Abstract:
Systems and methods for increasing the rate of evaporation for a liquid. Systems and methods include use of evaporation membranes having large surface areas exposed to the ambient environment.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to improving evaporation, and more particularly to improving rates of evaporation for water produced during the production stage of an oil well or gas well 
     2. Background and Related Art 
     Produced water is water trapped in underground formations that is brought to the surface along with oil or gas during the production state of an oil or gas well. Produced water is by far the largest volume byproduct or waste stream associated with oil and gas production. As part of the process of producing oil and natural gas, operators also must manage large quantities of production water. The quantity of produced water generated each year is substantial and therefore represents a significant component in the cost of producing oil and gas. 
     When hydrocarbons are produced, they are brought to the surface as a produced fluid mixture. The composition of this produced fluid is dependent upon whether crude oil or natural gas is being produced and generally includes a mixture of either liquid or gaseous hydrocarbons, produced water, dissolved or suspended solids, produced solids such as sand or silt, and injected fluids and additives that may have been placed in the formation as a result of exploration and production activities. Produced water may also include condensed water which includes higher contents of low molecular-weight aromatic hydrocarbons such as benzene, toluene, ethylbenzene, xylene and other volatile organic compounds. 
     Soluble organics are not easily removed from produced water. Accordingly, the cost for treating or recycling produced water is significant. A viable, yet costly alternative to treating produced water is to safely dispose of the produced water. As produced water is toxic, caution must be taken when disposing of produced water to ensure that the contaminated water does not interfere with vegetation or animal life. Further, caution must be taken to ensure that produced water does not contaminate freshwater wells or aquifers that supply water to humans, animals and/or vegetation. 
     Thus, it would be an improvement in the art to augment or even replace current techniques with other techniques. 
     SUMMARY OF THE INVENTION 
     The present invention relates generally to improving evaporation, and more particularly to improving rates of evaporation for water produced during the production stage of an oil well or gas well. 
     Some implementations of the present invention provide an evaporation device having an evaporation membrane which is partially disposed in a liquid, wherein the evaporation membrane is cycled through the liquid via a roller or other means for cycling the membrane. In some aspects of the invention, a motor is used to drive a roller that is in contact with a portion of the membrane, wherein the roller rotates or otherwise passes a portion of the membrane through the liquid in a continuous manner. 
     Some implementations further include a float that monitors the height of a liquid in a reservoir or container of an evaporation system or device. In some aspects of the invention, the float is operably coupled to a flow control valve, wherein the height of the float opens or closes the flow control valve to permit or prevent flow of fluid into the container or onto the membrane. 
     Some aspects of the present invention provide a disk membrane. Other aspects of the invention provide a tubular membrane. Further still, some aspects of the invention provide a loop or belt membrane. 
     Some configurations of the present invention utilize a plurality of rollers to move the membrane in a desired path and/or direction. Some membranes of the invention include a support tube or membrane support which defines and maintains an outer shape or circumference of the membrane. Some aspects of the invention further include a retainer or retaining mechanism to maintain a position of the membrane within the evaporation device. 
     Some implementations of the invention provide a method for increasing the rate of evaporation for a liquid, the method including steps for 1) providing a membrane having a first surface area and a second surface area; 2) providing a container having an opening; 3) positioning a first portion of the membrane in the container via the opening; 4) positioning a second portion of the membrane in an environment that is external to the container; 5) placing a liquid in the container such that the first portion of the membrane is submerged in the liquid; 6) replacing the first portion of the membrane with the second portion of the membrane; and 7) replacing the second portion of the membrane with the first portion of the membrane, wherein the second portion of the membrane is submerged in the liquid. Some methods further include a step for positioning a roller in the container and in contact with the membrane, wherein the roller repositions the first and second portions of the membrane within the container. Methods of the present invention further include a step for providing a plurality of rollers, wherein the plurality of rollers are in contact with the membrane, and wherein at least some of the rollers are positioned within the container. 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1A  shows a plan side view of an evaporation device incorporating a disk membrane in accordance with a representative embodiment of the present invention; 
         FIG. 1B  shows a detailed view of a membrane retaining mechanism of an evaporation device in accordance with a representative embodiment of the present invention; 
         FIG. 2  shows a plan end view of an evaporation device comprising a plurality of membranes in accordance with a representative embodiment of the present invention; 
         FIG. 3  shows a plan top view of an oil well site and evaporation station in accordance with a representative embodiment of the present invention; 
         FIG. 4  shows a perspective view of an evaporation device incorporating a tubular membrane in accordance with a representative embodiment of the present invention; 
         FIG. 5  shows a plan side view of an evaporation device incorporating a belt membrane in accordance with a representative embodiment of the present invention; 
         FIG. 6  shows a plan side view of an evaporation device incorporating a belt membrane in accordance with a representative embodiment of the present invention; 
         FIG. 7  shows a plan side view of an evaporation device incorporating a belt membrane in accordance with a representative embodiment of the present invention; and 
         FIG. 8  shows a plan end view of the evaporation device shown in  FIG. 7  in accordance with a representative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A description of embodiments of the present invention will now be given with reference to the Figures. It is expected that the present invention may take many other forms and shapes, hence the following disclosure is intended to be illustrative and not limiting, and the scope of the invention should be determined by reference to the appended claims. 
     Various embodiments of the present invention may be utilized to assist in evaporating a liquid. For example, some embodiments of the present invention are utilized to evaporate produced water. Other embodiments of the present invention are utilized to evaporate water containing a desired solute, such as sodium chloride or other desired minerals. Further, in some embodiments the present invention is utilized to increase the rate of evaporation over a presently available method or evaporation system. 
     Some implementations of the present invention comprise a single, stand-alone unit. In other embodiments, a plurality of single, stand-alone evaporation units are interconnected to provide a modular evaporation unit. Thus, some embodiments of the present invention provide a dynamic system of evaporation units, wherein multiple evaporation units may be interconnected to increase the overall rate of evaporation. 
     Referring now to  FIG. 1A , an evaporation device  10  is shown. In general, evaporation device  10  comprises a membrane  20  which is rotationally suspended within a rack or frame  12 , wherein a portion  22  of membrane  20  is positioned within a container  30 . Container  30  comprises a fluid-tight container having an opening  32  through which portion  22  of membrane  20  is inserted. In some embodiments, container  30  is a collection pool. In other embodiments, container  30  is a fluid reservoir. 
     Container  30  further comprises a volume which holds liquid  34 . In some embodiments, the level of height of liquid  34  in container  30  is configured such that portion  22  of membrane  20  is submerged in liquid  34 . In other embodiments, container  30  is merely positioned under membrane  20  so as to catch excess liquid from membrane  20 . 
     Container  30  further includes drive rollers  36 . Rollers  36  are positioned such that the rollers support an outer edge  24  of membrane  20 . In some embodiments, rollers  36  are positioned within container  30 , wherein the placement and height of rollers  36  determines the depth of portion  22  of membrane  20  within container  30 . In other embodiments, rollers  36  are positioned external to container  30  (not shown). 
     Membrane  20  is driven or rotated within container  30  via a motor  40  which is operably connected to at least one roller  36  via a drive belt  42 . Motor  40  drives or rotates drive belt  42  which rotates roller  36 , thereby rotating membrane  20  at a desired speed. In some embodiments, a desired rotation speed of membrane  20  is selected so as to enable evaporation of liquids trapped or otherwise associated with the portions of membrane  20  external to container  30  before those exposed portions are submerged in liquid  34  of container  30 . 
     In some embodiments, membrane  20  further comprises a membrane support tube  26  which is supported by drive rollers  36 . Support tube  26  generally comprises a rigid or semi-rigid material over which membrane  20  is stretched. For example, in some embodiments support tube  26  comprises polyvinylchloride tubing. Support tube  26  maintains a desired shape of membrane  20 , thereby enabling rollers  36  to rotate membrane  20  without distorting or otherwise disturbing the shape or function of membrane  20 . 
     In some embodiments, membrane  20  comprises a disk of stretched evaporation membrane or material. For example, in some embodiments membrane  20  comprises a webbing or knit material having interstices which hold liquid  34  via capillary action. In other embodiments, membrane  20  comprises an impermeable material having a hydrophilic coating, wherein liquid  34  is attracted to membrane  20 , thereby forming a thin layer of liquid  34  over the surface of membrane  20 . Further, in some embodiments membrane  20  comprises a webbing or knit material that is further coated with a hydrophilic coating material. 
     Frame  12  may include any material, size, and/or shape necessary to maintain the position of membrane  20  within container  30 . For example, in some embodiments frame  12  comprises square steel tubing. Frame  12  may further include a motor mount (not shown) for supporting motor  40 . In some embodiments, frame  12  further supports a tube  44  which distributes liquid  34  to membrane  20 . For example, in some embodiments tube  44  is connected to a fluid pump and a liquid source (not shown) wherein the liquid is pumped through tube  44  onto membrane  20 . The distributed fluid is dispersed over membrane  20  by gravity as membrane  20  is rotated via motor  40  and rollers  36 . In some embodiments, container  30  further comprises a float (not shown) which is connected to a flow control valve, wherein when the fluid  34  in container  30  reaches a maximum height, the float closes the flow control valve which in turn stops flow of fluid  34  through tube  44 . Following evaporation of fluid  34  from membrane  20  and container  30 , the fluid height in container  30  decreases thereby opening the flow control valve and resuming flow of fluid through tube  44 . 
     Referring now to  FIG. 1B , a detailed cross-section view of membrane  20  and roller  36  is shown. In some embodiments, device  10  further comprises a retainer  38  for preventing undesirable displacement of membrane  20  from rollers  36 . For example, in some embodiments membrane  20  comprises a lightweight material. As such, membrane  20  and support tube  26  are lightweight and may be disturbed or displaced by wind gusts or aberrant weather events. Accordingly, in some embodiments it is desirable to provide means for retaining a desired position of membrane  20  within container  30 . 
     Retainer  38  may comprise any features, size, shape or materials necessary to maintain the position of membrane  20 . For example, in some embodiments retainer  38  comprises a roller  50  having a contoured surface  52  for compatibly receiving and retaining an interior surface of support tube  26 . Roller  50  further comprises an arm  54  which maintains the desired position of roller  50 . In some embodiments, arm  54  is secured to a portion of frame  12 . In other embodiments, arm  54  is secured to a portion of container  30 . 
     Referring now to  FIG. 2 , an end view of an evaporation device  100  is shown which incorporates a plurality of parallel evaporation membranes  120 . In some embodiments, frame  12 , container  30  and rollers  36  are configured to support a plurality of evaporation membranes  120 . In general, the dimensions of frame  12 , container  30  and rollers  36  are lengthened to provide additional space for membranes  120 . As such, a single motor  40  and drive belt  42  are sufficient to rotate the membranes  120  via roller  36 . 
     In some embodiments, additional tubes  44  are provided for each membrane  120  thereby facilitating delivery of liquid  34  to membranes  120 . In other embodiments, membrane cleaners  46  are further provided. Membrane cleaners are generally provided to assist in removing accumulated debris and solute from the surface of the membrane  120 . In some embodiments, membrane cleaner  46  comprise a scraper that contacts a surface of the membrane to remove accumulated solids and/or residues which result from the evaporation process. In some embodiments, membrane cleaner  46  comprises a flexing pin which contacts membrane  120  to alter the membrane&#39;s planar configuration, thereby disrupting adhesion of solids or residues with the membrane  120 . 
     In some embodiments, the devices of the present invention are utilized at an oil well site  130  to facilitate evaporation of produced water in connection with a wellhead  140 , as shown in  FIG. 3 . In general, an oil well site  130  comprises a wellhead  140  and various other well producing machinery, such as a heater unit  142  and a separation tank  144 . In some embodiments, materials lifted from the well are heated and then pumped into a separation tank  144 , where the various components of the lifted material separate based upon their densities. Volatile components are separated as gases and removed from the separation tank  144  via a gas line  150 . Liquid hydrocarbon components, such as oil, are removed from the separation tank  144  via an oil loading spicket  152 . The remaining component is produced water which is removed from the separation tank  144  via a water line  154  and stored in a water tank  156 . 
     In some embodiments, produced water within water tank  156  is heated prior to be distributed to evaporation device  200 . This process is especially useful when ambient temperatures are below freezing. Where evaporation device  200  is used in freezing or below freezing ambient conditions, some embodiments of the present invention incorporate heating coils and thermal wraps into evaporation device  200 . Thus, evaporation device  200  may be utilized year round to dispose of produced water. 
     A control valve  160  is inserted between water tank  156  and a water supply line  162 . Water supply line  162  is further in fluid connection with tubes  44  which distribute produced water directly onto membranes  220  of evaporation device  200 . In some embodiments, control valve  160  is further connected to a float in container  30 , wherein the float monitors the height of the produced water in container  30 . When the height of produced water in container  30  exceeds a desired height, control valve  160  is closed thereby halting flow of produced water to membranes  220  via water supply line  162  and tubes  44 , as previously discussed. 
     As can been seen, the number of membranes  220  may be increased or decreased as needed for a specific application. The rate of evaporation is directly proportional to the surface area of the fluid exposed to the ambient environment. Thus, in some embodiments of the present invention the rate of evaporation is increased by increasing the number of evaporation membranes incorporated into the evaporation device. In other embodiments, the rate of evaporation is increased by increasing the surface area of the evaporation membrane or membranes. Further, in some embodiments a plurality of evaporation units or devices are combined to achieve a desired rate of evaporation. Thus, some embodiments of the present invention provide a modular evaporation system which may be dynamically adjusted based upon the user&#39;s needs. 
     Referring now to  FIG. 4 , in some embodiments the evaporation membrane comprises a tubular membrane  320  having a plurality of support tubes  326 . As with previously discussed embodiments, tubular membrane  320  comprises a portion which is submerged in liquid  34 . Tubular membrane is further supported and rotated by rollers  36  (not shown). In this embodiment, the parallel relationship between the planar membrane surface and the liquid  34  ensures complete application of liquid  34  to membrane  320  by merely rotating or passing a portion of membrane  320  through liquid  34  in a continuous manner. As such, distribution of liquid  34  via a delivery tube or water supply line is not needed. 
     Referring generally to  FIGS. 5-8 , some embodiments of the present invention provide an evaporation device which utilizes a continuous loop or belt membrane  420 . The basic underlying feature of these embodiments is to provide an evaporation device having a configuration wherein a first portion of the belt membrane  420  is routed through (i.e.: submerged in) a reservoir of liquid  34  which is provided in a container  30 . A second portion of the belt membrane  420  is routed through the ambient environment. As the belt membrane  420  is run through a series of rollers, the submerged portion of the belt membrane  420  exchanges positions with the portion of the membrane positioned in the ambient environment, thereby facilitating evaporation of the liquid into the ambient environment. 
     Referring now to  FIG. 5 , an evaporation device  400  is shown. Evaporation device  400  comprises a belt membrane  420  which is suspended between a first roller  430  and a second roller  432 , wherein the first roller  430  is submerged in liquid  34 , and second roller  432  is driven by motor  40 . Upon driving second roller  432 , belt membrane  420  runs in a circular path such that portions of belt membrane  420  are cycled between being submerged in liquid  34  and being exposed to ambient environment  410 . Evaporation device  400  is further distinguished as rollers  430  and  432  both contact the interior surface of belt membrane  420 . 
     Referring now to  FIG. 6 , an evaporation device  402  is shown. Evaporation device  402  comprises a belt membrane  420  which is suspended between a plurality of submerged rollers  431  and  433 , and a plurality of rollers  432  and  434  positioned in the ambient environment  410 . This configuration provides a second point at which belt membrane  420  is submerged in liquid  34 . Device  402  further provides a configuration wherein rollers  431 ,  432  and  434  contact an interior surface  422  of belt membrane  420 , and roller  433  contacts an exterior surface  424  of membrane  420 . Roller  432  is further coupled to motor  40  whereby belt membrane  420  is driven about rollers  431 - 434 . 
     Referring now to  FIGS. 7 and 8 , an evaporation device  404  is shown. Evaporation device  404  comprises an expanded or enlarged version of evaporation device  402 . In particular, evaporation device  404  comprises multiple submerged rollers  431  and multiple rollers  434  which are positioned in the ambient environment  410 . In some embodiments, device  404  further comprises a tensioning roller  426  which maintains the proper tension of belt membrane  420  about the plurality of various rollers. Device  404  may further include a thermal wrap  440  and heating coils  442  for application of device  404  that are used in cold weather conditions. As demonstrated, the rate of evaporation for device  404  is increased by increasing the surface area of belt membrane  420 . Thus, one having skill in the art will appreciate that the present devices  400 ,  402  and  404  may be dynamically modified and adjusted as needed to achieve a desired rate of evaporation. 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.