Abstract:
A system for conditioning drilling fluid includes a conditioning device having a first conduit configured to receive the drilling fluid, a flow restriction disposed adjacent the first conduit, the flow restriction comprising a fluid inlet and a fluid outlet, an impact plate disposed downstream of the flow restriction, a first chamber disposed between the flow restriction and the impact plate, and a second chamber disposed downstream of the impact plate, wherein the first chamber is fluidly connected to the second chamber. A method for conditioning drilling fluid using a conditioning device, includes pumping a drilling fluid through a flow restriction, accelerating the drilling fluid into a mixing chamber, subjecting the drilling fluid to elongational shearing, decelerating the drilling fluid against an impact plate, subjecting the drilling fluid to impact shearing, and emptying drilling fluid from the mixing chamber.

Description:
FIELD OF THE INVENTION 
       [0001]    Embodiments disclosed herein relate generally to mixing drilling fluids. In particular, embodiments disclosed herein relate generally to devices, systems, and methods for conditioning drilling fluids. 
       BACKGROUND ART 
       [0002]    When drilling or completing wells in earth formations, various fluids may be used in the well for a variety of reasons. Common uses for well fluids include: lubrication and cooling of drill bit cutting surfaces while drilling generally or drilling-in (i.e., drilling in a targeted petroliferous formation), transportation of “cuttings” (pieces of formation dislodged by the cutting action of the teeth on a drill bit) to the surface, controlling formation fluid pressure to prevent blowouts, maintaining well stability, suspending solids in the well, minimizing fluid loss into and stabilizing the formation through which the well is being drilled, fracturing the formation in the vicinity of the well, displacing the fluid within the well with another fluid, cleaning the well, testing the well, transmitting hydraulic horsepower to the drill bit, fluid used for emplacing a packer, abandoning the well or preparing the well for abandonment, and otherwise treating the well or the formation. 
         [0003]    In general, drilling fluids should be pumpable under pressure down through strings of drilling pipe, then through and around the drilling bit head deep in the earth, and then returned back to the earth surface through an annulus between the outside of the drill stem and the hole wall or casing. Beyond providing drilling lubrication and efficiency, and retarding wear, drilling fluids should suspend and transport solid particles to the surface for screening out and disposal. In addition, the fluids should be capable of suspending additive weighting agents (to increase specific gravity of the mud), generally finely ground barites (barium sulfate ore), and transport clay and other substances capable of adhering to and coating the borehole surface. 
         [0004]    Drilling fluids are generally characterized as thixotropic fluid systems. That is, they exhibit low viscosity when sheared, such as when in circulation (as occurs during pumping or contact with the moving drilling bit). However, when the shearing action is halted, the fluid should be capable of suspending the solids it contains to prevent gravity separation. In addition, when the drilling fluid is under shear conditions and a free-flowing near-liquid, it must retain a sufficiently high enough viscosity to carry unwanted particulate matter from the bottom of the well bore to the surface. The drilling fluid formulation should also allow the cuttings and other unwanted particulate material to be removed or otherwise settle out from the liquid fraction. 
         [0005]    Depending on the particular well to be drilled, a drilling operator selects between a water-based drilling fluid and an oil-based or synthetic drilling fluid. Each of the water-based fluid and oil-based fluid typically include a variety of additives to create a fluid having the rheological profile necessary for a particular drilling application. For example, a variety of compounds are typically added to water- or brine-based well fluids, including viscosifiers, corrosion inhibitors, lubricants, pH control additives, surfactants, solvents, thinners, thinning agents, and/or weighting agents, among other additives. Some typical water- or brine-based well fluid viscosifying additives include clays, synthetic polymers, natural polymers and derivatives thereof such as xanthan gum and hydroxyethyl cellulose (HEC). Similarly, a variety of compounds are also typically added to a oil-based fluid including weighting agents, wetting agents, organophilic clays, viscosifiers, fluid loss control agents, surfactants, dispersants, interfacial tension reducers, pH buffers, mutual solvents, thinners, thinning agents and cleaning agents. 
         [0006]    Rheological properties of certain drilling fluids may change when the shearing action is halted for extended periods of time. Many such periods exist during typical deepwater drilling projects due to other operational requirements. Because the fluid properties change during times of low shear, drilling operations may be delayed or restricted until the fluid has again been sheared sufficiently to recover original properties. Recirculating the drilling fluid through a drill string may help to restore the original rheological properties of the drilling fluid; however, circulating the entire volume of drilling fluid through the drill string until desired rheological properties are achieved may take from a few hours to more than a day. Because drilling cannot proceed until the drilling fluid has been reconditioned, drilling operations are halted while the drilling fluid is recirculated. 
         [0007]    Accordingly, there exists a need for improved techniques that enable efficient and effective conditioning of drilling fluids. 
       SUMMARY OF INVENTION 
       [0008]    In one aspect, embodiments disclosed herein relate to a system for conditioning drilling fluid including a pump configured to pump drilling fluid from a drilling fluid source to a conditioning device, and a second conduit fluidly connected to the second chamber, wherein the second conduit is configured to transport the drilling fluid from the second chamber to conditioned drilling fluid storage area. The conditioning device may include a first conduit configured to receive the drilling fluid, a flow restriction disposed adjacent the first conduit, the flow restriction comprising a fluid inlet and a fluid outlet, an impact plate disposed downstream of the flow restriction, a first chamber disposed between the flow restriction and the impact plate, and a second chamber disposed downstream of the impact plate, wherein the first chamber is fluidly connected to the second chamber. 
         [0009]    In another aspect, embodiments disclosed herein relate to a method for conditioning drilling fluid using a conditioning device, the method including pumping a drilling fluid through a flow restriction, accelerating the drilling fluid into a mixing chamber, subjecting the drilling fluid to elongational shearing, decelerating the drilling fluid against an impact plate, subjecting the drilling fluid to impact shearing, and emptying drilling fluid from the mixing chamber. 
         [0010]    Other aspects and advantages of the disclosed embodiments will be apparent from the following description and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIGS. 1A and 1B  are schematic representations of an offshore drilling system. 
           [0012]      FIGS. 2  is a cross sectional view of a fluid conditioning device in accordance with embodiments disclosed herein. 
           [0013]      FIGS. 3A ,  3 B,  3 C, and  3 D are cross sectional views of flow restrictions in accordance with embodiments disclosed herein. 
           [0014]      FIG. 4A  is a perspective view of an impact plate in accordance with embodiments disclosed herein. 
           [0015]      FIGS. 4B and 4C  are cross sectional views of an impact plate in accordance with embodiments disclosed herein. 
           [0016]      FIGS. 5A and 5B  are perspective views of impact plate carriers in accordance with embodiments disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    In one aspect, embodiments disclosed herein relate to a device, system, and method for mixing drilling fluids. In particular, embodiments disclosed herein relate generally to devices, systems, and methods for conditioning drilling fluids. 
         [0018]    Referring to  FIGS. 1A and 1B , two schematic representations of offshore drilling systems are shown. A floating platform  102  may be connected to an outer casing  104  disposed around an inner casing  106 . A drill string  108  may be disposed through inner casing  106  and an annulus  110  may be formed between an outer surface of drill string  108  and an inner surface of inner casing  106 . A drill bit  112  may be disposed on a distal end of drill string  108  as shown, and may extend into a wellbore  118  drilled into the surface of a sea floor  116 . A blow out preventer (“BOP”) stack  114  may be disposed on sea floor  116  around an outer surface of outer casing  104 . A drilling riser  120  may extend from BOP stack  114  to platform  102 , and may be configured to couple with outer casing  104  and inner casing  106 . Those of ordinary skill in the art will appreciate that outer casing  104 , inner casing  106 , and drilling riser  120  may be continuous or may be an assembly of multiple casing segments. In certain offshore drilling operations, riser assembly  120  may extend from platform  102  for miles through sea water before reaching sea floor  116 . 
         [0019]    As discussed above, drilling operations require drilling fluid to be pumped into drill string  108  and through drill bit  112  in order to lubricate and cool drill bit  112 , and to remove cuttings from wellbore  118 . At certain points during the drilling of a wellbore, procedures may be performed which require drilling operations to be stopped, e.g., repairing a drill string component or replacing a bit. Typically, circulation of drilling fluid down through drill string  108  and up through annulus  110  is also stopped. 
         [0020]    In offshore drilling environments, synthetic-based drilling fluid (“SBM”) and oil-based drilling fluid (“OBM”) may be used. Over time, when certain types of SBM and OBM remain static, rheology of the SBM and OBM may change. Specifically, in certain synthetic- and oil-based drilling fluids, gel strength may change, and the homogeneity of additives dispersed within the SBM and OBM may degenerate, resulting in a drilling fluid having undesirable rheological properties. As discussed above, drilling riser  120  may extend for miles, and thus, properties of the SBM and OBM disposed therein may vary significantly from platform  102  to sea floor  116 , and may be considered unreliable due to uncertainty about the ability of the drilling fluid to lubricate and cool drill bit  112 , to transport cuttings from well bore  118 , and to control an amount of hydrostatic pressure applied to the bottom of well bore  118 . Thus, the drilling fluid may require reconditioning to restore its desired rheological properties and homogeneity. 
         [0021]    As discussed above, one method of conditioning the drilling fluid is to pump the drilling fluid down drill string  108 , through drill bit  112 , and up annulus  110 . It may be necessary to circulate the entire volume of drilling fluid through the drill string  108  multiple times before desired rheological properties are restored to the drilling fluid. Because the length of drill string  108  may extend for miles, circulating the drilling fluid multiple times may take hours or days, and thus, significant costs associated with rig downtime may be incurred. Embodiments disclosed herein may provide a more efficient device, system, and method of conditioning drilling fluid. 
         [0022]    Referring specifically to  FIG. 1A , a first system  100 A for conditioning a drilling fluid is shown disposed on board platform  102 . Drilling fluid from a drilling fluid source  122  may be pumped to a conditioning device  126  using a pump  124 . Drilling fluid source  122  may include a mud pit, which may be a large tank that holds drilling fluid, or a storage pit disposed in the body of platform  120 . Pump  124  may be a pump specifically for the conditioning of drilling fluid or, alternatively, may be a pump that is used on board platform  120  for other purposes. For example, pump  124  may be a kill pump used to supply a kill fluid if well control is required. Additionally, those of ordinary skill in the art will appreciate that a boost pump (not shown) may be used to accelerate the drilling fluid to conditioning device  126 , which will be discussed in detail below. From conditioning device  126 , reconditioned drilling fluid may be directed back to drilling fluid source  122 , as indicated by arrow A. Alternatively, reconditioned drilling fluid may be pumped to a drilling fluid storage area  128  or may be pumped into drill string  108 , as indicated by arrow B and arrow C, respectively. 
         [0023]    Referring to  FIG. 1B , a second system  100 B for conditioning a drilling fluid is shown disposed on board platform  102 . In system  100 B, drilling fluid from annulus  110  may be pumped to conditioning device  126  using pump  122 . Reconditioned drilling fluid may be pumped to a drilling fluid storage area  128 , as indicated by arrow B, or may be pumped into drill string  108 , as indicated by arrow C. 
         [0024]    Referring now to  FIG. 2 , a conditioning device  126  in accordance with embodiments disclosed herein is shown. Conditioning device  126  may include a first conduit  202  configured to receive drilling fluid. The drilling fluid may then enter a fluid inlet  206  of a flow restriction  204  and may exit through a fluid outlet  208  into a first chamber  212 , as shown by arrow A. First chamber  212  may be defined as the area within a second conduit  224  disposed between fluid outlet  208  and an impact plate  210 . Impact plate  210  may be secured to an impact plate carrier  211  using any fastening means known in the art such as, for example, mechanical fasteners, adhesives, welding, etc. Alternatively, impact plate  210  may be integrally formed with impact plate carrier  211 . Impact plate  210  may include a surface feature  234  designed to provide a desired flow of drilling fluid through conditioning device  126 . Surface feature  234  may include a planar or convex surface (not shown), or may include a concave surface  236  as shown. Drilling fluid may flow from first chamber  212  through a fluid passage  216  to a second chamber  214  where it may exit conditioning device  126  through outlet  218 , as shown by arrow B. 
         [0025]    Referring now to  FIGS. 3A ,  3 B,  3 C, and  3 D, flow restrictions  204  in accordance with embodiments disclosed herein are shown. Referring initially to  FIG. 3A , a flow restriction  204  is shown having a single nozzle  302   a  of variable diameter. Specifically, nozzle  302   a  may include a decreasing diameter portion  304 , a constant diameter portion  306 , and an increasing diameter portion  308 . Alternatively, as shown in  FIG. 3B , flow restriction  204  may include a single nozzle  302   b  of constant diameter. Those of ordinary skill in the art will appreciate that any number of nozzles having any desired geometry may be disposed in flow restriction  204 . For example,  FIG. 3C  shows three nozzles  302   c  of constant diameter and  FIG. 3D  shows four nozzles  302   d  of variable diameter. Additionally, those of ordinary skill in the art will appreciate that nozzles of varying sizes and geometries may be disposed in the same flow restriction. 
         [0026]    Flow restriction  204  may experience high wear, and thus, may be formed from a wear-resistant material such as, for example, tungsten carbide or ceramic. Referring additionally to  FIG. 2 , flow restriction  204  may be designed to removably assemble within conditioning device  126 . In certain embodiments, flow restriction  204  may be assembled using, for example, mechanical fasteners such as clamps, bolts, screws, and threaded connections. In certain embodiments, flow restriction  204  may be disposed between two flanges  220 ,  222 , with a first flange  220  disposed on first conduit  202  and a second flange  222  disposed on second conduit  224 . 
         [0027]    Flow restriction  204  may be designed to accelerate a flow of drilling fluid therethrough, and may subject the drilling fluid to shear elongation as the drilling fluid passes therethrough. Shear elongation may reduce the gel strength of the drilling fluid, thereby helping to restore original rheological properties to the drilling fluid. 
         [0028]    In certain embodiments, drilling fluid may be pumped through flow restriction  204  at a flow rate between approximately 100 gallons per minute (“gpm”) and approximately 800 gpm. Additionally, drilling fluid may be pumped through flow restriction  204  at a pressure between approximately 100 pounds per square inch (“psi”) and approximately 3000 psi. 
         [0029]    Referring now to  FIG. 2  and  FIGS. 4A ,  4 B, and  4 C, embodiments of an impact plate  210  are shown in accordance with the present disclosure. A perspective view of impact plate  210   a  is shown in  FIG. 4A  and cross sectional views of impact plates  210   b  and  210   c  are shown in  FIGS. 4B and 4C , respectively. Impact plate  210   a  may include a first surface  402   a  having a surface feature  234  configured to contact a flow of drilling fluid exiting flow restriction  204 . While flow restriction  204  is configured to accelerate drilling fluid therethrough, impact plate  210  may be configured to decelerate drilling fluid quickly, thereby subjecting the drilling fluid to an impact shear. 
         [0030]    Impact plate  210  may include at least one of a planar surface, a convex surface, and a concave surface. As shown in  FIG. 4A , impact plate  210   a  may include a single convex protrusion  404  configured to impede accelerated drilling fluid from fluid outlet  208  of flow restriction  204  ( FIG. 2 ). Looking to  FIG. 4B , an impact plate  210   b  is shown having a plurality of surface features  234  including convex protrusions  404  separated by concave recesses  406 . Alternatively, as shown in  FIG. 4C , impact plate  210   c  may have a surface feature  234  including protrusion  408  with orthogonal surfaces. 
         [0031]    As shown in  FIGS. 4A ,  4 B, and  4 C, impact plate  210  may include a protrusion  404  centered with respect to fluid outlet  208  of flow restriction  204  ( FIG. 2 ); however, protrusions  404  and/or recesses  406  may be offset with respect to fluid outlet  208 . Additionally, protrusions  404  and/or recesses  406  may have any cross sectional shape such as, for example, circular, oval, triangular, square, etc. Those of ordinary skill in the art will appreciate that any number of protrusions and/or recesses having any desired geometry may be used. 
         [0032]    Referring to FIGS.  2  and  4 A-C together, impact plate  210  may be subjected to high wear conditions, and as such, impact plate  210  may be made from a wear resistant material such as, for example, tungsten carbide or ceramic. Additionally, impact plate  210  may be designed as a replaceable component of conditioning device  126 . In certain embodiments, impact plate  210  may be attached to impact plate carrier  211  using removable fasteners such as, for example, threaded connections, bolts, screws, rivets, etc. Those of ordinary skill in the art will appreciate that alternative removable couplings may be also used. 
         [0033]    The position of impact plate  210  with respect to fluid outlet  208  of flow restriction  204  may determine an amount of impact the drilling fluid experiences. In general, increasing a distance between fluid outlet  208  and impact plate  210  may decrease the amount of impact shear the drilling fluid experiences, while decreasing the distance between fluid outlet  208  and impact plate  210  may increase the amount of impact shear the drilling fluid experiences. 
         [0034]    Referring to  FIG. 2  and  FIGS. 5A and 5B , embodiments of an impact plate carrier  211  are shown. Looking to  FIG. 5A , an impact plate carrier  211   a  may include an arcuate slot  502  having an upper arc  504  configured to align with a lower portion of a circumference of impact plate  210  such that drilling fluid may contact impact plate  210  and may flow through slot  502  disposed therebelow and may flow into second chamber  214  ( FIG. 2 ). In certain embodiments, slot  502  may be sized to allow drilling fluid to exit first chamber  212  at a rate substantially equal to or greater than a rate at which the drilling fluid enters first chamber  212 . In such an embodiment, drilling fluid may be prevented from building up within first chamber  212 . 
         [0035]    Referring to  FIG. 5B , an alternative impact plate carrier  211   b  is shown. 
         [0036]    Impact plate carrier  211   b  may include a plurality of holes  506  such that drilling fluid may exit through holes  506  into second chamber  214  ( FIG. 2 ). Those of ordinary skill in the art will appreciate that any number of holes  506  having any desirable size may be used. In certain embodiments, holes  506  may be sized and positioned to allow drilling fluid to flow into second chamber  214  at a rate approximately equal to or greater than the rate at which drilling fluid flows into first chamber  212 . In such an embodiment, fluid may be prevented from filling up first chamber  212 . 
         [0037]    Referring to  FIGS. 5A and 5B  together, impact plate carriers  211   a,    211   b  may include a plurality of bores  508  disposed therethrough located around a periphery of the impact plate carriers  211   a,    211   b.  In certain embodiments, impact plate carriers  211   a,    211   b  may be assembled between a third flange  228  disposed around second conduit  224  and a fourth flange  230  disposed around a third conduit  226  ( FIG. 2 ). Third and fourth flanges  228 ,  230  may include a plurality of bores (not shown) corresponding to bores  508 , such that bolts  232  may be removably engaged therethrough. 
         [0038]    Referring to  FIG. 2 , after entering second chamber  214 , fluid may flow into a conduit (not shown) connected to second chamber  214  and may exit conditioning device  126  through outlet  218 . In certain embodiments, chamber  214  and the conduit (not shown) connected to second chamber  214  may be sized to allow drilling fluid to exit from second chamber  214  at a rate approximately equal to the rate at which the drilling fluid enters second chamber  214 . Thus, drilling fluid may be prevented from accumulating in second chamber  214 . Additionally, in certain embodiments, second chamber  214  may be positioned such that gravity drains drilling fluid from second chamber  214  through a connected conduit (not shown). 
         [0039]    After experiencing elongational shear and shear impact, rheological properties of the drilling fluid may improve, and thus, the reconditioned drilling fluid may be suitable for using during drilling. In embodiments wherein reconditioned drilling fluid is pumped into drill string  208 , drilling operations may resume without having to recirculate drilling fluid through annulus  210  and drill string  208  multiple times. 
         [0040]    Advantageously, embodiments disclosed herein may provide for reconditioning a drilling fluid in a decreased time period, thereby providing time and cost savings. Additionally, because the conditioning system disclosed herein may use equipment that is already present on offshore drilling platforms, the conditioning system may have a relatively small footprint. 
         [0041]    While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.