Patent Publication Number: US-10323485-B2

Title: Pressure exchanger system with integral pressure balancing system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 14/819,229, entitled “Pressure Exchanger System with Integral Pressure Balancing System,” filed Aug. 5, 2015, which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     The subject matter disclosed herein relates to fluid handling equipment such as hydraulic fracturing equipment. 
     Well completion operations in the oil and gas industry often involve hydraulic fracturing (often referred to as fracking or fracing) to increase the release of oil and gas in rock formations. Hydraulic fracturing involves pumping a fluid containing a combination of water, chemicals, and proppant (e.g., sand, ceramics) into a well at high pressures. The high-pressures of the fluid increases crack size and propagation through the rock formation releasing more oil and gas, while the proppant prevents the cracks from closing once the fluid is depressurized. Fracturing operations use high-pressure pumps to increase the pressure of the frac fluid. Unfortunately, certain components of the fluid handling equipment may be exposed to fluids with differing pressure, which may cause a pressure imbalance across the respective components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying figures in which like characters represent like parts throughout the figures, wherein: 
         FIG. 1  is a schematic diagram of an embodiment of a frac system with a hydraulic energy transfer system; 
         FIG. 2  is a perspective view of an embodiment of a rotary isobaric pressure exchanger (IPX); 
         FIG. 3  is a schematic view of an embodiment of a piston integral with an end cover of a rotary IPX; 
         FIG. 4  is a perspective view of the integral piston and end cover of  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of an embodiment of a piston integral with an end cover of a rotary IPX; 
         FIG. 6  is a cross-sectional view of an embodiment of a piston integral with an end cover of a rotary IPX; and 
         FIG. 7  is a cross-sectional view of an embodiment of a piston integral with an end cover of a rotary IPX. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present invention will be described below. These described embodiments are only exemplary of the present invention. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     As discussed in detail below, a hydraulic energy transfer system enables the transfer of work and/or pressure between first and second fluids, such as a pressure exchange fluid (e.g., a substantially proppant free fluid, such as water) and a hydraulic fracturing fluid (e.g., a proppant-laden frac fluid). In some embodiments, the hydraulic energy transfer system may be a rotating isobaric pressure exchanger (IPX) that transfers pressure between a high pressure first fluid (e.g., pressure exchange fluid, such as a first proppant free or substantially proppant free fluid) and a low pressure second fluid that may be highly viscous and/or contain proppant (e.g., frac fluid containing sand, solid particles, powders, debris, ceramics). In operation, certain components of the rotary IPX, such as the end covers, may be exposed to the high pressure first fluid and the low pressure second fluid, which may create a pressure imbalance across the respective components. Unfortunately, the pressure imbalance may cause deflection of the components (e.g., the end covers), which may enable the first and second fluids to mix outside of the rotor. As described in more detail below, the disclosed embodiments provide one or more pistons integral with one or more end covers of the IPX that create sealed off pressure areas to balance the forces acting on the end covers, which may reduce or minimize the deflection of the end covers. 
       FIG. 1  is a schematic diagram of an embodiment of a frac system  10  (e.g., fluid handling system) with a hydraulic energy transfer system  12 . For example, during well completion operations, the frac system  10  pumps a pressurized particulate laden fluid that increases the release of oil and gas in rock formations  14  by propagating and increasing the size of cracks  16  in the rock formations  14 . In order to block the cracks  16  from closing once the frac system  10  depressurizes, the frac system  10  uses fluids that have solid particles, powders, debris, etc. that enter and keep the cracks  16  open. 
     In order to pump this particulate laden fluid into the rock formation  14  (e.g., a well), the frac system  10  may include one or more high pressure pumps  18  and one or more low pressure pumps  20  coupled to the hydraulic energy transfer system  12 . For example, the hydraulic energy transfer system  12  may be a hydraulic turbocharger or an IPX (e.g., a rotary IPX). In operation, the hydraulic energy transfer system  12  transfers pressures without any substantial mixing between a first fluid (e.g., proppant free fluid) pumped by the high pressure pumps  18  and a second fluid (e.g., proppant containing fluid or frac fluid) pumped by the low pressure pumps  20 . In this manner, the hydraulic energy transfer system  12  blocks or limits wear on the high pressure pumps  18 , while enabling the frac system  10  to pump a high-pressure frac fluid into the rock formation  14  to release oil and gas. In order to operate in corrosive and abrasive environments, the hydraulic energy transfer system  12  may be made from materials resistant to corrosive and abrasive substances in either the first and second fluids (e.g., wear-resistant materials, such as corrosion, erosion, and/or abrasion resistant materials). For example, the hydraulic energy transfer system  10  may be made out of ceramics (e.g., alumina, cermets, such as carbide, oxide, nitride, or boride hard phases) within a metal matrix (e.g., Co, Cr or Ni or any combination thereof) such as tungsten carbide in a matrix of CoCr, Ni, NiCr or Co. 
     As used herein, the isobaric pressure exchanger (IPX) may be generally defined as a device that transfers fluid pressure between a high-pressure inlet stream and a low-pressure inlet stream at efficiencies in excess of approximately 50%, 60%, 70%, 80%, 90%, or more without utilizing centrifugal technology. In this context, high pressure refers to pressures greater than the low pressure. For example, the first fluid may be at a first pressure between approximately 5,000 kPa to 25,000 kPa, 20,000 kPa to 50,000 kPa, 40,000 kPa to 75,000 kPa, 75,000 kPa to 100,000 kPa or greater than a second pressure of the second fluid. The low-pressure inlet stream of the IPX may be pressurized and exit the IPX at high pressure (e.g., at a pressure greater than that of the low-pressure inlet stream), and the high-pressure inlet stream may be depressurized and exit the IPX at low pressure (e.g., at a pressure less than that of the high-pressure inlet stream). Additionally, the IPX may operate with the high-pressure fluid directly applying a force to pressurize the low-pressure fluid, with or without a fluid separator between the fluids. Examples of fluid separators that may be used with the IPX include, but are not limited to, pistons, bladders, diaphragms and the like. In certain embodiments, isobaric pressure exchangers may be rotary devices. Rotary isobaric pressure exchangers (IPXs), such as those manufactured by Energy Recovery, Inc. of San Leandro, Calif., may not have any separate valves, since the effective valving action is accomplished internal to the device via the relative motion of a rotor with respect to end covers. Rotary and IPXs may be designed to operate with internal pistons to isolate fluids and transfer pressure with relatively little mixing of the inlet fluid streams. Reciprocating IPXs may include a piston moving back and forth in a cylinder for transferring pressure between the fluid streams. Any IPX or plurality of IPXs may be used in the disclosed embodiments, such as, but not limited to, rotary IPXs, reciprocating IPXs, or any combination thereof. In addition, the IPX may be disposed on a skid separate from the other components of a fluid handling system, which may be desirable in situations in which the IPX is added to an existing fluid handling system. 
       FIG. 2  is an exploded view of an embodiment of a rotary IPX  30 . In the illustrated embodiment, the rotary IPX  30  may include a generally cylindrical body portion  40  that includes a housing  42  and a rotor  44 . The rotary IPX  30  may also include two end structures  46  and  48  that may include manifolds (e.g., end caps)  50  and  52 , respectively. Manifold  50  includes inlet and outlet ports  54  and  56  and manifold  52  includes inlet and outlet ports  60  and  58 . For example, inlet port  54  may receive a high-pressure first fluid and the outlet port  56  may be used to route a low-pressure first fluid away from the IPX  30 . Similarly, inlet port  60  may receive a low-pressure second fluid and the outlet port  58  may be used to route a high-pressure second fluid away from the IPX  30 . The end structures  46  and  48  include generally flat end covers (e.g., end covers)  62  and  64 , respectively, disposed within the manifolds  50  and  52 , respectively, and adapted for fluid sealing contact with the rotor  44 . 
     The rotor  44  may be cylindrical and disposed in the housing  42 , and is arranged for rotation about a longitudinal axis  66  of the rotor  44 . The rotor  44  may have a plurality of channels  68  extending substantially longitudinally through the rotor  44  with openings  70  and  72  at each end arranged symmetrically about the longitudinal axis  66 . The openings  70  and  72  of the rotor  44  are arranged for hydraulic communication with the end covers  62  and  64 , and inlet and outlet apertures  74  and  76 , and  78  and  80 , in such a manner that during rotation they alternately hydraulically expose fluid at high pressure and fluid at low pressure to the respective manifolds  50  and  52 . The inlet and outlet ports  54 ,  56 ,  58 , and  60 , of the manifolds  50  and  52  form at least one pair of ports for high-pressure fluid in one end element  46  or  48 , and at least one pair of ports for low-pressure fluid in the opposite end element  48  or  46 . The end covers  62  and  64  and inlet and outlet apertures  74  and  76 , and  78  and  80  are designed with perpendicular flow cross sections in the form of arcs or segments of a circle. 
     As noted above, the inlet port  54  of the manifold  50  may receive a high-pressure first fluid and the outlet port  56  of the manifold  50  may be used to route a low-pressure first fluid away from the IPX  30 . Similarly, inlet port  60  of the manifold  52  may receive a low-pressure second fluid and the outlet port  58  of the manifold  52  may be used to route a high-pressure second fluid away from the IPX  30 . Additionally, the inlet port  54  may route the high-pressure first fluid to the inlet aperture  74  (e.g., first fluid inlet, high-pressure first fluid inlet) of the end cover  62 , and the outlet port  56  may route the low-pressure first fluid from the outlet aperture  76  (e.g., first fluid outlet, low-pressure first fluid outlet) of the end cover  62 . Further, the inlet port  60  may route the low-pressure second fluid to the inlet aperture  78  (e.g., second fluid inlet, low-pressure second fluid inlet) of the end cover  64 , and the outlet port  58  may route the high-pressure second fluid away from the outlet aperture  80  (e.g., second fluid outlet, high-pressure second fluid outlet) of the end cover  64 . The high-pressure and low-pressure fluids flowing to and from the end covers  62  and  64  may cause a pressure differential across the end covers  62  and  64 , which may cause undesirable deflection of the end covers  62  and  64 . Accordingly, it may be desirable to provide pressure balancing techniques, as described below, for the end covers  62  and  64  to minimize deflection. 
       FIG. 4  is a cross-sectional view of an embodiment of the rotary IPX  30  that includes one or more pressure balancers, pressure-isolation sleeves (e.g., pistons)  100  configured to correct the pressure imbalance, as described above, across the end covers  62  and  64 . The piston  100  may create a sealed off low pressure area to balance the forces on the respective end cover, which may minimize deflection of the respective end cover. For example, a first surface  82  (e.g., an axial surface) of the end cover  62  that interfaces with a first axial end  83  of the rotor  44  may be exposed to pressures from the low-pressure first fluid (e.g., a low-pressure clean fluid) and the high-pressure first fluid (e.g., a high-pressure clean fluid) disposed within the channels  68  and/or within an interface region between the first surface  82  of the end cover  62  and the first axial end  83  of the rotor  44 . In particular, the first surface  82  may include a first low-pressure area  84  due to the low-pressure first fluid and a first high-pressure area  85  due to the high-pressure first fluid. Additionally, the first high-pressure area  85  may be disposed proximate to a second surface  86  (e.g., an axial surface) of the end cover  62  opposite from the first surface  82  due to the high-pressure first fluid within a high-pressure inlet chamber  89 . To balance the forces on the end cover  62 , a first piston  101  of the one or more pistons  100  may be integral with (e.g., manufactured as a single piece, adhesively coupled to, brazed to, welded to, bonded to, fused to, etc.) the second surface  86  (e.g., an axial surface) of the end cover  62 . The first piston  101  may create a sealed off low pressure area  102  that may be approximately (e.g., within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less) the same size (e.g., area) as the first low-pressure area  84  about the first surface  82  of the end cover  62 . The pressure of the sealed off low pressure area  102  may be based on the pressure of the low-pressure first fluid flowing through the first piston  100 . By creating the sealed off low pressure area  102  that is approximately the same size as the first low-pressure area  84 , the pressure differential across the end cover  62  may be reduced or minimized, which may reduce or minimize deflection of the end cover  62 . Additionally, the first piston  101  may also separate the low-pressure first fluid from the high-pressure inlet chamber  89  and from the high-pressure first fluid. In particular, the IPX  30  may not operate efficiently or operate at all without separating the low-pressure first fluid from the high-pressure first fluid in the high-pressure inlet chamber  89 . 
     Additionally, a first surface  91  (e.g., an axial surface) of the end cover  64  that interfaces with a second axial end  92  of the rotor  44  may be exposed to pressures from the low-pressure second fluid and the high-pressure second fluid disposed within the channels  68  and/or within an interface region between the first surface  91  of the end cover  64  and the second axial end  92  of the rotor  44 . In particular, the first surface  91  may include a first low-pressure area  93  due to the low-pressure second fluid and a first high-pressure area  94  due to the high-pressure second fluid. Additionally, the second high-pressure area  94  may be disposed proximate to a second surface  95  (e.g., an axial surface) of the end cover  64  opposite from the first surface  91  due to the high-pressure second fluid within a high-pressure outlet chamber  98 . To balance the forces on the end cover  64 , a second piston  103  of the one or more pistons  100  may be integral with (e.g., manufactured as a single piece, adhesively coupled to, brazed to, welded to, bonded to, fused to, etc.) the end cover  64 . The second piston  103  may create a sealed off low pressure area  104  that may be approximately (e.g., within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less) the same size (e.g., area) as the first low-pressure area  93  about the first surface  91  of the end cover  64 . The pressure of the sealed off low pressure area  104  may be based on the pressure of the low-pressure second fluid flowing through the second piston  103 . By creating the sealed off low pressure area  104  that is approximately the same size as the first low-pressure area  93 , the pressure differential across the end cover  64  may be reduced or minimized, which may reduce or minimize deflection of the end cover  64 . Additionally, the second piston  103  may also separate the low-pressure second fluid from the high-pressure outlet chamber  98  and from the high-pressure second fluid. 
     While the illustrated the first and second pistons  101  and  103  route low-pressure fluid and create sealed off low pressure areas  102  and  104 , respectively, it should be appreciated that in some embodiments, the first and second pistons  101  and  103  may route fluids at any suitable pressures (e.g., high-pressure fluid) and may create sealed off areas of any suitable pressures (e.g., sealed off high-pressure areas). Additionally, in some embodiments, the IPX  30  may include more than the first and second pistons  101  and  103 . For example, in some embodiments, the IPX  30  may include the illustrated first and second pistons  101  and  103  and may also include a third piston  100  to route the high-pressure first fluid and to create a sealed off high-pressure area and a fourth piston to route the high-pressure second fluid and to create a sealed off high-pressure area. 
     As noted above, the first piston  101  is integral with the end cover  62 , and the second piston  103  is integral with the end cover  64 . In some embodiments, the first piston  101  and end cover  62  may be manufactured as a single piece. Similarly, the second piston  103  and the end cover  64  may be manufactured as a single piece. In some embodiments, the pistons  101 ,  103  and the end covers  62 ,  64  may both be manufactured from a wear-resistant material, such as ceramics (e.g., alumina, cermets, such as carbide, oxide, nitride, or boride hard phases) within a metal matrix (e.g., Co, Cr or Ni or any combination thereof) such as tungsten carbide in a matrix of CoCr, Ni, NiCr or Co. In some embodiments, the pistons  101 ,  103  may be manufactured separately from the end covers  62 ,  64  and may be later coupled to and/or integrated with the end cover  62 ,  64 , respectively. For example, the first piston  101  and the end cover  62  may be re-fired in a kiln to fuse the first piston  101  and the end cover  62 . In some embodiments, the pistons  101 ,  103  may be brazed to, welded to, adhesively coupled to, fused to, and/or bonded to the end covers  62 ,  64 , respectively. Providing the integral pistons  101 ,  103  may provide increased reliability as compared to providing a piston that is coupled to the end cover  62 ,  64  (e.g., via a face seal. For example, a face seal configured to couple a piston to the end cover  62 ,  64  may separate due to pressure fluctuations, which may open clearance gaps between the end cover  62 ,  64  and the piston. 
     As illustrated, the first and second pistons  101  and  103  are disposed about the surfaces  86  and  95  of the end cover  62  and  64 , respectively. The first and second pistons  101  and  103  may be disposed about any suitable location of the surfaces  86  and  95 , respectively, such as the axial centers of the surfaces  86  and  95 , respectively. Each piston  100  (e.g., the first piston  101 , the second piston  103 ) includes one or more radial seals (e.g., seal rings)  108  within one or more grooves  110  (e.g., a circumferential groove) of the respective piston  100 . The one or more radial seals  108  may be any suitable seal, such as, but not limited to, an O-ring, a square ring, an X-ring, U-ring, or the like. The piston  100  therefore may maintain a seal while axially moving within the bore of the housing&#39;s end cap (e.g., within the manifold  50  or the manifold  52 ). For example, the internal cavity of the housing (e.g., the manifold  50  and/or the manifold  52 ) may deflect due to pressure and/or temperature induced expansion. Further, each piston  100  (e.g., the first and second pistons  101  and  103 ) may include a wing  112  (e.g., a shelf), which will be described in more detail below that extends radially from the respective piston  100 . 
       FIG. 5  is a perspective view of an embodiment of the piston  100  (e.g., the first piston  101  or the second piston  103 ) that is integral with an end cover (e.g., the end cover  62  or  64 ). The piston  100  includes an aperture  122  (e.g., a hydraulic flow path). The aperture  122  provides a hydraulic flow path that directs the incoming low pressure fluid to the low pressure inlet of the end cover  64  or directs the outgoing low pressure fluid from the low pressure outlet of the end cover  62 . The aperture  122  includes a diameter  124  at the top surface  126  of the piston  100 , which may be selected based upon the diameter of the low pressure inlet or outlet. The diameter of the aperture  122  may be constant or may vary throughout the hydraulic flow path. That is, the diameter  124  of the aperture  122  (e.g., the diameter  124  of the hydraulic flow path) may be constant over the length of the hydraulic flow path through the piston  100  or may vary over the length of the hydraulic flow path through the piston  100 . The piston also includes the one or more radial seals  108  disposed in the one or more circumferential grooves  110  of the piston  100 . As noted above, the one or more radial seals  108  may maintain a seal with the housing or end cap (e.g., manifold  50 , manifold  52 ) as the end cover (e.g., end cover  62 ,  64 ) moves axially due to temperature and/or pressure induced expansion, contraction, and deflection. 
     The wing  112  extends radially outward from the piston  100 . As illustrated, the wing  112  may be disposed about a portion of a body  128  (e.g., a generally cylindrical body) of the piston  100 . That is, the wing  112  may not extend about the entire circumference of the body  128  of the piston  100 . In other embodiments, the wing  112  may be disposed about the entire circumference of the piston  100 . The wing  112  may be generally conical, frustoconical, cylindrical, or any other suitable shape. In some embodiments, the wing  112  may facilitate brazing, fusing, welding, and/or adhesively bonding, the piston  100  to the end cover  62  or  64  by providing additional surface area for coupling. Additionally, the wing  112  may facilitate room for the hydraulic flow path. In some embodiments, the piston  100  may not include the wing  112 . In some embodiments, the piston  100  may include more than one wing  112  (e.g., 2, 3, 4, or more). 
       FIG. 6  is a cross-sectional view of the piston  100  that is integral with an end cover (e.g. the end cover  62  or  64 ). As illustrated, an upper portion  130  of the piston has a diameter  132  (e.g., d 1 ) and the wing  112  of the piston  100  has a length  134  (e.g., d 2 ) that is greater than the diameter  132 . In particular, the length  134  may be greater than the diameter  132  by a length  136  (e.g., d 3 ). The wing  112  may provide additional volume and surface area for the piston  100  that may enable a hydraulic flow path  138  through the piston  100  to be formed in a desired manner. For example, the aperture  122  may not be centered (e.g., axially aligned) about an aperture  140  (e.g., the inlet  74 , outlet  76 , inlet  78 , or outlet  80 ) of the end cover  62  or  64 . By providing the wing  112 , the piston  100  may include additional volume and surface area to enable the hydraulic flow path  138  to be formed (e.g., angled) in a desired manner from the aperture  122  to the aperture  140  of the end cover  62  or  64 . Thus, the hydraulic flow path  138  may be continuous through the aperture  140  and may be minimally obstructed (e.g., may not experience sharp changes in direction) through the aperture  140 . 
     As illustrated, the aperture  122  and the hydraulic flow path  138  may vary in diameter  124  (e.g., along a length  142  of the hydraulic flow path through the piston  100 ), which may help direct the incoming or outgoing low pressure fluid to the aperture  140  of the end cover  62  or  64 . The hydraulic flow path  138  may define a sealed off low pressure area  144  (e.g., the second low-pressure area  87 , the second low-pressure area  96 ). The pressure of the sealed off low pressure area  144  may be determined based on the pressure of the incoming/outgoing low pressure fluid. Further, as described in detail above, the sealed off low pressure area  144  may balance the forces on the respective end cover  62  or  64  to minimize the deflection of the end cover  62  or  64 . Additionally, as noted above, the piston  100  may be manufactured from one or more wear-resistant materials, such as, but not limited to, tungsten carbide, ceramics, steel, etc., which may enable the piston  100  to withstand external pressures exerted on the piston  100 . 
     While the above embodiment relates a piston including a wing, in other embodiments, the piston  100  may not include the wing  112 . For example, as illustrated in  FIG. 7 , which is a cross-sectional view of an embodiment of the piston  100 , the aperture  122  of the piston  100  may be centrally aligned (e.g., axially aligned) with the aperture  140  of the end cover  62  or  64 . Because of the alignment of the apertures  122  and  140 , the hydraulic flow path  138  may include a continuous and unobstructed pathway through the apertures  122  and  140  without providing the wing  112 . However, in some embodiments, the wing  112  may still be provided. For example, the wing  112  may facilitate the integration of the piston  100  to the end cover  62  or  64  during re-firing or brazing. Further, the wing  112  may not be included on the piston  100  for embodiments in which the apertures  122  and  140  are centrally aligned. For example, as illustrated in  FIG. 8 , the diameter  150  of the piston  100  may be sufficient such that the hydraulic flow path  138  may be angled toward the aperture  140  of the end cover  62  or  54  without the need for the additional volume provided by the wing  112 . 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.