Patent Publication Number: US-2006010865-A1

Title: Produced water disposal method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      The present application is a continuation-in-part of U.S. patent application Ser. No. 10/822,497, filed Apr. 12, 2004, by Weldon Walker. 
    
    
     BACKGROUND OF THE INVENTION  
      The present invention is related generally to methods of disposing of wellhead water separated from the production flow of gaseous hydrocarbons flowing out of a producing well. The present invention is further related generally to apparatus useful in methods of disposing of wellhead water which has been separated from the production flow of gaseous hydrocarbons flowing out of a producing natural gas well. More specifically, the present invention is related to devices and apparatus which create and discharge into the atmosphere steam created from the heating of fresh water separated from the flow of gaseous hydrocarbons available at the output of a natural gas producing well.  
      Many gaseous hydrocarbon producing wells lift large quantities of water along with the gaseous hydrocarbons from the well. Particularly this is true in the gas fields of Wyoming. This wellhead water is troublesome in that it must be separated from the gaseous hydrocarbons being produced and it must be disposed of in an environmentally friendly fashion.  
      There are several prior art methods of disposing of the fresh water pumped from the collection pond. One method used very often is to pump the water back into a disposal well. Disposal wells are attempts to put the fresh water pumped from the collection pond back into the geologic structure from whence it came. The gaseous hydrocarbon production wells in Wyoming are shallow wells, usually 300 to 1500 foot deep. The disposal well is typically deeper and of greater bore than a gaseous hydrocarbon production well. Several gaseous hydrocarbon production wells are usually served by a single disposal well.  
      Another method of disposing of the water pumped from the collection pond is to simply pump the water into a groundwater runoff region wince it can flow in a stream merging with natural water flows in the region and area of the producing wells.  
      Yet another method of disposing of the water pumped from the collection pond is to pump the water into an additional storage pond, either natural or artificial, where the water can be allowed to evaporate into the atmosphere.  
      A fourth prior art method of disposing of the water pumped from the collection pond is to spread the water over the surface of the surrounding land in a form of irrigation. This dispersion of the water over the surface of the surrounding land relies upon the rate of evaporation of the water from the surface of the land for the rate at which the water which can be disposed of. Additionally, various methods of treating the water being dispersed or of treating the land onto which the water is being dispersed are known to improve the rate of water disposal through irrigation techniques.  
      The instant invention is of a method of disposing of the water from the collection pond by creation of steam and discharge of the steam into the atmosphere and of the apparatus utilized to create that steam and discharge it into the atmosphere.  
      Numerous boilers and steam generating apparatus are taught by the prior art. All of such boilers and steam generating apparatus are deficient in one or more particulars for the task accomplished by the instant invention.  
      There are several problems with the prior art relative to devices and apparatus to generate steam, relative to use in a method of disposing of the water from the collection pond by creation of steam and discharge of the steam into the atmosphere. In particular, it is noted that the apparatus of the prior art is directed toward more efficient steam generation, toward creation of maximum energy steam at the lowest cost in heat energy and water feed. The apparatus of the instant invention is not an efficient generator of steam energy. The apparatus of the instant invention discharges spent steam into the atmosphere. The goal of the instant invention is to discharge the greatest possible quantity of moisture, in the form of steam, into the atmosphere. The instant invention is deliberately inefficient in its use of water to create steam. The more water used, the better.  
      The are also several problems with the prior art methods of disposing of the fresh water pumped from the collection pond of a producing gaseous hydrocarbon well.  
      The problems encountered with disposal wells arise because theses wells are injection wells, operated under high pressure and thus such wells are different in kind from the wells in the field of gaseous hydrocarbon wells that produce the fresh water that needs to be disposed of. Usually, therefore, the disposal wells are not located in the same geology as are the producing wells. Transport of the produced fresh water to the disposal wells becomes a problem, an insurmountable economic problem if it is necessary to utilize trucks to transport the fresh water to the site of the disposal wells. This is the case in the Powder River Basin field of gaseous hydrocarbon wells in Wyoming.  
      The problems encountered with pumping the produced freshwater into a groundwater runoff region is that the produced freshwater sometimes carries substantial quantities of mineral impurities which can act to poison the groundwater and therefore this method of disposal has been banned in most jurisdictions in the United States.  
      The problems encountered with the utilization of additional water storage tanks, either natural or artificial, is that actual disposal of the fresh water produced depends on the rate of evaporation from the additional water storage tanks. This rate of evaporation acts as a cap on the rate of production of gaseous hydrocarbons from the wells, an economically unacceptable cap.  
      The problems encountered with use of irrigation as a method of disposal of produced fresh water primarily are created by the local geography in the Wyoming gas fields. In those fields, and areas adjoining the fields, there is a layer of clay at or near the surface of the soil. The clay precludes absorption of the fresh water into the ground at any meaningful rate. This method is used commonly, but its success is limited to the rate of evaporation of the produced fresh water into the atmosphere that, as above-mentioned, is an unacceptable economic cap on the production from the wells.  
     SUMMARY OF THE INVENTION  
      In brief summary, the present invention is of a method of disposing of the fresh water from the collection pond for the output of a gaseous hydrocarbon producing well by creation of steam and discharge of the steam into the atmosphere. The instant invention is additionally of the apparatus specifically designed to practice such method and utilized to create and discharge the steam created from the water from the collection pond for the output of a gaseous hydrocarbon producing well.  
      Injecting produced water into disposal wells has been used in oil and gas fields as a standard disposal method for decades. These wells require governmental permits and are strictly monitored. Drilling a successful well is difficult at best and sometimes not possible. This seems to be the case in some of the natural gas fields of the Rocky Mountain region. The problem seems to be the tight geological formation simply prevents water injection. One of the few successful disposal methods is an irrigation system, however this system is expensive, labor intensive, and weather conditions limit use to six to eight months of the year. The temporary solution is to build more earth storage ponds as a means to continue production. The U.S. Department of Energy&#39;s case study report concludes that more than 39 trillion cubic feet of coalbed methane gas is technically recoverable. Actual production will depend on the success of the chosen water disposal method.  
      Several problems have been noted in prior art and the instant invention was developed to overcome such known problems. Accordingly, it is a general object of this invention to provide a method of disposing of the produced fresh water from the gaseous hydrocarbon wells that does not require use of disposal wells or transportation of the fresh water out of the gaseous hydrocarbon production fields.  
      It is another object of this invention to provide a method of disposing of the produced fresh water from the gaseous hydrocarbon wells that does not depend on the rate of evaporation of the produced fresh water into the atmosphere.  
      It is yet another object of this invention to provide a method of disposing of the produced fresh water from the gaseous hydrocarbon wells that does not depend on the rate of absorption of the produced fresh water into the ground.  
      It is a yet further and final object of this invention to provide an apparatus useful in the practice of a method of disposing of the produced fresh water from the gaseous hydrocarbon wells that creates steam and discharges that steam into the atmosphere.  
      Other objects and advantages of the present invention will be apparent upon reading the following description and appended claims.  
     DESCRIPTION OF THE NUMERIC REFERENCES  
      No. Description  
     
         
           10  Apparatus of the instant invention  
           20  Water Storage Tank and Gathering System  
           26  Electrical Signal Communication Line  
           40  Well and Wellhead  
           50  Natural Gas Production Line  
           100  Wellhead Production System using Steam disposal of produced freshwater  
           115  Fluid Communication Line from the Water Storage Tank to the Water Filter System  
           116  Fluid Communication Line from the Water Filter System to the Water Pump  
           120  Fluid Communication Line from the Production Wellhead to the Water Storage Tank  
           122  Water Pump  
           125  Fluid Communication Line from the Apparatus of the Instant Invention to the Water Storage Tank  
           127  Electrical Signal Communication Line  
           130  Input Water Flow Meter  
           135  Fluid Communication Line from the Inlet Certified Flow Meter to the Water Sample Valve  
           135   a  Fluid Communication Line from the Water Sample Valve to the Air Actuated High Pressure Safety Shutoff Valve  
           135   b  Fluid Communication Line from the Air Actuated High Pressure Safety Shutoff Valve  
           140  Water Sample Valve  
           145  Safety Low Pressure Sensor  
           150  Water Filter System  
           155  a Fluid Communication Line  
           160  a Fluid Communication Line  
           165  a Fluid Communication Line  
           166  a Fluid Communication Line  
           170  First Circulating Valve  
           175  Second Circulating Valve  
           180  Secondary Coils  
           185  a Fluid Communication Line  
           190  a Fluid Communication Line  
           198  Mineral Collection System  
           202  Mineral Filter  
           205  Eight Pass Manifold  
           210  Primary Coils  
           215  a Fluid Communication Line  
           222  Burner Exhaust  
           225  Burner Assembly  
           230  Output Water Flow Meter  
           235  Natural Gas Line  
           235   a  Input Natural Gas Line  
           240  Main Control Panel  
           245  an Electrical Signal Communication Line  
           246  an Electrical Signal Communication Line  
           250  an Electrical Communication Line  
           260  Steam/Water Separator  
           265  a Steam Communication Line  
           275  a Fluid Communication Line  
           280  Electric Safety Switch  
           287  Steam Flow Communication Line to Atmosphere  
           300  an Electrical Signal Communication Line  
           320  Air Actuated High Pressure Safety Shutoff Valve  
           325  Air Compressor With Holding Tank  
           330  a Compressed Air Communication Line  
           335  a Water Flow Valve  
           340  a Steam Flow Valve  
           345  High Pressure Safety Valve  
           350  a Fluid Communication Line  
           351  Water Flow Bypass Line  
           352  Fluid Communication Line  
           355  a Steam Flow Line  
           360  a Steam Flow Line  
           365  Water Pre-Heating Assembly  
       
    
    
    
     DESCRIPTION OF THE DRAWINGS  
      While the novel features of the instant invention are set forth with particularity in the appended claims, a full and complete understanding of the invention can be had by referring to the detailed description of the preferred embodiment(s) which is set forth subsequently, and which is as illustrated in the accompanying drawings, in which:  
       FIG. 1  is a block diagram of a system  100  practicing the method of the instant invention.  
       FIG. 2  is a schematic drawing of the apparatus  10  which disposes of the excess fresh water generated by the system  100  as steam.  
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT(S)  
      As is seen by reference to  FIG. 1 , the instant invention is of a method of disposing of the produced fresh water communicated  115  from the water storage tank  20  for the output of a gaseous hydrocarbon producing well  40  by creation of steam in the apparatus of the instant invention  10  and discharge of the steam through the steam flow communication line  287  into the atmosphere. The instant invention is additionally of the apparatus  10  specifically designed to practice such method and utilized to create and discharge the steam created from the water which was communicated  115  from the water storage tank and gathering system  20  at the output of a gaseous hydrocarbon producing well  40 .  
       FIG. 1  is a block diagram of a system  100  which practices the method of the instant invention and depicts the apparatus  10  of the instant invention in flow position relative to the other major components of the system  100 . The system  100  comprises a gaseous hydrocarbon producing well and wellhead  40  which is in fluid communication with a water storage tank and gathering system  20  via the fluid communication line  120 . The gaseous hydrocarbon producing well and wellhead  40  also has a natural gas output which is depicted as output via natural gas flow line  50 . The water storage tank and gathering system  20  is in fluid communication  115  with the input to the apparatus  10  and is in fluid communication  125  with an output of the apparatus  10 . Additionally, the apparatus  10  provides electrical signal communication of shutdown and other safety level violations to the water storage tank and gathering system  20  via electrical signal communication line  26 . The other outputs of the apparatus  10  are steam via the steam flow line  287 . Thus, the system  100  is seen to have two outputs: natural gas via the natural gas flow line  50  and steam via the steam flow line  287 ; and the system  100  is shown to have but a single input, the combined natural gas and fresh water produced from the well and wellhead  40 . The apparatus  10  of the instant invention utilizes the water input by fluid communication  115  from the water storage tank  20  to create steam which is output via the steam flow line  287  into the atmosphere.  
       FIG. 2  is a schematic diagram of the apparatus  10  of the instant invention.  FIG. 2  depicts the water flow from the water storage tank  20  to the apparatus  10  as taking place via fluid flow communication line  115 , and depicts the water flow from the apparatus  10  to the water storage tank  20  as taking place via fluid flow communication line  125 .  
      The apparatus  10  comprises in gross partition a fluid communication line  115  which provides fresh water into the apparatus  10 , a filter system  150  which filters the fresh water in, a set of primary heating coils  210  which are heated by a natural gas burner assembly  225 , a water pre-heating assembly  365  which pre-heats the filtered water being fed into the primary heating coils  210 , a water-steam separator  260  which permits the high pressure, live steam output of the primary heating coils  210  to flow into a steam communication line  265 , and permits the water output to flow into the fluid communication line  275 . The water flowing into fluid communication line  275  flow through a water flow valve  335  into the fluid communication line  350  through an output water flow meter  230  and thence through fluid communication line  125  back to the water storage tank  20 . The steam flowing into steam communication line  265  flows through a steam flow valve  340  into the steam flow communication line  360  into the mineral separator unit  198 .  
      In greater particularity, and continuing reference to  FIG. 2 , the apparatus  10  receives fresh water from the water storage tank  20  via the fluid communication line  115 . The fresh water received by the apparatus  10  through fluid flow line  115  is first filtered by the water filter system  150  then communicated through fluid communication line  116  to the water pump  122  from whence it is pumped to the input water flow meter  130  and metered. The output of the input water flow meter  130  is through fluid communication line  135  to the water sample valve  140 . The fresh water out of the normally closed water sample valve  140 , opened only when a sample is to be taken by diverting the flow out of the water sample valve  140  away from fluid communication line  135   a , is input to the air actuated high pressure safety shutoff valve  320  through fluid communication line  135   a . The air actuated high pressure safety shutoff valve  320  has two possible outputs, fluid communication line  135   b  which inputs fresh water to the water filter system  150  and fluid communication line  351  which inputs fresh water into fluid communication line  352 . If the fresh water is routed by the air actuated high pressure safety shutoff valve  320  into the fluid flow communication line  135   b , then the fresh water is input to the water filter system  150  and is filtered. If the fresh water is routed by the air actuated high pressure safety shutoff valve  320  into the fluid flow communication line  351 , then the fresh water flow will be via the fluid communication line  352  into the output water flow meter  230  and thence via fluid communication line  125  back into the water storage tank  20 .  
      The filtered fresh water output of the water filter system  150  is output from the filtering system  150  through fluid communication line  155 . Fluid communication line  155  splits into two fluid communication lines,  160  and  215 . The fresh water flow into fluid communication line  160  is controlled by the setting of the first circulating valve  170 . The fresh water flow into fluid communication line  215  is controlled by the setting of the second circulating valve  175 . Fresh filtered water output from the filtering system  150  flows through fluid communication line  160  into the first circulating valve  170  and is output from the first circulating valve  170  via fluid communication line  165 . Fresh filtered water output from the filtering system  150  also flows through fluid communication line  215  into the second circulating valve  175  and is output from the second circulating valve  175  via fluid communication line  185 . The output of the first circulating valve  170  is input to primary coils  210  of the eight pass manifold  205  through fluid communication line  166  via fluid communication line  165 . Fluid communication line  166  has as input the outputs of both fluid communication line  165  and fluid communication line  190 .  
      The output of the second circulating valve  175  is input to the secondary coils  180  through the fluid communication line  185 . The secondary coils  180  are contained within an exhaust heat exchanger  365  and serve to pre-heat the filtered fresh water output of the secondary coils  180 . The exhaust heat exchanger  365  is fed hot exhaust air by the air duct system surrounding the burner  225 . The pre-heated fresh filtered water output of the secondary coils  180  is output from the secondary coils  180  through fluid communication line  190 .  
      The fresh filtered water flow out of the fluid communication line  190  is input into the fluid communication line  166  which flows into the primary coils  210 . The eight pass manifold  205  and the primary coils  210  within it are heated by the burner assembly  225  which is fed natural gas through the natural gas line  235 . The hot gas output of the burner assembly  225  is vented into the atmosphere via burner exhaust  222 . The fresh filtered water in the primary coils  210  is heated to a high pressure steam-water mixture which is output from the primary coils  210  to the steam/water separator  260  through the steam flow line  355 .  
      The steam/water separator  260  acts to separate the steam from the hot water and let the steam pass into the steam flow line  265  while diverting the hot water into fluid communication line  275 . Hot water flowing into fluid communication line  275  flows into the water flow valve  335  and from water flow valve  335  out into fluid communication line  350 . The output of fluid communication line  350  is into fluid communication line  352  and the output of fluid communication line  352  is into the output water flow meter  230 .  
      The output of the output water flow meter  230  is into fluid communication line  125  which flows fresh water back into the water holding pond  20 , see  FIG. 1 . The steam flowing into steam flow line  265  is output into steam flow valve  340 . The steam output of the steam flow valve  340  is input as high pressure live steam to the mineral separator unit  198  through steam flow line  360 . The mineral separation unit  198  of the preferred embodiment is a mechanical baffle and mechanical mineral filter  202 . The high pressure wet steam input to the mineral separation unit  198  imparts the energy to the mineral separation unit  198  and its mechanical mineral filter  202  and, in the process, reduces the high pressure, live steam to low pressure, spent steam which is exhaust from the mineral separation unit  198  through the exhaust steam vent stack  287  where the steam is vented into the atmosphere.  
      The preferred embodiment of the apparatus, by continued reference to  FIG. 2 , also provides a safety and control system which prevents operation during excessive temperature and pressure conditions. The input flow of fresh water into the air actuated high pressure safety shutoff valve  320  will be diverted into fluid flow communication line  351  in the event that air actuated high pressure safety shutoff valve  320  senses a high pressure safety violation. The air actuated high pressure safety shutoff valve  320  is, as the name suggests, air actuated by the constant air pressure fed into it by the compressed air communication line  330 . The air actuated high pressure safety shutoff valve  320  of the preferred embodiment actually uses mechanical detection of the high pressure condition and uses the compressed air as power to divert the fresh water flow, ie. to change the valve position from its normal output into fluid communication line  135   b  to an output into fluid communication line  351 . The compressor  325  is powered by electricity input via electrical communication line  250  and electrical communication line  250  receives the electricity from the control panel  240 . When the air actuated high pressure safety shutoff valve  320  actuates, the flow of fresh water is no longer into fluid communication line  135   b  and the safety low pressure sensor  145  which is installed on fluid communication line  135   b  will detect the lack of fluid pressure in fluid communication line  135   b  and will generate an electrical signal which is communicated back to the control panel  240  via electrical communication line  246 . Upon receipt of the low pressure signal from the safety low pressure sensor  145 , the control panel  240  will generate an electrical signal which acts to cause electric safety switch  280  to stop the flow of natural gas into the natural gas line  235 . The electrical signal is communicated from the control panel  240  to the electric safety switch  280  via electrical signal communication line  245 . The normal flow of natural gas from the input natural gas line  235   a  into the natural gas line  235  is halted by the actuation of the electric safety switch  280 .  
      The high pressure safety valve  345  senses the pressure within the steam flow communication line  265  and acts to generate an electrical signal which is input to the control panel  240  via electrical signal communication line  300 . Upon receipt of the electrical signal from the high pressure safety valve  345  by the control panel  240 , the control panel  240  acts to generate an electrical signal which is conveyed to the electric safety switch  280  via the electrical signal communication line  245 . As above described, receipt of the electrical signal by the electric safety switch  280  causes the electric safety switch  280  to cut off the flow of natural gas into the natural gas line  235  which effectively closes down the operation of the apparatus  10 .  
      With reference to  FIG. 2 , in operation of the preferred embodiment, fresh water produced from the gas wells  40  is sent to water storage tanks  20 , and that the fresh water that is not converted into steam and discharged into the atmosphere is flowed back through fluid flow line  125  to the water storage tanks  20 . It should be noted that the result of this flow of water not converted to steam causes the water in the water storage tanks  20  to maintain an approximate temperature of 65 degrees F. Using a submersible pump placed into the water storage tank  20  with a skimming technique allows many of the particulates contained in the water to drop out and settle to the bottom of the water storage tank  20 . The system water flow, water flow within the apparatus  10 , begins with the submersible pump producing a minimum of 150 gallons per minute @ 200 PSI through a 3″ diameter pipe which serves as the input fluid flow communication line  115 . The certified flow meter  130 , being the next step, is the means utilized to track barrels of fresh water disposal by the apparatus  10 . Typically, a 3″ diameter is the required inlet and outlet size for the input and output fluid flow lines,  115  and  125  respectively. The sample valve  140  is required for testing the water flow into the apparatus  10  to maintain environmental control. A safety low pressure sensor  145  is required to monitor water flow into the apparatus  10  before it enters the filtering system  150  to address any unexpected problems concerning water flow blockage. The apparatus  10  has incorporated an air actuated high pressure safety shutoff valve  320  as an additional safety device. The air actuated high pressure safety shutoff valve  320  is air pressure actuated by a compressor and holding tank  325  acting through the compressed air communication line  330  and monitored from the control panel  240 . The requirements of the filtering system  150  are adjusted to fulfill governmental environment issues. In short, permits, indicating compliance with relevant governmental regulations, dictate size, content and flow rates within the apparatus  10 . One of the substantial advantages of the design of the apparatus  10  is the flexibility in size and flow rate that is possible, and thus the ability of the apparatus  10  to allow the production operator to comply with the various relevant regulations. The two circulating valves  170  and  175  are used during the apparatus&#39;  10  start up procedure and adjusted for desired system efficiency. The water flow returning to the storage tank  20  via fluid communication line  125  during this start up phase is monitored with a second certified flow meter, the output water flow meter  230 , for accurate disposal rates. The heat recovery method using the secondary set of coils  180  is designed to preheat the water flow. This secondary coil system  180  reduces the fuel consumption by recovering heat from the exhaust burner chamber. The manifold  205  and primary coil  210  design of the heat exchanger is of a specific, unusual in light of the prior art, nature. Historically, tubular boiler systems are designed to keep water consumption to a minimum, because water introduces an added expense to the process. The instant invention  10 , on the other hand, is designed to consume as much water as possible as a means of water disposal. The heat exchanger manifold  205  is constructed with an eight pass primary coil  210  arrangement and is fed by a 3″ header from fluid flow communication line  165 . Construction meets ASME Section I Specifications Stamped with the “S” Symbol and Registered with the National Board. The safety bypass system is used during startup procedure and when any temperature, pressure or flow problems are encountered. The burner assembly  225  features a natural gas fired up-draft type system with a maximum 16,000,000 BTU input with a dual direct spark ignition. A 1″ natural gas line  18  with a minimum 50 PSI is required for optimum burner  225  performance. Efficiency is monitored by use of the certified gas meter, not depicted. An electric natural gas flow safety switch  280  is attached to the gas line  235  which is monitored from the main control panel  240  for automatic shut down to ensure operation within safe pressure limits.  
      The primary tubular coils  210  represent the next stage of flow. Heated water is flashed to steam as the flow exits the primary coils  210  and passes through the steam/water separator  260 . Steam flow of 12,000 lbs/hr is expected.  
     Economic Benefit Statement  
      Economically, the instant invention provides certain advantages as a solution to the petroleum industry&#39;s problem of disposing of water produced at the wellhead. A current limitation on the production of natural gas fields in the Rocky Mountain region is the volumetric limitations on the disposal of co-produced freshwater from the gas wells. Such limitations are on the volume of water that can be re-injected into the field without affecting the groundwater tables and on the volume of water that can be added to the local surface water flows without environmentally impacting the areas surrounding the fields. Thus, increasing the volume of available freshwater disposal from natural gas fields in the Rocky Mountain region would have a substantial impact on the available increases in natural gas production. The simplicity and combination of well-known technologies provided by this invention creates a reliable, proficient, and efficient, workable method of increasing available natural gas production. Increased natural gas production will serve to make available energy at a lower overall cost and will help support the growth of the economy.  
     Conclusion  
      While the preferred embodiments of the method and apparatus of the instant invention  10  have been described in substantial detail and fully and completely hereinabove, it will be apparent to one skilled in the art that numerous variations of the instant invention  10  may be made without departing from the spirit and scope of the instant invention  10 , and accordingly the instant invention  10  is to be limited only by the following claims.