Abstract:
Apparatus and methods for bioremediating hydrocarbon contaminated solids. The method can include introducing a slurry comprising one or more drilling fluids and one or more hydrocarbon contaminated solids to a settling system. The settling system can include one or more housings having a receiving compartment at a first end thereof and a collecting compartment at a second end thereof. A barrier can be disposed in the receiving compartment, and at least one wall can be disposed transversely in the housing between the receiving and collecting compartments. The wall can have at least one aperture formed therethrough and at least one flow-restricting baffle disposed thereon, wherein the one or more baffles extend perpendicularly from the wall. The separated hydrocarbon contaminated solids can be contacted with one or more microorganism populations disposed between the receiving compartment and the collecting department.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application having Ser. No. 60/957,113, filed on Aug. 21, 2007, which is incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the present invention generally relate to systems and methods for oil field cutting bioremediation. More particularly, embodiments of the present invention relate to systems and methods for bioremediation of hydrocarbon contaminated drill cuttings from oil and gas wellbores. 
         [0004]    2. Description of the Related Art 
         [0005]    The drilling of wells in the recovery of oil and gas typically comprises a rig drilling the well with a hollow drill string. As the well is being drilled, drilling fluids are pumped down the bore of the string. The drilling fluid passes through openings in the drill bit and returns to the surface through the annulus surrounding the string, carrying the cuttings produced by the drill bit. The drilling fluid is then recycled to remove the cuttings so that it may be used again. 
         [0006]    Traditional methods of recycling drilling fluid include using a centrifuge to separate the liquid from the cuttings. In large drilling operations, to keep up with the volume of drilling fluid used, it is necessary to use either a very large centrifuge or to use a plurality of centrifuges. In either case, the cost of operating such a drilling fluid recycling system is substantial. 
         [0007]    Fluid recycling system using setting tanks and centrifuges have been used. The settling tank is used as a preliminary step to settle the cuttings from the fluid. The drill cuttings often remain in suspension in the fluid and are often referred to as “solids.” Flocculating agents may be introduced into the tank to assist in the settling of the solids. The drilling fluids are pumped into the receiving end of the tank. The tank has a plurality of transverse walls or baffles that form a plurality of compartments within the tank. Each wall has an opening to permit the flow of fluid from an upstream compartment to a downstream compartment. The openings are positioned on the walls in such a manner that the fluid follows a sinuous path as it flows from the receiving end to the collecting end of the tank. As fluid flows from compartment to compartment, solids in the fluid settle to the bottom of the tank. 
         [0008]    Once fluid reaches the collecting end of the tank, it is withdrawn from the tank to be re-used in the drilling operation. The settled or separated solids are conveyed towards the receiving end of the tank using an auger. A slurry of settled solids and fluid are withdrawn from the tank and pumped through a centrifuge. Fluid recovered from the centrifuge is re-introduced into the tank at the receiving end. 
         [0009]    While using the combination of settling tank and centrifuge is an improvement in comparison to using a centrifuge by itself, in practice, this circuit is often unable to keep up with the throughput of drilling fluid required in drilling a well. It is often necessary to temporarily stop drilling until the settling tank and centrifuge can catch up and recover enough drilling fluid for the drilling operation. 
         [0010]    Therefore, there is a need for a new system and method for recovering and recycling drilling fluid in sufficient quantity for typical drilling operations. 
       SUMMARY OF THE INVENTION 
       [0011]    Apparatus and methods for bioremediating hydrocarbon contaminated solids. In at least one specific embodiment, the method can include introducing a slurry comprising one or more drilling fluids and one or more hydrocarbon contaminated solids to a settling system. The settling system can include one or more housings having a receiving compartment at a first end thereof and a collecting compartment at a second end thereof. A barrier can be disposed in the receiving compartment, and at least one wall can be transversely disposed in the housing between the receiving and collecting compartments. The wall can have at least one aperture formed therethrough and at least one flow-restricting baffle disposed thereon, wherein the one or more baffles can extend perpendicularly from the wall. The slurry can flow across the barrier, and the hydrocarbon contaminated solids in the slurry can be separated from the drilling fluid by causing the slurry to reverse direction and flow around the barrier. The separated hydrocarbon contaminated solids can be contacted with one or more microorganism populations disposed between the receiving compartment and the collecting department. 
         [0012]    In at least one specific embodiment, the apparatus can include a housing having a receiving compartment at a first end thereof and a collecting compartment at a second end thereof. A substantially vertical flow-reversing barrier can be disposed in the receiving compartment. The barrier can be adapted to receive a slurry containing drilling fluid and one or more hydrocarbon contaminated solids, the barrier can be capable of causing the slurry to reverse direction and flow around the barrier and can cause at least some of the solids in the slurry to separate from the drilling fluid. At least one wall can be transversely disposed in the housing between the receiving and collecting compartments. The wall can have at least one aperture formed therethrough and at least one flow-restricting baffle disposed thereon, wherein the one or more baffles can extend perpendicularly from the wall. One or more microorganism populations can be present to selectively remove the hydrocarbons from the separated solids. A conveyor can be used for moving the separated solids from the housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    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. 
           [0014]      FIG. 1A  depicts a perspective view of a system for bioremediation of hydrocarbon contaminated solids from oil and gas wellbores, according to one or more embodiments. 
           [0015]      FIG. 1B  depicts a plan view of an illustrative settling system for separating solids from a used drilling fluid, according to one or more embodiments. 
           [0016]      FIG. 2  depicts a partial cross section view of the settling system depicted in  FIG. 1B . 
           [0017]      FIG. 3  depicts a cross-sectional end view of the settling system along lines III-III shown in  FIG. 2 . 
           [0018]      FIG. 4  depicts a perspective view of the flow-reversing barrier of the settling system depicted in  FIG. 1B , according to one or more embodiments. 
           [0019]      FIG. 5  depicts a front elevation view of the flow-reversing barrier of the settling system depicted in  FIG. 1B , according to one or more embodiments. 
           [0020]      FIG. 6  depicts a top plan view of the flow-reversing barrier of the settling system depicted in  FIG. 1B , according to one or more embodiments. 
           [0021]      FIG. 7  depicts a side elevation view of the flow-restricting baffle of the settling system depicted in  FIG. 1B , according to one or more embodiments. 
           [0022]      FIG. 8  depicts a perspective view of the flow-restricting baffle of the settling system depicted in  FIG. 1B , according to one or more embodiments. 
           [0023]      FIG. 9  depicts a front elevation view of the flow-restricting baffle of the settling system depicted in  FIG. 1B , according to one or more embodiments. 
           [0024]      FIG. 10  depicts a top plan view of the flow-restricting baffle of the settling system depicted in  FIG. 1B , according to one or more embodiments. 
           [0025]      FIG. 11  depicts a side elevation view of the flow-restricting baffle of the settling system depicted in  FIG. 1B , according to one or more embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    A detailed description will now be provided. Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims. Each of the inventions will now be described in greater detail below, including specific embodiments, versions and examples, but the inventions are not limited to these embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the inventions, when the information in this patent is combined with available information and technology. 
         [0027]      FIG. 1A  depicts a plan view of an illustrative system  100  for bioremediation of hydrocarbon contaminated solids from oil and gas wellbores, according to one or more embodiments. In one or more embodiments, the system  100  can include one or more wellbores  110 , drilling fluid pumps  115 , mud tanks  120 , mixing tanks  130 , shakers  140 , centrifuges  150 , disposal bins  160 , and settling system  10 . Drilling fluid from the mud tanks  120  can be conveyed to the one or more wellbores  110  via the pump  115 . Used drilling fluids and solids, such as drill cuttings, sand, gravel, and other particulates, from the wellbore  110  can be sent to and collected in the shaker  140  via line  112 . 
         [0028]    The shakers  140  can be any device or mechanism capable of separating liquids from solids. In one or more embodiments, the shaker  140  can have a wire cloth screen that vibrates as the drilling fluid and solids flow on top of the screen. The liquid and solids having a particle size less than the mesh openings can pass through the screen, while larger solids are retained on the screen. Those larger solids that are not allowed to pass through the mesh can eventually fall off the back of the shaker  140  into the disposal bins  160  via line  142  or simply allowed to pile behind the shaker  140 . Such disposal pile can be removed for treatment and/or disposal. 
         [0029]    From the shakers  140 , the used drilling fluid having smaller solids contained therein is sent to the settling system  10  via line  145 . The settling system  10  can include two or more zones or compartments  11  to separate the solids from the liquids. The settling system  10  is explained in more detail below. In operation, each zone  11  provides a torturous path and pressure drop for the drilling fluid having the solids dispersed therein, allowing the solids to drop while passing along the liquid phase. The liquid phase can flow through the settling system  10  to the one or more centrifuges  150 , which can separate any fines or smaller particles that remain entrained in the drilling fluid. The drilling fluid that is free or essentially free of any solids can be returned to the mud tanks  120  via line  155  for subsequent drilling operations. The separated solids or fines from the centrifuges  150  can be directed to the one or more disposal bins  160  via line  165 , where the contents therein can be removed for treatment and/or disposal. 
         [0030]    In one or more embodiments, any one of the one or more zones  11  can include one or more microorganism populations to selectively remove any hydrocarbons from the separated solids that collect at the bottom thereof. As mentioned above, the hydrocarbon-containing solids or hydrocarbon contaminated solids in the used drilling fluids separate and settle at the bottom of the settling system  10  while the liquid phase passes over a top portion thereof. A hydrocarbon-containing solid or hydrocarbon contaminated solid can contain as much as 99 wt % hydrocarbon. Such solids can contain of from 1 wt % to 99 wt %; or 5 wt % to 95 wt %; or 10 wt % to 90 wt %; or 15 wt % to 85 wt %; or 20 wt % to 80 wt %; or 30 wt % to 70 wt %; or 40 wt % to 60 wt %; or about 50 wt % hydrocarbon. Such solids can have a mesh size of 200 or less, such as 190 or less, 180 or less, 170 or less, 160 or less, 150 or less, 140 or less, 130 or less, 120 or less, 110 or less, 100 or less, or 50 or less. 
         [0031]    The solids are typically slurried in the bottom of the settling system  10  with some of the drilling fluid that remains in the bottom. The microorganisms can convert the hydrocarbons on or entrained in the solids into carbon dioxide, water, and/or biomass. The resulting biomass can be disposed or further converted to useful energy. For example, the biomass can be used in conjunction with a gasification system to produce a syngas. 
         [0032]    Suitable microorganisms have a particular appetite for hydrocarbons. As such, the microorganisms are selective toward hydrocarbons and not drilling fluids. Illustrative microorganisms include but are not limited to bacteria and fungi. Preferred microorganisms are commercially available from Rapid Energy Services. 
         [0033]    As used herein, the term “drilling fluid” refers to any fluid that is not a hydrocarbon that is used in hydrocarbon drilling operations, including muds and other fluids that contain suspended solids, emulsified water or oil. The term “mud” as used herein refers to all types of water-base, oil-base and synthetic-base drilling fluids, including all drill-in, completion and work over fluids. 
         [0034]      FIG. 1B  depicts a plan view of an illustrative settling system  10  for separating solids from a drilling fluid, and  FIG. 2  depicts a partial cross section view of the settling system  10 , according to one or more embodiments. The settling system  10  can include one or more settling tanks or housings  12  arranged in parallel or series. Each settling tank  12  can include a first end wall  8 , a second end wall  9 , side walls  13 , and a bottom  19 . The settling tank  12  can have a shape that is rectangular, square, spherical, or the like. In one or more embodiments, the settling tank  12  is rectangular having a length to width ratio of at least 5:1 (5 to 1), such as 6:1; 7:1; 8:1; 9:1; or 10:1. The height of the settling tank  12  can vary depending on the volume of drilling fluid to be processed. In one or more embodiments, the settling tank  12  has a height of about 1 foot or more, such as 3 ft, 5 ft, or 10 ft or more. In one or more embodiments, the settling tank  12  has the capacity to handle at least 10,000 gallons of fluid, such as 12,000 gallons or more, 15,000 gallons or more, or 20,000 gallons of more. 
         [0035]    In one or more embodiments, the settling tank  12  can include two or more dividing or transverse walls  15  (three are shown) defining two or more zones therebetween. In one or more embodiments, a first transverse wall  15  can define the receiving zone  14  adjacent to the first end wall  8 ; a second transverse wall  15  can define the collecting zone  16  adjacent the second end wall  9 ; and a third transverse wall  15  can define the two intermediate zones  18  between the receiving zone  14  and the collecting zone  16 . The transverse walls  15  can define and separate the receiving zone  14 , intermediate zones  18 , and collecting zone  16 , which are within the tank  12 . Each transverse wall  15  can have an aperture or opening  23  located near or at the top thereof. In one or more embodiments, each opening  23  can be approximately 12 inches high by 18 inches wide. A flow-restricting baffle  22  can be mounted on the downstream side of each transverse wall  15  and can be aligned with the opening  23 . 
         [0036]    In one or more embodiments, the settling system  10  can include one or more mixing zones  36  disposed or otherwise attached to the tank  12  at an end opposite the receiving zone  14 . The mixing zone  36  can contain one or more mixers  37 , as best depicted in  FIG. 2 . As discussed in more detail below, the used drilling fluid having solids disposed therein can be mixed with one or more additives or agents in the mixing zone  36  to facilitate separation of the solids from the liquids. For example, the mixer  37  can be used to prepare a flocculating chemical agent that assists in settling solids from the drilling fluid. In one or more embodiments, the microorganisms can be added to the drilling fluid within the mixing zone  36 . 
         [0037]    The used drilling fluid containing one or more solids can be collected in the holding tank  24 . The drilling fluid can be pumped or allowed to gravity flow from the holding tank  24  into the receiving zone  14  and can be directed towards the flow-reversing barrier  20  via the inlet  26 . In one or more embodiments, the used drilling fluid can be sent directly to the receiving zone  14 . Within the receiving zone  14 , the fluid flow is impeded or stopped by the flow-reversing barrier  20  and reversed around the side panels. The flow-reversing barrier  20  can be supported by a bar  40  that can run transverse across the top of the settling tank  12 . The flow-reversing panel  20  can be best understood with reference to  FIGS. 4-7 . The reversal of fluid flow causes heavier solids to settle to the bottom  19  of the settling tank  12 , within the troughs  38  and  60 . As the fluid level rises in the receiving zone  14 , the fluid can overflow into the adjacent downstream intermediate zones  18  through the openings  23  in the transverse walls  15 . The fluid that flows through the openings  23  encounters the flow-restricting baffles  22  and deflects downwards to the bottom  19  of the tank  12 . The flow of the fluid through the baffle  22  causes solids in the fluid to settle to the bottom of settling tank  12 . Fluid can flow from zone to zone, by passing through successive baffles  22  in each transverse wall  15 , until the fluid reaches the collecting zone  16 . Fluid can be withdrawn from the collecting zone  16 , by the pump  34 , to be used again in the drilling operations, recycled to the holding tank  24 , and/or the receiving zone  14 . 
         [0038]    The solids that have settled to the bottom  19  of settling tank  12  can be conveyed by the augers  30  and  31  through the troughs  38  and  60  towards the collecting zone  16 . The augers  30  and  31  can expel a slurry of solids and fluid through the outlets  32  on the end wall  9 . The augers  30  and  31  can be rotated by drive mechanism  28 . The interaction between augers  30  and  31  and the drive mechanism  28  can be best understood with reference to  FIG. 3 . In one or more embodiments, the outlets  32  can be coupled to one or more pipes  33 . Each pipe  33  can be about 10 inches in diameter. The pipes  33  can extend to intersect with the plenum  56 . The plenum  56  can be made of 10 inch diameter pipe. The plenum  56  can have one or more end covers  57 . The end covers  57  can be removable to allow for cleaning-out of the plenum  56 . The plenum  56  can receive the slurry discharged from the outlets  32  and direct the slurry to the centrifuge  150  via the discharge ports  58 . The ports  58  can be about 4 inches in diameter and can be connected via tubes, pipes or hoses (not shown) to a pump (not shown) to transfer the slurry to the centrifuge  150 . 
         [0039]    In one or more embodiments, drilling fluid can be skimmed from the collecting zone  16  and mixed with one or more chemicals, agents, and/or microorganisms in the mixer  37 . The resulting mixture can be pumped via pump  34  to the receiving zone  14 , i.e. recycled, to mix with the received drilling fluid and assist in the settling of solids contained therein. In one or more embodiments, the settling system  10  can include a walkway or grating  64 . The walkway or grating  64  can be mounted on a sidewall  13  to permit an operator to inspect the fluid as it passes through settling tank  12 . One or more sampling stations for collecting and measuring the hydrocarbon content of the slurry can be located along the sidewall  13 . 
         [0040]    Referring to  FIG. 3 , the bottom wall  19  of the settling tank  12  in combination with one or more inverted V-shaped ribs  62  can form one or more troughs (two are shown  38 ,  60 ) that run lengthwise along the tank  12  from the first end wall  8  to the second end wall  9 . In troughs  38  and  60 , respectively, one or more augers (two are shown  30 ,  31 ) can be used to move settled solids towards the outlets  32  located on the second end wall  9 . In at least one specific embodiment, each auger  30  and  31  can be 10 inches in diameter and have a pitch of 10 inches. The augers  30  and  31  can be operated at any speed depending on the requirements of the drilling operation. For example, the augers  30  and  31  can be designed to turn at approximately 9 revolutions per minute or more. 
         [0041]    Each drive mechanism  28  can include an electric motor in the 2 to 3 horsepower range coupled to a gearbox (not shown). The output of the gearbox can be coupled to each auger via a belt and pulley system (not shown). To synchronize the augers  30  and  31  to turn at the same rate, each auger  30  and  31  can have a chain sprocket and can be coupled to one another via a drive chain (not shown). It should be obvious to one skilled in the art that drive mechanism  28  can also use an internal combustion engine or a hydraulic drive system as the motive power to turn the augers. It should also be obvious that the gear ratio of the gearbox and the pulley sizes are dependent on the type of motive power used in order to obtain the desired turning rate of the augers  30  and  31 . 
         [0042]    Referring to  FIGS. 4 ,  5 ,  6  and  7 , the flow-reversing barrier  20  can have a vertical main back panel  46  and two vertical side panels  42  perpendicular to the back panel  46 . The barrier vertical main back panel  46  and the two vertical side panels  42  can form a U-shaped structure. The flow-reversing barrier  20  can also have a bottom plate  44  disposed between the vertical side panels  42 . The bottom plate can extend from the back panel  46  and along the bottom edge of the vertical side panels  42 . The top of the flow-reversing barrier  20  can be supported by the support bar  40 . The bottom plate  44  can rest on top of the v-shaped rib  62 . One or more struts  41  can further support the flow-reversing barrier  20 . The struts  41  can extend diagonally upward from the rib  62  to the bottom edge of the back panel  46 . The top of the flow-reversing barrier  20  can be substantially flush with the top of the tank  12 . 
         [0043]    Referring to  FIGS. 8-11 , each flow-restricting baffle  22  can include a vertical back plate  52  and two vertical side walls  50  perpendicular to the vertical back plate  52 . The vertical side walls  50  are preferably arranged in a U-shape. In one or more embodiments, each vertical side wall  50  can be approximately 24 inches high by 8 inches wide. Each vertical side wall  50  of the flow-restricting baffle  22  can have two or more horizontal openings (five are shown)  54  stacked vertically on side wall  50 . In one or more embodiments, each horizontal opening can be approximately 6 inches wide by 2 inches high. When the fluid encounters the flow-restricting baffles  22 , as described above, the fluid will strike the vertical back plate  52 . Fluid can also pass through the slots  54  in the side walls  50  of the flow-restricting baffle  22 . The interaction between the fluid and vertical back plate  53  and slots  54  can increase the rate at which solids are removed from the fluid. 
         [0044]    The settling system  10  can incorporate the use of microorganisms to help to remove hydrocarbons from the solids deposited on the bottom  19  of settling tank  12 . The microorganisms can be located within the troughs  38  and  60  at the bottom of the settling tank  12 . After a given period of time, i.e. a sufficient time for the microorganisms to convert the hydrocarbons therein to water and carbon dioxide, the augers  30  and  31  can be used to empty the tank  12 . A water flush can also be used. Afterwards, the tank  12  can be re-loaded with a fresh microorganism population and ready to process another batch of used drilling mud with cuttings. 
         [0045]    The bioremediation of the solids in the settling tank  12  can also be continuous by employing two trains of settling tanks  10  working in parallel. One tank  12  can be off-line in clean-out mode while the other tank  12  can be in operation. This allows one tank  12  to operate at all times while the other is being flushed and/or re-loaded with the bioremediation material. 
         [0046]    The bioremediation process can be controlled by controlling the temperature, pH, and moisture levels within settling tank  12 . In addition, the augers  30  and  31  can be useful in the bioremediation process by providing mechanical agitation to stimulate the microorganism population. The augers  30  and  31  can be co-rotating or counter-rotating depending on the amount and/or degree of agitation desired within the settling tank  12 . The moisture level can be controlled by adding or removing water to the various zones of the settling tank  12 . Other nutrients can also be added to the settling tank  12 , if needed, to accelerate or enhance the remediation process and/or to control the pH of the hydrocarbon contaminated drill cuttings. 
         [0047]    In one or more embodiments, the microorganism population can be located in the collecting zone  16 . After the solids have had sufficient time to settle toward the bottom  19  of the tank  12 , the augers  30  and  31  can be activated to push the settled slurry to the collecting zone  16 , as described above. In the collecting zone  16 , the microorganisms can contact the solids slurry and degrade the hydrocarbon contaminated solids. In this configuration, the settling system  10  can be operated continuously with only a single tank  12 . For example, the single settling tank  12  can have zones  14  and  18  with enough capacity to handle a rate of used drilling fluid that is commensurate with the rate of remediation in the collecting zone  16 . 
         [0048]    In one or more embodiments, the system  10  can accommodate a flow rate of drilling fluid in the range of 1 to 500 gallons per minute. It should be obvious to those skilled in the art that the size of the settling tank  12  and the volume of each zone is a function of the volume of drilling fluid to be recycled and the amount of solids that need to be removed from the drilling fluids to facilitate their reuse. The size and dimensions of the settling tank  12  can be scaled larger or smaller, accordingly, to suit the associated drilling operation. The number of transverse walls within the settling tank  12  can be varied, as necessary, to accommodate the volume of drilling fluid required for the drilling operations. 
         [0049]    Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values are “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. 
         [0050]    Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted. 
         [0051]    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.