Patent Publication Number: US-11047181-B2

Title: Diffuser assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Ser. No. 16/105,556, filed on Aug. 20, 2018, which is a continuation-in-part of U.S. Ser. No. 15/061,493, filed on Mar. 4, 2016, now U.S. Pat. No. 10,053,960. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in part to devices and methods used in oil and gas drilling operations to diffuse aggregations of lost circulation materials (LCM) which are used to resolve lost circulation and fluid losses, and more particularly to such devices which include elements for breaking down larger masses of LCM during the diffusion step. 
     2. Prior Art 
     When drilling oil and gas wells, under proper conditions during the drilling process, drilling fluids and drill cuttings are circulated away from the drill bit into the annulus around the drill stem and brought to the surface. Such drilling fluids are also important for providing hydrostatic pressure to prevent formation fluids from entering into the well bore, keeping the drill bit cool and clean during drilling, and suspending the drill cuttings while drilling is paused and when the drilling assembly is brought in and out of the hole. Because proper circulation is critical to the drilling process, any lost circulation is a significant problem that must be overcome for drilling to recommence. 
     Lost circulation is the partial or complete loss of drilling fluid or cement slurry to the formation during drilling or cementing operations or both. Lost circulation can be brought on by natural causes, such as naturally fractured formations or unconsolidated zones, or induced causes, such as when the hydrostatic fluid column pressure exceeds the fracture gradient of the formation and the formation pores break down enough to receive (rather than resist) the fluid. When lost circulation occurs, it typically results in the new expenditure of time and mud or cement, adding substantially to the overall cost of a well. 
     The consequences of lost circulation can be as little as the loss of a few dollars of drilling fluid, or as disastrous as a blowout and loss of life. If the amount of fluid in the well bore drops due to lost circulation (or any other reason), hydrostatic pressure is reduced, which can allow a gas or fluid which is under a higher pressure than the reduced hydrostatic pressure to flow into the well bore. Another consequence of lost circulation is dry drilling. Dry drilling occurs when fluid is completely lost from the well bore without actual drilling coming to a stop. The effects of dry drilling range from as minor as destroying a bit to as serious as major damage to the well bore requiring a new well to be drilled. Dry drilling can also cause severe damage to the drill string, including snapping the pipe, and the drilling rig itself. 
     Lost circulation material (LCM) is the collective term for substances added to drilling fluids when drilling fluids are being lost to the formations downhole. Commonly used LCM types include fibrous (cedar bark, shredded cane stalks, mineral fiber and hair), flaky (mica flakes and pieces of plastic or cellophane sheeting) or granular (ground and sized limestone or marble, wood, nut hulls, Formica, corncobs and cotton hulls). The LCM, in combination with other fluids with increased viscosity, are used to fill fractures and heal the loss zone quickly. 
     As the LCM is delivered to the loss zone, accumulations and aggregations of the LCM can occur which may obstruct the necessary flow of fluids to the site. Therefore, it is desirable to prevent such obstructions by diffusing such aggregations or “clumps” as early and as quickly as possible. Given the nature of some types of LCM and their tendency to aggregate into such clumps, one solution is to cause such clumps to contact blades or cutters placed into the fluid path, but while not substantially decreasing the proper fluid flow during the healing process of the loss zone. 
     In addition to diffusion near the loss zone, there is also a need for diffusion of LCM clumps that form as the fluids are delivered through the drill pipe at the rig floor, as well as diffusion of LCM clumps which may form after leaving the mixing tank where the LCM is added to the drilling fluids. Furthermore, once drilling operations are concluded, the diffuser can also be deployed in various locations for LCM diffusion in completion and workover operations. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide a diffuser assembly, comprising a diffuser adapted to reside within a conduit, having an upper mounting member mountable within the conduit and having an fluid inlet port, and a lower section having a diffuser screen; and a plurality of diffusing members radially oriented relative to a central axis of the diffuser. 
     Another object of the present invention is to provide a diffuser assembly, wherein the diffuser screen is a cylinder having a plurality of diffuser slots formed therein and a bottom cap having a fluid port. 
     Another object of the present invention is to provide a diffuser assembly, wherein each of the plurality of diffusing members includes a diffusing edge. 
     Another object of the present invention is to provide a diffuser assembly, wherein a first set of diffusing members is mounted at a first selected height along the central axis of the diffuser screen, and wherein a second set of diffusing members is mounted at a second selected height along the central axis of the diffuser screen. The diffusing members may be mounted to the diffuser screen such that the diffusing edges are either internal or external to the diffuser screen. 
     Yet another object of the present invention is to provide a diffuser assembly, which further includes a plurality of centralizing members adjacent to the diffuser screen. 
     Another object of the present invention is to provide a diffuser assembly that can be positioned in different locations, including within a downhole carrier sub inside a well bore, within a drill pipe at the rig floor, or within a conduit in fluid communication between a mixing tank and a pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements. 
         FIG. 1  shows a side sectional view of a carrier sub, such as a stabilizer or other type of downhole sub, containing a preferred embodiment of a diffuser screen of the present invention. 
         FIG. 2  shows a side view of the diffuser screen of  FIG. 1 . 
         FIG. 3  shows a bottom view of the diffuser screen of  FIG. 1 . 
         FIG. 4  shows a top view of the diffuser screen of  FIG. 1 . 
         FIG. 5  shows a perspective view of the diffuser screen of  FIG. 1  depicting the screening cylinder having internal cutters. 
         FIG. 6  shows a perspective view of the diffuser screen of  FIG. 1  without the screening cylinder to better depict the placement of the internal cutters. 
         FIG. 7  shows an alternate embodiment of the diffuser screen having external cutters and a lower slotted screening cylinder. 
         FIG. 8  shows a bottom view of the diffuser screen of  FIG. 7 . 
         FIG. 9  shows a top view of the diffuser screen of  FIG. 7 . 
         FIG. 10  shows a perspective view of the diffuser screen of  FIG. 7  depicting the screening cylinder having external cutters. 
         FIG. 11  shows a perspective view of the diffuser screen of  FIG. 7  without the screening cylinder to better depict the placement of the external cutters. 
         FIG. 12  shows a further alternate embodiment of the diffuser screen having external cutters and a lower screening constructed from vertical rods. 
         FIG. 13  shows a bottom view of the diffuser screen of  FIG. 12 . 
         FIG. 14  shows a top view of the diffuser screen of  FIG. 12 . 
         FIG. 15  shows a perspective view of the diffuser screen of  FIG. 12  depicting the screening cylinder having external cutters. 
         FIG. 16  shows a perspective view of the diffuser screen of  FIG. 12  without the screening cylinder to better depict the placement of the external cutters. 
         FIG. 17  shows the diffuser deployed within a stabilizer. 
         FIGS. 18A and 18B  show retrievable and nonretrievable diffusers deployed within a section of drill pipe at the rig floor. 
         FIG. 19  shows the diffuser deployed within a conduit between a drilling fluid mixing tank and a pump. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Before the subject invention is further described, it is to be understood that the invention is not limited to the particular embodiments of the invention described below, as variations of the particular embodiments may be made and still fall within the scope of the appended claims. It is also to be understood that the terminology employed is for the purpose of describing particular embodiments, and is not intended to be limiting. Instead, the scope of the present invention will be established by the appended claims. 
     In this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Unless otherwise specified herein, all materials of construction are preferably steel resistant to the corrosive effects common in oil and gas production environments. As used herein the term “conduit” shall mean any tubular member into which the diffuser  1  can be installed for the purpose of allowing LCM-containing fluid to flow through the conduit and be broken apart, or diffused, by the diffuser  1 . Non-limiting examples of conduits may be a carrier sub, drill pipe, stabilizer, or other tubular member such as shown in the figures. 
     Turning now to the figures, a preferred embodiment of the present invention is shown in  FIGS. 1-6  as a diffuser assembly  1  comprising a diffuser  2  adapted to reside within a conduit in the form of a carrier sub  3 , having an upper mounting member  4  mountable within the carrier sub  3  and having an fluid inlet port  5 , and a lower section having a diffuser screen  6 . As shown in more detail in  FIGS. 4 and 6 , a plurality of cutters  7  are removably attached to the diffuser screen  6 , wherein the cutters  7  are radially oriented relative to a central axis  8  of the diffuser screen  6 . The diffuser screen  6  is a cylinder having a plurality of diffuser slots  9  formed therein and a bottom cap  10  having a fluid port  11 . 
     In the embodiment shown in  FIGS. 1-6 , the diffuser assembly  1  further includes a plurality of centralizing members  16  adjacent to the diffuser screen  6 , wherein each of the centralizing members  16  extends between the mounting member  4  and the bottom cap  10 . The three centralizing members  16  serve to keep the diffuser screen  6  centered within the carrier sub  3 . It should be understood that the centralizing members  16  can take a wide range of structural forms which accomplish the purpose of centering the diffuser screen  6  within the carrier sub  3 . 
     As shown best in  FIG. 6 , with the cylindrical diffuser screen  6  removed for clarity, each of the plurality of cutters  7  includes a cutting edge  12  and a mounting flange  13 , and wherein the mounting flange  13  is adapted to matably engage one of the plurality of diffuser slots  9  of the diffuser screen  6 . In a preferred embodiment, a first set  14  of cutters  7  is mounted at a first selected height H 1  along the central axis  8  of the diffuser screen  6 , and a second set  15  of cutters  7  is mounted at a second selected height H 2  along the central axis  8  of the diffuser screen  6 . In this embodiment shown in  FIGS. 1-6 , the cutters  7  are mounted to the diffuser screen  6  such that the cutting edges  12  are internal to the diffuser screen  6 . It should be understood that each individual cutter  7  may reside in any slot  9  to provide a varied and irregular pattern of cutters  7  on the diffuser screen  6 . However, it is believed that having organized sets of cutters  7  at selected heights may provide more consistent separation of LCM aggregations during the diffusion of the fluid through the diffuser assembly  1 . 
     As best shown in  FIG. 6 , the diffuser assembly  1  further includes a bottom diffusing device  17  extending from a post  19  affixed to the bottom cap  10  internal to the diffuser screen  6 , wherein the bottom diffusing device  17  includes a plurality of radially disposed cutting edges  18  similar to the cutters  7  positioned above the cutting device  17 . The bottom diffusing device  17  essentially serves as a third stage cutting step in addition to the first and second set  14 ,  15  of cutters  7 , prior to the fluid  20  exiting the diffuser screen  6  through fluid port  11 . 
     In an operational configuration, fluid  20  flows through the carrier sub  3 , such as a stabilizer or other type of downhole sub, and into the inlet port  5  of the mounting member  4 . Any LCM aggregations or clumps in the fluid  20  pass against the cutting edges  12  of cutters  7 , and are separated into smaller portions to collect within the diffuser screen  6 , while the fluid  20  can exit the diffuser screen  6  through diffuser slots  9  and the fluid port  11 . 
     The preferred embodiment described above, as well as the alternate embodiments described below, are effective for diffusion of a wide range of fluids and materials, including oil and water based muds, barite drilling muds, cement, all drilling fluids, spotting acids for break-up of limestone formations, blended materials mixed in blending tanks, breakup of larger masses of carbide bombs, and any other “cake balls” mud clumps, LCM, cement, and the like that form in the string or from poor blending. 
     In an alternate embodiment shown in  FIGS. 7-11 , a similar diffuser assembly is configured to allow the flow of fluid  20  such that LCM aggregations are caused to contact cutters  24  positioned external to the diffuser screen  21 , and where LCM too large for the diffuser slots  9  is collected on the outside of the diffuser screen  21 . A mounting member  22  (similar to mounting member  4 ) includes an inlet port  23  for entry of fluids  20 . The fluid  20  is then diverted by a cone-shaped diversion member  25  attached to a bridge  26  inside mounting member  22  and disposed between the fluid inlet port  23  of the mounting member  22  and the diffuser screen  21 . 
     As shown best in  FIG. 11 , with the cylindrical diffuser screen  21  removed for clarity, each of the plurality of cutters  24  includes a cutting edge  27  and a mounting flange  28 , and wherein the mounting flange  28  is adapted to matably engage one of the plurality of diffuser slots  9  of the diffuser screen  21 . In this embodiment, three sets of cutters  7  are mounted at selected heights along the central axis  8  of the diffuser screen  21 , similar to the arrangement seen in  FIG. 6 . 
     As shown in  FIGS. 7-11 , the diffuser assembly  1  further includes a lower diffuser element  30  attached below the diffuser screen  21 , wherein the lower diffuser element  30  is constructed from a slotted cylinder. A bottom cap  31  is attached to the bottom of lower diffuser element  30 , and which includes a fluid exit port  32 . A further embodiment is shown in  FIGS. 12-16  that is identical to the embodiment of  FIGS. 7-11 , except for the lower diffuser element  30 , which is constructed from vertical rods  33 . 
     As shown in  FIG. 17 , the diffuser assembly  1  is deployed within another type of conduit in the form of a stabilizer  40 , which supports the bottom hole assembly (BHA) in the well bore in order to avoid unintentional sidetracking or vibrations, and ensures the quality of the hole being drilled. 
     As shown in  FIGS. 18A and 18B , the diffuser assembly  1  is deployed within a section of drill pipe  50  at the level of the rig floor  52 . Note that in  FIG. 18A , the diffuser screen  6  includes a retrievable neck  51 , as is common in the art, that enables retrieval of the diffuser by conventional fishing tools.  FIG. 18B  includes an opening as shown in  FIG. 5  and elsewhere herein. In this operation, the diffuser  1  is installed in the drill pipe  51  while drilling fluids containing LCM are pumped into the well bore during drilling. As the drill string moves deeper into the well bore and another section of drill pipe  51  is needed, the diffuser  1  is removed, and the next section of drill pipe  51  is threaded onto the drill string at the rig floor  52 . After the next section of drill pipe  51  is connected, the diffuser  1  is re-installed into the drill pipe  51 , after which the drilling and fluid flow can be restarted. Thus, any clumps of LCM that enter into the drill pipe  51  are diffused by the diffuser  1 . 
     As shown in  FIG. 19 , the diffuser  1  deployed within a conduit  60  between a drilling fluid mixing tank  61  and a pump  62  located in proximity to the rig floor  52 . Tank  61  may be a fixed tank, or it may be a mobile tank located on a vehicle such as a truck or other vessel. The left side of  FIG. 19  depicts the arrangement in a partial exploded view, while the right side of  FIG. 19  depicts a fully assembled view with typical valves, hoses, and connectors to enable fluid flow from the mixing tank  61  to the rig floor  52 . Thus, any clumps of LCM that exist when the fluid leaves the mixing tank  61  can be diffused by the diffuser  1  prior to being pumped to the rig floor  52 . 
     All references cited in this specification are herein incorporated by reference as though each reference was specifically and individually indicated to be incorporated by reference. The citation of any reference is for its disclosure prior to the filing date and should not be construed as an admission that the present invention is not entitled to antedate such reference by virtue of prior invention. 
     It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention set forth in the appended claims. The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.