Patent Publication Number: US-9422688-B2

Title: Secondary containment mat

Description:
BACKGROUND 
     This applications claims priority to U.S. Provisional Patent Application no. 61/904,363, filed on Nov. 14, 2013 and entitled “Secondary Containment Mat,” the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     Certain aspects of the present disclosure generally relate to containment mechanisms for oil and gas drilling operations, and more particularly to a secondary containment mat for use at oil and gas drilling sites. 
     2. Background 
     Oil and gas drilling operations generally involve a drilling rig and associated support equipment that are used to drill and line oil and gas wells, as is well known. During drilling operations, a significant amount of activity occurs at the drilling site involving many different pieces of drilling equipment and support equipment. In order to reduce environmental impact to the areas adjacent and nearby to drilling sites, sites are commonly lined with liner to help prevent any liquids spilled at the drill site from penetrating the ground or entering a water supply. Additionally, matting may be installed around the drill site to provide a working surface and keep traffic from directly contacting liner material and potentially damaging the liner. Additionally, matting may help reduce impact on the ground area around drill sites from traffic and equipment at the drill site, such as ruts, erosion, excessive soil compaction, etc. 
     While helping to reduce environmental impacts, current lining and matting may take a significant amount of time and cost to install. Additionally, as liner material is often placed directly on the ground surface, tears and/or punctures may occur, thereby reducing the effectiveness of the liner. Accordingly, it may be desirable to have more efficient and reliable containment and matting systems. 
     SUMMARY 
     The described features generally relate to one or more improved secondary containment mats and systems of secondary containment mats. According to certain examples, a secondary containment mat includes a top surface and a bottom surface, with a liner material placed between the top and bottom surfaces. The mat thus provides a modular structural mat that may be installed at a drill site adjacent to a number of other mats to provide containment of potential spills, a reliable working surface for drilling operations, and relatively fast and less expensive installation. In some examples, the top surface may include a number of adjacent boards, and the bottom surface may include a number of boards at least some of which include gaps therebetween. The liner may be, for example, a 100 mil well pad liner, and may extend beyond the edges of the top and bottom surfaces. In some embodiments, the liner of adjoining mats may be joined together to provide enhanced spill protection. The top and bottom surfaces may be interconnected through any of a number of techniques, such as nails or bolts, for example. In some embodiments, boards of the top and bottom surfaces are bolted together, and a traction surface may be applied to the top surface of the mat to provide enhanced traction for people and vehicles that may use the mat. 
     Further scope of the applicability of the described methods and apparatuses will become apparent from the following detailed description, claims, and drawings. The detailed description and specific examples are given by way of illustration only, since various changes and modifications within the spirit and scope of the description will become apparent to those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further understanding of the nature and advantages of the present invention may be realized by reference to the following drawings. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. 
         FIG. 1  is a top view of a secondary containment mat apparatus in accordance with various aspects of the present disclosure; 
         FIG. 2  shows a side view of the secondary containment mat apparatus of  FIG. 1  in accordance with various aspects of the present disclosure; 
         FIG. 3  shows a side view of two adjacent secondary containment mats in accordance with various aspects of the present disclosure; 
         FIG. 4  shows a top view of a portion of a secondary containment mat in accordance with various aspects of the present disclosure; 
         FIGS. 5 and 6  show cross section views of the mat illustrated in  FIG. 5  in accordance with various aspects of the present disclosure; 
         FIG. 7A  is a top view of another example of a secondary containment mat apparatus in accordance with various aspects of the present disclosure; 
         FIG. 7B  shows a top view of a portion of the example secondary containment mat of  FIG. 7A  in accordance with various aspects of the present disclosure; 
         FIGS. 8 and 9  show cross section views of the mat illustrated in  FIG. 7  in accordance with various aspects of the present disclosure; 
         FIG. 10  shows a top view of another secondary containment mat apparatus in accordance with various aspects of the present disclosure; 
         FIG. 11  shows a side view of the secondary containment mat apparatus of  FIG. 10  in accordance with various aspects of the present disclosure; 
         FIG. 12  shows a side view of two adjacent secondary containment mats of  FIG. 10  in accordance with various aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Described embodiments are directed to apparatuses, systems and methods for improved secondary containment mats and systems of secondary containment mats. According to embodiments, a secondary containment mat includes a top surface and a bottom surface, with a liner material placed between the top and bottom surfaces. The mat thus provides a modular structural mat that may be installed at a drill site adjacent to a number of other mats to provide containment of potential spills, a reliable working surface for drilling operations, and relatively fast and less expensive installation. In some embodiments, the top surface may include a number of adjacent boards, and the bottom surface may include a number of boards at least some of which include gaps therebetween. The liner may be, for example, a 100 mil well pad liner, and may extend beyond the edges of the top and bottom surfaces. In some embodiments, the liner of adjoining mats may be joined together to provide enhanced spill protection. The top and bottom surfaces may be interconnected through any of a number of techniques, such as nails or bolts, for example. In some embodiments, boards of the top and bottom surfaces are bolted together using structural spiral shank fasteners. Thus, a modular structural mat may be provided for use in all stages of, for example, oil and gas well development (e.g., from pad development to drilling, to completions to production). Such mats may also be used for other applications, such as pipeline companies or utility companies that may use a series of interconnected mats to build a road or other traveling/staging surface during construction, to name but a couple of examples. It will be readily understood by one of skill in the art that such modular structural mats may be used in numerous different applications and environments. 
     Thus, the following description provides examples, and is not limiting of the scope, applicability, or configuration set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the spirit and scope of the disclosure. Various embodiments may omit, substitute, or add various procedures or components as appropriate. Also, features described with respect to certain embodiments may be combined in other embodiments. 
     Referring first to  FIGS. 1 and 2 , top and side views, respectively, of a mat  100  are illustrated. In this embodiment, the mat is approximately 16 feet (4.88 meters) by 8 feet (2.44 meters). The mat  100  has a top surface made up of dimensional lumber that in this embodiment includes 13 adjacent “2×8” pieces of kiln dried lumber, designated as boards A through M in  FIGS. 1 and 2 . As will be readily recognized by one of skill in the art, a “2×8” piece of dimensional lumber may have an actual net board size of 1.5 inches (38.1 mm) by 7.25 inches (184 mm), and thus the 13 adjacent boards A through M result in a width of the mat  100  of approximately 8 feet (2.44 meters). In this embodiment, the boards A-M of the top surface are 16 feet (4.88 meters) long. 
     The bottom surface in this embodiment includes 20 pieces of dimensional lumber, indicated as  1  through  20  in  FIGS. 1 and 2 . Boards  1  through  20  are arranged transversely to boards A through M. In this example, the mat  10  includes two adjacent boards ( 1 ,  2 , and  19 ,  20 ) at each end that have little or no gap, with 16 equally spaced boards ( 3  through  18 ) with gaps of approximately 2⅞ inches (73 mm) Of course, it is to be understood that the dimensions provided here are for purposes of illustration and discussion only, and other dimensions and arrangements may be utilized as will be readily recognized by one of skill in the art. Also, it is to be noted that the figures are not drawn to scale, and various elements may be illustrated as being enlarged or reduced in order to illustrate various concepts and techniques described herein. 
     Between top and bottom surfaces is a liner  205 . Such a liner may be a well pad liner such as commonly used in present day drilling operations, and in some embodiments is a 100 mil (2.54 mm) liner located between the top and bottom surfaces with a 12 inch (304.8 mm) overlap on all 4 sides. This, the mat  100  provides a two-ply secondary containment with a liner between the plys. The liner  205  may be, for example, a polypropylene composite liner having a number of barrier films sandwiched by geotextile with heat fused surfaces. Such a liner  205  may absorbs relatively small leaks and spills, and help prevent larger spills from reaching the ground and/or water supplies. 
     During installation, multiple mats  100  may be placed adjacent to one another to provide a lined working surface.  FIG. 3  illustrates a partial side view of an intersection of two adjacent mats  100 - a  and  100 - b . In this example, each mat  100  has a 2 inch lap joint (illustrated in  FIG. 1 ) that may overlap with a corresponding extension of the bottom surface of an adjoining mat  100 . These may be adjoined, as illustrated at  210  in  FIG. 3 , to provide adjoining mats  100  that are partially interlocked. As noted above, liner  205  may extend beyond edges of the mats  100 , and overlapping areas of adjoining liners may be connected, as indicated at  210  in  FIG. 3 . Portions of adjoining liners  205  may be sealed together to provide enhanced containment of any spills. Such sealing may be through heat sealing, adhesive, taping, or any other suitable means to interconnect liners  205 . The joined liners may be folded down onto the top surface, or excess liner may be cut away. In some deployments, interconnected mats  100 , after being interconnected and any sealing completed, may have a top sealing coat applied thereto to provide enhanced containment of potential spills, In some examples, such a top sealing coat may be sprayed onto the mats  100 , and gravel, sand, or other enhanced gripping material may be applied with the sealing coat, or separate from the sealing coat, and may provide an enhanced gripping surface on the top surface of the mats  100 . In some examples, the top coat may be a two part polymer that protects the mat and the liner below. Sand, or other abrasive material, may be integrated into the polymer creating a traction surface to assist with personnel safety. 
     As mentioned above, top and bottom layers of mats  100  may be secured together through any of a number of interconnection techniques. With reference now to  FIGS. 4-6 , an embodiment is described that utilizes nails  405  for securing boards together. In this example, each intersection of boards in the top and bottom surfaces include four opposed angle structural spiral shank nails. In some embodiments, nails  405  are coated to prevent rusting (which with a ‘common nail’ is one of the prime reasons for loosening). A structural spiral shank nail also have relatively high resistance to pull out, which may enhance reliability of the mat  100 . Nails  405 , in some embodiments, are three inch nails. Each nail may be angled, as illustrated in cross-section views of  FIGS. 5 and 6 , from the outer edge of the board intersection, towards the center of the intersection. In some embodiments, this angle is approximately 12 degrees, and may provide enhanced structural support to mats  100 . While nails  405  are illustrated in  FIGS. 4-6 , it will be readily understood by one of skill in the art that other techniques may be used to secure top and bottom surfaces to one another, such as, for example, different types of nails, bolts, rivets, interlocking members, or other fasteners, or combinations thereof. One such example of another technique to secure top and bottom layers of mats  100  is illustrated in  FIGS. 7-9 , and uses bolts  705  for securing boards together. In this example, a number of intersections of boards in the top and bottom surfaces include a bolt  705  for securing the boards together. In some examples, boards  1 - 26  and A-M may be secured together with ⅜″ (9.5 mm) by 3″ (76.2 mm) inch long carriage bolts with 1 inch (25.4 mm) flanged nuts. As discussed above, it will be readily understood by one of skill in the art that other techniques may be used to secure top and bottom surfaces to one another. 
     Referring next to  FIGS. 10 and 11 , top and side views, respectively, of another exemplary mat  1000  are illustrated. In this embodiment, the mat is again approximately 16 feet (4.88 meters) by 8 feet (2.44 meters). The mat  1000  in this example is made of an engineered wood product and is a single piece of material. In some examples, the mat may be formed from multiple plys of laminated wood material that may be arranged with different orientations to provide substantial strength and durability. In some examples, the mat may be formed from cross laminated timber, such as Crosslam™ Ultracore available from StructureLam of Penticton, British Columbia, Canada. Again, it is to be understood that the dimensions provided here are for purposes of illustration and discussion only, and other dimensions and arrangements may be utilized as will be readily recognized by one of skill in the art. Also, it is to be noted that the figures are not drawn to scale, and various elements may be illustrated as being enlarged or reduced in order to illustrate various concepts and techniques described herein. In certain examples, mats  1000  may be configured to be interconnected through a joint  1025 , shown in  FIG. 12 , having a bottom shelf  1010  and a top extension  1015 . Of course, other types of joints  1025  may be implemented, such as a tongue and groove, etc. 
     A liner  1020  may be placed under some or all of a number of mats  1000 , as illustrated in  FIGS. 11 and 12 , in some examples. Such a liner may be a well pad liner such as commonly used in present day drilling operations, and in some embodiments is a 100 mil liner. The liner  1020  may be, for example, a polypropylene composite liner having a number of barrier films sandwiched by geotextile with heat fused surfaces. Such a liner  1020  may absorb relatively small leaks and spills, and help prevent larger spills from reaching the ground and/or water supplies. 
     During installation, multiple mats  1000  may be placed adjacent to one another to provide a lined working surface.  FIG. 12  illustrates a partial side view of an intersection of two adjacent mats  1000 - a  and  1000 - b . In this example, each mat  1000  is interconnected at joint  1025 , to provide adjoining mats  1000  that are partially interlocked. In some deployments, as discussed above, interconnected mats  1000 , before or after being interconnected, may have a top sealing coat applied thereto to provide enhanced containment of potential spills, In some examples, such a top sealing coat may be sprayed onto the mats  1000 , and gravel, sand, or other enhanced gripping material may be applied with the sealing coat, or separate from the sealing coat, and may provide an enhanced gripping surface on the top surface of the mats  1000 . 
     The previous description of the disclosure is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Throughout this disclosure the term “example” or “exemplary” indicates an example or instance and does not imply or require any preference for the noted example. Thus, the disclosure is not to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.