Patent Publication Number: US-9901982-B2

Title: Insulation enclosure with varying thermal properties

Description:
BACKGROUND 
     The present disclosure relates to oilfield tool manufacturing and, more particularly, to insulation enclosures that help control the thermal profile of drill bits during manufacture to prevent manufacturing defects. 
     Rotary drill bits are often used to drill oil and gas wells, geothermal wells, and water wells. One type of rotary drill bit is a fixed-cutter drill bit having a bit body comprising matrix and reinforcement materials, i.e., a “matrix drill bit” as referred to herein. Matrix drill bits usually include cutting elements or inserts positioned at selected locations on the exterior of the matrix bit body. Fluid flow passageways are formed within the matrix bit body to allow communication of drilling fluids from associated surface drilling equipment through a drill string or drill pipe attached to the matrix bit body. The drilling fluids lubricate the cutting elements on the matrix drill bit. 
     Matrix drill bits are typically manufactured by placing powder material into a mold and infiltrating the powder material with a binder material, such as a metallic alloy. The various features of the resulting matrix drill bit, such as blades, cutter pockets, and/or fluid-flow passageways, may be provided by shaping the mold cavity and/or by positioning temporary displacement material within interior portions of the mold cavity. A preformed bit blank (or steel shank) may be placed within the mold cavity to provide reinforcement for the matrix bit body and to allow attachment of the resulting matrix drill bit with a drill string. A quantity of matrix reinforcement material (typically in powder form) may then be placed within the mold cavity with a quantity of the binder material. 
     The mold is then placed within a furnace and the temperature of the mold is increased to a desired temperature to allow the binder (e.g., metallic alloy) to liquefy and infiltrate the matrix reinforcement material. The furnace typically maintains this desired temperature to the point that the infiltration process is deemed complete, such as when a specific location in the bit reaches a certain temperature. Once the designated process time or temperature has been reached, the mold containing the infiltrated matrix bit is removed from the furnace. As the mold is removed from the furnace, the mold begins to rapidly lose heat to its surrounding environment via heat transfer, such as radiation and/or convection in all directions, including both radially from a bit axis and axially parallel with the bit axis. Upon cooling, the infiltrated binder (e.g., metallic alloy) solidifies and incorporates the matrix reinforcement material to form a metal-matrix composite bit body and also binds the bit body to the bit blank to form the resulting matrix drill bit. 
     Typically, cooling begins at the periphery of the infiltrated matrix and continues inwardly, with the center of the bit body cooling at the slowest rate. Thus, even after the surfaces of the infiltrated matrix of the bit body have cooled, a pool of molten material may remain in the center of the bit body. As the molten material cools, there is a tendency for shrinkage that could result in voids forming within the bit body unless molten material is able to continuously backfill such voids. In some cases, for instance, one or more intermediate regions within the bit body may solidify prior to adjacent regions and thereby stop the flow of molten material to locations where shrinkage porosity is developing. In other cases, shrinkage porosity may result in poor metallurgical bonding at the interface between the bit blank and the molten materials, which can result in the formation of cracks within the bit body that can be difficult or impossible to inspect. When such bonding defects are present and/or detected, the drill bit is often scrapped during or following manufacturing or the lifespan of the drill bit may be dramatically reduced. If these defects are not detected and the drill bit is used in a job at a well site, the bit can fail and/or cause damage to the well including loss of rig time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following figures are included to illustrate certain aspects of the present disclosure and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, without departing from the scope of this disclosure. 
         FIG. 1  illustrates an exemplary fixed-cutter drill bit that may be fabricated in accordance with the principles of the present disclosure. 
         FIGS. 2A-2C  illustrate progressive schematic diagrams of an exemplary method of fabricating a drill bit, in accordance with the principles of the present disclosure. 
         FIG. 3  illustrates a cross-sectional side view of an exemplary insulation enclosure, according to one or more embodiments. 
         FIG. 4  illustrates a cross-sectional side view of another embodiment of the exemplary insulation enclosure of  FIG. 3 , according to one or more embodiments. 
         FIG. 5  illustrates a cross-sectional top view of another exemplary insulation enclosure, according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to oilfield tool manufacturing and, more particularly, to insulation enclosures that help control the thermal profile of drill bits during manufacture to prevent manufacturing defects. 
     The present disclosure describes various embodiments of an insulation enclosure configured to help control the thermal profile of a mold, and thereby enhance directional solidification of molten contents positioned within the mold. More specifically, the exemplary insulation enclosures described herein exhibit varying thermal properties along a longitudinal direction and/or a circumference of the insulation enclosure. In some embodiments, for instance, the thermal resistance or thermal conductivity of insulation material may vary in the longitudinal direction, thereby yielding an insulation enclosure with insulating properties that vary along the longitudinal direction, such as along a vertical direction with respect to the mold in its upright orientation during cooling. For example, some embodiments have higher insulating properties in the topmost region of the insulation enclosure and lower insulating properties in the bottommost region. In other embodiments, one or more heating elements, such as an active or passive heating element, which may include a heat exchanger, an induction heater, or other examples further described below, may be employed to maintain higher temperatures in the topmost region of the insulation enclosure and lower temperatures in the bottommost region. As a result, the rate of thermal energy loss through the insulation enclosure may be graded longitudinally, with most thermal energy being lost out of the bottommost region. Advantageously, the presently described embodiments may facilitate a more controlled cooling process for a mold and thereby optimize the directional solidification of any molten contents within the mold and also mitigate shrinkage porosity. 
       FIG. 1  illustrates a perspective view of an example of a fixed-cutter drill bit  100  that may be fabricated in accordance with the principles of the present disclosure. As illustrated, the fixed-cutter drill bit  100  (hereafter “the drill bit  100 ”) may include or otherwise define a plurality of cutter blades  102  arranged along the circumference of a bit head  104 . The bit head  104  is connected to a shank  106  to form a bit body  108 . The shank  106  may be connected to the bit head  104  by welding, such as using laser arc welding that results in the formation of a weld  110  around a weld groove  112 . The shank  106  may further include or otherwise be connected to a threaded pin  114 , such as an American Petroleum Institute (API) drill pipe thread. 
     In the depicted example, the drill bit  100  includes five cutter blades  102 , in which multiple pockets or recesses  116  (also referred to as “sockets” and/or “receptacles”) are formed. Cutting elements  118 , otherwise known as inserts, may be fixedly installed within each recess  116 . This can be done, for example, by brazing each cutting element  118  into a corresponding recess  116 . As the drill bit  100  is rotated in use, the cutting elements  118  engage the rock and underlying earthen materials, to dig, scrape or grind away the material of the formation being penetrated. 
     During drilling operations, drilling fluid (commonly referred to as “mud”) can be pumped downhole through a drill string (not shown) coupled to the drill bit  100  at the threaded pin  114 . The drilling fluid circulates through and out of the drill bit  100  at one or more nozzles  120  positioned in nozzle openings  122  defined in the bit head  104 . Formed between each adjacent pair of cutter blades  102  are junk slots  124 , along which cuttings, downhole debris, formation fluids, drilling fluid, etc., may pass and circulate back to the well surface within an annulus formed between exterior portions of the drill string and the interior of the wellbore being drilled (not expressly shown). 
       FIGS. 2A-2C  are schematic diagrams that sequentially illustrate an example method of fabricating a drill bit, such as the drill bit  100  of  FIG. 1 , in accordance with the principles of the present disclosure. In  FIG. 2A , a mold  200  is placed within a furnace  202 . While not specifically depicted in  FIGS. 2A-2C , the mold  200  may include and otherwise contain all the necessary materials and component parts required to produce a drill bit including, but not limited to, reinforcement materials, a binder material, displacement materials, a bit blank, etc. 
     For some applications, two or more different types of matrix reinforcement materials or powders may be positioned in the mold  200 . Examples of such matrix reinforcement materials may include, but are not limited to, tungsten carbide, monotungsten carbide (WC), ditungsten carbide (W 2 C), macrocrystalline tungsten carbide, other metal carbides, metal borides, metal oxides, metal nitrides, natural and synthetic diamond, and polycrystalline diamond (PCD). Examples of other metal carbides may include, but are not limited to, titanium carbide and tantalum carbide, and various mixtures of such materials may also be used. Various binder (infiltration) materials that may be used include, but are not limited to, metallic alloys of copper (Cu), nickel (Ni), manganese (Mn), lead (Pb), tin (Sn), cobalt (Co) and silver (Ag). Phosphorous (P) may sometimes also be added in small quantities to reduce the melting temperature range of infiltration materials positioned in the mold  200 . Various mixtures of such metallic alloys may also be used as the binder material. 
     The temperature of the mold  200  and its contents are elevated within the furnace  202  until the binder liquefies and is able to infiltrate the matrix material. Once a specified location in the mold  200  reaches a certain temperature in the furnace  202 , or the mold  200  is otherwise maintained at a particular temperature within the furnace  202  for a predetermined amount of time, the mold  200  is then removed from the furnace  202 . Upon being removed from the furnace  202 , the mold  200  immediately begins to lose heat by radiating thermal energy to its surroundings while heat is also convected away by cold air from outside the furnace  202 . In some cases, as depicted in  FIG. 2B , the mold  200  may be transported to and set down upon a heat sink  206 . The radiative and convective heat losses from the mold  200  to the environment continue until an insulation enclosure  208  is lowered around the mold  200 . 
     The insulation enclosure  208  may be a rigid shell or structure used to insulate the mold  200  and thereby slow the cooling process. In some cases, the insulation enclosure  208  may include a hook  210  attached to a top surface thereof. The hook  210  may provide an attachment location, such as for a lifting member, whereby the insulation enclosure  208  may be grasped and/or otherwise attached to for transport. For instance, a chain or wire  212  may be coupled to the hook  210  to lift and move the insulation enclosure  208 , as illustrated. In other cases, a mandrel or other type of manipulator (not shown) may grasp onto the hook  210  to move the insulation enclosure  208  to a desired location. 
     In some embodiments, the insulation enclosure  208  may include an outer frame  214 , an inner frame  216 , and insulation material  218  positioned between the outer and inner frames  214 ,  216 . In some embodiments, both the outer frame  214  and the inner frame  216  may be made of rolled steel and shaped (i.e., bent, welded, etc.) into the general shape, design, and/or configuration of the insulation enclosure  208 . In other embodiments, the inner frame  216  may be a metal wire mesh that holds the insulation material  218  between the outer frame  214  and the inner frame  216 . The insulation material  218  may be selected from a variety of insulative materials, such as those discussed below. In at least one embodiment, the insulation material  218  may be a ceramic fiber blanket, such as INSWOOL® or the like. 
     As depicted in  FIG. 2C , the insulation enclosure  208  may enclose the mold  200  such that thermal energy radiating from the mold  200  is dramatically reduced from the top and sides of the mold  200  and is instead directed substantially downward and otherwise toward/into the heat sink  206  or back towards the mold  200 . In the illustrated embodiment, the heat sink  206  is a cooling plate designed to circulate a fluid (e.g., water) at a reduced temperature relative to the mold  200  (i.e., at or near ambient) to draw thermal energy from the mold  200  and into the circulating fluid, and thereby reduce the temperature of the mold  200 . In other embodiments, however, the heat sink  206  may be any type of cooling device or heat exchanger configured to encourage heat transfer from the bottom  220  of the mold  200  to the heat sink  206 . In yet other embodiments, the heat sink  206  may be any stable or rigid surface that may support the mold  200 , and preferably having a high thermal capacity, such as a concrete slab or flooring. 
     Accordingly, once the insulation enclosure  208  is arranged about the mold  200  and the heat sink  206  is operational, the majority of the thermal energy is transferred away from the mold  200  through the bottom  220  of the mold  200  and into the heat sink  206 . This controlled cooling of the mold  200  and its contents (i.e., the matrix drill bit) allows a user to regulate or control the thermal profile of the mold  200  to a certain extent and may result in directional solidification of the molten contents of the drill bit positioned within the mold  200 , where axial solidification of the drill bit dominates its radial solidification. Within the mold  200 , the face of the drill bit (i.e., the end of the drill bit that includes the cutters) may be positioned at the bottom  220  of the mold  200  and otherwise adjacent the thermal heat sink  206  while the shank  106  ( FIG. 1 ) may be positioned adjacent the top of the mold  200 . As a result, the drill bit may be cooled axially upward, from the cutters  118  ( FIG. 1 ) toward the shank  106  ( FIG. 1 ). Such directional solidification (from the bottom up) may prove advantageous in reducing the occurrence of voids due to shrinkage porosity, cracks at the interface between the bit blank and the molten materials, and nozzle cracks. 
     While  FIG. 1  depicts a fixed-cutter drill bit  100  and  FIGS. 2A-2C  discuss the production of a generalized drill bit within the mold  200 , the principles of the present disclosure are equally applicable to any type of oilfield drill bit or cutting tool including, but not limited to, fixed-angle drill bits, roller-cone drill bits, coring drill bits, bi-center drill bits, impregnated drill bits, reamers, stabilizers, hole openers, cutters, cutting elements, and the like. Moreover, it will be appreciated that the principles of the present disclosure may further apply to fabricating other types of tools and/or components formed, at least in part, through the use of molds. For example, the teachings of the present disclosure may also be applicable, but not limited to, non-retrievable drilling components, aluminum drill bit bodies associated with casing drilling of wellbores, drill-string stabilizers, cones for roller-cone drill bits, models for forging dies used to fabricate support arms for roller-cone drill bits, arms for fixed reamers, arms for expandable reamers, internal components associated with expandable reamers, sleeves attached to an uphole end of a rotary drill bit, rotary steering tools, logging-while-drilling tools, measurement-while-drilling tools, side-wall coring tools, fishing spears, washover tools, rotors, stators and/or housings for downhole drilling motors, blades and housings for downhole turbines, and other downhole tools having complex configurations and/or asymmetric geometries associated with forming a wellbore. 
     According to the present disclosure, the thermal profile of the mold  200  may be controlled by altering the configuration and/or design of the insulation enclosure  208 , providing an insulation enclosure that exhibits varying thermal properties along a longitudinal direction (e.g., from the bottom to the top of the insulation enclosure). In some cases, the thermal resistance or thermal conductivity of the insulation material  218  may vary in the longitudinal direction, thereby yielding an insulation enclosure with insulating properties that increase with height. In one example, such an enclosure may have its highest insulating properties in the topmost region and lowest insulating properties in the bottommost region. In other cases, the insulation enclosure may employ one or more heating elements (e.g., a heat exchanger, an induction heater, etc., or other examples further described below) configured to maintain higher temperatures in the topmost region of the insulation enclosure and lower temperatures in the bottommost region. As a result, the rate of thermal energy loss through the insulation enclosure may be graded in the longitudinal direction, such that during the cooling of the mold, the heat flux out of the insulation enclosure increases toward the bottom, and may be at a maximum value at the bottommost region. The embodiments disclosed herein may facilitate a more controlled cooling process for the mold  200  and optimize the directional solidification of the molten contents within the mold  200  (e.g., a drill bit). Through directional solidification, any potential defects (e.g., voids) may be formed at higher and/or more outward positions of the mold  200  where they can be machined off later during finishing operations. 
       FIG. 3  is a cross-sectional side view of an exemplary insulation enclosure  300  set upon the thermal heat sink  206 , according to one or more embodiments. The insulation enclosure  300  may be similar in some respects to the insulation enclosure  208  of  FIGS. 2B and 2C  and therefore may be best understood with reference thereto, where like numerals indicate like elements or components not described again. The insulation enclosure  300  may include a support structure  306  and insulation material  308  supported by the support structure  306 . The insulation enclosure  300  (e.g., the support structure  306 ) may be an open-ended cylindrical structure having a top end  302   a  and bottom end  302   b . The bottom end  302   b  may be open or otherwise define an opening  304  configured to receive the mold  200  so that the mold  200  can be arranged within the interior of the insulation enclosure  300  (e.g., the support structure  306 ) as the insulation enclosure  300  is lowered around the mold  200 . The top end  302   a  may be closed and provide the hook  210  on its outer surface, as described above. 
     The insulation material  308  may generally extend between the top and bottom ends  302   a,b  of the support structure  306 . The insulation material  308  may be supported by the support structure  306  via various configurations of the insulation enclosure  300 . For instance, as depicted in the illustrated embodiment, the support structure  306  may include the outer frame  214  and the inner frame  216 , as generally described above, which may be collectively referred to herein as the support structure  306 . The outer and inner frames  214 ,  216  may cooperatively define a cavity  310 , and the cavity  310  may be configured to receive and otherwise house the insulation material  308  therein. In some embodiments, as illustrated, the support structure  306  may further include a footing  312  at the bottom end  302   b  of the insulation enclosure  300  that extends between the outer and inner frames  214 ,  216 . The footing  312  may serve as a support for the insulation material  308 , and may prove especially useful when the insulation material  308  includes stackable and/or individual component insulative materials that may be stacked atop one another within the cavity  310 . 
     In other embodiments, however, the outer frame  214  may be omitted from the insulation enclosure  300  and the insulation material  308  may alternatively be coupled to the inner frame  216  and/or otherwise supported by the footing  312 . In yet other embodiments, the inner frame  216  may be omitted from the insulation enclosure  300  and the insulation material  308  may alternatively be coupled to the outer frame  216  and/or otherwise supported by the footing  312 , without departing from the scope of the disclosure. 
     The support structure  306 , including one or both of the outer and inner frames  214 ,  216 , may be made of any rigid material including, but not limited to, metals, ceramics (e.g., a molded ceramic substrate), composite materials, combinations thereof, and the like. In at least one embodiment, the support structure  306 , including one or both of the outer and inner frames  214 ,  216 , may be a metal mesh. The support structure  306  may exhibit any suitable horizontal cross-sectional shape that will accommodate the general shape of the mold  200  including, but not limited to, circular, ovular, polygonal, polygonal with rounded corners, or any hybrid thereof. In some embodiments, the support structure  306  may exhibit different horizontal cross-sectional shapes and/or sizes at different vertical or longitudinal locations. 
     The insulation material  308  may be similar to the insulation material  218  of  FIGS. 2B and 2C . The insulation material  308  may include, but is not limited to, ceramics (e.g., oxides, carbides, borides, nitrides, and silicides that may be crystalline, non-crystalline, or semi-crystalline), polymers, insulating metal composites, carbons, nanocomposites, foams, fluids (e.g., air), any composite thereof, or any combination thereof. The insulation material  308  may further include, but is not limited to, materials in the form of beads, particulates, flakes, fibers, wools, woven fabrics, bulked fabrics, sheets, bricks, stones, blocks, cast shapes, molded shapes, foams, sprayed insulation, and the like, any hybrid thereof, or any combination thereof. Accordingly, examples of suitable materials that may be used as the insulation material  308  may include, but are not limited to, ceramics, ceramic fibers, ceramic fabrics, ceramic wools, ceramic beads, ceramic blocks, moldable ceramics, woven ceramics, cast ceramics, fire bricks, carbon fibers, graphite blocks, shaped graphite blocks, polymer beads, polymer fibers, polymer fabrics, nanocomposites, fluids in a jacket, metal fabrics, metal foams, metal wools, metal castings, and the like, any composite thereof, or any combination thereof. 
     Suitable materials that may be used as the insulation material  308  may be capable of maintaining the mold  200  at temperatures ranging from a lower limit of about −200° C. (−325° F.), −100° C. (−150° F.), 0° C. (32° F.), 150° C. (300° F.), 175° C. (350° F.), 260° C. (500° F.), 400° C. (750° F.), 480° C. (900° F.), or 535° C. (1000° F.) to an upper limit of about 870° C. (1600° F.), 815° C. (1500° F.), 705° C. (1300° F.), 535° C. (1000° F.), 260° C. (500° F.), 0° C. (32° F.), or −100° C. (−150° F.), wherein the temperature may range from any lower limit to any upper limit and encompass any subset therebetween. Moreover, suitable materials that may be used as the insulation material  308  may be able to withstand temperatures ranging from a lower limit of about −200° C. (−325° F.), −100° C. (−150° F.), 0° C. (32° F.), 150° C. (300° F.), 260° C. (500° F.), 400° C. (750° F.), or 535° C. (1000° F.) to an upper limit of about 870° C. (1600° F.), 815° C. (1500° F.), 705° C. (1300° F.), 535° C. (1000° F.), 0° C. (32° F.), or −100° C. (−150° F.), wherein the temperature may range from any lower limit to any upper limit and encompass any subset therebetween. Those skilled in the art will readily appreciate that the insulation material  308  may be appropriately chosen for the particular application and temperature to be maintained within the insulation enclosure  300 . 
     In some embodiments, in addition to the materials mentioned above, or independent thereof, a reflective coating or material may be positioned on an inner surface of the support structure  306 . More particularly, the reflective coating or material may be applied to, adhered to and/or sprayed onto the inner surface of one or both of the outer and inner frames  214 ,  216  in order to reflect an amount of thermal energy emitted from the mold  200  back toward the mold  200 . Furthermore, an insulative coating  313 , such as a thermal barrier coating, may be applied to one or both of the outer and inner frames  214 ,  216 . Such an insulative coating  313  could provide a thermal barrier between adjacent materials, such as the inner frame  216  and insulation material  308  or the insulation material  308  and the outer frame  214 . In other embodiments, or in addition thereto, the inner surface of one or both of the outer and inner frames  214 ,  216  may be polished so as to increase its emissivity. 
     The insulation enclosure  300  may be configured to control the thermal profile of the mold  200  during cooling by varying one or more thermal properties along a longitudinal direction A of the insulation enclosure  300 . More particularly, one or more thermal properties of the insulation enclosure  300  may be altered from the bottom end  302   b  of the insulation enclosure  300  to the top end  302   a . Exemplary thermal properties that may be varied in the longitudinal direction A include, but are not limited to, thermal resistance (i.e., R-value), thermal conductivity (k), specific heat capacity (C P ), density (i.e., weight per unit volume of the insulation material  308 ), thermal diffusivity, temperature, surface characteristics (e.g., roughness, coating, paint), emissivity, absorptivity, and any combination thereof. 
     By varying the thermal properties in the longitudinal direction A, higher insulating properties at or near the top end  302   a  of the insulation enclosure  300  and lower insulating properties at or near the bottom end  302   b  may result. As a result, the rate of thermal energy loss through the insulation enclosure  300  may be graded in the longitudinal direction A, with more thermal energy being lost at or near the bottom end  302   b  as opposed to the top end  302   a . Consequently, the thermal profile of the mold  200  may thereby be controlled such that directional solidification of the molten contents within the mold  200  is substantially achieved from the bottom  220  of the mold  200  axially upward in the longitudinal direction A, rather than radially through the sides of the mold  200 . 
     In some embodiments, the sidewalls of the insulation enclosure  300  may be divided into a plurality of insulation zones  314  (shown as insulation zones  314   a ,  314   b ,  314   c , and  314   d ). While four insulation zones  314   a - d  are depicted, those skilled in the art will readily appreciate that more or less than four insulation zones  314   a - d  may be employed in the insulation enclosure  300 , without departing from the scope of the disclosure. Indeed, the number of discrete insulation zones  314   a - d  may vary depending upon the specifications of the tool or device being fabricated within mold  200  (e.g., the drill bit  100  of  FIG. 1 ). 
     Varying at least one of the thermal resistance, thermal conductivity, specific heat capacity, density, thermal diffusivity, temperature, emissivity, and absorptivity along the longitudinal direction A of the insulation enclosure  300  may be accomplished passively by configuring the insulation zones  314   a - d  such that more thermal energy losses are permitted through the insulation zones  314   a - d  arranged at or near the bottom end  302   b  of the insulation enclosure  300  as compared to thermal energy losses permitted through the insulation zones  314   a - d  arranged at or near the top end  302   a.    
     In at least one embodiment, for example, the support structure  306  and/or the insulation material  308  may be varied such that the thermal resistance (R-value) of the insulation zones  314   a - d  arranged at or near the bottom end  302   b  of the insulation enclosure  300  is less than the thermal resistance (R-value) of the insulation zones  314   a - d  arranged at or near the top end  302   a . In such an embodiment, the first insulation zone  314   a  may exhibit a first R-value “R 1 ,” the second insulation zone  314   b  may exhibit a second R-value “R 2 ,” the third insulation zone  314   c  may exhibit a third R-value “R 3 ,” and the fourth insulation zone  314   d  may exhibit a fourth R-value “R 4 ,” where R 1 &gt;R 2 &gt;R 3 &gt;R 4 . Accordingly, the R-value of the insulation enclosure  300  may increase in the longitudinal direction A from the bottom end  302   b  of the insulation enclosure  300  toward the top end  302   a  such that more thermal energy is retained at or near the top of the mold  200  while thermal energy is drawn out of the bottom  220  via the thermal heat sink  206 . 
     As will be appreciated by those skilled in the art, the graded R-values R 1 -R 4  for each insulation zone  314   a - d  may be achieved in various ways, such as by using different materials for one or both of the support structure  306  and the insulation material  308  at each insulation zone  314   a - d . The graded R-values for each insulation zone  314   a - d  may also be achieved by varying the thickness and/or density of one or both of the support structure  306  and the insulation material  308  at each insulation zone  314   a - d . For instance, in one or more embodiments, the insulation material  308  of the insulation zones  314   a - d  arranged at or near the top end  302   a  of the insulation enclosure  300  may include multiple layers or wraps of insulation material  308 , such as multiple layers or wraps of a ceramic fiber blanket (e.g., INSWOOL®). The increased thickness and/or density of the insulation material  308  of the insulation zones  314   a - d  arranged at or near the top end  302   a  may correspondingly increase the R-value. 
     In other embodiments, the support structure  306  and/or the insulation material  308  may be varied such that the thermal conductivity (k) of the insulation zones  314   a - d  arranged at or near the bottom end  302   b  of the insulation enclosure  300  is greater than the thermal conductivity (k) of the insulation zones  314   a - d  arranged at or near the top end  302   a . In such an embodiment, the first insulation zone  314   a  may exhibit a first thermal conductivity “k 1 ,” the second insulation zone  314   b  may exhibit a second thermal conductivity “k 2 ,” the third insulation zone  314   c  may exhibit a third thermal conductivity “k 3 ,” and the fourth insulation zone  314   d  may exhibit a fourth thermal conductivity “k 4 ,” where k 1 &lt;k 2 &lt;k 3 &lt;k 4 . Accordingly, the thermal conductivity of the insulation enclosure  300  may decrease in the longitudinal direction A from the bottom end  302   b  of the insulation enclosure  300  toward the top end  302   a  such that more thermal energy is retained at or near the top of the mold  200  while thermal energy is drawn out of the bottom  220  via the thermal heat sink  206 . 
     Similar to the graded R-values, those skilled in the art will readily appreciate that the graded thermal conductivities k 1 -k 4  for each insulation zone  314   a - d  may be achieved in various ways, such as by using more thermally conductive materials for one or both of the support structure  306  and the insulation material  308  at the insulation zones  314  at or near the bottom end  302   b  of the insulation enclosure  300 . In at least one embodiment, for instance, the support structure  306  at the insulation zones  314  at or near the bottom end  302   b  of the insulation enclosure  300  may be at least partially made of a steel cage or metal mesh, which exhibits a high thermal conductivity. The graded thermal conductivities for each insulation zone  314   a - d  may also be achieved by varying the thickness and/or density of one or both of the support structure  306  and the insulation material  308  at each insulation zone  314   a - d . Accordingly, this may yield an insulation enclosure  300  with highest insulating properties in the insulation zones  314   a - d  near the top end  302   a  of the insulation enclosure  300  and lowest insulating properties in the insulation zones  314   a - d  near the bottom end  302   b.    
       FIG. 4  illustrates a cross-sectional side view of another embodiment of the exemplary insulation enclosure  300 , according to one or more embodiments. Similar to the embodiment of  FIG. 3 , the insulation enclosure  300  of  FIG. 4  may be configured to control the thermal profile of the mold  200  during cooling by varying one or more thermal properties along the longitudinal direction A of the insulation enclosure  300 . As a result, the rate of thermal energy loss through the insulation enclosure  300  may be graded such that most thermal energy is lost at or near the bottom end  302   b  of the insulation enclosure  300  as opposed to the top end  302   a.    
     In the illustrated embodiment, the insulation enclosure  300  may include one or more heating elements  402  (shown as heating elements  402   a ,  402   b,    402   c , and  402   d ) arranged in thermal communication with the support structure  306  and, therefore, with the mold  200 . As illustrated, the first heating element  402   a  is arranged in the first insulation zone  314   a , the second heating element  402   b  is arranged in the second insulation zone  314   b , the third heating element  402   c  is arranged in the third insulation zone  314   c , and the fourth heating element  402   d  is arranged in the fourth insulation zone  314   d . Each heating element  402   a - d  may be configured to actively vary the temperature of the mold  200  along the longitudinal direction A such that higher temperatures are maintained at or near the top end  302   a  of the insulation enclosure  300  as compared to lower temperatures being maintained at or near the bottom end  302   b . As a result, more thermal energy losses are permitted through the insulation zones  314   a - d  arranged at or near the bottom end  302   b  of the insulation enclosure  300  as compared to thermal energy losses permitted through the insulation zones  314   a - d  arranged at or near the top end  302   a.    
     Each heating element  402   a - d  may be any device or mechanism configured to impart thermal energy to the mold  200  and, more particularly, through the sidewalls of the support structure  306 . For example, each heating element  402   a - d  may be, but is not limited to, a heating element, a heat exchanger, a radiant heater, an electric heater, an infrared heater, an induction heater, a heating band, heated coils, a heated fluid (flowing or static), an exothermic chemical reaction (e.g., combustion or exhaust gases), or any combination thereof. Suitable configurations for a heating element may include, but is not limited to, coils, plates, strips, finned strips, and the like, or any combination thereof. 
     While only four heating elements  402   a - d  are depicted in  FIG. 4 , it will be appreciated that any number of heating elements  402   a - d  may be employed in the insulation enclosure  300 , without departing from the scope of the disclosure. Indeed, multiple heating elements  402   a - d  may be required in one or more of the insulation zones  314   a - d  at or near the top end  302   a  of the insulation enclosure  300  to maintain elevated temperatures. 
     The heating elements  402   a - d  may be in thermal communication with the mold  200  via a variety of configurations of the insulation enclosure  300 . In the illustrated embodiment, for instance, the heating elements  402   a - d  are depicted as being embedded within the insulation material  308  in the sidewalls of the support structure  306 . In other embodiments, however, the heating elements  402   a - d  may interpose the support structure  306  and the mold  200 , such as being attached to the inner walls/surfaces of the support structure  300 . The heating elements  402   a - d  may be useful in helping facilitate the directional solidification of the molten contents of the mold  200  as they provide increased thermal energy to the top of the mold  200  in the longitudinal direction A, while the thermal heat sink  206  draws thermal energy out the bottom  220  of the mold  200 . 
     In the illustrated embodiment, the heating elements  402   a - d  are heating coils embedded within the insulation material  308  (e.g., a ceramic insulating material) in corresponding insulation zones  314   a - d . In operation, each heating element  402   a - d  may be independently controlled and/or operated such that the thermal input to the mold  200  at each insulation zone  314   a - d  varies in the longitudinal direction A. Accordingly, the first insulation zone  314   a  may exhibit a first temperature “T 1 ,” the second insulation zone  314   b  may exhibit a second temperature “T 2 ,” the third insulation zone  314   c  may exhibit a third temperature “T 3 ,” and the fourth insulation zone  314   d  may exhibit a fourth temperature “T 4 ,” where T 1 &gt;T 2 &gt;T 3 &gt;T 4 . Accordingly, the temperature within the insulation enclosure  300  may increase in the longitudinal direction A from the bottom end  302   b  of the insulation enclosure  300  toward the top end  302   a  such that more thermal energy is retained at or near the top of the mold  200  while thermal energy is drawn out of the bottom  220  via the thermal heat sink  206 . 
     In other embodiments, several heating elements  402   a - d  (more than the four illustrated) may be arranged in a uniform array along the longitudinal direction A. In such embodiments, each heating element  402   a - d  may be independently controlled and/or operated to vary the thermal input at varying longitudinal locations across the height of the insulation enclosure  300 . In yet other embodiments, the heating elements  402   a - d  may form part of a single heating coil wrapped multiple times about/within the support structure  306  and the single heating coil may be controlled from a single point source. In such embodiments, the temperature within the insulation enclosure  300  may be varied in the longitudinal direction A by varying the density of the revolutions of the heating coil about/within the support structure  306 . For instance, the revolutions of the heating coil may be more dense at or near the top end  302   a  of the insulation enclosure  300  as opposed to the bottom end  302   b , which may result in increased thermal input at the top end  302   a.    
     In yet other embodiments, the temperature of the mold  200  may be actively varied along the longitudinal direction A by resistively heating the support structure  306  and, more particularly, the outer and/or inner frames  214   216 . In such embodiments, the outer and/or inner frames  214 ,  216  may be a metallic cage or metal mesh and may be communicably coupled to one or more resistive heat sources (not shown). In operation, electric current passing through the outer and/or inner frames  214 ,  216  may encounter resistance, thereby resulting in heating of the outer and/or inner frames  214 ,  216 . Through such resistive heating, higher temperatures may be maintained adjacent the mold  200  at or near the top end  302   a  of the insulation enclosure  300  as compared to lower temperatures maintained at or near the bottom end  302   b . Consequently, the thermal profile of the mold  200  may thereby be controlled such that directional solidification of the molten contents within the mold  200  is substantially achieved from the bottom  220  of the mold  200  axially upward in the longitudinal direction A, rather than radially through the sides of the mold  200 . 
       FIG. 5  illustrates a cross-sectional top view of another exemplary insulation enclosure  500 , according to one or more embodiments. The insulation enclosure  500  may be substantially similar to the insulation enclosures  300  of  FIGS. 3 and 4  and therefore may be best understood with reference thereto, where like numerals will indicate like elements or components that will not be described again. The mold  200  is depicted in  FIG. 5  as exhibiting a substantially circular cross-section. Those skilled in the art will readily appreciate, however, that the mold  200  may alternatively exhibit other cross-sectional shapes including, but not limited to, ovular, polygonal, polygonal with rounded corners, or any hybrid thereof. 
     As illustrated, the insulation enclosure  500  may include the support structure  306 , including the outer and inner frames  214 ,  216 , and the insulation material  308  positioned within the cavity  310  and otherwise supported by the support structure  306 . Unlike the insulation enclosures  300  of  FIGS. 3 and 4 , however, the thermal properties of the insulation enclosure  500  may vary about a circumference of the insulation enclosure  500  (e.g., the support structure  306 ). Varying the thermal properties of the insulation enclosure  500  about its circumference may be configured to affect different geometries or structures in the tool or device being formed within the mold  200 . 
     For instance, it may prove useful to vary thermal properties of the insulation enclosure  500  that may be placed radially or angularly adjacent portions of the mold  200  where cutter blades  102  ( FIG. 1 ) of a drill bit  100  ( FIG. 1 ) are being formed, as opposed to portions of the mold  200  containing junk slots  124  ( FIG. 1 ). More particularly, it may prove advantageous to cool portions of the mold  200  where the cutter blades  102  are being formed slower than portions of the mold  200  containing the junk slots  124  so that any potential defects (e.g., voids) in the cutter blades  102  may be more effectively pushed or otherwise urged toward the top regions of the mold  200  where they can be machined off later during finishing operations. 
     In the illustrated embodiment, one or more arcuate portions of a first insulation material  502   a  and one or more arcuate portions of a second insulation material  502   b  may be arranged within the cavity  310 . The first and second insulation materials  502   a,b  may be made of any of the materials listed above with respect to the insulation material  308 . The first insulation material  502   a  may exhibit one or more first thermal properties and the second insulation material  502   b  may exhibit one or more second thermal properties. In some embodiments, for instance, the first insulation material  502   a  may exhibit an R-value “R 1 ” and the second insulation material  502   b  may exhibit an R-value “R 2 ,” where R 1 &gt;R 2 . In other embodiments, the first insulation material  502   a  may exhibit a thermal conductivity “k 1 .” and the second insulation material  502   b  may exhibit a thermal conductivity “k 2 ,” where k 1 &lt;k 2 . Accordingly, it may prove advantageous to radially and/or angularly align the arcuate portions of the first insulation material  502   a  with portions of the mold  200  that are preferred to cool more slowly than angularly adjacent portions where the arcuate portions of the second insulation material  502   b  are angularly aligned with. 
     It will be appreciated that the thermal properties of the insulation enclosure  500  may also be varied about its circumference by varying the thermal conductivity of the support structure  306  over corresponding arcuate portions or segments, without departing from the scope of the disclosure. Moreover, it will further be appreciated that the embodiments disclosed in all of  FIGS. 3-5  may be combined in any combination, in keeping within the scope of the disclosure. For example, the thermal properties of the insulation enclosure  500  may be varied about its circumference and in the longitudinal direction A simultaneously. Such an example design might include circumferential insulation material  502   a,b  in insulation zone  314   d  with insulation material  308  in insulation zones  314   a - c . In such an embodiment, the insulation material  308  might be the same as the insulation material  502   a  and the geometry of insulation material  502   b  might correspond to the junk slots  124  of a drill bit (e.g., the drill bit  100  of  FIG. 1 ). Many other such configurations are possible without departing from the scope of the disclosure. 
     Embodiments disclosed herein include: 
     A. An insulation enclosure that includes a support structure having a top end, a bottom end, and an interior, the bottom end defining an opening, and insulation material supported by the support structure and extending at least from the bottom end to the top end, wherein one or more thermal properties of at least one of the support structure and the insulation material varies longitudinally from the bottom end to the top end. 
     B. A method that includes removing a mold from a furnace, the mold having a top and a bottom, placing the mold on a thermal heat sink with the bottom adjacent the thermal heat sink, lowering an insulation enclosure around the mold, the insulation enclosure including a support structure having a top end, a bottom end, and an interior for receiving the mold via an opening defined in the bottom end, the insulation enclosure further including insulation material supported by the support structure and extending at least from the bottom end to the top end, varying one or more thermal properties of at least one of the support structure and the insulation material longitudinally from the bottom end to the top end, and cooling the mold axially upward from the bottom to the top. 
     C. An insulation enclosure that includes a support structure having a top end, a bottom end, and an interior, the bottom end defining an opening, and insulation material supported by the support structure and extending at least from the bottom end to the top end, wherein one or more thermal properties of at least one of the support structure and the insulation material varies about a circumference of the support structure. 
     D. A method that includes introducing a drill bit into a wellbore, the drill bit being formed within a mold heated in a furnace and subsequently cooled, wherein cooling the drill bit comprises removing the mold from the furnace, the mold having a top and a bottom, and placing the mold on a thermal heat sink with the bottom adjacent the thermal heat sink, lowering an insulation enclosure around the mold, the insulation enclosure including a support structure having a top end, a bottom end, and an interior for receiving the mold via an opening defined in the bottom end, the insulation enclosure further including insulation material supported by the support structure and extending at least from the bottom end to the top end, varying one or more thermal properties of at least one of the support structure and the insulation material longitudinally from the bottom end to the top end, and cooling the mold axially upward from the bottom to the top, and drilling a portion of the wellbore with the drill bit. 
     Each of embodiments A, B, C, and D may have one or more of the following additional elements in any combination: Element 1: wherein the support structure includes at least one of an outer frame and an inner frame. Element 2: wherein the support structure comprises the outer and inner frames and the insulation material is positioned within a cavity defined between the outer and inner frames. Element 3: wherein the insulation enclosure further comprises an insulative coating positioned on at least one of the inner frame and the outer frame. Element 4: wherein the support structure is made of a material selected from the group consisting of a metal, a metal mesh, ceramic, a composite material, and any combination thereof. Element 5: wherein the insulation material is a material selected from the group consisting of ceramics, ceramic fibers, ceramic fabrics, ceramic wools, ceramic beads, ceramic blocks, moldable ceramics, woven ceramics, cast ceramics, fire bricks, carbon fibers, graphite blocks, shaped graphite blocks, polymer beads, polymer fibers, polymer fabrics, nanocomposites, fluids in a jacket, metal fabrics, metal foams, metal wools, metal castings, any composite thereof, and any combination thereof. Element 6: further comprising a reflective coating positioned on an inner surface of the support structure. Element 7: wherein the one or more thermal properties are selected from the group consisting of thermal resistance, thermal conductivity, specific heat capacity, density, thermal diffusivity, temperature, surface characteristics, emissivity, absorptivity, and any combination thereof. Element 8: wherein the one or more thermal properties is thermal resistance and the thermal resistance of at least one of the support structure and the insulation material increases longitudinally from the bottom end to the top end. Element 9: wherein the one or more thermal properties is thermal conductivity and the thermal conductivity of at least one of the support structure and the insulation material decreases longitudinally from the bottom end to the top end. Element 10: further comprising one or more heating elements in thermal communication with the mold, wherein the one or more thermal properties is temperature and the one or more heating elements increases the temperature of at least one of the support structure and the insulation material longitudinally from the bottom end to the top end. Element 11: wherein the one or more heating elements is selected from the group consisting of a heating element, a heat exchanger, a radiant heater, an electric heater, an infrared heater, an induction heater, a heating band, heated coils, a heated fluid, an exothermic chemical reaction, and any combination thereof. Element 12: wherein the one or more heating elements is embedded within the insulation material. Element 13: wherein the one or more heating elements comprises a plurality of independently controlled heating coils. Element 14: wherein the one or more heating elements comprises a heating coil wrapped multiple revolutions about or within the support structure, and wherein a density of the revolutions of the heating coil is greater at the top end than the bottom end. Element 15: wherein the one or more thermal properties of at least one of the support structure and the insulation material are further varied about a circumference of the support structure. Element 16: wherein the one or more thermal properties include thermal resistance and thermal conductivity of at least one of the support structure and the insulation material. 
     Element 17: wherein the one or more thermal properties are selected from the group consisting of thermal resistance, thermal conductivity, specific heat capacity, density, thermal diffusivity, temperature, surface characteristics, emissivity, absorptivity, and any combination thereof. Element  18 : wherein the one or more thermal properties is thermal resistance, the method further comprising increasing the thermal resistance of at least one of the support structure and the insulation material longitudinally from the bottom end to the top end. Element 19: wherein the one or more thermal properties is thermal conductivity, the method further comprising decreasing the thermal conductivity of at least one of the support structure and the insulation material longitudinally from the bottom end to the top end. Element 20: wherein the one or more thermal properties is temperature, the method further comprising increasing the temperature of at least one of the support structure and the insulation material longitudinally from the bottom end to the top end with one or more heating elements in thermal communication with the mold. Element 21: wherein the one or more heating elements comprises a plurality of heating coils, the method further comprising independently controlling each heating coil to increase the temperature of at least one of the support structure and the insulation material longitudinally from the bottom end to the top end. Element 22: further comprising varying the one or more thermal properties of at least one of the support structure and the insulation material about a circumference of the support structure, the one or more thermal properties being at least one of thermal resistance and thermal conductivity of at least one of the support structure and the insulation material. Element 23: further comprising drawing thermal energy from the bottom of the mold with the thermal heat sink. 
     Therefore, the disclosed systems and methods are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the teachings of the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope of the present disclosure. The systems and methods illustratively disclosed herein may suitably be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted. 
     As used herein, the phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (i.e., each item). The phrase “at least one of” allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C.