each inlet valve 231, 232 may be biased toward a closed flow position by a spring or another biasing member 233, 234, which may be held in place by an inlet valve stop 235, 236. Each inlet valve 231, 232 may be actuated to an open flow position by a predetermined differential pressure between the corresponding fluid inlet channel 225, 226 and volume 221, 222.

[0037] Each volume 221, 222 of the fluid chamber 206 may also be fluidly connected with a corresponding fluid outlet 241, 242 of the fluid section 204, 205 via a fluid outlet channel 237, 238 extending between a corresponding volume 221, 222 and fluid outlet 241, 242. The fluid outlets 241, 242 may be in fluid communication with a corresponding fluid conduit 144. Each fluid section 204, 205 may also comprise an outlet valve 243, 244 operable to control fluid flow between the corresponding fluid outlet 241, 242 and volume 221, 222 via the fluid outlet channel 237, 238. Each outlet valve 243, 244 may be biased toward a closed flow position by a spring or another biasing member 245, 246, which may be held in place by an outlet valve stop 247, 248. Each outlet valve 243, 244 may be actuated to an open flow position by a predetermined differential pressure across each valve 243, 244, namely between each corresponding fluid inlet channel 237, 238 and volume 221, 222.

[0038] During pumping operations, portions of the power section 202 may actuate the plunger assembly 210, causing the plunger assembly 210 to reciprocate or otherwise move longitudinally within the chamber 206, thereby alternatingly drawing and displacing fluid into and from the volumes 221, 222 of the chamber 210. For example, the plunger assembly 210 may be actuated to move in a first direction within the chamber 206 (indicated in FIG. 3 by arrow 251) to discharge fluid from the volume 221 and draw fluid into the volume 222. The plunger assembly 210 may be actuated to move in a second (i.e., opposing) direction within the chamber 206 (indicated in FIG. 3 by arrow 252) to discharge fluid from the volume 222 and draw fluid into the volume 221.

[0039] As the plunger assembly 210 is actuated to move in the first direction 251, the pressure of the fluid within the volume 221 begins to increase, thus creating a differential pressure across the corresponding fluid outlet valve 243. The pressure within the volume 221 continues to increase until the pressure is high enough to overcome the pressure of the fluid inside the fluid outlet channel 237 and/or compress the biasing member 245, thus actuating the fluid outlet valve 243 to the open flow position and permitting the pressurized fluid to flow from the volume 221 and the pump 200 via the fluid outlet channel 237 and the fluid outlet 241. As the fluid exits the volume 221, the plunger assembly 210 continues to move in the first direction 251 until the pressure difference between the fluid within the volume 221 and the fluid channel 237 is low enough to return the fluid outlet valve 243 to the closed flow position, such as low enough to permit the biasing member 245 to close the fluid outlet valve 243.

[0040] Simultaneously, as the plunger assembly 210 moves in the first direction 251 and the fluid is discharged from the volume 221, the pressure of the fluid within the volume 222 decreases, thus creating a differential pressure across the corresponding fluid inlet valve 232. The pressure differential operates to move the fluid inlet valve 232 to an open flow position, such as by compressing the biasing member 234, thus permitting fluid to enter the fluid inlet channel 226 and the volume 222 via the fluid inlet 230. As the fluid enters the volume 222, the plunger assembly 210 continues to move in the first direction 251 until the pressure difference between the fluid within the volume 222 and the fluid within the fluid channel 226 is low enough to return the fluid inlet valve 232 to the closed flow position, such as low enough to again be overcome by the biasing member 234.

[0041] The plunger assembly 210 may then be actuated by the power section 202 to move in the second direction 252. During such pumping operation, the fluid within the volume 222 may be discharged from the volume 222 via the outlet 242 and drawn into the volume 221 via the inlet 229 in a similar manner as described above when the plunger assembly 210 is actuated to move in the first direction 251.

[0042] The plunger assembly 210 may also define another volume 223 between the volumes 221, 222. For example, the sealing portions 212, 213 may fluidly isolate a central portion of the chamber 206 from the fluid within the volumes 221, 222, thus forming the volume 223.

Accordingly, the volume 223 may not be exposed to the fluid within the volumes 221, 222, and may thus be referred to hereinafter as a "dry volume."

[0043] The pump 200 may further comprise one or more position sensors 280 each operable to generate a signal or information indicative of a position of the plunger assembly 210, such as to monitor the position and/or velocity of the plunger assembly 210 with respect to the chamber 206 in real-time. The position sensors 280 may be disposed in association with the plunger assembly 210 in a manner permitting sensing of the position and/or velocity of the plunger assembly 210 during pumping operations. For example, the position sensor 280 may be disposed within the wall 207 of the chamber 206 to monitor the position and/or velocity of a feature of the plunger assembly 210, such as a marker 282 carried with the plunger assembly 210. The position sensor 280 may also or instead be disposed in association with the inlet valve stop 235. Each sensor 280 may sense one or more magnets on the plunger assembly 210, one or more features of the plunger assembly 210 that can be optically detected, conductive portions or members on the plunger assembly 210 that can be sensed with an electromagnetic sensor, and/or facets or other features on the plunger assembly 210 that can be detected with an ultrasonic sensor, among other examples. Each sensor 280 may be or comprise a linear encoder, a linear potentiometer, a capacitive sensor, an inductive sensor, a magnetic sensor, a linear variable- differential transformer (LVDT), a proximity sensor, a Hall effect sensor, and/or a reed switch, among other examples. [0044] The fluid flow rate generated by the pump 200 may depend on the physical size of the plunger assembly 210 and chamber 206, as well as operating speed of the pump 200, which may be defined by the speed or rate at which the plunger assembly 210 reciprocates or moves within the chamber 206. The maximum pressure generated by the pump 200 may be defined by the force with which the plunger assembly 210 reciprocates or moves within the chamber 206.

Accordingly, the fluid flow rate and fluid pressure generated by the pump 200 may be controlled by controlling the operation or manner in which the power section 202 actuates the plunger assembly 210.

[0045] Although the pump 200 is shown in FIGS. 2 and 3 as a double-acting pump comprising one power section 202 and two fluid sections 204, 205, other implementations of the pump 200 within the scope of the present disclosure may comprise other quantities of power sections 202 and/or fluid sections 204, 205. For example, the pump 200 may be implemented as a single-acting pump comprising one of the fluid sections 204, 205 connected on one side of the power section 202. Such implementation of the pump 200 may be operable to receive and discharge the fluid similarly to as described above, but just on one side of the pump 200. The pump 200 may be implemented as a single-acting pump when lower fluid flows are utilized. Implementations of the pump 200 may also comprise multiple power sections 202 to actuate one or more of the fluid sections 204, 205. Implementations of the pump 200 may comprise multiple power sections 202 when higher fluid pressures are utilized.

[0046] The power section 202 may comprise an outer housing 261 and an inner housing 262, one or both of which may be connected with the fluid sections 204, 205. The power section 202 may further comprise at least a portion of a linear electric motor (LEM) 203 housed within the outer housing 261 and operable to receive an electrical input to drive or otherwise impart movement to the plunger assembly 210. FIG. 4 is an enlarged view of a portion of an example implementation of the LEM 203 shown in FIG. 3 according to one or more aspects of the present disclosure. The following description refers to FIGS. 3 and 4, collectively.

[0047] The LEM 203 may include a stator 260 having an array of magnets 264. Each magnet 264 may be or comprise electro-magnetic windings, such as wire wound into electromagnetic coils, each operable to generate a magnetic field when powered by electric current. Non-magnetic and/or electrically insulating spacers 265 may interpose the magnets 264. The stator 260 may define an axial opening at least partially defining the chamber 206 and accommodating therein at least a portion of the plunger assembly 210. The stator 260 may be disposed about the inner housing 262, such as may support the stator 260 in position within the power section 202. The inner housing 262 may comprise a non-magnetic material or a material causing little or no magnetic path resistance or magnetic distortion.

[0048] The LEM 203 may also include at least a portion of the plunger assembly 210 driven by the magnetic fields generated by the stator 260. When electrically activated, the magnets 264 of the stator 260 may drive the plunger assembly 210 by electro-magnetic means. For example, the shaft 214 may comprise a plurality of magnets 266, such as windings or permanent magnets, disposed about or carried by an inner shaft 268. Non-magnetic and/or electrically insulating spacers 267 may interpose the magnets 266. Instead of or in addition to the magnets 266, the shaft 214 may comprise iron or another material comprising strong magnetic properties and, thus, responsive to an electro-magnetic driving force. A magnetic form of stainless steel may also be utilized. Although the shaft 214 is shown as comprising a hollow space 216, the shaft 214 may comprise an inner core of ferrous material and an outer layer of conductive material around the inner core. For example, the shaft 214 may include an iron or steel core with alternating bands of copper and iron.

[0049] The stator 260 may be operated in a polyphase manner (e.g., from magnet to magnet) in order to drive the linear movement of the plunger assembly 210 in the first and second directions 251, 252. For example, the magnets 264 along the stator 260 may be electrically operated to form waves or sequences of alternating electro-magnetic field polarities moving along the length of the stator 260 in a predetermined direction. Such waves of alternating electro-magnetic field polarities may be out of phase with the polarities of the magnets 266 along the plunger assembly 210, resulting in magnetic attraction and/or repulsion between such magnets 264, 266 to move the plunger assembly 210 within the chamber 206. The speed of the plunger assembly 210 may be controlled by adjusting the speed of the waves of the alternating electro-magnetic field polarities generated along the stator 260. The maximum force at which the plunger assembly 210 moves may be controlled by adjusting the strength of the magnetic field generated by the stator 206, such as by adjusting electric current transmitted through the coil windings of the magnets 264.

[0050] As further shown in FIG. 3, the stator 260 may comprise a length 263 and the plunger assembly 210 may comprise a length 21 1, wherein both lengths 263, 21 1 may be measured substantially parallel to a longitudinal axis 201 of the pump 200. The plunger length 21 1 may be substantially greater than the stator length 263. For example, as shown in FIG. 3, the plunger length 21 1 may be about two times greater than the stator length 263.

[0051] During pumping operations, the plunger assembly 210 may have a range of motion or stroke length 208. The stroke length 208 may be substantially equal to the stator length 263. In other example implementations, the stroke length 208 may be substantially greater (e.g., between about 10% and about 300% or more) than the stator length 263, such as in implementations in which the plunger length 21 1 may be more than two times greater than the stator length 263.

[0052] The stroke length 208 may be limited between the opposing valve stops 235, 236 or other mechanical stops. Furthermore, the stroke length 208 may be limited or otherwise controlled such that the sealing portions 212, 213 are maintained on opposing sides of the inner housing 262 of the power section 202 and, thus, on opposing sides of the stator 260, such that the stator 260 may be located alongside or extend about at least a portion of the dry volume 223 of the chamber 206, and not about the first and second volumes 221, 222 of the chamber 206.

Accordingly, the power section 202, including the stator 260, may be exposed just to the dry volume 223 of the chamber 206, and isolated from the fluid and the pressures within the volumes 221, 222.

[0053] The stator 260 may be operable to impart movement to the plunger assembly 210 in a substantially precise manner. That is, the electrical power supplied to the stator 260 may be controlled by a variable frequency drive (VFD), such as may be a part of the control center 160 and/or electrical power source 170 shown in FIG. 1. Such degree of control permits a wide range of achievable forces and speeds of the plunger assembly 210.

[0054] The stator 260 may also comprise other structural configurations (not shown) and/or means for switching magnetic polarities. For example, instead of wire windings, the stator 260 may comprise copper-etched conductors embedded or printed onto a multi-layered circuit board, which may operate in conjunction with a permanent magnet arrangement of the plunger assembly 210. Such stator configuration may provide an increased copper density per unit area of the stator 260, which may provide greater precision and/or other control aspects of the movement of the plunger assembly 210. Instead of the wire windings, the stator 260 may comprise magnets or other magnetic field generating features printed on one or more boards of magnetic material in a predetermined pattern. Surfaces of both types of boards may be laminated, encapsulated, or sealed by a coating, such as to protect the stator 260 from the fluid pumped by the pump assembly 200 and/or other corrosive materials encountered at the wellsite 102.

[0055] During pumping operations, the stator 260 and/or other portions of the LEM 203 may generate waste heat. Accordingly, the pump 200 may further comprise an array of cooling fins 270 connected with the stator 260, such as may help to remove the heat from the stator 260. A cooling fluid may also be utilized to increase the rate of heat removal from the stator 260. For example, the outer housing 261, the stator 260, and perhaps the inner housing 262 may define a fluid chamber 272, such as may retain the cooling fluid about the stator 260 and in contact with the cooling fins 270. The fluid chamber 272 may be or comprise a fluid channel adapted to direct cooling fluid along and/or through the cooling fins 270. The cooling fluid may be injected into the fluid chamber 272 via an inlet 274 and discharged via an outlet 276.

[0056] For example implementation, the well treatment fluid being pumped by the pump 200 may be utilized as the cooling fluid. That is, because large volumes of well treatment fluid may be injected into the wellbore 104, the well treatment fluid may provide a large thermal mass that may be utilized to extract the waste heat generated by the LEM 203. Depending on the subterranean well treatment operation, the fluid may be water-based, oil-based, emulsion, foam, solids laden, and/or other materials. Efficient cooling of the LEM 203 may permit use of a smaller sized LEM 203, which may reduce wellsite footprint. Air and/or another gas may also or instead be communicated through the fluid chamber 272 to absorb and remove heat from the LEM 203.

[0057] FIG. 5 is a sectional view of at least a portion of an example implementation of a pump 300 according to one or more aspects of the present disclosure. The pump 300 may comprise one or more features similar to those of the pump 200 shown in FIGS. 2-4, including where indicated by like reference numbers, except as described below. Similarly to the pump 200, the pump 300 may be utilized in various implementations of a wellsite system. However, for the sake of clarity and ease of understanding, the pump 300 is described below in the context of the wellsite system 100 shown in FIG. 1. Thus, the following description refers to FIGS. 1 and 5, collectively.

[0058] The pump 300 may comprise a power section 302 and one or more fluid sections 204, 205 connected with the power section 302. A chamber 306 may extend through the power section 302 and at least partially into the fluid sections 204, 205. A plunger assembly 310 may be slidably disposed within the chamber 306 and movable through the chamber 306 between the fluid sections 204, 205. The power section 302 may be operable to actuate the plunger assembly 310 to move within the chamber 306 to draw and discharge fluid into and from the chamber 306.

[0059] The plunger assembly 310 may comprise fluid seals 312 sealingly engaging an inner surface or wall 307 of the chamber 306. The plunger assembly 310 may be solid or uniform throughout, or the plunger assembly 310 may comprise a bore or hollow space 314 extending within the plunger assembly 310, such as to decrease the weight of the plunger assembly 310. The plunger assembly 310 may divide the chamber 306 into a volume 321 on one side of the plunger assembly 310 and a volume 322 on an opposing side of the plunger assembly 310.

[0060] Each volume 321, 322 of the chamber 306 may be fluidly connected with a corresponding fluid inlet 229, 230 (shown in FIG. 2) of the fluid section 204, 205 via a fluid inlet channel 225, 226 extending between the corresponding volume 321, 322 and fluid inlet 229, 230. The fluid inlets 229, 230 may be in fluid communication with a corresponding fluid conduit 142. Each fluid section 204, 205 may further comprise an inlet valve 231, 232 operable to control fluid flow between the corresponding fluid inlet 229, 230 and volume 321, 322 via the fluid inlet channel 225, 226. Each inlet valve 231, 232 may be biased toward a closed flow position by a spring or another biasing member 233, 234, which may be held in place by an inlet valve stop 235, 236. Each inlet valve 231, 232 may be actuated to an open flow position by a

predetermined differential pressure between the corresponding volume 321, 322 and fluid inlet channel 225, 226.

[0061] Each volume 321, 322 of the fluid chamber 306 may also be fluidly connected with a corresponding fluid outlet 241, 242 (shown in FIG. 2) of the fluid section 204, 205 via a fluid outlet channel 237, 238 extending between a corresponding volume 321, 322 and the fluid outlet 241, 242. The fluid outlets 241, 242 may be in fluid communication with a corresponding fluid conduit 144. Each fluid section 204, 205 may also comprise an outlet valve 243, 244 operable to control fluid flow between the corresponding fluid outlet 241, 242 and volume 321, 322 via the fluid outlet channel 237, 238. Each outlet valve 243, 244 may be biased toward a closed flow position by a spring or another biasing member 245, 246, which may be held in place by an outlet valve stop 247, 248. Each outlet valve 243, 244 may be actuated to an open flow position by a predetermined differential pressure between the corresponding volume 321, 322 and fluid outlet channel 237, 238.

[0062] During pumping operations, portions of the power section 302 may actuate the plunger assembly 310, causing the plunger assembly 310 to reciprocate or otherwise move longitudinally within the chamber 306, thereby alternatingly drawing and displacing fluid into and from the volumes 321, 322. For example, the plunger assembly 310 may be actuated to move in the first direction 251 to discharge fluid from the volume 321 and draw fluid into the volume 322. The plunger assembly 310 may be actuated to move in the second direction 252 to discharge fluid from the volume 322 and draw fluid into the volume 321. The pumping operation of the pump 300 may be substantially similar to the pumping operation of the pump 200, as described above.

[0063] The pump 300 may further comprise one or more of the position sensors 280 described above, such as to monitor the position and/or velocity of the plunger assembly 310 within the chamber 306 in real-time. For example, a position sensor 280 may be disposed within the wall 307 of the chamber 306 to monitor the position and/or velocity of a marker 282 and/or other feature of the plunger assembly 310. A position sensor 280 may also or instead be disposed in association with the inlet valve stop 235 to monitor the position and/or velocity of a marker and/or other feature 282 of the plunger assembly 310. Each sensor 280 and marker 282 may comprise the same or similar structure and/or mode of operation as the sensors 280 and marker 282 described above in association with the pump 200.

[0064] Although the pump 300 is shown in FIG. 5 as a double-acting pump comprising one power section 302 and two fluid sections 204, 205, other implementations of the pump 300 within the scope of the present disclosure may comprise other quantities of power sections 302 and/or fluid sections 204, 205. For example, the pump 300 may be implemented as a single- acting pump comprising one of the fluid sections 204, 205 connected on one side of the power section 302. Such pump 300 may be operable to receive and discharge the fluid similarly to as described above, but on just one side of the pump 300. For example, the pump 300 may be implemented as a single-acting pump when lower fluid flows are utilized. Implementations of the pump 300 may also comprise multiple power sections 302 to actuate one or more of the fluid sections 204, 205. For example, the pump 300 may comprise multiple power sections 302 when higher fluid pressures are utilized. [0065] The fluid flow rate and fluid pressure generated by the pump 300 may be controlled by controlling the operation or manner in which the power section 302 actuates the plunger assembly 310. Similar to as described above, the power section 302 may comprise an outer housing 318 and an inner housing 320. The power section 302 also comprises at least a portion of an LEM 303 operable to receive electrical input to drive or otherwise impart movement to the plunger assembly 310.

[0066] The LEM 303 may include a stator 330 having an array of magnets similar to the magnets 264 shown in FIG. 4. The stator 330 may define an axial opening at least partially defining the chamber 306 for accommodating the plunger assembly 310. The stator 330 may be disposed about the inner housing 320, such as may support the stator 330 in position within the power section 302.

[0067] The inner housing 320 may comprise a non-magnetic material or a material causing little or no magnetic path resistance or magnetic distortion. Because the inner housing 320 may be exposed to the fluid being pumped into and out of the volumes 321, 322, the interface of the inner housing 320 and the fluid sections 204, 205 may include fluid seals (not shown) to prevent or reduce fluid leakage between the inner housing 320 and the fluid sections 204, 205. The inner housing 320 may also be exposed to the high fluid pressures generated within each volume 321, 322. Accordingly, the inner housing 320 may comprise a thickness and/or material having strength sufficient to withstand the high fluid pressures generated during the pumping operations. The inner housing material may comprise, for example, aluminum, stainless steel, or a composite material, such as a carbon-fiber-reinforced polymer.

[0068] The housing 320 may be located around or encompass both the stator 330 and the plunger assembly 310. Such implementations may aid in reducing or eliminating magnetic resistance or distortion between the stator 330 and the plunger assembly 310, which might otherwise be caused by the inner housing 320 if located between the stator 330 and the plunger assembly 310. An inner tube (not shown) may be provided within the axial opening of the stator 330, around the plunger assembly 310, to define the chamber 306 and fluidly isolate the stator 330 from the fluid within the volumes 321, 322. The stator 330 may be surrounded by an inert, non-conductive, and/or non-corrosive fluid or other material provided between the inner tube and the inner housing 320 to equalize the pressure around the stator 330 with the fluid pressures within the volumes 321, 322 during pumping operations. [0069] The stator length 331 may be substantially greater than the plunger length 311. For example, as shown in FIG. 5, the stator length 331 may be about four times greater than the plunger length 311. As shown in FIG. 5, the stator 330 may extend substantially along the length of the chamber 306 within the power section 302, such as along the entire portion of the chamber 306 not within the fluid sections 204, 205. Accordingly, the chamber length 308 and the stator length 331 may be substantially equal, and the chamber length 308 may be substantially greater than the plunger length 311, such as about two, three, four, or more times greater than the plunger length 311. Thus, the stroke length 313 may also be substantially greater than the plunger length 311. For example, the stroke length 313 may be substantially equal to the stator length 331.

[0070] The pump 300 may also comprise an array of cooling fins 316 connected with the stator 330, as described above. A cooling fluid may also be utilized to increase the rate of heat removal from the stator 330. For example, the outer housing 318, the stator 330, and perhaps the inner housing 320 may define a fluid chamber 317, such as may retain the cooling fluid about the stator 330 and in contact with the cooling fins 316. The fluid chamber 317 may be or comprise a fluid channel operable to direct cooling fluid along and/or through the cooling fins 316. The cooling fluid may be injected into the fluid chamber 317 via an inlet 323 and discharged via an outlet 324.

[0071] The pumps 200, 300 within the scope of the present disclosure provide stators 260, 330, chambers 206, 306, and plunger assemblies 210, 310 configured to facilitate relatively long strokes, which may increase operational life of the pumps 200, 300 due to the corresponding reduction in cycling rates of the plunger assemblies 210, 310 and the inlet and outlet valves 231, 232, 243, 244. The pumps 200, 300 may also omit bearings and/or other rotating parts typically associated with rotating motors and engines to help increase the operational life of the pumps 200, 300.

[0072] Multiple instances of the pump 200 shown in FIGS. 2-4, the pump 300 shown in FIG. 5, and/or other pump implementations within the scope of the present disclosure may be packaged, arranged, and/or integrated as part of a pumping unit, such as the pumping unit 150 shown in FIG. 1. For example, FIGS. 6-8 are schematic views of examples of such

implementations according to one or more aspects of the present disclosure, in which the pumping units 150 are designated by reference numerals 351, 352, 353 and the pumps 200, 300 are designated by reference numeral 350.

[0073] Each pump 350 has a length 356 measured parallel to a longitudinal axis 355 of the pump 350, and a width 357 perpendicular to the longitudinal axis 355. As described above, each pump 350 may have a generally elongated geometry, such that the length 356 is substantially greater than the width 357. For example, the length 356 may be three, four, five, or more times greater than the width 357, although perhaps limited by length of the mobile carriers 152 or skids carrying the pumping units 351, 352, 353.

[0074] The pumping unit 351 depicted in FIG. 6 comprises three pumps 350 arranged horizontally. The longitudinal axes 355 of each of the pumps 350 may be substantially parallel. The horizontal arrangement of multiple pumps 350 may provide an increased flow capacity, relative to a single pump 350, while maintaining the same height as a single pump 350.

[0075] The pumping unit 352 depicted in FIG. 7 comprises three pumps 350 stacked vertically instead of horizontally. The longitudinal axes 355 of each of the pumps 350 may be substantially parallel. The vertical arrangement of multiple pumps 350 may provide an increased flow capacity, relative to a single pump 350, while maintaining the same footprint as a single pump 350.

[0076] The pumping unit 353 depicted in FIG. 8 comprising nine pumps 350 in three horizontally arranged vertical stacks of three pumps 350. The longitudinal axes 355 of each of the pumps 350 may be substantially parallel. Such implementations may provide an increased flow capacity over the pumping units 351, 352 depicted in FIGS. 6 and 7.

[0077] Although FIGS. 6-8 show the pumping units 351, 352, 353 comprising three and nine pumps 350, it is to be understood that other implementations of the pumping units 150 within the scope of the present disclosure may comprise other quantities of pumps 350. For example, a pumping unit 150 within the scope of the present disclosure may comprise two, four, or more pumps 350 arranged horizontally as depicted in FIG. 6, vertically as depicted in FIG. 7, or horizontally and vertically as depicted in FIG. 8. Examples of such implementations include a two-by-two arrangement having two horizontally arranged stacks of two pumps 350, a three-by- two arrangement, a four-by-three arrangement, a four-by-four arrangement, and other arrangements. However, the quantity of pumps 350 that can be packaged as part of the same pumping unit 150 may be limited by size and weight considerations, the combined power requirement of the pumps 350 making up the pumping unit 150, and/or the quantity of pumping units 150 at the well site 102.

[0078] FIG. 9 is a schematic view of at least a portion of an example implementation of a pumping unit 360 according to one or more aspects of the present disclosure. The pumping unit 360 comprises three pumps 361, 362, 363, each comprising one or more aspects in common with the apparatus shown in one or more of FIGS. 1-8. The following description refers to FIGS. 1-9, collectively.

[0079] Similarly to as described above with respect to FIGS. 1-8, each pump 361, 362, 363 may comprise a power section 365 operable to actuate two opposing fluid sections 366, 367. Each fluid section 366, 367 may be operable to receive fluid via a corresponding inlet 371, 372 and discharge fluid via a corresponding outlet 373, 374. The inlets 371, 372 of each pump 361, 362, 363 may be fluidly connected via a conduit system 376, and the outlets 373, 374 of each pump 361, 362, 363 may be fluidly connected via a conduit system 378. The conduit system 376 may be fluidly connected with the conduit system 142 to fluidly connect the fluid inlets 371, 372 of the pumping unit 360 with the suction line 138 of the common manifold 136. The conduit system 378 may be fluidly connected with the conduit system 144 to fluidly connect the fluid outlets 373, 374 of the pumping unit 360 with the discharge line 140 of the common manifold 136.

[0080] A flow rate sensor 145 may be disposed along the conduit system 144 in a manner permitting monitoring of the fluid flow rate of the fluid discharged by the pumping unit 360 via the fluid conduit 144. For example, the flow rate sensor 145 may be a flow meter operable to measure the volumetric and/or mass flow rate of the fluid discharged by the pumping unit 360. The flow rate sensor 145 may be operable to generate signals or information indicative of the flow rate of the fluid and utilized by a controller 410 (such as shown in FIG. 11) to, for example, facilitate intended changes to the flow rate of the fluid.

[0081] When utilizing pumping units 150, 360 comprising a plurality of pumps, such as the pumps 361, 362, 363, to discharge the fluid into a common manifold, such as the manifold 136, the movement of the corresponding plunger assemblies 210, 310 may be synchronized such that the plunger assemblies 210, 310 are out of phase with respect to each other. FIG. 10 is a graph showing example flow rate profiles generated by the pumping unit 360 during pumping operations in which the pumps 361, 362, 362 are operating out of phase. [0082] The graph depicts discharge flow rates of each pump 361, 362, 363 at each outlet 373, 374, shown along the vertical axis, with respect to time, shown along the horizontal axis. Curve 381 represents flow rate of the fluid discharged by the pump 361 via the outlet 373. During the pumping operations, the stator 260, 330 of the pump 361 may progressively increase or accelerate the speed of the corresponding plunger assembly 210, 310 in the first direction 251 to progressively increase the flow rate of fluid discharged via the outlet 373 until a predetermined flow rate is reached. The stator 260, 330 of the pump 361 may then maintain the speed of the plunger assembly 210, 310 as substantially constant to maintain the flow rate of fluid discharged via the outlet 373 as substantially constant for a period of time 387. Thereafter, the stator 260, 330 of the pump 361 may progressively decrease or decelerate the speed of the corresponding plunger assembly 210, 330 to progressively decrease the flow rate of fluid discharged via the outlet 373 until the flow rate reaches zero. As shown in FIG. 10, the curve 381 comprises an upwardly sloping portion representing the progressively increasing flow rate of fluid discharged via the outlet 373, a downwardly sloping portion representing the progressively decreasing flow rate of fluid discharged via the outlet 373, and a substantially horizontal portion interposing the first and second portions, representing the substantially constant flow rate of fluid discharged via the outlet 373.

[0083] Curve 384 represents flow rate of the fluid discharged by the pump 361 via the outlet 374. The stator 260, 330 of the pump 361 may progressively increase or accelerate the speed of the corresponding plunger assembly 210, 310 in the second direction 252 to progressively increase the flow rate of fluid discharged via the outlet 374 until a predetermined flow rate is reached. The stator 260, 330 of the pump 361 may then maintain the speed of the plunger assembly 210, 310 as substantially constant to maintain the flow rate of fluid discharged via the outlet 374 as substantially constant for the time period 387 (or some other time period).

Thereafter, the stator 260, 330 of the pump 361 may progressively decrease or decelerate the speed of the corresponding plunger assembly 210, 310 to progressively decrease the flow rate of fluid discharged via the outlet 374 until the flow rate reaches zero. As shown in FIG. 10, the curve 384 comprises a downwardly sloping portion representing the progressively increasing flow rate of fluid discharged via the outlet 374, an upwardly sloping portion representing the progressively decreasing flow rate of fluid discharged via the outlet 374, and a substantially horizontal portion interposing the first and second portions, representing the substantially constant flow rate of fluid discharged via the outlet 374.

[0084] Curves 382, 385 represent flow rates of the fluid discharged by the pump 362 via corresponding outlets 373, 374, respectively, while curves 383, 386 represent flow rates of the fluid discharged by the pump 363 via corresponding outlets 373, 374, respectively. Similarly as described above with respect to the curves 381, 384, the stators 260, 330 of the pumps 362, 363 may be operable to progressively increase speed of the corresponding plunger assemblies 210, 310 to progressively increase flow rates of the fluid discharged by the pumps 362, 363 via the outlets 373, 374, maintain the speed of the corresponding plunger assemblies 210, 310 substantially constant to maintain the flow rates of the fluid discharged by the pumps 362, 363 via the outlets 373, 374, and progressively decrease the speed of the corresponding plunger assemblies 210, 310 to progressively decrease the flow rates of the fluid discharged by the pumps 362, 363 via the outlets 373, 374.

[0085] The motions of the plunger assemblies 210, 310 of the pumps 361, 362 may be synchronized such that the combined flow rate discharged by the pumps 361, 362 may be maintained substantially constant. Similarly, the motions of the plunger assemblies 210, 310 of the pumps 362, 363 may also be synchronized such that the combined flow rate discharged by the pumps 362, 363 may also be maintained substantially constant.

[0086] For example, as the flow rate discharged by the pump 361 via the outlet 373 progressively decreases, the flow rate discharged by the pump 362 via the outlet 373 may progressively increase, perhaps by a proportional amount and/or rate, such that the combined flow rate of the pumps 361, 362 may be maintained substantially constant. Similarly, as the flow rate discharged by the pump 362 via the outlet 373 progressively decreases, the flow rate discharged by the pump 363 via the outlet 373 may progressively increase, perhaps by a proportional amount and/or rate, such that the combined flow rate of the pumps 362, 363 may be maintained substantially constant. Similarly, as the flow rate discharged by the pump 361 via the outlet 374 progressively decreases, the flow rate discharged by the pump 362 via the outlet 374 may progressively increase, perhaps by a proportional amount and/or rate, such that the combined flow rate of the pumps 361, 362 may be maintained substantially constant. Similarly, as the flow rate discharged by the pump 362 via the outlet 374 progressively decreases, the flow rate discharged by the pump 363 via the outlet 374 may progressively increase, perhaps by a proportional amount and/or rate, such that the combined flow rate of the pumps 362, 363 may be maintained substantially constant.

[0087] Accordingly, the substantially horizontal portions of the curves 381, 382, 383, representing the substantially constant flow rates generated by each pump 361, 362, 363 via the outlets 373, may not occur simultaneously or otherwise overlap. Similarly, the substantially horizontal portions of the curves 384, 385, 386, representing the substantially constant flow rates generated by each pump 361, 362, 363 via the outlets 374, may also not occur simultaneously or otherwise overlap.

[0088] The fluid collectively discharged by the pumps 361, 361, 363 may be communicated to the common manifold 136 via the fluid conduits 378, 144. The substantially constant flow rate generated by the pumping unit 360, and/or other aspects of the present disclosure, may reduce pressure spikes or fluctuations downstream from the pumping unit 360, such as may decrease instances of equipment failure linked to the pressure spikes. The combined flow rate of the pumps 361, 362, 363 discharged via the outlet 373 is shown by the curve 388, while the combined flow rate of the pumps 361, 362, 363 discharged via the outlet 374 is shown by the curve 389. One or more aspects described above with respect to synchronizing the plunger assemblies 210, 310 out of phase with respect to each other to achieve a substantially constant flow rate of the fluid collectively discharged by the pumps 361, 362, 363 may also be applicable or readily adaptable to other pumping unit implementations within the scope of the present disclosure, including implementations comprising fewer or more than three pumps.

[0089] Various portions of the apparatus described above and shown in FIGS. 1-9, may collectively form and/or be controlled by a control system, such as may be operable to monitor and/or control at least some operations of the wellsite system 100. FIG. 11 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. 1-11.

[0090] The control of the individual pumps 200, 300 of a pumping unit 150, such as the increasing, decreasing, and constant flow profiles and the speed and timing of the corresponding plunger assemblies 210, 310, may be performed by the controller 410 based on the position and/or velocity information generated by the corresponding position and flow sensors 280, 145. If one or more pumps 200, 300 fails to operate as intended, the controller 410 may execute a control logic that adapts to such an event by, for example, re-timing and/or re-offset the movement of the plunger assemblies 210, 310 to maintain a target objective function, such as speed up the plunger assemblies 210, 310 to maintain a predetermined flow rate or re-offset the plunger assemblies 210, 310 to maintain a substantially constant flow rate (but not necessarily a target flow rate).

[0091] The control system 400 may comprise the above-mentioned controller 410, which may be in communication with the material containers 1 10, 1 12, 126, the mixers 108, 124, the electrical power source 170, the manifold 136, the flow sensors 145, and the pumps 200, 300 of the pumping units 150, including individual stators 260, 330 and position sensors 280 of each pump 200, 300, 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 flow and position sensors 145, 280, 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 center 160.

[0092] 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 100, the pumping units 150, and/or the pumps 200, 300 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.

[0093] 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.

[0094] 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.

[0095] 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, fluid flow rate set- points, pumping speed set-points, fluid pressure set-points, and/or plunger assembly position set- points, such as may collectively control the fluid being received and discharged by the pumps 200, 300 and/or pumping units 150 for injection into the well 104. 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.

[0096] 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.

[0097] 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.

[0098] The coded instructions 432 may include program instructions or computer program code that, when executed by the processor 412, may cause the wellsite system 100, the pumping units 150, and/or the pumps 200, 300 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 145, 280, the controller 410 may send signals or information to the various controlled equipment to cause the material containers 110, 112, 126, the mixers 108, 124, the electrical power source 170, the manifold 136, the flow sensors 145, and the pumps 200, 300 of the pumping units 150 to automatically perform and/or undergo one or more operations or routines described herein or otherwise within the scope of the present disclosure.

[0099] 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 a method comprising establishing communication between a controller and a plurality of pumps, wherein: (A) the controller comprises a processor and a memory storing computer program code that, when executed, is operable to control operation of the pumps; (B) the pumps collectively discharge a fluid into a common conduit; (C) each pump comprises: (1) a chamber; (2) a plunger slidably disposed within the chamber; (3) a stator disposed about at least a portion of the chamber; and (4) a sensor operable to generate information indicative of the plunger position within the chamber. The method also comprises operating the controller, based on the information generated by the sensors, to control magnetic fields generated by the stators that move the plungers within the corresponding chambers, thereby controlling the pumps so that the fluid collectively discharged by the pumps to the common conduit is at a substantially constant flow rate.

[00100] The plungers may move out of phase with respect to each other.

[00101] The pumps may include a first pump and a second pump, such that the plunger and chamber of the first pump may be a first plunger and a first chamber, and the plunger and chamber of the second pump may be a second plunger and a second chamber. In such implementations, controlling the pumps to collectively discharge the fluid at the substantially constant flow rate may include, at the same time: controlling the first pump to progressively decrease speed of the first plunger to progressively decrease flow rate of the fluid discharged from the first chamber; and controlling the second pump to progressively increase speed of the second plunger to progressively increase flow rate of the fluid discharged from the second chamber. The pumps may also include a third pump, such that the plunger and chamber of the third pump may be a third plunger and a third chamber, and such that controlling the pumps to collectively discharge the fluid at the substantially constant flow rate may include, at the same time: controlling the second pump to progressively decrease speed of the second plunger to progressively decrease flow rate of the fluid discharged from the second chamber; and controlling the third pump to progressively increase speed of the third plunger to progressively increase flow rate of the fluid discharged from the third chamber.

[00102] Operating the controller to control the pumps and the substantially constant flow rate of the fluid collectively discharged by the pumps may comprise, with respect to each pump, controlling each stroke of the plunger within the chamber to include: a first portion in which the plunger speed within the chamber, and thus the flow rate of fluid discharged from the chamber, progressively increases; a second portion in which the plunger speed within the chamber, and thus the flow rate of fluid discharged from the chamber, progressively decreases; and a third portion in which the plunger speed within the chamber, and thus the flow rate of fluid discharged from the chamber, is substantially constant, wherein the third portion interposes the first and second portions. There may be no two pumps that simultaneously have a plunger in the third stroke portion.

[00103] Each plunger and corresponding chamber may define a first volume on a first side of the plunger and a second volume on a second side of the plunger, and operating the controller to control the pumps may comprise, with respect to each pump: controlling the pump to

magnetically move the plunger in a first direction to discharge the fluid from the first volume and draw the fluid into the second volume; and controlling the pump to magnetically move the plunger in a second direction to discharge the fluid from the second volume and draw the fluid into the first volume. Each plunger and corresponding chamber may further define a third volume centrally located between the first and second volumes, wherein the third volume may be substantially free of the fluid, and wherein operating the controller to control the pumps may further comprise, with respect to each pump, controlling the pump to magnetically move the plunger such that the stator is located alongside the third volume.

[00104] Each stator may comprise a length, and operating the controller to control the pumps may comprise, with respect to each pump, operating the stator to move the plunger a distance that is substantially equal to the length of the stator, a distance that is substantially greater than the length of the stator, or a distance that is substantially greater than the length of the plunger.

[00105] Each pump may comprise a generally elongated geometry extending along a longitudinal axis, and the method may further comprise arranging the pumps on a wellsite in association with each other such that the longitudinal axes of the pumps are substantially parallel with respect to each other. Arranging the pumps on the wellsite may comprise vertically stacking the pumps.

[00106] The method may further comprise injecting the fluid collectively discharged from the pumps into a well during a subterranean well treatment operation.

[00107] The present disclosure also introduces an apparatus comprising a pump assembly comprising: a chamber; a plunger having a plunger length and slidably disposed within the chamber; and a stator having a stator length and disposed about at least a portion of the chamber, wherein the stator length is substantially greater than the plunger length, and wherein the stator is operable to generate magnetic fields operable to reciprocatingly move the plunger within the chamber and thereby draw and discharge a fluid into and from the chamber.

[00108] The stator length may be more than two times greater than the plunger length.

[00109] The chamber may have a chamber length, and the chamber length and the stator length may be substantially equal. The chamber length may instead be more than two times greater than the plunger length.

[00110] The pump assembly may have a pump width and a pump length, and the pump length may be more than four times greater than the pump width.

[00111] The plunger may be operable to move a stroke distance within the chamber, and the stroke distance and the stator length may be substantially equal. The stroke distance may be substantially greater than the plunger length. For example, the stroke distance may be more than two times greater than the plunger length.

[00112] The stator may comprise an electro-magnetic coil operable to generate the magnetic fields, and the plunger may comprise a permanent magnet responsive to the magnetic fields.

[00113] The plunger may comprise a fluid seal operable to form a fluid seal against a wall of the chamber.

[00114] The pump assembly may further comprise a housing disposed about the stator. The housing may define a fluid pathway extending between the housing and the stator. The fluid pathway may be operable to communicate cooling fluid to remove heat from the stator.

[00115] The plunger and the chamber may collectively define a first volume on a first side of the plunger and a second volume on a second side of the plunger. Movement of the plunger in a first direction within the chamber may discharge the fluid from the first volume and draw the fluid into the second volume, and movement of the plunger in a second direction within the chamber may discharge the fluid from the second volume and draw the fluid into the first volume. The pump assembly may further comprise: a first inlet operable to communicate the fluid into the first volume; a first outlet operable to discharge the fluid from the first volume; a second inlet operable to communicate the fluid into the second volume; and a second outlet operable to discharge the fluid from the second volume.

[00116] The pump assembly may comprise a generally elongated geometry having a pump length measured along a longitudinal axis of the pump assembly. The pump length may be more than four times greater than a pump width perpendicular to the longitudinal axis. The apparatus may further comprise additional instances of the pump assembly, and the longitudinal axis of each pump assembly may be substantially parallel to the longitudinal axes of each of the other pump assemblies. Ones of the pump assemblies may be vertically stacked.

[00117] The pump assembly may be operable to discharge the fluid for injection into a well in a subterranean well treatment operation. The well treatment operation may comprise one of drilling, fracturing, gravel packing, cementing, and dosing.

[00118] The present disclosure also introduces an apparatus comprising a pump assembly comprising: a chamber; a plunger having a plunger length and slidably disposed within the chamber; and a stator having a stator length and disposed about at least a portion of the chamber, wherein the plunger length is substantially greater than the stator length, wherein the stator is operable to generate magnetic fields operable to reciprocatingly move the plunger a stroke distance within the chamber and thereby draw and discharge a fluid into and from the chamber, and wherein the stroke distance is not less than the stator length.

[00119] The plunger length may be about two times greater than the stator length.

[00120] The plunger length may be more than two times greater than the stator length.

[00121] The pump assembly may have a pump width and a pump length, and the pump length may be more than four times greater than the pump width.

[00122] The stroke distance and the stator length may be substantially equal.

[00123] The stroke distance may be substantially greater than the stator length.

[00124] The stator may comprise an electro-magnetic coil operable to generate the magnetic fields, and the plunger may comprise a permanent magnet responsive to the magnetic fields.

[00125] The plunger may comprise a fluid seal operable to form a fluid seal against a wall of the chamber.

[00126] The pump assembly may further comprise a housing disposed about the stator. The housing may define a fluid pathway extending between the housing and the stator. The fluid pathway may be operable to communicate cooling fluid to remove heat from the stator.

[00127] The plunger and the chamber may collectively define a first volume on a first side of the plunger and a second volume on a second side of the plunger. Movement of the plunger in a first direction within the chamber may discharge the fluid from the first volume and draw the fluid into the second volume, and movement of the plunger in a second direction within the chamber may discharge the fluid from the second volume and draw the fluid into the first volume. The pump assembly may further comprise: a first inlet operable to communicate the fluid into the first volume; a first outlet operable to discharge the fluid from the first volume; a second inlet operable to communicate the fluid into the second volume; and a second outlet operable to discharge the fluid from the second volume. The plunger and the chamber may collectively further define a third volume centrally located between the first and second volumes. The third volume may be substantially free of the fluid. The stator may extend around the third volume but not around the first and second volumes. The third volume may be defined between opposing first and second sealing portions of the plunger such that each form a fluidic seal against a surface of the chamber.

[00128] The pump assembly may comprise a generally elongated geometry having a pump length measured along a longitudinal axis of the pump assembly. The pump length may be more than four times greater than a pump width perpendicular to the longitudinal axis. The apparatus may further comprise additional instances of the pump assembly, and the longitudinal axis of each pump assembly may be substantially parallel to the longitudinal axes of each of the other pump assemblies. Ones of the pump assemblies may be vertically stacked.

[00129] The pump assembly may be operable to discharge the fluid for injection into a well in a subterranean well treatment operation. The well treatment operation may comprise one of drilling, fracturing, gravel packing, cementing, and dosing.

[00130] 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.

[00131] 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. A method comprising:

establishing communication between a controller and a plurality of pumps, wherein:

the controller comprises a processor and a memory storing computer program code that, when executed, is operable to control operation of the pumps;

the pumps collectively discharge a fluid into a common conduit;

each pump comprises:

a chamber;

a plunger slidably disposed within the chamber;

a stator disposed about at least a portion of the chamber; and

a sensor operable to generate information indicative of the plunger position within the chamber; and

operating the controller, based on the information generated by the sensors, to control magnetic fields generated by the stators that move the plungers within the corresponding chambers, thereby controlling the pumps so that the fluid collectively discharged by the pumps to the common conduit is at a substantially constant flow rate.

2. The method of claim 1 wherein the plungers move out of phase with respect to each other.

3. The method of claim 1 wherein:

the pumps include a first pump and a second pump;

the plunger and chamber of the first pump are a first plunger and a first chamber;

the plunger and chamber of the second pump are a second plunger and a second chamber; and controlling the pumps to collectively discharge the fluid at the substantially constant flow rate includes, at the same time:

controlling the first pump to progressively decrease speed of the first plunger to

progressively decrease flow rate of the fluid discharged from the first chamber; and controlling the second pump to progressively increase speed of the second plunger to progressively increase flow rate of the fluid discharged from the second chamber.

4. The method of claim 3 wherein:

the pumps include a third pump;

the plunger and chamber of the third pump are a third plunger and a third chamber; and controlling the pumps to collectively discharge the fluid at the substantially constant flow rate includes, at the same time:

controlling the second pump to progressively decrease speed of the second plunger to progressively decrease flow rate of the fluid discharged from the second chamber; and

controlling the third pump to progressively increase speed of the third plunger to

progressively increase flow rate of the fluid discharged from the third chamber.

5. The method of claim 1 wherein operating the controller to control the pumps and the

substantially constant flow rate of the fluid collectively discharged by the pumps comprises, with respect to each pump, controlling each stroke of the plunger within the chamber to include:

a first portion in which the plunger speed within the chamber, and thus the flow rate of fluid discharged from the chamber, progressively increases;

a second portion in which the plunger speed within the chamber, and thus the flow rate of fluid discharged from the chamber, progressively decreases; and

a third portion in which the plunger speed within the chamber, and thus the flow rate of fluid discharged from the chamber, is substantially constant, wherein the third portion interposes the first and second portions.

6. The method of claim 5 wherein no two pumps simultaneously have a plunger in the third stroke portion.

7. The method of claim 1 wherein each plunger and corresponding chamber define a first volume on a first side of the plunger and a second volume on a second side of the plunger, and wherein operating the controller to control the pumps comprises, with respect to each pump: controlling the pump to magnetically move the plunger in a first direction to discharge the fluid from the first volume and draw the fluid into the second volume; and

controlling the pump to magnetically move the plunger in a second direction to discharge the fluid from the second volume and draw the fluid into the first volume.

8. The method of claim 1 wherein each stator comprises a length, and wherein operating the controller to control the pumps comprises, with respect to each pump, operating the stator to move the plunger a distance that is substantially equal to the length of the stator.

9. The method of claim 1 wherein each stator comprises a length, and wherein operating the controller to control the pumps comprises, with respect to each pump, operating the stator to move the plunger a distance that is substantially greater than the length of the stator.

10. The method of claim 1 wherein each plunger comprises a length, and wherein operating the controller to control the pumps comprises, with respect to each pump, operating the stator to move the plunger a distance that is substantially greater than the length of the plunger.

11. An apparatus comprising:

a pump assembly comprising:

a chamber;

a plunger having a plunger length and slidably disposed within the chamber; and a stator having a stator length and disposed about at least a portion of the chamber,

wherein the stator length is substantially greater than the plunger length, and wherein the stator is operable to generate magnetic fields operable to reciprocatingly move the plunger within the chamber and thereby draw and discharge a fluid into and from the chamber.

12. The apparatus of claim 11 wherein the stator length is more than two times greater than the plunger length.

13. The apparatus of claim 11 wherein the plunger is operable to move a stroke distance within the chamber, and wherein the stroke distance is substantially greater than the plunger length.

14. The apparatus of claim 11 wherein the stator comprises an electro-magnetic coil operable to generate the magnetic fields, and wherein the plunger comprises a permanent magnet responsive to the magnetic fields.

15. The apparatus of claim 11 wherein the pump assembly further comprises a housing disposed about the stator, wherein the housing defines a fluid pathway extending between the housing and the stator, and wherein the fluid pathway is operable to communicate cooling fluid to remove heat from the stator.

16. The apparatus of claim 11 wherein the pump assembly comprises a generally elongated geometry having a pump length measured along a longitudinal axis of the pump assembly, wherein the pump length is more than four times greater than a pump width perpendicular to the longitudinal axis, wherein the apparatus further comprises additional instances of the pump assembly, and wherein the longitudinal axis of each pump assembly is substantially parallel to the longitudinal axes of each of the other pump assemblies.

17. The apparatus of claim 16 wherein ones of the pump assemblies are vertically stacked.

18. An apparatus comprising:

a pump assembly comprising:

a chamber;

wherein the plunger length is substantially greater than the stator length, wherein the stator is operable to generate magnetic fields operable to reciprocatingly move the plunger a stroke distance within the chamber and thereby draw and discharge a fluid into and from the chamber, and wherein the stroke distance is not less than the stator length.

19. The apparatus of claim 18 wherein the plunger length is more than two times greater than the stator length.

20. The apparatus of claim 18 and wherein the stroke distance is substantially greater than the stator length.