Abstract:
A method and system is provided for reducing produced water disposal volumes utilizing waste heat generated by thermal oxidation. Waste heat generated by thermal oxidation can be used to vapourize excess water, and to treat and scrub the water vapour for final release into the atmosphere. The system can utilize excess heat remaining after thermal oxidation to produce water vapour.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. provisional patent application Ser. No. 62/214,067 filed Sep. 3, 2015, which is incorporated by reference into this application in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure is related to the field of reducing waste water produced by hydrocarbon wells, in particular, methods and systems for reducing produced water by vapourization utilizing waste heat. 
       BACKGROUND 
       [0003]    Considerable volumes of waste water are generated in all industries as a result of processing. In some sectors, such as oil and gas, water is used to fracture reservoirs during wellbore completion activity and then disposed of. Water is also produced during well production along with hydrocarbons and, after separation, disposed of alone with impurities. 
         [0004]    Hydrocarbon production typically has a component of water that is association with its exploration, stimulation and recovery. This water, which is produced with the hydrocarbon, is generally referred to as “produced water”, and must be separated from the produced hydrocarbons to make the produced hydrocarbons salable and usable. With the majority of the high producing wells and wells located in infrastructure accessible areas moving into secondary and tertiary recovery modes, the amount of produced water production is increasing making water disposal a significant component of operating costs; in addition, as producing wells are drilled further away from any infrastructure, trucking and disposal of the produced water presents an economic, logistic and production challenge which makes some areas nearly impossible to explore. 
         [0005]    It is, therefore, desirable to provide a method and system that reduces the volume of produced water, which reduces transportation and disposal costs and requirements. 
       SUMMARY 
       [0006]    In some embodiments, a method and system are provided that can utilize heat generated through the combustion of available hydrocarbons to raise the waste water stream to such a temperature that the water portion will be converted to a vapour. Sufficient control of the gas temperature, prior to contact with the waste water, is required in order to generate a concentration of a reduced waste water volume and impurities. 
         [0007]    In some embodiments, the method and system can use thermal energy and physics in unique measures and methods to vapourize a significant portion of the waste water. The method and system can reduce the original volume of waste water into a minimal and manageable, waste stream of impurities and a small volume of residual water. 
         [0008]    Broadly stated, in some embodiments, a method can be provided for reducing water produced by a hydrocarbon-producing well, the method comprising the steps of: filtering an incoming stream of untreated produced water from the well to remove solids, hydrocarbons and hydrogen sulphide therefrom to produce treated water; injecting the treated water into an enclosed recirculation system; heating the treated water with waste heat from a thermal oxidizer to produce saturated water vapour; scrubbing the saturated water vapour to remove minerals and ions disposed therein, thereby leaving a concentrated solution of the removed minerals and ions; and exhausting the scrubbed saturated water vapour to atmosphere. 
         [0009]    Broadly stated, in some embodiments, the method can further comprise the step of extracting the concentrated solution from the enclosed recirculation system to produce an outgoing waste stream. 
         [0010]    Broadly stated, in some embodiments, the method can further comprise the step of exchanging heat from the outgoing waste stream to the incoming stream. 
         [0011]    Broadly stated, in some embodiments, the method can further comprise the step of disposing of the outgoing waste stream. 
         [0012]    Broadly stated, in some embodiments, a system can be provided for reducing water produced by a hydrocarbon-producing well, the system comprising: a first filter configured to filter an incoming stream of untreated produced water from the well to remove solids, hydrocarbons and hydrogen sulphide therefrom to produce treated water; an enclosed recirculation tank configured to receive the treated water; an oxidizer configured to provide a source of heated flue gas to heat the treated water to produce saturated water vapour; a scrubbing system configured to recirculate fluid disposed in the tank water through a nozzle disposed in the tank onto the saturated water vapour to precipitate minerals and ions disposed in the saturated water vapour from the saturated water vapour to produce scrubbed saturated water vapour and a concentrated solution of the removed minerals and ions in the tank; and a vent fan for exhausting the scrubbed saturated water vapour to atmosphere. 
         [0013]    Broadly stated, in some embodiments, the system can further comprise a brine pump configured for extracting the concentrated solution from the enclosed recirculation tank to produce an outgoing waste stream. 
         [0014]    Broadly stated, in some embodiments, the system can further comprise a storage tank configured for receiving the outgoing waste stream. 
         [0015]    Broadly stated, in some embodiments, the scrubbing system can further comprise a recirculating pump configured for pumping the concentrated solution through the nozzle. 
         [0016]    Broadly stated, in some embodiments, the system can further comprise a temperature controller configured to operate the vent fan to exhaust scrubbed saturated water vapour from the enclosed recirculation tank when a temperature of the heated flue gas reaches a predetermined temperature. 
         [0017]    Broadly stated, in some embodiments, the enclosed recirculation tank can further comprise a second filter configured to filter the scrubbed saturated water vapour being exhausted from the enclosed recirculation tank. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a block diagram depicting a process flow diagram of one embodiment of an evaporation process. 
           [0019]      FIG. 2  is a block diagram depicting a piping and instrumentation diagram of the process of  FIG. 1 . 
           [0020]      FIG. 3  is an isometric view depicting a scrubbing tower for use in the process of  FIG. 1  and  FIG. 2 . 
           [0021]      FIG. 4A  is a side elevation view depicting the scrubbing tower of  FIG. 3 . 
           [0022]      FIG. 4B  is a cross-section view depicting the scrubbing tower of  FIG. 4A  along section lines A-A. 
           [0023]      FIG. 5A  is a side elevation view depicting one embodiment of a vapourizing system for use in the process of  FIG. 1 . 
           [0024]      FIG. 5B  is an isometric view depicting the vapourizing system of  FIG. 5A . 
           [0025]      FIG. 6  is a block diagram depicting one embodiment of a level controller for use with the processes of  FIGS. 1 and 2 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0026]    In some embodiments, methods and systems can be provided that can address three (3) problems in the hydrocarbon production process: 1) the reduction of produced water to be handled; 2) the reduction of overall production costs; and 3) the reduction of water removed from the surface water cycle. 
         [0027]    Referring to  FIGS. 1 and 2 , one embodiment of a method to reduce the amount of final produced water required to be disposed of during hydrocarbon well production is illustrated. Produced water stream  03  can be treated by filtering out particulates and hydrocarbon droplets by coalescing filter  01 A disposed in vessel  01 . In some embodiments, ‘sweetener’ chemicals can be added to the water at  02  to bond and render inert any Hydrogen Sulfide atoms in solution. In some embodiments, the sweetener chemicals can comprise one or more compounds from the class of compounds known as alkanolamines, as well known to those skilled in the art, which can further comprise one or more of monoethanolamine (“MEA”), diglycolamine (“DGA”), diethanolamine (“DEA”), diisopropanolimaine (“DIPA”), triethanolamine (“TEA”) and methyldiethanolamine (“MDEA”). In some embodiments, the sweetener chemicals can comprise physical solvents, which can further comprise one or more of dimethyl ether of polyethylene glycol, propylene carbonate and N-methylpyrrolidone. In some embodiments, the sweetener chemicals can comprise triazine used in a scavenger process, as well-known to those skilled in the art. In some embodiments, the sweetener chemicals can comprise one or more of iron oxide, wood chips impregnated with iron oxide, walnut shells and walnut shell fragments. 
         [0028]    The treated produced water can then be introduced into mix nozzle  14 , where it can be mixed and heated with flue gas from oxidizer  12  via vent ducting  13  to vapourize the treated produced water to release clean water vapour through vent stream  04 , and concentrate the minerals and ions in accumulation tank  05 . The highly concentrated solution can then be released through stream  06 , and then cooled in a cross-flow heat exchanger  07  prior to storage in storage tank  08 . Vent stream  4  can be drawn through coalescing filter  09  by induced draft fan  10 , and can then be released through vent  11 . The flue gas from thermal oxidizer  12  can be drawn through vent ducting  13 , and then cooled by water injection at mixer  14  and drawn into scrubbing tower  15 . The water saturated stream can then be pulled through scrubbing tower  15  where the bottoms are distributed through spray nozzles  16  to scrub any particulate, and to coalesce smaller droplets to prevent carry over. In some embodiments, oxidizer  12  can comprise a direct-fired thermal oxidizer used in another industrial application. As an example, oxidizer  12  can comprise a burner system used to dispose of associated gas and produced water from a gas well that is not tied into a pipeline transporting the associated gas away from the well. In some embodiments, oxidizer  12  can comprise a heater that cleanly combusts the associated gas from the gas well that can be used to vapourize the produced water from the well. 
         [0029]      FIG. 2  is the Piping and Instrumentation diagram illustrating one embodiment of the piping, control and operation that can be used with the methods and systems described herein. The inlet temperature of flue gas can be controlled by temperature control loop  20  which can control the position of temperature control valve (“TCV”)  50  to pull more or less flue gas through vent ducting  13 . In some embodiments, the inlet temperature to scrubbing tower  15  can be regulated by the amount of flue gas that can be pulled in from vent ducting  13 . In some embodiments, TCV  50  can be a damper or flow control device. Temperature Controller (“TC”)  52  can receive a signal from thermocouple  54  disposed at inlet  56  of scrubbing tower  15 , and send a control signal via temperature control loop  20  to a motor-controlled damper disposed in TCV  50 . If the temperature at inlet  56  is below a predetermined low temperature, temperature control loop  20  can send a signal to TCV  50  to open the damper disposed therein. Conversely, if the temperature at inlet  56  is above a predetermined high temperature, temperature control loop  20  can send a signal to TCV  50  to close the damper disposed therein. In some embodiments, TCV  50  can comprise a model HCDR-050 damper manufactured by Greenheck Fan Corporation of Schofield, Wis., U.S.A. In some embodiments, TCV  50  can further comprise a model EFB24-SR-S N4 actuator manufactured by Belimo Automation AG of Switzerland to operate the damper therein. In some embodiments, temperature control loop  20  can comprise an EZ-Zone model PM4C1F1 PID controller manufactured by Watlow Electric Manufacturing Company of St. Louis, Mo., U.S.A. In some embodiments, thermocouple  54  can comprise a model RTD RT7 resistance temperature detector probe manufactured by Aircom Instrumentation Ltd. of Edmonton, Alberta, Canada. The overall level of fluid in accumulation tank  05  can be controlled by level control loop  21 , which can increase or decrease the speed of concentrated brine pump  22 . In some embodiments, as the level of fluid in tank  05  increases, fluid level switch  60  can send a signal to Level Controller (“LC”)  58  to turn on brine pump  22  so as to drain the fluid from tank  05 . Once the fluid level in tank  05  drops below a predetermined level, fluid level switch  60  can send a signal to LC  58  to turn off brine pump  22 . Referring to  FIG. 6 , one embodiment of switch  60  is shown for use with LC  58 . In some embodiments, switch  60  can comprise top or high level switch  60 A connected in series with bottom or low level switch  60 B, high level switch  60 A further connected in series with a coil of relay  66 , the combination of these components connected between a line and a neutral of AC power. Contact  66 A of relay  66  can be connected in parallel with high level switch  60 A. In some embodiments, contact  66 B of relay  66  can connected in series with brin3 pump  22 , the combination of these components connected between line and neutral of the AC power. In some embodiments, when the fluid level in tank  05  is high enough to close high level switch  60 A, low level switch  60 B is also closed. Under this condition, relay  66  can be energized to close contact  66 B to provide AC power to brine pump  22  to pump fluid out of tank  05 . When relay  66  energizes, contact  66 A also closes to keep relay  66  energized when the fluid level in tank  05  falls below high level switch  60 A, thus making it go open circuit. As fluid is continued to be pumped out of tank  05  by brine pump  22 , the fluid level will eventually drop below the level of low level switch  60 B, thus making it go open circuit to de-energize relay  66  that will, in turn, open contacts  66 A and  66 B which will disconnect AC power to brine pump  22  and, thus, make it stop pumping fluid out of tank  05 . 
         [0030]    In some embodiments, the system can comprise high fluid level sensor (“LSH”)  62  and low fluid level sensor (“LSL”)  64  disposed on tank  05 , wherein LSH  62  and LSL  64  can be operated connected to LC  58  to sense when fluid in tank  05  reaches predetermined high and levels. In the event that brine pump  22  fails to drain the fluid in tank  05  such that the level of the fluid therein can be sensed by LSH  62 , LSH  62  can send a signal to LC  58  to generate a high fluid level alarm wherein the system can be shut down. In the event that there is insufficient fluid in tank  05  to recirculate such that the level of the fluid therein can be sensed by LSL  64 , LSL  64  can send a signal to LC  58  to generate a low level alarm wherein the system can be shut down. In some embodiments, LC  58  can comprise a model 1012DQ2X Level Control Panel as manufactured by Alderon Industries, Inc. of Hawley, Minn., U.S.A. In some embodiments, fluid level switch  60  can comprise a model 2110 Liquid Level Switch as manufactured by Emerson Process Manufacturing Rosemount Inc. of Chanhassen, Minn., U.S.A. In some embodiments, one or both of LSH  62  and LSL  64  can comprise a model 324D proximity sensor as manufactured by John C. Ernst &amp; Co., Inc. of Sparta, N.J., U.S.A. 
         [0031]    Referring to  FIG. 3 , an isometric view of scrubbing tower  15  is shown, displaying the details and configuration of scrubbing tower  15 , with integral accumulation tank  05  and nozzles and openings for flue gas ducting  13 , wash stream  24 , vent stream  4 , and highly concentrated solution stream  6 . 
         [0032]      FIG. 4A  illustrates a side elevation view of scrubbing tower  15 .  FIG. 4B  illustrations a cross-section view of scrubbing tower  15 , showing the details of spray nozzles  16 , coalescing filter  09  and integral accumulation tank  05 . In some embodiments, coalescing filter  09  can comprise a corrosion resistant vane pack demister. In some embodiments, coalescing filter  09  can comprise any structured material comprising sufficient pressure drop, surface area and corrosion resistance properties, as well known to those skilled in the art, to be used as a coalescing filter. In some embodiments, coalescing filter  09  can comprise a model LDP Vane Type Mist Extractor as manufactured by Fabco Products, Inc. of Hawkins, Tex., U.S.A. 
         [0033]      FIGS. 5A and 5B  illustrate on embodiment of a complete general arrangement showing all the components included in the methods and systems described herein. In some embodiments, the systems described herein can be mounted on a structural skid, which can take any size or shape that allows for the systems described herein to be safely and securely transported and installed at location including the addition of a number of structural skids if required by transportation logistics or facility layout. 
         [0034]    In some embodiments, coalescing filter  01 A can comprise any size and media required to filter sediment, hydrocarbons and impurities out of produced water stream  3 , as well known to those skilled in the art. In some embodiments, filter housing  01  and filter  01 A can comprise a bag filter having a corrosion resistant strainer basket, the size of which can depend on the particulate loading of the disposal waster. In some embodiments, filter  01 A can comprise any structured material with an adequate mesh size, surface area and corrosion resistance properties can be used as well known to those skilled in the art. In some embodiments, filter  01 A can comprise a model L44121NB615 bag filter housing and a model BT-4-ML-O-40-6 strainer basket, as both manufactured by Pentair, Inc. of Milwaukee, Wis., U.S.A. 
         [0035]    In some embodiments, thermal oxidizer  12  can be any size thermal oxidizer with sufficient excess heat available to flash the required amount of water, as well known to those skilled in the art. In some embodiments, vent ducting  13  can be any size to accommodate the required flue gas flow from thermal oxidizer  12 . In some embodiments, mixer section  14  can comprise of single or multiple inlet spray nozzles and mixers to accommodate the design flow rates and atomization requirements in the inlet stream. In some embodiments, scrubbing tower  15  can be any size to accommodate the design flow rates and the emissions requirements, be constructed from either coated carbon steel or any exotic material that can resist the corrosive nature of the fluids, as well known to those skilled in the art. 
         [0036]    In some embodiments, spray nozzle assembly  16  can comprise of any number and pattern of nozzles required to get appropriate coverage and droplet size to remove entrained and undersized droplets and any other atomized contaminants. Discharge vent  11  and induced draft fan  10  can be of any size and design that can handle the nature and flow rates of discharge stream  04 . Recycle pump  25  and the requisite piping can be any size or type that can accommodate wash stream  24  material and flow requirements. In some embodiments, heat exchanger  07  can be of any type and size as required (including, without limitation, shell and tube, plate and frame and pin) to provide adequate cooling for highly concentrated brine stream  06 . Concentrated brine pump  22  can be of any size or type required to handle concentrated brine stream  06  and the flow rates required. Storage tank  08  can be of any size and material as required to contain concentrated brine stream  06  and provide sufficient storage to handle any logistical concerns. 
         [0037]    Although a few embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications can be made to these embodiments without changing or departing from their scope, intent or functionality. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the invention is defined and limited only by the claims that follow.