Abstract:
Pump apparatus and methods of making and using same are disclosed. One inventive apparatus includes at least two pump stages having different performance characteristics combined in series to substantially match an intended pumping application. An inventive method includes selecting two or more pump stages having different performance characteristics that when combined in series overcome limitations of at least one of the pump stages. This abstract allows a searcher or other reader to quickly ascertain the subject matter of the disclosure. It will not be used to interpret or limit the scope or meaning of the claims.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to the field of fluid transfer, and more specifically to submersible and surface pump apparatus and methods of making and using same.  
         [0002]     Electrical submersible pumps (ESPs) are used for artificial lifting of fluid from a well or reservoir. An ESP typically comprises: (1) an electrical submersible motor—which is the driver—each motor may be up to about 30 feet in length, with multiple sections of motors available based on the power requirement; (2) a seal section (sometimes referred to in the art as a protector)—which functions to equalize the pressure between the inside of the system and the outside of the system and also acts as a reservoir for compensating the internal oil expansion from the motor; and (3) a submersible pump—the driven portion—having one or more pump stages inside a housing. One pump may be 24 feet or more in length, and multiple identical pump stages may be installed based on the pressure that has to be developed. The order in which the sections are typically installed in the well is motor, seal section and pump, but alternative arrangements may be used. Each pump stage is capable of producing certain pressure (head) which is cumulative—for example, if a stage can produce 20 feet of head, 100 stages will produce 100×20=2000 feet of head.  
         [0003]     In a variety of applications, it is advantageous to utilize a surface pump, such as a horizontal pumping system (“HPS”), which generally includes a driver, which may be a motor, turbine, diesel or non-diesel internal combustion engine, generator, and the like, in some cases combined with a protector, seal chamber, and the like, and a pump mounted on a horizontal skid. For example, an HPS may be used in applications such as water floods, liquid propane injection, water supply, booster service, salt water disposal and crude oil transfer.  
         [0004]     Whether used in surface applications or downhole, each pump stage has definite performance characteristics limited by and/or based on the slope of head versus flow rate curve, amount of head (lift) produced, efficiency, brake horsepower, and down thrust. For gas handling in downhole applications, a taper pump unit approach has been used. A taper pump unit consists of two or more pump housings, each pump housing having different pump stages in it. Taper pumps can not overcome the limitations of a single pump stage.  
         [0005]     From the above it is evident that there is a need in the art for improvement in surface pumps and downhole pumps, such as electrical submersible pumps.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with the present invention, pump apparatus and methods of making and using same are described that reduce or overcome problems in previously known apparatus and methods. By combining two or more pump stages having different performance characteristics, one or more limitations of performance characteristics of one of the pump stages can be overcome by the performance characteristics of other pump stage. Two or more pumps stages, having different performance characteristics, may be combined as a single unit to match the application requirements by changing head flow characteristics, brake horsepower characteristics, operating range and thrust characteristics. The change in performance characteristics is based on the stage mixing percentage or ratio, as defined herein. The inventive pumps may, for example, provide a solution for the 3000 to 4000 BPD flow range of pumps in downhole applications in 5.5 inch diameter casing. This is a specific example and this idea can be easily used for different size pump stages in any application.  
         [0007]     A first aspect of the invention are apparatus comprising:  
         [0008]     (a) a driver, which may be a motor, turbine, diesel or non-diesel internal combustion engine, generator, and the like, in some cases combined with a protector, seal chamber, thrust chamber, gear box and the like;  
         [0009]     (b) a driver shaft turned by the driver; and  
         [0010]     (c) at least two pump stages on a pump shaft arranged in series and having different performance characteristics, the at least two pump stages adapted to work together to substantially match an intended pumping application.  
         [0011]     The driver shaft may be one and the same as the pump shaft in certain embodiments, and in certain other embodiments the pump shaft may be mechanically coupled to and driven by the driver shaft. In other embodiments, the driver shaft and the pump shaft may be distinct and not be coupled mechanically, such as in magnetic couplings wherein the driver shaft drives a magnetic coupling comprising magnets on the driver shaft which interact with magnets in a protector, in which case the protector shaft mechanically connects to and drives the pump shaft.  
         [0012]     Apparatus of the invention include those apparatus wherein the at least two pump stages comprise a first set of pump stages each having a first defined set of performance characteristics, and a second set of pump stages each having a second defined set of performance characteristics. Apparatus of the invention include those wherein the performance characteristics are selected from head flow characteristics, brake horsepower characteristics, operating range, thrust characteristics, efficiency, net positive suction head (NPSH), and two or more thereof.  
         [0013]     The inventive apparatus may further include a having a stage mixing ratio ranging from about 1:99 to about 99:1. The stage mixing ratio may in some embodiments range from about 1:9 to about 9:1. In certain other embodiments the stage mixing ratio may range from about 3:7 to about 7:3, and in other embodiments the stage mixing ratio may be 1:1.  
         [0014]     Certain embodiments of the apparatus of the invention, such as those suitable for use downhole, may include a motor protector, which may or may not be integral with the motor, and may include integral instrumentation adapted to measure one or more downhole parameters. Apparatus of the invention may be adapted to produce a dynamic head up to 7,500 feet. Surface communication to apparatus of the invention may be through use one or more communication links, including but not limited to hard wire, optical fiber, radio, or microwave transmission. The inventive apparatus and methods may include a chemical detector at or near the motor of the apparatus, which enables an operator to stop the motor, or allows an automated relay to stop the motor, long before hydrocarbons or other chemicals can reach the motor and pose a safety and/or loss of production risk. The chemical detector, if used, may be selected from any functioning system, or future functioning system, or combination of systems.  
         [0015]     Another aspect of the invention are methods of making a pump, one method of the invention comprising:  
         [0016]     (a) selecting a first pump stage comprising a first set of pump stages, the first set of pump stages having a first pump characteristic;  
         [0017]     (b) selecting a second pump stage comprising a second set of pump stages, the second set of pump stages having a second pump characteristic; and  
         [0018]     (c) attaching the first and second sets of pumps in series on a common pump shaft.  
         [0019]     Methods of the invention include those wherein the performance characteristics are selected from head flow characteristics, brake horsepower characteristics, operating range, thrust characteristics, efficiency, NPSH, and two or more thereof.  
         [0020]     Yet another aspect of the invention are methods of pumping fluids, one method comprising:  
         [0021]     (a) determining a pumping requirement for transferring a fluid;  
         [0022]     (b) selecting at least two pump stages to operate in series to form a pump, the at least two pump stages of the pump having different performance characteristics; and  
         [0023]     (c) pumping the fluid using the pump to meet the pumping requirement.  
         [0024]     Apparatus and methods of the invention will become more apparent upon review of the brief description of the drawings, the detailed description of the invention, and the claims that follow. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]     The manner in which the objectives of the invention and other desirable characteristics can be obtained is explained in the following description and attached drawings in which:  
         [0026]      FIG. 1  is a front elevation view of an exemplary electrical submersible pump disposed within a wellbore;  
         [0027]      FIG. 2  is a diagrammatical cross-section of the pump of  FIG. 1  having a bellows assembly to separate well fluid from motor fluid, which is positively pressurized within the motor housing;  
         [0028]      FIG. 3  is a schematic side elevation view, partially in cross-section, of one apparatus in accordance with the invention;  
         [0029]      FIGS. 4A and 4B  are slightly larger schematic side elevation views, partially in cross section, of the apparatus of  FIG. 3 ;  
         [0030]      FIGS. 5 and 6  are performance characteristic charts for two different prior art electrical submersible pumps;  
         [0031]      FIG. 7  is a performance characteristic chart for an electrical submersible pump of the invention constructed from the different pumps stages of  FIGS. 5 and 6 .  
         [0032]      FIG. 8  is a schematic side elevation view of one alternative apparatus in accordance with the invention;  
         [0033]      FIG. 9  is a schematic side elevation view, partially in cross section, of another alternative apparatus of the invention; and  
         [0034]      FIG. 10  is a schematic side elevation view, partially in cross section, of yet another apparatus of the invention. 
     
    
       [0035]     It is to be noted, however, that the appended drawings are not to scale and illustrate only typical embodiments of this invention, and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
       DETAILED DESCRIPTION  
       [0036]     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.  
         [0037]     All phrases, derivations, collocations and multiword expressions used herein, in particular in the claims that follow, are expressly not limited to nouns and verbs. It is apparent that meanings are not just expressed by nouns and verbs or single words. Languages use a variety of ways to express content. The existence of inventive concepts and the ways in which these are expressed varies in language-cultures. For example, many lexicalized compounds in Germanic languages are often expressed as adjective-noun combinations, noun-preposition-noun combinations or derivations in Romanic languages. The possibility to include phrases, derivations and collocations in the claims is essential for high-quality patents, making it possible to reduce expressions to their conceptual content, and all possible conceptual combinations of words that are compatible with such content (either within a language or across languages) are intended to be included in the used phrases.  
         [0038]     The invention describes pump apparatus and methods of making and using same for pumping fluids, for example, to and from wellbores, although the invention is applicable to pumps designed for any intended use, including, but not limited to, so-called surface fluid transfer operations. A “wellbore” may be any type of well, including, but not limited to, a producing well, a non-producing well, an experimental well, and exploratory well, and the like. Wellbores may be vertical, horizontal, some angle between vertical and horizontal, and combinations thereof, for example a vertical well with a non-vertical component. As discussed, pump stages have definite performance characteristics based on the slope of the head versus flow rate curve (typically known as the pump curve), amount of head (lift), net positive suction head (NPSH), efficiency, brake horsepower and down thrust. Operating range of the pump stage is limited by the slope of the head flow curve, thrust, efficiency and head. In inventive apparatus, two or more pump stages, having different performance characteristics, are combined to overcome limitations of one of the pump stages.  
         [0039]     Given that there is considerable investment in existing equipment, it would be an advance in the art if existing pump stages could be combined using existing apparatus to increase operating range and efficiency during pumping, with minimal interruption of well operations. This invention offers methods and apparatus for these purposes.  
         [0040]      FIGS. 1-9  focus on submersible pumps only as examples of the inventive apparatus and methods, but the invention is not so limited. Referring generally to  FIG. 1 , a prior art pumping system  10 , such as a submersible pumping system, is illustrated. Pumping system  10  may comprise a variety of components depending on the particular application or environment in which it is used. Typically, system  10  has at least a submersible pump  12 , a motor  14  and a protector  16 . Motor  14  may comprise any electric motor or other motor that requires volume compensation based on, for instance, the thermal expansion and/or contraction of internal fluid. The submersible pump  12  may be of a variety of types, for example a centrifugal pump, an axial flow pump, or a mixture thereof, although the principles of the invention are pertinent only to the centrifugal pump portion of the pump. System  10  may also comprise a gearbox, thrust chamber, seal chamber, and the like, as is known in the art.  
         [0041]     In the illustrated example, pumping system  10  is designed for deployment in a well  18  within a geological formation  20  containing desirable production fluids, such as petroleum. In a typical application, a wellbore  22  is drilled and lined with a wellbore casing  24 . Wellbore casing  24  typically has a plurality of openings  26 , for example perforations, through which production fluids may flow into wellbore  22 .  
         [0042]     Pumping system  10  is deployed in wellbore  22  by a deployment system  28  that may have a variety of forms and configurations. For example, deployment system  28  may comprise tubing  30  connected to pump  12  by a connector  32 . Power is provided to submersible motor  14  via a power cable  34 . Motor  14 , in turn, powers centrifugal pump  12 , which draws production fluid in through a pump intake  36  and pumps the production fluid to the surface via tubing  30 .  
         [0043]     It should be noted that the illustrated submersible pumping system  10  is merely an exemplary embodiment. Other components can be added to the system, and other deployment systems may be implemented. Additionally, the production fluids may be pumped to the surface through tubing  30  or through the annulus formed between deployment system  28  and wellbore casing  24 . In any of these configurations of submersible pumping system  10 , it may be desirable to be able to use two or more centrifugal pump stages having different operating characteristics in accordance with the present invention.  
         [0044]     In certain embodiments, system  10  may have multiple sections of motor protector  16  disposed about motor  14 . A diagrammatical cross-sectional view of an exemplary embodiment of system  10  is provided in  FIG. 2 . As illustrated, system  10  comprises pump  12 , motor  14 , and various motor protection components disposed in a housing  38 . Pump  12  is rotatably coupled to motor  14  via a shaft  40 , which extends lengthwise through the housing  38  (for example, one or more housing sections coupled together). System  10  and shaft  40  may have multiple sections, which can be intercoupled via couplings and flanges. For example, shaft  40  has couplings  42  and  44  and an intermediate shaft section  46  disposed between pump  12  and motor  14 .  
         [0045]     A variety of seals, filters, absorbent assemblies and other protection elements also may be disposed in housing  38  to protect motor  14 . A thrust bearing  48  is disposed about shaft  40  to accommodate and support the thrust load from pump  12 . A plurality of shaft seals, such as shaft seals  50  and  52 , are also disposed about shaft  40  between pump  12  and motor  14  to isolate a motor fluid  54  in motor  14  from external fluids, such as well fluids and particulates. Shaft seals  50  and  52  also may include stationary and rotational components, which may be disposed about shaft  40  in a variety of configurations. System  10  also may include a plurality of moisture absorbent assemblies, such as moisture absorbent assemblies  56 ,  58 , and  60 , disposed throughout housing  38  between pump  12  and motor  14 . These moisture absorbent assemblies  56 - 60  absorb and isolate undesirable fluids (for example, water, H 2 S, and the like) that have entered or may enter housing  38  through shaft seals  50  and  52  or though other locations. For example, moisture absorbent assemblies  56  and  58  may be disposed about shaft  40  at a location between pump  12  and motor  14 , while moisture absorbent assembly  60  may be disposed on an opposite side of motor  14  adjacent a bellows assembly  64 . In addition, the actual protector section above the motor may include a hard bearing head with shedder.  
         [0046]     As illustrated in  FIG. 2 , the motor fluid  54  is in fluid communication with an interior  66  of the bellows assembly  64 , while well fluid  68  is in fluid communication with an exterior  70  of the bellows assembly  64 . Accordingly, the bellows assembly  64  seals the motor fluid  54  from the well fluid  68 , while positively pressurizing the motor fluid  54  relative to the well fluid  68  (e.g., a 50 psi pressure differential). The spring force, or resistance, of the bellows assembly  64  ensures that the motor fluid  54  maintains a higher pressure than that of the well fluid  68 . A separate spring assembly or biasing structure also may be incorporated in bellows assembly  64  to add to the spring force, or resistance, which ensures that the motor fluid  54  maintains a higher pressure than that of the well fluid  68 .  
         [0047]     The bellows assembly  64  may embody a variety of structural features, geometries and materials as known in the art to utilize the pressure of the well fluid  68  in combination with a spring force of the bellows assembly  64  to positively pressurize the motor fluid  54 . Initially, the motor fluid  54  is injected into the motor  14  and the bellows assembly  64  is pressurized until a desired positive pressure is obtained within the motor  14 . For example, the system  10  may set an initial pressure, such as 25-100 psi, prior to submerging the system  10  into the well. The exterior chamber  70  adjacent the bellows assembly  64  also may be filled with fluid prior to submerging the system into the well. The well fluid  68  enters the housing  38  through ports  72  and mixes with this fluid in exterior chamber  70  as the system  10  is submersed into the well. Operation of the bellows assembly  64  illustrated by  FIG. 2  is well known in the art and requires no further explanation to the skilled artisan. The bellows assembly  64  also may have various protection elements to extend its life and to ensure continuous protection of the motor  14 . For example, a filter  74  may be disposed between the ports  72  and the exterior  70  of the bellows assembly  64  to filter out undesirable fluid elements and particulates in the well fluid  68  prior to fluid communication with the exterior  70 . A filter  76  also may be provided adjacent the interior  66  of the bellow assembly  64  to filter out motor shavings and particulates. As illustrated, the filter  76  is positioned adjacent the moisture absorbent assembly  60  between the motor cavity  62  and the interior  66  of the bellows assembly  64 . Accordingly, the filter  76  prevents solids from entering or otherwise interfering with the bellows assembly  64 , thereby ensuring that the bellows assembly  64  is able to expand and contract along with volume variations in the fluids.  
         [0048]     A plurality of expansion and contraction stops also may be disposed about the bellows assembly  64  to prevent over and under extension and to prolong the life of the bellows assembly  64 . For example, a contraction stop  78  may be disposed within the interior  66  of the bellows assembly  64  to contact an end section  80  and limit contraction of the bellows assembly  64 . An expansion stop  82  also may be provided at the exterior  70  of the bellows assembly  64  to contact the end section  80  and limit expansion of the bellows assembly. These contraction and expansion stops  78  and  82  can have various configurations depending on the material utilized for the bellows assembly  64  and also depending on the pressures of the motor fluid  54  and the well fluid  68 . A housing  84  also may be disposed about the exterior  70  to guide the bellows assembly  64  during contraction and expansion and to provide overall protection about the exterior  70 .  
         [0049]     As the system  10  is submersed and activated in the downhole environment, the internal pressure of the motor fluid  54  may rise and/or fall due to temperature changes, such as those provided by the activation and deactivation of the motor  14 . A valve  86  may be provided to release motor fluid  54  when the pressurization exceeds a maximum pressure threshold. In addition, another valve may be provided to input additional motor fluid when the pressurization falls below a minimum pressure threshold. Accordingly, the valves maintain the desired pressurization and undesirable fluid elements are repelled from the motor cavity  62  at the shaft seals  50  and  52 . The system  10  also may have a wiring assembly  87  extending through the housing  38  to a component adjacent the bellows assembly  64 . For example, a variety of monitoring components may be disposed below the bellows assembly  64  to improve the overall operation of the system  10 . Exemplary monitoring components comprise temperature gauges, pressure gauges, and various other instruments, as should be appreciated by those skilled in the art.  
         [0050]      FIG. 3  is a schematic side elevation view, partially in cross-section, and not necessarily to scale, of one pump apparatus  90  in accordance with the invention. Apparatus  90  includes two different pump stages indicated by dashed line boxes  91  and  92  and connected through a connector  93 . Also illustrated is a pump housing  94  which houses both pump stages  91  and  92 . Pump intake  95  allows well or reservoir fluids to enter pump apparatus  90 . A first set of impellers  96  and diffusers  97  move fluid through stage  92  as depicted by curved line  98  (upwards in  FIG. 3 , although the invention is not so limited) toward second stage  91 , having a different set of impellers  96 ′ and diffusers  97 ′, eventually forcing fluid out through a discharge  99 . Impellers  96  and  96 ′ are all removably fastened to a pump shaft  100 , which is powered by one or more motors (not illustrated).  FIGS. 4A and 4B  illustrate the same features as  FIG. 3  but in a more expanded view, illustrating in more detail pump stages  91  and  92 . In certain embodiments, the stage producing the higher flow rate may be positioned on the “bottom”, in this case stage  92 , although the invention is not so limited. Sealing rings (not illustrated) may be installed in stages directly below connector  93 . Bearing housings may be placed at the first stage below the top or last diffuser in stage  92 . The bearing housing location may increase one stage for each housing length required. The top-most diffuser (nearest the pump discharge) may have its male nest removed.  
         [0051]     As an example of the invention, head flow characteristics and operating ranges of two pump stages individually and as combined in accordance with the invention are now discussed in reference to  FIGS. 5, 6 , and  7 . A stage mixing percentage or stage mixing ratio of 1:1 may be used as an example. A stage mixing ratio of 1:1 means that in a pump having 100 total stages, one set of 50 stages are of a pump stage type having a first head flow characteristic and operating range, and a second set of 50 pump stages are comprised of a pump stage type having a second head flow characteristic different from the first set. In a similar way, other performance parameters like thrust, efficiency, and brake horsepower can be considered and different stage mixing ratios can be used. The different performance characteristics of two different pump stages, known under the trade designation D4300N and D3000N, available from Schlumberger Technology Corporation (Sugar Land, Tex.), are illustrated in  FIGS. 5 and 6 , respectively. The operating range for these pumps is given in Table 1. By combining the two stages, using 1:1 stage mixing ratio, head flow characteristics and operating range are changed to that indicated for the pump D3400N in Table 1 and  FIG. 7 .  
         [0052]     The operating range of the pump known under the trade designation D4300N is from about 3500 to about 5400 barrels per day (BPD) at 60 Hertz (Hz) as illustrated in  FIG. 5  by curve  102 . Note that the head curve  101  is relatively flat below a flow rate of about 3500 BPD. Therefore, the useable operating range of this pump may not reach lower than about 3500 BPD due to very flat head flow characteristics, which may cause the pump operation in the field to be unstable and unreliable, as well as inefficient as depicted by curve  103 . The operating range of the pump known under the trade designation D3000N is from about 2200 to about 3700 BPD at 60 Hz as illustrated in  FIG. 6  by curve  102  and may not exceed more than about 3700 BPD due to lower efficiency (curve  103 ) and lower head (curve  101 ). However, if the two stages represented by the pump characteristics in  FIGS. 5 and 6  are combined, in accordance with one embodiment of the invention, the operating range limitations of both pumps may be reduced or overcome. Performance characteristics of the new pump stage, D3400N at 60 Hz are illustrated in  FIG. 7  by curves  101  (head), capacity ( 103 ) and useful capacity operating range (between vertical lines  104  and  105 ). In this way, limitations of the pump known under the trade designation D4300N of not being able to operate below about 3500 BPD flow and of the pump known under the trade designation D3000N of not being able to exceed more than 3700 BPD flow may be overcome. Pump performance characteristics for other electrical frequencies may be computed using methods known in the art.  
                                                   TABLE 1                           Combining pump stages in 1:1 stage mixing ratio:                D4300N   D3000N   D3400N                        Operating Range   3500-5400   2200-3700   2200-4100       (BPD) @ 60 Hz                  
 
         [0053]      FIG. 8  illustrates another electrical submersible pump  110  of the invention, which is a modified version of a pumping system known under the trade designation Axia™, available from Schlumberger Technology Corporation. Pumps of this type may feature a simplified two-component pump-motor configuration, with pump illustrated generally at  111  having two stages  111   a  and  111   b  in accordance with the invention inside a housing  118 , and a combined motor and protector at  112 . Pump  110  may be built with integral intakes  114  and discharge heads  116 . Fewer mechanical connections may contribute to faster installation and higher reliability of this embodiment. The combined motor and protector assembly  112 , known under the trade designation ProMotor™, may be prefilled in a controlled environment, and may include integral instrumentation that measures downhole temperatures and pressures.  
         [0054]      FIG. 9  illustrates another alternative electrical submersible pump configuration  130  in accordance with the invention. As discussed herein, ESPs are designed to certain specifications so problems may appear when the equipment is mis-applied or misoperated. There are limitations regarding pressure, temperature, motor horsepower, and the like, which may be interrelated. How close to the envelope the ESP is operated may ultimately effect system longevity. Very often the ESP cost is a fraction of the workover costs. In an effort to mitigate the life cycle costs, alternative methods of ESP deployment have been investigated. This has included, over the past 20 years, an ESP deployed on cable, an ESP deployed on coiled tubing with power cable strapped to the outside of the coiled tubing (the tubing acts as the producing medium), and more recently a system known under the trade designation REDACoil™ as illustrated in  FIG. 9  with a power cable  132  deployed internally in coiled tubing  25 . In the embodiment  130  illustrated in  FIG. 9 , three “on top” motors  14   a ,  14   b , and  14   c  drive three pump stages  136   a ,  136   b , and  138 , all pump stages enclosed in a housing  141 . Pump stages  136   a  and  136   b  may be identical in number of pump stages and performance characteristics, while pump stage  138  has different performance characteristics, in accordance with the invention. A separate protector  16  is provided, as well as an optional pressure/temperature gauge  140 . Also provided in this embodiment is a sub-surface safety valve (SSSV)  142  and a chemical injection mandrel  144 . A lower connector  134  is employed, which may be hydraulically releasable with power cable  135 , and may include a control line and instrument wire feedthrough. A control line set packer,  146 , completes this embodiment. The technology of bottom intake ESPs (with motor on the top) has been established over a period of years. It is important to securely install pump stages, motors, and protector within coiled tubing  25 , enabling quicker installation and retrieval times plus cable protection and the opportunity to strip in and out of a live well. This may be accomplished using a deployment cable  132 , which may be a cable known under the trade designation REDACoil™, including a power cable and flat pack with instrument wire and one or more, typically three hydraulic control lines, one each for operating the lower connector release, SSSV, and packer setting/chemical injection.  
         [0055]     In a variety of applications, it is advantageous to utilize a surface pump, such as a horizontal pumping system (“HPS”). Referring generally to  FIG. 10 , an exemplary horizontal pumping system (“HPS”)  150  is illustrated according to the present invention in perspective, with parts broken away. The HPS  150  includes a pump  152 , a motor  154  drivingly coupled to pump  152 , and a horizontal skid  156  for supporting pump  152  and motor  154 . As with submersible pumps of the invention, the principles of the invention are pertinent only when pump  152  comprises a centrifugal pump, while motor  154  may be substituted for any of a number of drivers, such as turbines, generators, and the like. However, the HPS may comprise other pumps, such as positive displacement pumps, in conjunction with the centrifugal pump, and other drivers for a given application. Pump  152  includes a first set of impellers  96  and diffusers  97  designed move fluid through pump  152  toward second stage having a different set of impellers  96 ′ and diffusers  97 ′, eventually forcing fluid out through a discharge  169 , wherein the other pump conduit  169  is a pump intake. Apparatus  150  includes two different pump stages connected through a connector  93 . As may be seen a single pump housing houses both pump stages.  
         [0056]     As explained in assignee&#39;s U.S. Pat. No. 6,425,735, motor  154  may be fixedly coupled to horizontal skid  156  at a motor mount surface  158  of horizontal skid  156 . Pump  152  may be coupled to horizontal skid  156  by a mount assembly  160 . Mount assembly  160  may include a support  162  (e.g., a fixed support) and clamp assemblies  164  and  166 . Support  162  extends outwardly from the motor mount surface  158  at an axial position  168  lengthwise along horizontal skid  156 . Pump  152  is drivingly coupled to motor  154  through support  162 .  
         [0057]     Alternatively, support  162  may be an external conduit assembly configured for attachment to a pump conduit, such as one of two pump conduits  169  extending from pump  152 . Support  162 , in either the illustrated configuration or as an external conduit assembly, may axially fix pump  152  or may allow axial movement of pump  152  with respect to support  162 . Pump conduits  169  are configured to receive and expel a fluid, or vice versa, as pump  152  operates. For example, pump  152  may displace water, salt water, sewage, chemicals, oil, liquid propane, or other fluids in through one of the pump conduits  169  and out of the other pump conduit  169 . In addition, the temperature of the fluids may vary. For example, some applications may involve pumping hot fluids, while others may involve pumping cold fluids. In addition, the temperature may change during the pumping operation, either from the source of the fluid itself, or possibly due to the heat generated by the operation of pump  152  and/or motor  154 . In addition, temperature may change dramatically due to weather change.  
         [0058]     Pump  152  may have a fixed end  170  and a free end  172 , fixed end  170  being axially fixed at support  162 . Clamp assemblies  164  and  166  may be coupled to horizontal skid at axial positions  174  and  176 , respectively, and preferably generally parallel with support  162 . Clamp assemblies  164  and  166  have base members  178  and  180  and upper clamps  182  and  184 , creating clamping conduits  186  and  188 , respectively, for mounting pump  152  in clamping conduits  186  and  188 .  
         [0059]     Clamp assemblies  164  and  166  may be configured to allow axial movement of pump  152  through clamping conduits  186  and  188 . This axial freedom is intended to reduce stresses and fatigue, and possible mechanical failure, due to vibrations and thermal expansion/contraction of pump  152 . Furthermore, the number and geometry of clamp assemblies may vary depending on the application, size of pump  152 , and other factors.  
         [0060]     Apparatus of the invention may include many optional items. One optional feature of apparatus of the invention is one or more sensors located at the protector  16  to detect the presence of hydrocarbons (or other chemicals of interest) in the internal lubricant fluid  54 . The chemical indicator may communicate its signal to the surface over a fiber optic line, wire line, wireless transmission, and the like. When a certain chemical is detected that would present a safety hazard or possibly damage motor  14  if allowed to reach the motor, the pump may be shut down long before the chemical creates a problem.  
         [0061]     A typical use of apparatus of this invention will be in situations when available pumps on-site are not adequate to meet a required pumping requirement. Production of fluid using coiled tubing or other tubing may become more difficult as a well&#39;s pressure changes at a constant depth, or if the well is drilled deeper than originally planned. In these situations, forcing available pumps to do the pumping job may not only be inefficient, but may be unsafe. Apparatus of the invention may then be employed to solve the problem, particularly if the technicians have the equipment, tools, and know-how to connect two or more different pump stages having different performance characteristics.  
         [0062]     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, no clauses are intended to be in the means-plus-function format allowed by 35 U.S.C. § 112, paragraph 6 unless “means for” is explicitly recited together with an associated function. “Means for” clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.