Abstract:
A method and device for treating contaminated water where the device is portable. The method includes the steps of moving contaminated water into a first tank to settle out large solids such as cuttings and metallic particles while adding a pH modifier, a coagulant, and gaseous ozone. Moving the contaminated water into a second tank where the pre-treated water is subjected to an electro-coalescing process that subjects the water to a strong DC current as the water passes between several bi-metallic plates. After the electro-coalescing process the water may be filtered to remove the remaining solids resulting from the pre-treatment and the electro-coalescing process or the solids may be allowed to settle. The resulting water may then be re-used in the fracturing or drilling processes.

Description:
FIELD OF INVENTION 
       [0001]    This invention relates to the field of water treatment and, in particular to provide water for fracturing and drilling, as well as reducing the need for off-site treatment. Such treatment may include reclaiming the water from drilling fluids, flowback fluids, and produced water from oil and gas wells. 
       BACKGROUND 
       [0002]    The oil and gas industry has a requirement for water that is needed for oil and gas drilling and fracturing. Typically it is useful to add particular chemicals to enhance the function of the water for both drilling and fracturing operations. Unfortunately these chemicals may be sensitive to salts or other chemicals that may be present in the water. One potential source of water near a drilling site is flowback water and produced water from other nearby wells. However, flowback and produced water is typically highly contaminated with various salts, acids, hydrocarbons, solids, and other contaminants. There is a need in the oil and gas industry to have a relatively uncontaminated water source to use in drilling and fracturing procedures. Additionally, once the drilling and fracturing procedures are over there is a need to remove the various contaminants from the drilling and fracturing fluids in order to properly dispose of the fluids. There may also be water that is produced from the well along with the various desired hydrocarbons, such water is preferably separated out from the hydrocarbons at the well site and must then be able to be disposed of properly. 
       SUMMARY 
       [0003]    One solution is outlined as follows. The initial step is the introduction of the contaminated water into a tank, such as a 10,000 gallon overflow tank. This first tank is usually the first step in the treatment process as it enables solids such as rock cuttings, metals, or other solids produced in oil and gas operations to settle out of the water while ozone is diffused into the water. Additionally the pH of the water may also be adjusted at this stage, usually by the addition of NaOH to adjust the pH to about 9.2. As the water is moved from this initial tank it is pumped through a tank or tanks where the water is subjected to an electro-coalescing process. 
         [0004]    The electro-coalescing process typically consists of moving the contaminated water out of the first tank and into a second tank where the water passes through bimetallic electrodes. A direct current power supply, supplies a DC electric current to electrodes. The power passing through the water between the at least two bi-metallic electrodes tends to enhance the formation of additional solids to be extracted from the water being treated. As the contaminated water, that has both organic and nonorganic pollutants, is pumped through a series of coalescing cells or between the electrodes in a single tank, the DC the current creates a charge in the pollutants. The now electrically charged pollutants tend to coalesce into large enough particles so that the pollutant particles will either settle in the overflow tank or may be filtered out. 
         [0005]    After passing through the pre-treatment in the first tank or cell as well as passing through the electro-coalescing process, the contaminated water in the overflow tank typically shows signs of clarity but continues to have a level of turbidity due to the complex chemistry of the flow back water and continues to have high levels of pollutants such as various chemical agents, petroleum hydrocarbons, and volatile organic compounds that tend to be too stable for the electro-coalescing process to completely eradicate them. The water may have to be treated by injecting an additional coagulant into the flow to coalesce the final pollutants into solids that are then removed thereby rendering the water suitable for reuse in the fracturing and drilling processes or for other environmentally friendly disposal. The coagulant or flocculant may be a polymer. 
         [0006]    One embodiment of the invention includes injecting ozone into the contaminated water and adjusting the pH of the water in the first tank. Typically the pH of the water is modified by injecting NaOH into the water, usually to at least 9.2 pH. Then flowing the water between at least two electrodes where an electric current is supplied to the electrodes. Typically the electrodes are metal and in some instances the metal electrodes are bimetallic. Usually the electric current is direct current (DC). Typically, the current supplied to the electrodes is reversed at after a period of time. Injecting a polymer into the water and allowing a coagulated material to settle out of the water. 
         [0007]    In another embodiment of the invention the fluid treatment system has a skid with a first tank and an ozone source. Usually the contaminated water is introduced into the first tank along with ozone from the ozone source. Then a multiplicity of first solid particles are allowed to settle out in the first tank. The fluid treatment system skid may have a second tank and an electric power supply, wherein power supply is connected to electrodes in the second tank. The electric power supply is usually DC and the electrodes are bimetallic. The contaminated water from the first tank passes between the electrodes in the second tank. A polymeric coagulant may be added after the water passes through the electrodes. Typically the skid has a pH modifying agent and the modifying agent is introduced into the first tank. In most instances the pH modifying agent is NaOH. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0009]      FIG. 1  depicts a schematic flow chart of the water treatment process. 
           [0010]      FIG. 2  depicts a schematic layout of a fluid treatment system control system and electrocoalescing tanks on a first skid. 
           [0011]      FIG. 3  depicts a schematic layout of a fluid treatment system ozone injection tank and a coagulation tank on a second skid. 
           [0012]      FIG. 4  depicts a schematic layout of a fluid treatment system on a single skid. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The description that follows includes exemplary apparatus, methods, techniques, and instruction sequences that embody techniques of the inventive subject matter. 
         [0014]    The methodology employs electrical energy, ozone, and chemical modification to alter the molecular structure of waterborne contaminants to remove those contaminants.  FIG. 1  depicts a flow chart outlining a process for treating drilling or fracturing fluids as well as produced, flowback, or otherwise contaminated water. A representative fluid management system uses a high flow design to process and recycle fracturing, flowback, or other wastewater. 
         [0015]    The typical water processing cycle is a continuous process although a quantitative or timed process may be used. Typically, contaminated water enters the first tank  10  as indicated by arrow  12 . While the contaminated water is in the first tank  10  at least a portion of the solids may be allowed to settle. Also, the first tank  10  may provide a large enough basin for the pretreatment of the contaminated water to begin. The pre-treatment process may include injecting gaseous ozone from the ozone tank  40  into the contaminated water in the first tank  10 , as indicated by arrow  14 . 
         [0016]    It is been found that typically produced water is slightly acidic, usually with a pH between 5.0 and 6.5. However the treatment process has been found to be most successful with the pH above about 9.1. In order to modify the pH, a base such as sodium hydroxide (NaOH), may be metered from a tank  44  containing the base into the contaminated water in the first tank  10 , as indicated by arrow  15 , as the contaminated water makes its way through the first tank  10 . 
         [0017]    Once the water has been pre-treated and many of the solids have been settled out in the first tank, the contaminated water is moved into a second tank  20 , as indicated by arrow  28  where the treating process moves into the next phase. In the second tank  20  the contaminated water moves through at least one, but typically a series of ten electrode assemblies  22 , two such electrode assemblies  22  are shown, where the water and contaminants are subjected to electro-coalescing. Typically each electrode assembly  22  has a number of paired sacrificial metallic electrodes  24 , typically the electrodes are bimetallic and are iron and aluminum. The electrodes  24  are energized by source of DC power  26 . Typically the DC power source  26  supplies three phase 220 volt power between 200 and 400 amps. 
         [0018]    As DC current is supplied to each pair of electrodes  24  positive DC power is applied to one electrode  25  while negative DC power is applied to the other electrode  27 . Every so often the polarity of the electrodes  24  is reversed so that previously positively charged electrode  25  becomes negatively charged while previously negatively charged electrode  27  becomes positive. Each electrode  25  and  27  does not retain a positive or negative charge long enough to impact the collection of sediment near each electrode  25  or  27 . Typically by reversing the polarity the pairs of electrodes  25  and  27  are only subject to degradation by ion displacement. 
         [0019]    As a result of the pretreatment in the first tank  10 , including ozone injection and pH adjustment and the electro-coalescing treatment in the second tank  20  the contaminated water typically begins to clarify. However usually microscopic suspended solids, stable sulfates, surfactants, emulsifying agents, petroleum hydrocarbons, and volatile organic compounds are still present in the water. Therefore in certain instances a chemical coagulation process is called for. 
         [0020]    Typically the water is then moved into a third tank  30 , as indicated by arrow  32 , where a low molecular weight, high charge cationic polymer, such as any of the polyacrylamides including polyethylene-imines, polyamides-amines, or polyamines, is added to the water from the tank  42  into the water in the third tank  30 , as indicated by arrow  34 , causes additional gathering and coagulation of the remaining suspended colloids, including the stable sulfates, surfactants, emulsifying agents, petroleum hydrocarbons, and volatile organic compounds into large clusters of solids that may range from 20-100 microns in size. Usually the low molecular weight, high charge cationic polymer is a solution of polyaluminum chloride and dodecylmethylallylchloride is used to cause the additional gathering and coagulation of the remaining suspended colloids. These coalesced solids are then capable of being settled or filtered out of the water for off-site removal. After the solids are extracted and removed the water is now ready to return to the oil exploration well site, as indicated by arrow  36 , where it may be removed from the site for proper local disposal or the water may be re-used in either a drilling or fracturing process. 
         [0021]      FIG. 2  depicts the main components of a fluid treatment system on a first skid. Fluid, as depicted by arrow  100 , enters the first pump  102  from the ozone injection tank on the second skid as depicted in  FIG. 3 . The first pump  102  then forces the fluid to flow, in the direction indicated by the arrows, through pipe  104  and into multiple electro-coalescing tubes  106 . As the fluid flows through the electro-coalescing tubes  106  power is supplied from the power supply  108  through cables  110  to the electrodes (not shown) in each of the electro-coalescing tubes  106 . Typically 220 V three phase power is supplied to the power supply  108  by input cables  112 . After the fluid has passed through the electro-coalescing tubes  106  the fluid then enters a second pump  114  that in turn forces the fluid out through tubular  118  and into a coagulation tank on the second skid as depicted in  FIG. 3 . Typically the first skid will also incorporate a polymer injection pump  120  and the polymer tank  122 . The polymer injection pump  120  will then supply the coagulating polymer from tank  122  to the coagulation tank on the second skid, as depicted in  FIG. 3 , via pipe  124 . Typically the first skid will also incorporate the sodium hydroxide pump  126  and the sodium hydroxide tank  130 . The sodium hydroxide pump  126  supplies the chemical to adjust the pH in the ozone injection tank on the second skid, as depicted in  FIG. 3 , via pipe  128 . Also, the first skid usually includes an ozone generator  132  that supplies of zone to the ozone injection tank on the second skid, as depicted in  FIG. 3 , via pipe  134 . 
         [0022]      FIG. 3  depicts the ozone injection tank  140  and the coagulation tank  150  on a second skid. Typically untreated fluid flows into the ozone injection tank  140  through pipe  142 . Ozone is then injected into the fluid in the ozone injection tank through pipe  134  that is connected to ozone generator  132  on the first skid as depicted in  FIG. 2 . At the same time a pH modifier, such as sodium hydroxide, is injected into the fluid in the ozone injection tank, as needed, through pipe  128  that is connected to the sodium hydroxide pump  126  on the first skid as depicted in  FIG. 2 . Treated fluid is then removed from the ozone injection tank  140  through pipe  144  that is connected to the first pump  102  on the first skid as depicted in  FIG. 2 . 
         [0023]    The fluid is forced into the coagulation tank  150  by the second pump  114  on the first skid, depicted in  FIG. 2 , via pipe  118 . Typically while the fluid is in the coagulation tank  150  an inorganic polymer is injected into the fluid in the coagulation tank through pipe  124  that is connected to the polymer pump  120  on the first skid as depicted in  FIG. 2 . The fluid typically resides in the coagulation tank  150  long enough for particulant matter to settle to the bottom. The now clean, treated water is removed from the coagulation tank  150  through pipe  152 . 
         [0024]      FIG. 4  depicts the main components of a fluid treatment system on a single skid. Fluid, as depicted by arrow  200 , enters the first pump  202  from the ozone injection tank  240 . The first pump  202  then forces the fluid to flow, in the direction indicated by the arrows, through pipe  204  and into multiple electro-coalescing tubes  206 . As the fluid flows through the electro-coalescing tubes  206  power is supplied from the power supply  208  through cables  210  to the electrodes (not shown) in each of the electro-coalescing tubes  206 . Typically 220 V three phase power is supplied to the power supply  208  by input cables  212 . After the fluid has passed through the electro-coalescing tubes  206  the fluid then enters a second pump  214  that in turn forces the fluid out through tubular  218  and into a coagulation tank  250 . Typically the single skid will also incorporate a polymer injection pump  220  and the polymer tank  222 . The polymer injection pump  120  will then supply the coagulating polymer from tank  222  to the coagulation tank  250 , via pipe  224 . Typically the skid will also incorporate the sodium hydroxide pump  226  and the sodium hydroxide tank  230 . The sodium hydroxide pump  226  supplies the chemical to adjust the pH in the ozone injection tank  240  via pipe  228 . Also, the skid usually includes an ozone generator  232  that supplies of zone to the ozone injection tank  240  via pipe  234 . 
         [0025]    Typically untreated fluid flows into the ozone injection tank  240  through pipe  242 . Ozone is then injected into the fluid in the ozone injection tank  240  through pipe  234  that is connected to ozone generator  232 . At the same time a pH modifier, such as sodium hydroxide, is injected into the fluid in the ozone injection tank  240 , as needed, through pipe  228  that is connected to the sodium hydroxide pump. Treated fluid is then removed from the ozone injection tank  240  through pipe  244  that is connected to the first pump  202 . 
         [0026]    The fluid is forced into the coagulation tank  250  by the second pump  214  via pipe  218 . Typically while the fluid is in the coagulation tank  150  an inorganic polymer is injected into the fluid in the coagulation tank  250  through pipe  224 . The fluid typically resides in the coagulation tank  250  long enough for particulant matter to settle to the bottom. The now clean, treated water is removed from the coagulation tank  250  through pipe  252 . 
         [0027]    Each of the arrows in  FIG. 2 ,  FIG. 3 , and  FIG. 4  are used to indicate the direction of fluid flow through a pipe. 
         [0028]    The entire operation is conducted on equipment that is typically portable. By mounting the equipment on a skid or trailer the fluid management system may be easily moved from site to site as needed. Additionally should the need arise the fluid management system may easily be scaled up to handle any amount of fluid that needs treatment. 
         [0029]    While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible. 
         [0030]    Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter. 
         [0031]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.