Abstract:
A proppant collection system for a hydraulic fracturing well site, the well site having one or more proppant handling apparatuses and a closed proppant storage device. The system includes a dust capture system having a hatch in the one or more proppant storage devices, a dust collection cap on the hatch, and a conduit attached to each dust collection cap for receiving dust that enters the dust collection cap from the proppant storage device through the hatch. A central vacuum unit is attached to the conduits of the dust capture system, the central vacuum unit including a slurry tank for receiving dust that is collected by the dust capture system. The slurry tank is adapted to aggregate the dust collected from the proppant storage device.

Description:
CROSS REVERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of U.S. Provisional Application Ser. No. 61/648,775, which was filed May 18, 2012, the full disclosure of which is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates in general to well site safety and maintenance systems and, in particular, to a system and method to contain proppant spillage during drilling and fracturing operations at a well site. 
         [0004]    2. Description of the Related Art 
         [0005]    Hydraulic fracturing has been used for decades to stimulate production from conventional oil and gas wells. The practice consists of pumping fluid into a wellbore at high pressure. Inside the wellbore, the fluid is forced into the formation being produced. When the fluid enters the formation, it fractures, or creates fissures, in the formation. Water, as well as other fluids, and some solid proppants, are then pumped into the fissures to stimulate the release of oil and gas from the formation. 
         [0006]    The proppants used in hydraulic fracturing operations are typically stored in sand bins, or other proppant storage devices. As the proppant is deposited in the sand bins, or as it exits the sand bins, a large amount of dust may be propagated, which will accumulate within the sand bin. This dust can create dangerous conditions. For example, in open sand bins, the dust may leave the sand bin and spread to surrounding areas, causing health hazards to people in the vicinity of the fracturing operation. 
         [0007]    In addition, the proppant exits the sand bins onto conveyor belts that carry the proppant on to a blender, which incorporates the proppant into the fracturing fluid to be pumped into the well. During the course of depositing the proppant onto the conveyors, and conveying the proppant to the blenders, some of the proppant may be spilled onto the ground around the machinery. Such a waste of proppant can be costly. 
       SUMMARY OF THE INVENTION 
       [0008]    The present technology provides a proppant technology that overcomes the disadvantages of the prior art by providing a vacuum system that collects proppant that spills off a conveyor, and that removes dust from the inside of a proppant storage device. 
         [0009]    In one embodiment, the technology includes a proppant collection system for a hydraulic fracturing well site having a dust capture system. The dust capture system includes a closed. (proppant storage device with hatches in the top thereof. The dust collection system further includes dust collection caps on the hatches, and a conduit attached to each dust collection cap for receiving dust that enters the dust collection cap from the proppant storage device through the hatch. 
         [0010]    A central vacuum unit is attached to the conduits of the dust capture system. The central vacuum unit has a suction line attached to each conduit, and includes a slurry tank for receiving dust that is collected by the dust capture system. The pressure inside the central vacuum unit is lower than the pressure inside the proppant storage device, so that dust generated within the proppant storage device will be drawn of through the dust collection cap and conduit, and into the central vacuum unit. The dust collection cap may also be open to the ambient environment at an upper end thereof so that ambient air can flow into the proppant storage device through the dust collection cap. A weather barrier may be attached to the dust collection cap adjacent the opening. The weather barrier is adapted to allow ambient air to enter the proppant storage device, while simultaneously blocking other environmental elements, such as, for example, rain, from entering the proppant storage device. 
         [0011]    Another embodiment of the present technology includes a moveable suction hose for collecting proppant that spills off, or is deposited adjacent to, proppant handling apparatuses, such as conveyors. A central vacuum unit is attached to the moveable suction hose and is adapted to generate pressures below an ambient air pressure. The central vacuum unit includes a slurry tank for receiving proppant that is collected by the moveable suction hose. The slurry tank has an outlet and is adapted to aggregate the proppant collected by the moveable suction hose, and to reintroduce the proppant to the proppant handling apparatuses. 
         [0012]    The central vacuum unit may further includes a filter positioned within the central vacuum unit to intersect the proppant received from the moveable suction hose before the proppant enters the slurry tank, and to separate the proppant from other material that may be drawn through the moveable suction hose. In addition, protective sheeting may be placed around the proppant handling apparatuses to create a barrier between the spilled proppant underlying earth surface. Such a barrier decreases the amount of non-proppant material pulled into the slurry tank by the moveable suction hose. 
         [0013]    Some embodiments of the present technology include both a suction hose for collecting spilled proppant, and a dust collection system. In such embodiments, a vacuum system may be connected to both the hose and the dust collection system, and is adapted to generate pressures below an ambient air pressure at the well site, as well as pressures within the proppant storage devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained, and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the appended drawings that form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and are therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
           [0015]      FIG. 1  is a schematic plan view of a well site where hydraulic fracturing is being used to induce production in accordance with an embodiment. 
           [0016]      FIG. 2  is a schematic plan view of a sand conveyance system at the well site of  FIG. 1  in accordance with an embodiment. 
           [0017]      FIG. 3  is a side perspective schematic view of a vacuum system of the hydraulic fracturing well site of  FIG. 1  in accordance with an embodiment. 
           [0018]      FIG. 4  is a top view of a dust collection cap of the sand conveyance system of  FIG. 2  in accordance with an embodiment. 
           [0019]      FIG. 5  is a side elevation view of the dust collection cap of the sand conveyance system of  FIG. 2  in accordance with an embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings which illustrate embodiments of the invention. This invention may, however, he embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and the prime notation, if used, indicates similar elements in alternative embodiments. 
         [0021]    In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. Additionally, for the most part, details concerning well drilling, running operations, general hydraulic fracturing processes and the like have been omitted inasmuch as such details are not considered necessary to obtain a complete understanding of the present invention, and are considered to be within the skills of persons skilled in the relevant art. 
         [0022]    Referring to  FIG. 1 , an example of a well site  11  for the production of oil and gas is shown. As shown, a process known as hydraulic fracturing is being used to induce the flow of desired substances, such as oil and gas into a previously drilled and cased wellbore. In the illustrated embodiment, a plurality of pumps  13  pump fluid into a plurality of wells  15  along with a mixture of proppant, such as sand, and other substances, such as acids and other chemicals. The substances are used to fracture openings within a formation in a production zone. Particulate matter in the proppant is forced into the fractures to hold open the fractures for production fluids to flow around the proppants into wells  15 . Generally, pumps  13  are connected to wells and a plurality of blenders  17  via a manifold (not shown) and flow lines (not shown) that permit pumps  13  to draw fluid blended with proppant and other chemicals for pressurization of the fluid and pumping of the fluid into wells  15 . Blenders  17  may include one or more units adapted to receive a base fluid, proppant, and other substances and mix or blend the materials into a generally uniform mixture for further pumping into wells  15 . Each blender may be hydraulically coupled to a hydration unit  19  that is further hydraulically coupled to pumps  13  and wells  15 . Hydration unit  19  controls the flow of fluid, such as water or brine, into blenders  17 . Hydration unit  19  may he hydraulically fed by acid units  21 , chemical trailer  23 , and working tanks  25 . Acid units  21  supply an acid solution to the fluids pumped into wells  15 . Chemical trailer  23  supplies a proprietary mixture of chemicals to the fluids pumped into wells  15  and may serve as the control point for the flow of chemicals into both hydration unit  19  and blenders  17 . Working tanks  25  store a base fluid, such as water or brine, into which the acid, chemicals, and proppant are mixed so that the fluid may be readily and easily accessed by hydration unit  19 . 
         [0023]    Blenders  17  are fed with proppant by a conveyor  27 , such as a T-belt conveyor. Conveyor  27  may be any suitable conveyor system capable of carrying or moving proppant from a first location to a second location spaced apart from the first location. In the illustrated embodiment, conveyor  27  may include a plurality of pulleys (not shown) having a continuous loop of material or a belt rotatable about the pulleys. The pulleys may be powered by a motor and drive system that is capable of supplying sufficient power to the pulleys to move the belt forward while the belt is under load or subject to loading perpendicular to the movement of the belt. Conveyor  27  carries proppant, such as sand, deposited at a distal end  29  of conveyor  27  to a hopper or feed point of blender  17  for mixing of the proppant with the fluid. Proppant is carried to distal end  29  of conveyor  27  from a plurality of sand bins  31  on one or more conveyors  33 . Conveyors  33  may be belt type conveyors similar to conveyor  27 . A person skilled in the art will understand that conveyors  27 ,  33  may be of different sizes and load capabilities and configured to operate at different speeds. A person skilled in the art will also understand that conveyors  27 ,  33  may also be any other suitable conveyor system adapted to transport proppant or other particulate material. Sand bins  31  may be any suitable proppant storage device capable of containing proppant for use as part of the hydraulic fracturing process. In the illustrated embodiments, sand bins  31  include hatches  47  (shown in  FIG. 2  and described in more detail below) through which proppant may be supplied into sand bins  31 . Sand bins  31  may also include an opening in a lower portion through which proppant may be gravity fed or fed through by a motorized device such as an auger or similar device. 
         [0024]    Still referring to  FIG. 1 , a vacuum system  35  may be disposed proximate to T-belt conveyor  27 . Vacuum system  35  is adapted to capture proppant that may spill off of conveyors  33  and  27  during transport of proppant into blenders  17  as described in more detail below. Vacuum system  35  may also be pneumatically coupled to sand bins  31  as described in more detail below. Various other equipment may be disposed around well site  11  to provide other necessary operations of the hydraulic fracturing process, for example, by providing control systems for operation of the previously described equipment and the like. 
         [0025]    Referring to  FIG. 2 , vacuum system  35  may include a central unit  36  and a movable suction hose  37  coupled to central unit  36 . Central unit  36  may be any suitable industrial portable vacuum system. In the illustrated embodiment, central unit  36  may be an Industrial Vacuum Equipment Corporation Hurricane 500 having a 170 hp diesel or electric powered vacuum. The vacuum may include a positive displacement blower capable of 2,350 CFM at 27″ Hg pressure. A person skilled in the art will recognize that other suitable central units  36  may be used, provided the central unit operates generally as described herein. Generally, central unit  36  may include a motor, a centrifugal blower/exhauster or the like, a storage receptacle, a filtration system, and the appropriate interconnections between the components for operation thereof. Central unit  36  may generate pressures lower than the ambient atmospheric pressure of well site  11 , i.e. generate suction, so that objects and particulates at well site  11  may be drawn into suction hose  37 . 
         [0026]    Referring to the example of  FIG. 3 , vacuum system  35  includes a slurry tank  61  and an engine  63 . Hose  37  couples to vacuum system  35  so that hose  37  feeds slurry tank  61  as indicated by notation A. Engine  63  will have sufficient horsepower to generate suction in hose  37  so that proppant spilled off of conveyors  27 ,  33  may be drawn into a suction nozzle  39  shown mounted on an open end of hose  37 . Hose  37  will be sufficiently flexible to allow a user to manipulate suction nozzle  39  proximate to conveyors  27 ,  33  to draw spilled proppant into hose  37 . The collected proppant may be stored in slurry tank  61  and added to the blended materials pumped downhole through outlet  65  of slimy tank  61 . 
         [0027]    As proppant moves from sand bin  31  to conveyor  33  and from conveyor  33  to conveyor  27 , a portion of the proppant may spill off of conveyors  27 ,  33  and be deposited adjacent conveyors  27 ,  33 . This portion of spilled proppant represents lost material to operators of well site  11 , necessitating acquirement of more proppant than may be needed to complete the hydraulic fracturing process. This represents significant extra expense to operators of well site  11 . In addition, excess buildup of spilled proppant adjacent conveyors  27 ,  33  may cause conveyors  27 ,  33  to bind, or sand-off as the weight of the proppant may halt movement of the pulleys and belt of conveyors  27 ,  33 , halting their operation and causing a halt of the hydraulic fracturing process. Again, this results in a significant cost to the operator of the well site  11 . Generally, a laborer may operate vacuum system  35  and manipulate hose  37  so as to draw an end of hose  37  having suction nozzle or scoop  39  adjacent to areas of conveyors  27 ,  33  where proppant has spilled or fallen off of conveyors  27 ,  33 . The suction generated by central unit  36  will draw the spilled proppant into vacuum system  35 , where the proppant may be aggregated and reintroduced into the hydraulic fracturing system at either sand bin  31 , conveyors  27 ,  33 , or blenders  17 . In this manner, the additional costs due to spillage of proppant are reduced as some or all of the spilled proppant may be collected and used. In an exemplary embodiment, 97% of spilled proppant is collected and reintroduced into the hydraulic fracturing system. 
         [0028]    Central unit  36  may also include one or more filter systems  38  adapted to separate proppants from other material that may be drawn through hose  37 . The separated proppant may be deposited into slurry tank  61 , where a screw type auger  40  may push the proppant through outlet  65 . In the illustrated embodiment, outlet  65  deposits the sand onto conveyor  27 . A person skilled in the art will understand that the collected proppant may be stored or otherwise reintroduced into the hydraulic fracturing process to reduce loss of proppant. The undesired material collected by vacuum system  35  may be disposed of by any suitable means, for example by spreading the material around the site, or by hauling the material to a landfill or other disposal facility. In an embodiment, plastic sheeting may be placed around sand bins  31 , conveyors  27 ,  33 , and blenders  17  as a barrier between spilled proppant and the underlying earth surface at well site  11 . In an exemplary embodiment, the plastic sheeting acts as a barrier to prevent inadvertent collection of ambient well site  11  material into vacuum system  35  and the hydraulic fracturing process. In an exemplary embodiment, the plastic sheeting also acts as a barrier to prevent loss of proppant into the ambient well site  11  material and to prevent contamination of well site  11  with non-native materials. 
         [0029]    Referring back to  FIG. 2 , a dust capture system  41  may also be pneumatically coupled to vacuum system  35 , and further coupled to sand bin  31 . Typically, the sand bin  31  is filled with sand from a truck (not shown) that conveys the sand to the well site. The truck deposits the sand into the sand bin  31  using a hose by spraying the sand into the sand bin  31  through the hose. In some systems, the sand bin  31  may be open. This may lead to problems, however, because the spraying of the sand into the sand bin  31  can generate large amounts of dust, which can billow out of the sand bin  31  into the surrounding environment. This dust presents hazards to the surrounding environment, as well as to people near the site of the fracturing operation. In some embodiments, therefore, the sand bin  31  may be closed, thereby preventing dust from leaving the sand bin  31  and entering the surrounding environment during filling of the sand bin  31 . 
         [0030]    Dust capture system  41  may include a main line  43  shown having an end connected to an inlet on central unit  36 , and four feeder lines  45  that each connect to main line  43 . A person skilled in the art will understand that more or fewer feeder hues  45  may be used as needed for the particular application of dust capture system  41  as described in more detail below. Feeder lines  45  communicate with hatches  47  of the sand bin  31  on an upper surface of sand bin  31 . The hatches  47  are coupled to dust collection caps  49  adapted to be tit over hatches  47 . Feeder lines  45 , main line  43 , and central unit  36  are thus communication with a space inside of sand bin  31 . In an exemplary embodiment, sand bin  31  has four hatches  47  and four corresponding feeder lines  45 . Dust capture system  41  will generate a lower pressure in main line  43  and feeder lines  45  than the pressure in sand bin  31 , so that dust generated from movement of proppant within sand bin  31 , such as during filling of the sand bin  31 , will be drawn off through collection caps  49 , feeder lines  45 , and main line  43 . In one example embodiment, main line  43  and feeder lines  45  may be 2″ PVC pipe that is pneumatically coupled to a suction side of central unit  36 . A person skilled in the art will understand that main line  43  and feeder lines  45  may be any suitably sized suction lines formed of any suitable material adapted to operate as described above. 
         [0031]    In the example of  FIG. 2 , hatches  47  are formed in upper surfaces of sand bins  31  and permit access to interiors of sand bins  31 . Hatches  47  permit an operator or user of sand bin  31  monitor proppant movement within sand bin  31  during draw off of proppant through the lower portion of sand bin  31 . Hatches  47  may also permit an additional opening for sand to be passed into sand bin  31  when sand bin  31  is being filled. Generally, proppant is drawn from sand bin  31  from a lower portion of sand bin  31  through an opening (not shown) in sand bin  31 . Proppant will be deposited on an end of conveyor  33  positioned underneath the opening in the lower portion of sand bin  31 . Conveyors  33  then operate to carry proppant to conveyor  27 . Proppant may be deposited on conveyor  27  at distal end  29  of conveyor  27 , or anywhere else along the length of conveyor  27 . Conveyor  27  carries the proppant from distal end  29  to blenders  17 . Generally, the proppant will be deposited in an upper portion of blender  17 , where the proppant is mixed with chemicals, acids, and water for pumping down wells  15 . In an example, hatches  47  are opened during this process to maintain an equal pressure between the interior of sand bin  31  and the ambient environment in which sand bin  31  resides. This prevents generation of a pressure differential that may cause catastrophic failure of sand bin  31 . While four hatches  47  are shown in the illustrated embodiment, a person skilled in the art will recognize that sand bins  31  may include more or fewer hatches  47 . 
         [0032]    Referring to  FIG. 4 , hatch  47  may be a square shaped opening in the upper portion of sand bin  31  as shown. A person skilled in the art will understand that hatch  47  may be any suitable opening in the upper portion of an upper deck of sand bin  31 . Hatch  47  may include an upwardly extending lip to define a barrier between the upper portion of sand bin  31  and hatch  47 . As shown in  FIGS. 4 and 5 , dust caps  49  include a lower portion  51  adapted to fit over hatch  47 . Lower portion  51  may be a substantially planar member having a lip  53  depending normal to lower portion  51 . In the illustrated embodiment, lip  53  may fit around the upwardly extending lip of hatch  47  so that lower portion  51  may rest on the upwardly extending lip of hatch  47  having lip  53  surrounding the lip portion of hatch  47 . In this manner, dust collection cap  49  may mount over hatch  47 . Dust collection cap  49  includes an upwardly extending portion  55 . In the illustrated embodiment, upwardly extending portion  55  is a cone shaped member sealingly joined at a wider end to lower portion  51 . Upwardly extending portion  55  may have a hollow interior to allow for a flow of matter through upwardly extending portion  55 . Feeder line  45  is pneumatically coupled to upwardly extending portion  55  proximate to lower portion  51 , and in fluid communication with hatch  47 . In an example of operation, vacuum system  35  draws fluid from lines  43 ,  45  to generate a lower pressure in upwardly extending portion  55  of dust collection cap  49 . As proppant is drawn from sand bin  31  to conveyors  27 ,  33 , dust develops within sand bin  31  and billows upward toward hatches  47 . The dust enters upwardly extending portion  51  and will be drawn into feeder line  45  to be carried back to vacuum system  35 . Upwardly extending portion  55  has an opening  57  at its upper end opposite lower portion  51 . Opening  57  permits ambient air to flow into sand bin  31  through dust collection cap  49  to prevent generation of excessive suction in sand bin  31 . A weather cap  59  fits over opening  57  to prevent passage of rain or other moisture into dust collection cap  49  and sand bin  31 . Weather cap  59  may be raised from or otherwise partially separated from opening  57  to permit air flow around weather cap  59  into opening  57 . A person skilled in the art will understand, that dust collection cap  49  may have any other suitable shape, for example, pyramidal, cuboid, spherical, or the like. 
         [0033]    A person skilled in the art will understand that by having one or more laborers proximate to the proppant movement apparatus, conveyors  27 ,  33 , the laborers will be suitably placed to conduct sampling operations of the proppant during proppant movement operations. In this manner, a laborer may procure proppant samples from conveyors  27 ,  33  and test the samples to ensure that the proppant used during that particular stage of the hydraulic fracturing process matches the specifications of the proppant needed for that particular stage of the hydraulic fracturing process. 
         [0034]    Accordingly, the disclosed embodiments provide numerous advantages. For example, the disclosed embodiments provide a dust collection system that substantially eliminates waste and decreases loss of proppant that may billow into the atmosphere as dust or spill off of a conveyor during the hydraulic fracturing process. This reduces costs, and operators may eliminate the requirement to purchase excess proppant to accommodate for this spillage and dust loss. In addition, the disclosed embodiments decrease downtime of the system by eliminating sanding off the belt events that cause partial or total shut down of the system while the conveyors are cleaned and brought back online. Still further, the disclosed embodiments increase workplace safety by eliminating sand piles adjacent the conveyors that may trip or otherwise injure workers and eliminate airborne particles that may cause asthma or other lung related ailments in site workers. 
         [0035]    It is understood that the present invention may take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or scope of the invention. Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, sonic features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.