Abstract:
A ventless gas-driven pumping system controlled via a plurality of pneumatic valves and associated switches, for driving a diversity of process pumps at a natural gas well site. The ventless pumping system is readily interconnected with any gas pipeline location and uses flowing well gas and consequent differential pressure to drive a plurality of pumps and related pneumatic controls exclusively using a continuous self-generated air supply. Only self-generated air and no well gas is vented into the atmosphere during pumping operations.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority based upon Provisional U.S. Application Ser. No. 60/015,744 filed Jun. 8, 2005. 
     
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates to pumping systems, and, more particularly, relates to an apparatus and methodology for a gas-driven ventless pumping system that operate process pumps and is controlled by pneumatic valves. 
       BACKGROUND OF THE INVENTION 
       [0003]    Gas-driven pumping systems known in the art commonly use gas-driven process pumps that inherently exhaust substantial amounts of well gas into the atmosphere. Such gaseous emissions into the atmosphere have long been integral to conventionally-designed and operated pumps. Thus, normal well gas pumping operations typically pollute the ambient and engender safety hazards. Moreover, valuable well gas is simultaneously wasted. 
         [0004]    It will also be understood by those skilled in the art that the contemplated applications usually exist at well sites where no electrical power is available. While, under such circumstances, gas-driven pumps are commonly used, operation thereof inherently wastes gas, pollutes the atmosphere, and constitutes hazardous conditions. But, even under circumstances wherein electrical power is available, it would still be more economical and advantageous to use ventless gas-driven pumps contemplated by the present invention rather than to use conventional electric-driven pumps since neither electricity nor gas consumption is prerequisite for sustaining pumping operations 
       SUMMARY OF THE INVENTION 
       [0005]    The ventless gas-driven pumping system taught by the present invention relies upon in situ gas flow and differential pressure to drive the pumping system. It will become evident that embodiments of this pumping system may be readily interconnected with any gas pipeline. For example, an embodiment of the present invention may be interconnected with a gas flow line situated near a natural gas production well. More particularly, as will be appreciated by those skilled in the art, the inlet to this pumping system should be interconnected at an appropriate point in the gas flow line; the outlet from this pumping system should similarly be interconnected back with the flow line at a point of lower pressure than the inlet. 
         [0006]    It will be seen that this in situ pump configuration creates a closed-loop system having differential pressure across the pumping system, thereby providing a prerequisite energy source for driving and operating pumping action. Adopting conventional terminology in the natural gas well art, pipeline gas will be referenced herein as “well gas” and a pipeline will be referenced herein as a “flowline.” 
         [0007]    The ventless gas-driven pumping system of the present invention uses inherent flow characteristics of well gas and concomitant differential pressure thereof to power a drive cylinder and the like. It will be appreciated that the drive cylinder, in turn, drives conventional process pumps such as glycol pumps, chemical pumps and air pumps. As will be hereinafter described, operation of this pumping system is controlled through a series of pneumatic valves and associated switches. 
         [0008]    It is another feature of the present invention that pumping system embodiments generate their own low pressure air supply for actuating a pair of switching valves and a cycling valve. It is a feature and advantage that such embodiments inherently do not vent well gas to the atmosphere. Indeed, being contained within a closed pumping system, the well gas preferably is recycled to the flowline. Accordingly, during normal operation, the instant pumping system vents only air to the ambient. 
         [0009]    Those skilled in the art will recognize that pumping system embodiments of the present invention are therefore “clean machines,” wherein contaminants or the like are not emitted into the atmosphere. Ergo, embodiments taught hereunder may be designated as being “ventless.” Such ventless gas-driven pumping systems replace commonly used gas-driven process pumps that routinely emit significant quantities of well gas into the atmosphere. It should be evident that normal operation of such commonly-used process pumps engender emission of pollutants and contaminants constituting safety and health hazards; and effect substantial waste of valuable well gas. 
         [0010]    It will be understood that this gas-driven pumping protocol usually persists at well sites where there is a paucity of available electrical power. Nevertheless, even under circumstances wherein electrical power is available at well sites, it typically would be more economical to use a ventless gas-driven pumping system contemplated by the present invention than to use a conventional electricity-driven pumping system. Besides the obvious advantageous of not being dependent upon costly electricity for operation, a ventless pumping system avoids wasteful and potentially hazardous emission of well gas. 
         [0011]    These and other objects and features, and advantages of the present invention will become apparent from the following Detailed Description, wherein reference is made to the figures in the accompanying drawings. 
     
     
       IN THE DRAWINGS 
         [0012]    The file of this patent contains at least one drawing executed in color. Copies of this patent with the color drawing ( FIG. 1 ) will be provided by the Patent and Trademark Office upon request and payment of the necessary fee. 
           [0013]      FIG. 1  depicts a schematic diagram of the components and associated functionality of the preferred embodiment of the present invention. 
           [0014]      FIG. 2  depicts a front perspective view of a generalized representative embodiment of the present invention 
           [0015]      FIG. 3  depicts a side perspective view of the embodiment depicted in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIGS. 1-3  collectively depict the pumping system contemplated under the present invention. In particular,  FIG. 1  depicts a schematic of the preferred embodiment of the present invention interconnected with a typical natural gas production well scenario as contemplated hereunder.  FIGS. 2 and 3  generally depict a representative physical configuration of the various components that comprise a pumping system embodiment. It should be understood, of course, that arrangements of physical components and the like vary substantially as a function of well site logistics, diversity of components selected to constitute an embodiment, and process pumps being driven. Accordingly, other embodiments hereof may indeed have components configured and arranged differently from that which is depicted in  FIGS. 2 and 3 . Notwithstanding, the teachings of the present invention should be clearly understood from the schematic representation shown in  FIG. 1 . 
         [0017]    As will become clear to those skilled in the art, interdependent flow paths or circuits are shown for each of well gas, glycol, air, chemical, and gas-operated diaphragm (“AOD”) pump. It will be understood that AOD pump may be operated by air or another suitable gas. Each of these circuits is rendered in a different color to clearly identify its functionality and its interrelationship with the other circuits that afford synergy to the embodiments of the ventless pumping systems contemplated herein. The well gas circuit is colored red; the glycol circuit is colored blue; the air supply circuit is colored green; the chemical circuit is colored lavender; and the AOD supply circuit is colored brown. 
         [0018]    Drive cylinder  100  operates a dual-acting glycol piston pump  200  and a beam chemical injection pump  400 . In a manner known in the art, glycol pump  100  is used to circulate hot glycol through heat exchanger tubes in a process loop including the wellhead, a gas-liquid separator, and a water storage tank (to prevent freezing); and then, the hot glycol is circulated to the glycol heater and recycled back to the glycol pump  200 . The chemical injection pump  400  is used to pump methanol or the like down the well annulus to help prevent formation of hydrates in the well. 
         [0019]    As will become evident to those skilled in the art, prerequisite differential pressure for operating an embodiment of the instant pumping system is generated by differential pressure control valve  190 . More particularly, differential pressure (“ΔP”) control valve  190  is preferably interconnected with flowline  180  in order to generate a pressure differential between well gas inlet  140  and well gas outlet  145 . It will be understood that the pressure at well gas inlet  140  is higher than the pressure at well gas outlet  145 . 
         [0020]    Pneumatically-controlled cycling valve  310  supplies higher pressure inlet well gas first to one side of dual-acting drive cylinder  100 , thereby pushing drive cylinder piston  105  in one direction while simultaneously exhausting lower pressure well gas out of the other, opposite side thereof to well gas outlet  145 , and then, in turn, back into flowline  180 . 
         [0021]    It should be understood that, when drive cylinder piston  105  reaches the end of its stroke, drive cylinder piston rod  110  mechanically actuates a pneumatic switching valve of pair of pneumatic switching valves  305  which, in turn, actuates cycling valve  310 . The higher pressure inlet well gas is then switched to flow to the other, opposite side of drive cylinder  100 , thereby pushing drive cylinder piston  105  back in the opposite direction. Simultaneously, lower pressure well gas is expelled out the other side of drive cylinder  100  to well gas outlet  145  and then back into flowline  180 . 
         [0022]    It will be appreciated that, when drive cylinder piston  105  reaches the end of its current stroke, drive cylinder piston rod  110  mechanically actuates another pneumatic switching valve of pair of pneumatic switching valves  305 . The present invention contemplates that this valve-switching aspect of each pumping cycle continually repeats itself during pumping operations as herein described. 
         [0023]    Referring now collectively to  FIGS. 1-3 , it will be observed that pair of drive cylinder piston rods  110  extend from both ends of drive cylinder  100 . Pair of piston rods  110  mechanically drive a plurality of process pumps—illustrated with glycol pump  200  and chemical injection pump  400 . In this exemplary embodiment, in particular, glycol pump  200  corresponds to a conventional dual acting piston pump having four check valves  205 ; and chemical injection pump  400  corresponds to a conventional beam actuated pump. As will be understood by those skilled in the art, piston rods are inherently sealed within its cylinder commensurate with its normal performance. The prerequisite drive cylinder force available to operate this plurality of pumps may be calculated by the well known formula shown in equation 1: 
         [0000]        F =(Δ P×A )·  Friction (1) 
         [0024]    wherein F corresponds to the drive cylinder force; ΔP corresponds to the differential pressure; A corresponds to the area of the piston less the concentric area of the piston rod; and Friction corresponds to the internal friction within the drive cylinder. Those skilled in the art will understand that this contemplated pressure differential varies from one gas well application to another; moreover, friction considerations are empirically guesstimated in the field. 
         [0025]    The pumping system of the present invention is controlled by pneumatic valves and switches. It will be appreciated that embodiments of the instant pumping system self-generate low-pressure air supply for actuating pneumatic valves and switches. Thus, drive cylinder  100  drives air cylinder  300  which supplies air to air bottle  315  or other suitable container, and interconnected air lines. The air pressure within air bottle  315  is regulated by adjustable vent valve  320 . 
         [0026]    According to the present invention, at pumping system start-up, a very small, virtually insignificant amount of low-pressure inlet well gas is supplied to the control system through gas regulator  150  and shuttle valve  325 . This small amount of low-pressure inlet well gas is necessary only for operating pair of switching valves  305  and cycling valve  310  for a short period of time in order to begin the stroking of drive cylinder  100  which drives air cylinder  300  which, in turn, supplies air to the to air bottle or reservoir  315  and interconnected air lines. 
         [0027]    To illustrate the infinitesimal amount of low-pressure well gas that is actually consumed and vented during this limited start-up phase of pumping system operation, it has empirically been found that a mere 30-40 cubic inches of gas is consumed which is approximately 2% of one cubic foot thereof which is vented into the atmosphere. It will be appreciated that as one or two cylinder drive strokes are effectuated as herein described, approximately only a few seconds have elapsed. Only intended to be a representative illustration, if typical drive stroke frequency were assumed to be about 10 strokes per minute, taken as being in the range of 8-15 strokes per minute, then there would be one stroke nominally about every 6 seconds. Ergo, system startup as contemplated hereunder has a very short duration with an infinitesimal loss of well gas. It should be evident that this start-up phase has no significant impact upon the ventless aspect of the present invention. 
         [0028]    It will be understood that the air pressure inside air container  315  is preferably regulated by adjustable vent valve  320 . It has been found that adjustable vent valve  320  should preferably be set to sustain the air pressure in air bottle  315  in the range of about 10-15 psi. Similarly, gas regulator  150  should preferably be set to supply well gas in the range of about 5-10 psi. Then, when the air supply in air bottle  315  reaches a pressure slightly higher than the pressure of the well gas coming from gas regulator  150 —preferably after approximately one or two drive cylinder strokes and enough prerequisite air has been pumped-shuttle valve  325  switches off the well gas from gas regulator  150  and then switches on the supply air from air bottle  315 . 
         [0029]    It should be evident that the pumping system embodiment then continues operating using only its self-generated air supply to actuate pair of switching valves  305  and cycling valve  310 . Therefore, during start-up, unlike conventional pumping systems known in the art, embodiments taught by the present invention vent a very small amount of low pressure well gas to the ambient. But, after a short start-up period of approximately one drive cylinder stroke, pumping system embodiments hereof use only self-generated air to actuate pair of switching valves  305  and cycling valve  310 . Accordingly, during normal operations, a pumping system embodiment vents only air and no well gas to the atmosphere; hence, the present invention contemplates and teaches a substantially “ventless” gas-driven pumping system. 
         [0030]    It has been found that, if gas flow from a well has been interrupted, differential pressure control valve  190  may be unable to generate a sufficient differential pressure between well gas inlet  140  and well gas outlet  145  prerequisite to actuate drive cylinder  100 . For instance, an interruption in the gas flow from the well may be due to the well loading-up with water, plugging-up due to hydrate formation, valve closure or otherwise. To cope with such flow interruptions, ventless gas driven pumping system embodiments should preferably be configured with a backup system affording continued pumping of liquid or gas product, e.g., glycol, until such gas flow interruption has been remedied. 
         [0031]    Thus, for an embodiment pumping glycol, a backup system of the present invention would comprise glycol pressure switch  500  and gas-operated diaphragm pump (“AOD” pump)  510 . As will be appreciated by those skilled in the art, when there is an interruption in well gas flow, contemplated ventless gas-driven pumping system embodiments will ordinarily be unable to generate adequate glycol discharge pressure. However, if glycol pressure switch  500  detects a low glycol discharge pressure condition, indicative of a gas flow interruption, it will switch on low pressure AOD supply gas whereupon AOD pump  510  will be activated and begin pumping glycol. Then, when normal well gas flow resumes, ventless gas-driven pumping system embodiments will begin generating adequate glycol discharge pressure, and the backup system will no longer need to be activated. Accordingly, glycol pressure switch  500  will then switch off the low pressure AOD supply gas to AOD pump  510 . And, the ventless gas-driven pumping system will resume normal operation as contemplated hereunder. 
         [0032]    It will be appreciated by those skilled in the art that a ventless gas-driven pumping system contemplated hereunder can be connected into any gas pipeline in any flowing process gas stream. Such a ventless pumping system affords a convenient and efficient replacement that eliminates pumping systems that inherently exhaust well gas to the atmosphere. As a result of this pumping system replacement taught by the present invention, wasting of valuable well gas, polluting the atmosphere, and creating safety and health hazards are essentially terminated. It has been found that a common application of such pumping system replacement is especially advantageous at or near natural gas production well sites where electrical power is typically unavailable. 
         [0033]    The natural gas production well applications depicted in  FIGS. 1-3  generally illustrate how the drive cylinder of the present invention operates a dual-acting glycol piston pump and a beam chemical pump, wherein the glycol pump circulates hot glycol throughout heat exchanger tubes—with process loop including the wellhead, gas-liquid separator, water storage tank, glycol heater, and cycle back to the glycol pump. The chemical pump is used to pump methanol down the well annulus to help prevent formation of hydrates in the well. 
         [0034]    Other potential applications of the present invention include interconnection with any gas processing facility to enable replacement of gas-drive pumps and/or to enable replacement of air supply for pneumatic controllers, actuators and level controllers. The ventless gas driven pumping system pays for itself severalfold. As a first example, since the ventless gas-driven pumping system fundamentally does not vent valuable well gas, there is a savings equal to the value of the well gas that would be currently vented to atmosphere by conventional gas-driven pumps. As a second example, since a ventless gas-driven pumping system does not vent well gas pollutants or the like, there is an environmental beneficial value that can be calculated based upon particular circumstances. 
         [0035]    Indeed, it will be readily appreciated that such environmental value not only transcends affording tangible benefits—as in the instance of carbon credits—but also affords intangible benefits—as in the instance of substantially enhanced good will and concomitant public image. Since ventless gas-driven pumping system embodiments inherently do not vent flammable and harmful well gas, such pumping sites are significantly safer and healthier than conventional gas well sites. 
         [0036]    Other variations and modifications will, of course, become apparent from a consideration of the apparatus and concomitant methodology hereinbefore described and depicted. Accordingly, it should be clearly understood that the present invention is not intended to be limited by the particular features and structures hereinbefore described and depicted in the accompanying drawings, but that the present invention is to be measured by the scope of the appended claims herein.