Patent Publication Number: US-8523542-B2

Title: Pumping device for pumping fluid

Description:
FIELD OF THE INVENTION 
     The invention relates to a pumping device, in particular to a sucker rod pump, and a method for pumping fluid as well as a use of the pumping device. 
     BACKGROUND OF THE INVENTION 
     Sucker rod pumps are used throughout the entire industry and are adapted for pumping various kinds of liquids. These pumps are also very popular in oil well production and cover a large percentage of oil wells on artificial lift worldwide. There are three basic types of constructions like insert pumps, tubing pumps and casing pumps. 
     However, the pump principle is similar for the three different pump types. In such pump devices, in particular in sucker rod pumps, a pump is actuated in a defined depth by the sucker rod string which is hence reciprocated by a beam pumping unit at the surface. The pump is basically composed of a pump plunger that is movably supported in the bore hole and that comprise a travelling valve. At the bottom of the bore hole a pump barrel is installed that includes a standing valve. 
     During an upstroke of the pump, the plunger is lifted together with the entire column of liquid that is gathered in the bore hole above the plunger. The travelling valve at the lower end of the pump plunger is therefore closed and hinders the liquid column to flow back at the bottom of the bore hole. At the same time the standing valve of the pump barrel is open and allows fluid to fill the pump. 
     During a downstroke the standing valve of the pump is closed while at the same time the travelling valve opens in order to make all the fluid in the pump flowing through the plunger above into a tubing string. 
     Thus, the sucker rod string is under tension during the upstroke due to the lifting of the plunger and thus the lifting of the fluid. During the downstroke, the plunger is pushed downwards by the self weight of a sucker rod and therefore the sucker rod is under compression. Due to this compression of the sucker rods, string buckling of the sucker rods may be caused which results in higher friction and wear of the surrounding tubing so that eventually the entire production from the well may be disturbed. 
     U.S. Pat. No. 4,049,365 discloses an oil well pump with plunger pull-down and descending assembly. One embodiment involves a tension member that extends downwardly below the plunger so that this tension member keeps the plunger under tension without applying compressive force to the pump rod or sucker rod. An embodiment of the pump provides a weight attached to the bottom of the plunger. 
     OBJECT AND SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an efficient pumping device. 
     In order to achieve the object defined above, a pump device and a method for pumping fluids as well as a method of using the device for pumping fluid according to the independent claims are provided. 
     According to an exemplary embodiment of the invention, a pumping device (such a sucker rod pump) for pumping fluid (such as oil) is provided. The pumping device comprises a force transmitting element, a tension unit coupled to the force transmitting element and a seal element. The force transmitting element is adapted for transferring an upstroke (that is an upward motion) and a downstroke (that is a downward motion) to a pump plunger for pumping fluid. The tension unit is adapted for applying a tension force (which may be directed downwardly) to the force transmitting element for keeping the force transmitting element under tension during the upstroke and during the downstroke. The seal element is adapted for sealingly preventing (that is disabling) pumping fluid during the downstroke and for enabling pumping fluid during the upstroke. A part of the sealing element is rigidly coupled with (or fixedly connected to) the force transmitting element. 
     According to a further exemplary embodiment, a method for pumping fluid is provided. An upstroke and a downstroke is transferred to a pump plunger for pumping fluid by a force transmitting element. A tension force is applied to the force transmitting element by a tension unit for keeping the force transmitting element under tension during the upstroke and the downstroke. During the downstroke a pumping of fluid is sealingly prevented, and a pumping of fluid is enabled during the upstroke by a seal element. A part of the seal element is rigidly coupled with the force transmitting element. 
     According to a further exemplary embodiment, a use of an above-described device is provided for drainage purposes, oil production, water catchment or geothermic systems, for instance. 
     The term “force transmitting element” may describe an element such as a (stiff solid) rod, a (bendable) rope, a belt or a drive belt, that transmits driving force to a pumping device. 
     The term “seal element” may describe all kinds of known sealing mechanisms, such as ball valves, cylindrical valves, poppet valves, inclined seat valves, pinch valves or plug valves. 
     The term “part of the sealing element” may describe the movable part of a valve, such as the valve piston etc. 
     According to an embodiment of the present invention, an incomplex pumping device as well as a pumping device with a reduced amount of parts is provided. The force transmitting element moves during the upstroke and the downstroke the pump plunger so that the fluid is pumped in a predetermined direction. For instance, during an upstroke, the plunger pushes the fluid on the upper side of the pump plunger and simultaneously sucks the fluid on the opposed side in a bore hole. In contrary, in case of a downstroke the plunger is permeable to fluids, for instance by using a travelling valve, so that the plunger can move downwardly in a first position. Thus, on a bottom of the pumping device the seal element is installed, wherein during the upstroke and the sucking below the plunger, fluid may be passed through the seal element. During the downstroke and the movement of the pump plunger to the first position, the sealing element may be closed. 
     According to the present invention, a part of the seal element is rigidly coupled with the force transmitting element so that a combined system may be provided wherein one and the same movable system provides a sealing ability and an anti-buckling ability. By rigidly adding the part of the seal element to the force transmitting element, the implementation of further sealing elements on the one hand and of further tension units on the other hand may be dispensible. Thus, the system complexity as well as the high amount of parts may be reduced. 
     Further on, by rigidly coupling the part of the seal element with the force transmitting element, the sealing element is automatically synchronized with the movement, respectively the upstroke and downstroke of the force transmitting element, so that no further installation for synchronizing the sealing element are necessary. Thus, a high sealing performance may be provided. 
     According to a further exemplary embodiment, the tension unit comprises a tension mass. Thus, by using a tension mass, a dedicated weight force may be applied to the force transmitting element for keeping the force transmitting element under tension during the upstroke and the downstroke. Thus, due to the weight and gravity of the tension mass, a downwardly oriented tension force may be applied in an easy and incomplex way. Further installations may be omitted. 
     According to a further exemplary embodiment of the present invention, the tension unit comprises a spring unit such as coil spring, a flat spring, or the like. By using a spring unit, the tension unit is independently of a gravity that may be necessary for applying a tension force. Thus, even in inclined boreholes that are not vertically, the spring unit may apply the spring force that may allow providing the tension force to the force transmitting element so that buckling may be provided during a downward motion. During an upward motion, the spring may advantageously contribute to an upwardly oriented force, thereby promoting the upward motion. 
     According to a further exemplary embodiment, the spring unit is an extension spring, wherein the extension spring is adapted for being biased or pre-stressed during the upstroke and a spring tensile force is applied to the force transmitting element during the downstroke. By the movement of the upstroke the extension spring is elongated and thus a spring tension against the upstroke movement will be applied. This spring tension may act as a tension force. Thus, the spring element may be located in a preferred location wherein a spring tensile force may be used as tension force. 
     According to a further exemplary embodiment, the spring unit comprises a compression spring. The compression spring is adapted for being compressed during the upstroke and for applying a spring compressive force during the downstroke. Thus, further options for installing the spring unit may be provided so that the pumping system may be more flexible and thus more installation areas of the spring may be available. 
     According to a further exemplary embodiment, the tension unit comprises a hydraulic unit for applying the tension force to the force transmitting element for keeping the force transmitting element under tension during the upstroke and the downstroke. Additionally or alternatively to the tension mass and/or the spring unit, also hydraulic units for applying the tension force may be provided. Thus, by using a hydraulic unit, the tension force may be changed and adjusted by changing a hydraulic pressure so that a variable tension force may be applied. Further on, as hydraulic medium in the hydraulic unit, the pump fluid itself may be used. As an alternative to the hydraulic unit, also pneumatic units may be applied. 
     According to a further exemplary embodiment, the pump device further comprises the pump plunger. The tension unit is adapted to transfer a weight force of the fluid to an upper surface of the pump plunger in such a way that by use of the weight force the force transmitting element is kept under tension. Thus, the gravity of a column of fluid that is located above the pump plunger may be used in order to provide a tension force. Thus, the need for further installation elements for applying a tension force may be reduced. 
     According to a further exemplary embodiment, the force transmitting element comprises a tension rod. The tension rod is adapted for transferring the tension force from the tension unit to the force transmitting element. The tension rod may connect the force transmitting element and the tension unit over a certain distance. Thus, the installation locations of the force transmitting element and the tension unit may differ. Therewith, restrictions due to the design of the pump device may be obsolete. 
     According to a further exemplary embodiment, the device further comprises a pump barrel with a duct. The duct is adapted for connecting a fluid reservoir with the pump barrel. The part of seal element is adapted for opening the duct during the upstroke and for sealing the duct during the downstroke. The pump barrel is adapted for being filled with a fluid during the upstroke and for being discharged during the downstroke. Thus, by the use of a pump barrel into which for instance the pump plunger may be movably supported, a defined pump volume for the fuel is provided. Further on, the pump barrel provides a separation from the pump device to the fluid reservoir, such as the oil field. The pump barrel comprises the duct through which the pumped fluids may be pumped in the pump barrel during the upstroke. The duct may further be provided with filters for filtering the fluid or may also be variable in its diameter for controlling the amount of fluid and the fluid flow respectively. 
     According to a further exemplary embodiment of the present invention, the tension unit is located below the pump barrel in a vertical direction. Thus, the tension unit may be located external of the pumping process, so that the tension unit is not exposed to wear or aggressive fluids and corrosion, respectively. 
     According to a further exemplary embodiment, the seal element is adapted for guiding the force transmitting element. Thus, further stabilization and guidance of the force transmitting element may be provided, if the seal element further acts as bush bearing, for instance. The seal element may therefore comprise a valve seat into which the part of the seal element or the force transmitting element may be movably supported over a certain length. Thus, also horizontal or other directions besides the vertical moving direction may be possible for the force transmitting element, without touching the walls of the pumping device or without to wedge during an upstroke or a downstroke. 
     According to a further exemplary embodiment, the seal element comprises a cylindrical valve. The cylindrical valve improves the guidance of the force transmitting element or the tension rod. By using the cylindrical valve, it may be possible to guide the force transmitting element or the tension rod through the centre of a valve piston of the cylindrical valve. The valve piston may be the part of the seal element that is rigidly coupled with the force transmitting element to follow any motion of the force transmitting element. The valve piston may be moved according to the upstroke and downstroke and thus being lifted from a valve seat or pressed into the valve seat of the cylindrical valve. The valve seat may be formed in a hole provided in a central portion of a disk or plate which is installed spatially fixed in the pumping device. The force transmitting element may then extend through the hole and may reciprocate to alternatingly open or close the valve, thereby alternatingly enabling or disabling pumping. Thus, the cylindrical valve comprises firstly a mechanical guiding ability of the moving force transmitting element and secondly a sealing ability of the pumping device. Thus, further installations between the cylindrical valve, such as further ducts or further valves in particular ball valves, may be prevented. Thus, by using one cylindrical valve, no further installation elements may be necessary for providing sealing ability and anti-buckling abilities. Further on, in comparison to ball type valves, the cylindrical valve may enable a conduit for the force transmitting element or the tension rod. However, alternative valve geometries are possible as well. 
     According to a further exemplary embodiment, the pumping device further comprises a control unit such as a microprocessor or a CPU (central processing device). The control unit may be adapted for controlling a flow of the fluid. The control unit may be adapted to control the sealing element in such a way, that a predetermined flow of the fluid, respectively a predetermined flow rate may be provided and adjusted, without being dependent on the downstroke or upstroke movement of the force transmitting element. Thus, stress for the force transmitting element due to a high amount of fluid, respectively due to a high weight of the pumped fluid may be prevented, so that damages of the pump system may be prevented. 
     According to a further exemplary embodiment, the fluid may be crude oil, gas or water. The term “fluid” may denote any liquid and/or gaseous substance, optionally comprising also solid particles. 
     According to a further exemplary embodiment, the force transmitting element is selected from one of the group consisting of tension rod strings and pull ropes. Besides the use of tension rod strings (that is solid rods, for instance made of a metallic material), also pull ropes (changing shape upon application of small compression forces) are possible, wherein a pull rope is adapted for pulling the force transmitting element in such a way that a tension force may always be provided to the force transmitting element during the upstroke and the downstroke to prevent bending of the rope. 
     Because of the above-described tension unit, the entire system is under tension any time and therefore buckling and all the resulting problems coming along with this phenomenon are eliminated. By using in particular the exemplary embodiments there is no restriction in terms of media composition, dimension and borehole trajectory. 
     The above-described pumping device may be used for drainage purposes, oil protection, water catchment and geothermic systems. Also gas pumping may be possible. 
     The exemplary embodiments for the pumping device may be also provided to the method and vice versa. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited: 
         FIG. 1  illustrates a sucker rod pumping system; 
         FIG. 2  illustrates a schematical view of a conventional pumping system of a sucker rod pump; 
         FIG. 3  illustrates a schematical view of an exemplary embodiment of a pumping device according to the present invention; 
         FIG. 4   a ,  4   b  illustrate a schematical view of a seal element according to an exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The illustrations in the drawings are schematical. In different drawings, similar or identical elements are provided with the same reference signs. 
       FIG. 3  illustrates a pumping device  1  according to an exemplary embodiment of the present invention. 
     The pumping device  1  is shown in an upstroke status (left-hand side) and a downstroke status (right-hand side). 
     The pumping device  1  comprises a force transmitting element  2 , a tension unit  3  coupled to the force transmitting element  2  and a seal element  10 . The force transmitting element  2  is adapted for transferring an upstroke force and a downstroke force to a pump plunger  5  for pumping fluid  12 , namely crude oil. A tension unit  3  is adapted for applying or superpositioning a tension force F to the force transmitting element  2  for keeping the force transmitting element  2  under tension during both the upstroke and the downstroke. The seal element  10  is adapted for sealing for preventing pumping fluid  12  during the downstroke, and for enabling pumping fluid during the upstroke. A part  16  of the seal element  10  is rigidly coupled with the force transmitting element  2 . 
     A pumping principle of a sucker rod pump  1  is illustrated in  FIG. 1 . A prime mover  17  drives the pump plunger  5  and transmits the driving force by the force transmitting element  2 . In  FIG. 1 , the force transmitting element  2  is a sucker rod. The pump plunger  5  is movably supported in the pump barrel  9 . Further on, the pump plunger  5  comprises a travelling valve  11  that is able to pass fluid  12  during a down movement respectively the downstroke of the pump plunger  5  and is closed during an upward movement respectively an upstroke of the pump plunger  5 . Thus, fluid  12  may be pumped. 
       FIG. 2  illustrates a schematical view of a conventional sucker rod pump  1  during an upstroke (left-hand side) and a downstroke (right-hand side) of the pump plunger  5 . During the upstroke, shown on the left side of  FIG. 2 , the pump plunger  5  is moved upwardly such that the pump plunger  5  pumps fluid  12  on the upper surface  7  of the pump plunger  5  and sucks during the upward movement fluid  12  into the pump barrel  9 . Thus, the seal element  10  is open and the travelling valve  11  is closed. 
     During the downstroke, shown on the right side of  FIG. 2 , the travelling valve  11  is opened and the seal element  10  is closed. Thus, during a downstroke or a downward movement of the pump plunger  5  in the pump barrel  9  the fluid  12  passes the pump plunger  5  through the opened travelling valve  11  so that the fluid  12  is located above the upper surface  7  of the pump plunger  5 . Then, again during the upstroke, the fluid  12  is pumped upwardly, because the travelling valve  11  is closed again and further fluid  12  is sucked into the pump barrel  9 . 
     As illustrated in  FIG. 2 , during the downstroke a compressive force acts on the force transmitting element  2 . Therefore, compression buckling may occur such that the force transmitting element  2  may burst or may contact the sidewalls during the downstroke movement. In the latter scenario, wear of all movable parts may occur such that these parts have to be exchanged only after a short pumping period. 
       FIG. 3  illustrates an exemplary embodiment of a pumping device  1  according to the present invention. 
     As illustrated in  FIG. 3 , a tension unit  3  may apply a tension force F to the force transmitting element  2  for keeping the force transmitting element  2  under tension during the upstroke, shown on the left side of  FIG. 3 , and the downstroke, shown on the right side of  FIG. 3 . 
     In one exemplary embodiment, the tension force F may be applied by a tension mass  6  of the tension unit  3 . Therewith, the weight  6  has to be connected to the pump plunger  5  or the force transmitting element  2 , for instance by a tension rod  8 . In order to provide an open status of the seal element  10  during the upstroke, a part  16  of the seal element  10  is rigidly coupled with the force transmitting element  2  or the tension rod  8 . The part  16  of a seal element  10  may comprise or consist of a valve piston, for instance. 
     Thus, by the rigid connection of the part  16  of the seal element  10  to the force transmitting element  2  or the tension rod  8 , the opening state and the closed state of the seal element  10  is automatically synchronized with the upstroke phase and the downstroke phase of the pump device  1 . No further regulation elements may be necessary, and the provision of an anti-buckling feature is simplified. 
     Additionally or alternatively to the provision of the tension mass  6 , the tension force F may be applied to the force transmitting element  2  by a spring unit  4 . If the spring unit  4  is located for being pre-tensioned during the upstroke, an extension spring may be installed. Thus, during the downstroke, the extension spring applies a tension force F during the downstroke. 
     If the spring unit  4  is located at a location where the spring is elongated during the upstroke a compression spring may be installed such that during the downstroke a compressive force provides the tension force F. 
     Referring to  FIG. 3 , also a hydraulic unit  18  may be installed in order to provide a tension force F to the force transmitting element  2 . The hydraulic unit  18  may comprise a hydraulic cylinder that is telescopically extendable in the direction of the upstroke or the downstroke. Therewith, by controlling the hydraulic pressure, a desirable tension force F may be applied. Beneath the hydraulic cylinder  18 , also pneumatical installations may be applied in order to act as hydraulic unit  18 . 
     Further on, it is possible to provide the tension unit  3  for using the pumped fluid  12  on the upper surface  7  of the pump plunger  5  for applying a tension force F to the force transmitting element  2 . By keeping the pump fluid  12  on the upper surface  7  of the pump plunger  5  during the downstroke, the weight force FW generated due to the mass of the fluid  12  applies a tension force F to the force transmitting element  2 . Thus, no further complex installations may be needed. 
       FIG. 3 , as well as  FIG. 4   a  and  FIG. 4   b , shows also a possibility to guide the force transmitting element  2 , respectively the tension rod  8  of the force transmitting element  2  through the part  16  of the seal element  10 . The part  16  of the seal element  10  may act as a seal piston and may close the seal element  10  by a connection to a valve seat  13 . Thus, the movement of the force transmitting element  2  and the part  16  of the seal element  10  open and close a duct  14  of the seal element  10  in order to control a fluid flow of the pump device  1 . The tension unit  3  may be located below the seal element  10  respectively the pump barrel  9  in vertical direction. Thus, the seal element  10  respectively the part  16  of the seal element  10  may guide the force transmitting element  2  or the tension rod  8 . Thus, also in inclined boreholes the pump device  1  according to the present invention is applicable. In inclined boreholes, because of the guiding ability of the duct  14  in the seal element  10 , the force transmitting element  2  is not in contact with the sidewalls due to gravity. 
     For a better guiding ability the seal elements  10  may consist of a cylindrical valve, as illustrated in more detail in  FIG. 4   a ,  4   b . Thus, the part  16  of the seal element  10  may consist of a valve piston and thus comprise an elongated cylindrical surface that can be in slidable contact with the force transmitting element  2 . Further on, in comparison to ball type valves, the cylindrical valve may enable a conduit for the force transmitting element  2  or the tension rod  8 . 
     Further on, a control unit (not shown) may be installed that opens the seal element  10  in a variable manner. The control unit may flexibly control the opening of the seal element  10  during the upstroke so that a desirable fluid flow during the upstroke into the pump barrel  9  may be adjusted. 
     With the pump device  1  of the present invention a variety of fluids  12  may be pumped such as crude oil, water, thermal water or gas. 
       FIGS. 4   a  and  4   b  illustrate a detailed view of the seal element  10  during an upstroke and a downstroke. The force transmitting element  2  or the tension rod  8  are rigidly connected to the part  16  of the seal element  10 . The part  16  is adapted for being form closed with the sidewalls of the duct  14  in the valve seat respectively the seal element  10 . During the upstroke, the part  16  is lifted from the valve seat  13 . The lift of the upstroke may be terminated by a seal cage  19 . Due to the form closed contact of the part  16  and the valve seat  13 , a good guiding ability of the force transmitting element  2  may be provided. 
     Finally, it should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parentheses shall not be construed as limiting the claims. The words “comprising” and “comprises”, and the like, do not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice-versa. In a device claim enumerating several means, several of these means may be embodied by one and the same item of software or hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. 
     LIST OF REFERENCE SIGNS 
     
         
           1  pump device 
           2  force transmitting element 
           3  tension unit 
           4  spring unit 
           5  pump plunger 
           6  tension mass 
           7  upper surface of the pump plunger 
           8  tension rod 
           9  pump barrel 
           10  seal element 
           11  traveling valve 
           12  fluid 
           13  valve seat 
           14  duct 
           15  fluid reservoir 
           16  part of the seal element 
           17  prime mover 
           18  hydraulic unit 
           19  seal cage 
         F tension force 
         FW weight force of the fluid