Patent Publication Number: US-2013242688-A1

Title: Pill preparation, storage, and deployment system for wellbore drilling and completion

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 13/416,767, which was filed Mar. 9, 2012 and is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present disclosure relates generally to subterranean drilling and completion operations and, more particularly, to a method and apparatus for preparing, storing, and/or deploying a pill. The term “pill” as used herein refers to a batch of specialized fluid used to serve a particular function during drilling and/or completion operations. 
     Drilling and completion operations play an important role when developing oil, gas or water wells or when mining for minerals and the like. During drilling operations, a drill bit passes through various layers of earth strata as it descends to a desired depth. Drilling fluids are commonly employed during the drilling operations and perform several important functions including, but not limited to, removing the cuttings from the well to the surface, controlling formation pressures, sealing permeable formations, minimizing formation damage, and cooling and lubricating the drill bit. When performing drilling operations in a reservoir, it is desirable to use special fluids that minimize damage to the formation. During subsequent completion operations, steps may be taken to enhance well productivity and additional downhole equipment may be installed. 
     When the drill bit passes through porous, fractured or vugular strata such as sand, gravel, shale, limestone and the like, the hydrostatic pressure caused by the vertical column of drilling fluid may exceed the ability of the surrounding earth formation to support this pressure. As a result, fluid communication with the surrounding formation may occur immediately in an open hole and after the perforation step for a cased wellbore. Once there is fluid communication between the wellbore and the formation, the hydrostatic pressure caused by the drilling fluid or a completion fluid may exceed the pore pressure of the earth formation. Consequently, some drilling or completion fluid may be lost to the formation and may fail to return to the surface. During drilling operations, the general practice is to add any number of fluid loss control materials to the drilling fluid which act to form a wellbore filter cake that reduces the loss of fluid to the formation. 
     To help optimize or maintain drilling and completion operations, it may be necessary to prepare and then pump one or more pills down hole. These pills are usually made or built in a step-by-step batch process at the drill site. The composition and rheology of pills may vary considerably and may be complex in nature, making it difficult to prepare, store, and deploy these pills on the surface using standard fluid processing equipment. In some cases, such as in the case of displacement pills, it may be desirable to sequentially pump a series of specialized pills downhole without pausing. It is therefore advantageous to be able to prepare and then sequentially pump multiple pills downhole. 
     Some examples of pills include, but are not limited to, Loss Control Material (LCM), barriers, sweeps, spacers, cleaners, push, wetting agents, lubricants, and thermal insulations. To improve downhole performance, pills may be highly viscous and/or highly thixotropic in nature. Such pills may also be formulated with high concentrations of solids to increase fluid density and/or to cause bridging once downhole. The term “thixotropic” as used herein refers to a shear thinning property of a fluid. Accordingly, highly thixotropic materials are thick (viscous) under static conditions and become thinner (or less viscous) when shaken, agitated, pumped, or otherwise exposed to a sufficient shear stress. Thus, highly thixotropic pills may form semisolids or gels under static conditions in a vessel that must be broken by applying a shear stress before discharging from the vessel. Some highly thixotropic mixtures isolate fluid motion in a vessel and prevent the desired formation of a homogenous mass unless a combination of multiple agitation units equipped with custom impellers are employed. 
     In some cases, standard blending and mixing systems commonly utilized at rig sites cannot build and handle pills that possess desired downhole properties such as high viscosity, high suspension capability, high density, gel formation under static conditions, bridging capabilities, and/or thermal isolation. These standard drill site blending and mixing systems typically include a vessel equipped with a single agitator unit, a discharge/circulation pump, hatches or an open deck for adding materials, and an inline hopper to add powders to a high-shear zone. Many powders used to prepare pills tend to quickly encapsulate, forming “fish eyes” if the powder and surrounding fluid does not quickly enter into a high-shear zone. As used herein, “fish eyes” are encapsulated gelled particles that may result in yield loss, plugging of surface equipment such as pump suction strainers, and plugging of the reservoir formation resulting in lower permeability. 
     With respect to certain pill formulations, some of the common deficiencies observed when utilizing standard drilling rig site blending and mixing systems include, but are not limited to, an inability to evenly blend larger quantities of highly thixotropic fluids, an inability to completely break down large quantities of gel into a free-flowing fluid, an inability to provide high intensity microshear when adding powders that are prone to form fish eyes, an inability to provide a variety of different mixing actions simultaneously, an inability to adequately discharge the vessel due to pump limitations, an inability to adequately discharge the vessel due to vessel configuration, an inability to create and discharge a homogeneous fluid, an inability to provide gentle agitation during storage to prevent the settling of solids, an inability to discharge high-viscosity sludge and slurries by pumping, an inability to reduce fluid viscosity by heating the fluid, and an inability to avoid freezing of some fluids during long-term storage. 
     Standard rig site blending equipment is also limited as to the turn-down ratio of the pill batch size that can be prepared and deployed without compromising downhole pill performance. The term “turn-down ratio” refers to the maximum pill volume divided by the minimum pill volume that can be effectively blended and mixed in a system. Typically, pills of smaller size as related to the vessel total volume may not be able to be prepared and deployed by standard equipment because of critical agitator impellers that sit above the fluid level, resulting in inadequate mixing and poor drainage from the bottom of the vessel. 
     Standard mobile blending equipment typically rented for special applications may have only one agitated vessel and may require considerable drill site deck space or drill site ground space to operate. Limitation in drill site deck space or ground space may make it impractical to prepare, store, and deploy multiple pills in an optimized sequence. 
     Additionally, thixotropic fluids having thick slurry, high viscosity, high concentration of solids, and/or those that can form a semisolid mass under static conditions, may remain in a semisolid state and withstand motion unless several different mixing actions are applied simultaneously using the correct combination of impellers rotated at different speeds. 
     Thus, it is desirable to have a mobile integrated blending and mixing system for eliminating common deficiencies observed with standard drilling rig site blending systems discussed above. 
     Drilling operations for oil and gas continue to become more challenging as easy to extract hydrocarbons become more difficult to find or access. For example, drilling operations such as ultra-deep water, high pressure high temperature, drilling to great depths, long reach horizontal drilling through fractured shale, managed pressure drilling, underbalanced drilling, and drilling through reactive shale may increase the need for more specialized pills, more frequent pumping of pills, high volumes of pills that may exceed the limited number of suitable agitated pits, pit capabilities with respect to fluid thickness and gel strength, and limited availability of rig contractor personnel to operate and clean the pill pits. In addition, the high cost of drilling and completing wells may help justify additional steps to maximize recovery of hydrocarbons by using additional pills and special fluid systems designed to prevent damage to pay zones and more complete removal of well bore filter cake. It is therefore advantageous to bring out integrated mobile pill preparation, storage, and deployment systems that overcome traditional drill site limitations. 
     SUMMARY 
     Systems and methods for preparation, storage, and/or deployment of a specialized fluid are disclosed. A system for preparation, storage, and/or deployment of a specialized fluid comprises a fluid vessel, a first, second, and third agitation unit, wherein each of the agitation units is at least partially disposed within the fluid vessel, a first, second, and third motor coupled to each of the agitation units, respectively, wherein each of the motors are independently operable. A method for preparing, storing, and/or deploying one or more specialized fluids comprises mixing a first specialized fluid in a first fluid vessel using any combination of a first, second, and third agitation unit and removing the first specialized fluid from the first fluid vessel. 
     The features and advantages of the present invention will be apparent to those skilled in the art from the description of the preferred embodiments which follows when taken in conjunction with the accompanying drawings. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These drawings illustrate certain aspects of some of the embodiments of the present invention, and should not be used to limit or define the invention. 
         FIG. 1  depicts a mobile integrated pill preparation, storage, and deployment system configured for a single vessel in accordance with an illustrative embodiment of the present disclosure. 
         FIG. 2  depicts a mobile single vessel modular skid as transported to the drill site for integration into preparing, storing, and/or deploying the mobile integrated pill preparation, storage and deployment system of  FIG. 1 . 
         FIG. 3  depicts a mobile pill preparation, storage, and deployment system configured for a single vessel in accordance with an illustrative embodiment of the present disclosure. 
         FIG. 4  depicts a front view of a three-vessel system for preparing, storing, and/or deploying pills in accordance with an illustrative embodiment of the present disclosure. 
         FIG. 5  depicts a mobile power and pump skid for preparing, storing, and/or deploying pills in accordance with an illustrative embodiment of the present disclosure. 
         FIG. 6  depicts a flow chart for preparing, storing, and/or deploying pills in accordance with an illustrative embodiment of the present disclosure. 
     
    
    
     While embodiments of this disclosure have been depicted and described and are defined by reference to example embodiments, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure. 
     DETAILED DESCRIPTION 
     The present disclosure relates generally to subterranean drilling and completion operations and, more particularly, to a method and apparatus for preparing, storing, and/or deploying pills that may be thixotropic in nature. 
     Illustrative embodiments of the present invention are described in detail herein. In the interest of clarity, not all features of an actual implementation may be described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions may be made to achieve the specific implementation goals, which may vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of the present disclosure. 
     To facilitate a better understanding of the present disclosure, the following examples of certain embodiments are given. In no way should the following examples be read to limit, or define, the scope of the disclosure. Embodiments of the present disclosure may be applicable to horizontal, vertical, deviated, or otherwise nonlinear wellbores in any type of subterranean formation. Embodiments may be applicable to injection wells as well as production wells, including hydrocarbon wells. 
     The present disclosure is directed to a system and method for preparing, storing, and/or deploying pills including, but not limited to, difficult to handle pills. The difficult to handle pills may include one or more of the following: a viscous sludge, a slurry, a semisolid fluid, a highly viscous fluid, and a thixotropic fluid. 
     Turning now to  FIG. 1 , a mobile single-vessel integrated system for preparing, storing, and/or deploying a pill in accordance with an illustrative embodiment of the present disclosure is denoted generally with reference number  100 . The system  100  includes a fluid vessel  102 . The fluid vessel  102  may be configured to monitor temperature, pressure, fluid level, and/or fluid weight. The fluid vessel  102  may be made of any suitable materials, including, but not limited to, hard plastic, metal, or any other sufficiently robust material. The fluid vessel  102  may have any suitable geometry. For instance, in certain embodiments, the fluid vessel  102  may be generally cylindrical, have a dished bottom, and may be accessible through at least one opening (not shown). In other embodiments, the bottom section of the fluid vessel  102  may be conical in shape instead of dished to facilitate a more complete discharge of a viscose fluid. The fluid vessel  102  may be a multiple purpose vessel that may function as an agitated batch reactor, a temporary storage vessel, a blending vessel, a dilution vessel, and/or a heating or cooling device. 
     For safe transportation, lifting, and access to heights, the fluid vessel  102  may be incorporated inside a modular vessel skid as discussed in greater detail with respect to  FIG. 2 . The fluid vessel  102  may be couplable to an operating skid  103  for transportation. The fluid vessel  102  and operating skid  103  may be transported coupled together or independently. Additionally, the fluid vessel  102  may be coupled to a pump and power skid  104 , a safe access ramp  105 , a safe access platform  106 , a set of hand rails  107 , a safe access ladder  108 , a ladder safety cage  109 , and a control panel  121 . As would be appreciated by those of ordinary skill in the art, with the benefit of the present disclosure, the control panel  121  may be communicatively coupled to the system through a wired or wireless connection. Structure and operation of such connection systems is well known to those of ordinary skill in the art, having the benefit of the present disclosure and will therefore not be discussed in detail herein. Similarly, a pump  116 , a pump drive  117 , a generator  118 , a reciprocating engine  119 , batteries  140 , and related components may be mounted to the pump and power skid  104  for transportation. The control panel  121  may be contained in a sealed box designed to hold all components that require isolation from a potentially hazardous environment. The function of the control panel  121  is discussed in further detail with respect to  FIG. 3 . The operating skid  103  and pump and power skid  104  may be designed for safe lifting with a fork lift or crane. Further, the operating skid  103  and the pump and power skid  104  may be transported by any suitable means typically used for transport of such components. For instance, these components may be safely transported by truck, rail, air or marine vessels such as a boat or barge. The safe access ramp  105 , safe access platform  106 , hand rails  107 , safe access ladder  108 , and ladder safety cage  109  may be designed to provide access to the fluid vessel  102 . The fluid vessel  102  may further include one or more of a first agitation unit  110 , a second agitation unit  120 , and a third agitation unit  130 , each capable of different mixing actions. The agitation units  110 ,  120 , and  130  may include variable speed controllers for adjusting the rotational speed of the agitator shafts. The function and operation of each of the agitation units  110 ,  120 , and  130  is discussed in further detail with respect to  FIG. 3 . 
     As shown in  FIG. 1 , the fluid vessel may be coupled to the pump  116  for discharge of fluid. The fluid vessel  102  may be supported by feet  122  that may be mounted on top of strain gauge load cells  114 . The weight of the content in the fluid vessel  102  may be continuously monitored by totaling the force exerted on each of the load cells  114 . In certain implementations, four load cells may be used. The fluid vessel  102  may include a bottom vessel discharge valve  115 . The bottom vessel discharge valve  115  may be a ram type of valve suited for high viscosity fluids that may contain solids. The bottom vessel discharge valve  115  may be coupled to the pump  116  by piping, flexible hose, or any other conduit known to those of skill in the art having the benefit of this disclosure. The material discharged through valve  115  may flow to the pump  116  that transfers this material to the next location through piping or flexible hose. The pump  116  may be a progressing cavity pump capable of transferring high-viscosity fluids that contain solids. The pump  116  may be coupled to the pump drive  117 . The pump drive  117  may include an electric motor/variable speed controller that allows for the fluid discharge rate from the fluid vessel  102  to be varied and controlled. The power from the generator  118  may be coupled to the pump drive  117  and to the first, second, and third agitation units  110 ,  120 ,  130 . The generator  118  may provide the power for all the agitation units  110 ,  120 , and  130  and the pump  116 . The generator  118  may be designed for operation in hazardous locations. The generator  118  may be coupled to and powered by a reciprocating engine  119  that may be designed for operation in hazardous locations. The reciprocating engine  119  may use any suitable fuels including, but not limited to, diesel, gasoline, or natural gas fuel. Batteries  140  may be used to start reciprocating engine  119  and to provide backup power for critical instrumentation and lighting systems. 
     Turning now to  FIG. 2 , a mobile single-vessel system for preparing, storing, and/or deploying in accordance with an illustrative embodiment of the present disclosure is depicted generally with reference numeral  200 . In certain embodiments, the mobile single-vessel system  200  may be used to house and/or transport the fluid vessel  102  of  FIG. 1 . The system  200  is shown in  FIG. 2  in the form that it could be transported to a drilling site. A modular vessel skid  224  may include the fluid vessel  102  mounted inside a protective frame  221 . The protective frame  221  may be made of steel or any other strong material known to those of skill in the art having the benefit of this disclosure. The protective frame  221  may be covered by a removable grid platform  222 , and may be mounted on a base  223 . In certain implementations, the base  223  may be designed to accommodate fork truck lifts. The fluid vessel  102  may include the bottom discharge valve  115  as discussed above in conjunction with  FIG. 1 . Additionally, the fluid vessel  102  may include a vent valve  225 , one or more lower agitator assemblies  226 , one or more removable protective caps  227 , and support legs  228 . The base  223  may include slots  229  to accommodate prongs of a fork lift or other mechanism that may be used to move the system  200 . The protective frame  221  may be coupled to the base  223  and may include crane lift eyes  230  and a safe access ladder  208 . Once the system  200  has arrived at the drill site, the modular vessel skid  224  may be mounted on a mobile single vessel integrated system  100  depicted in  FIG. 1  or it may be mounted on a three-vessel system  400  as depicted in  FIG. 4 . The fluid vessel  102  may be transported to the drill site empty or with one or more fluids inside. 
     Turning now to  FIG. 3 , a system for preparing, storing, and/or deploying a pill in accordance with an illustrative embodiment of the present disclosure is denoted generally with reference numeral  300 . The system  300  includes the fluid vessel  102 . A weight of a fluid contained in the fluid vessel  102  may be measured by one or more load cells  114  coupled to the fluid vessel  102 . 
     In the embodiment shown in  FIG. 3 , a funnel  352  is coupled to a full port valve  353  that connects to feed line  384  for transferring materials prone to form fish eyes into a high shear zone within the fluid vessel  102 . The preferred zone to introduce additive materials that may form fish eyes is near a top impeller  364 . Additional openings may be incorporated into the fluid vessel  102 . In some embodiments, such as the one shown in  FIG. 3 , the fluid vessel  102  may be a closed vessel that may be isolated from the atmosphere. However, in other embodiments, the top of the fluid vessel  102  may be open to the atmosphere and covered with a grid work deck (not shown). In the embodiment shown in  FIG. 3 , a fluid addition line  362  is coupled to a valve  363 , which may be coupled to a feed line  385  that continues past the wall of the fluid vessel  102 . The valve  363  may be used to regulate and shut off fluid flow through the fluid addition line  362 . The valve  363  may be of any suitable design including, but not limited to, a ball, plug, gate, butterfly, pinch, or needle configuration. The fluid addition line  362  may be used to add liquid, fluid, gel, sludge, or slurry components to the fluid vessel  102 , while the funnel  352  may be used to add powders, solids, or dry components to the fluid vessel  102 . Materials, including solids, that are not prone to cause fish eyes may be added through quick open hatch  350 . 
     In certain embodiments, the specialized fluid may be prepared in the fluid vessel  102  located at a drilling site. In other embodiments, the specialized fluid may be prepared in the fluid vessel  102  located off-site and then the fluid vessel  102  may later be transported to a drilling site. Thus, the system  100  is mobile such that the fluid vessel  102  may be transported to a drilling site once the specialized fluid is prepared within it or moved empty. 
     Thus, in certain embodiments, the system  300  may be mobile and mounted to one or more skids as shown in  FIGS. 1 and 2  to facilitate transportation to and from land and offshore drill sites. The system  300 , when mounted to the skids as discussed herein, may be designed and certified for ground and/or marine transport when the fluid vessel  102  is empty. The skids may facilitate easy transport, set-up, and rig down. Once at the drill site, the system  300  may be set up and may be used for preparing, storing, and/or deploying pills. When no longer needed, the system  300  may be cleaned, rigged down, and transported to another location. The described configuration is advantageous because it provides quick set-up, allows the system  300  to occupy minimum ground or deck space at the drill site, allows safe lifting by a fork lift or a crane, allows the system  300  to meet all air, truck, and marine transport requirements, and allows safe access to heights. The various skids depicted in  FIGS. 1 ,  2 ,  4 , and  5  function to facilitate modular lifting, transportation, set-up, and rig-down of one or more systems  300 . 
     Still referring to  FIG. 3 , the system  300  may further include the first agitation unit  110  that is at least partially disposed in the fluid vessel  102 . The first agitation unit  110  may include a first motor  301 , a shaft coupler  303  coupled to the first motor  301 , and an impeller  304  coupled to the shaft coupler  303 . In certain embodiments, the first agitation unit  110  may be a bulk blender. The impeller  304  may include a variety of configurations and may be capable of creating fluid movement throughout the fluid vessel  102  even when the fluid in the fluid vessel  102  is of a high viscosity. Fluid movement is created throughout the fluid vessel  102  when the impeller  304  is rotated. The shape, length, and positioning of the impeller  304  as well as the number of impellers attached to the shaft coupler  303  may be varied without departing from the scope of the present disclosure. Moreover, any number of impellers  304  may be used without departing from the scope of the present disclosure. The one or more impellers  304  may have a large combined surface area, may be designed to prevent any static zones within the fluid vessel  102 , may increase heat transfer into the fluid vessel  102 , and/or may primarily provide macro-scale blending. The impeller  304  may be of a design that includes holes, slots, and/or screens that may reduce power consumption. The illustrative impeller  304  depicted in  FIG. 3  is shown with holes. 
     Still referring to  FIG. 3 , the system  300  may further include the second agitation unit  120  that is at least partially disposed in the fluid vessel  102 . The second agitation unit  120  may include a second motor  361 , a shaft coupler  363  coupled to the second motor  361 , and an upper and lower impeller  364  and  365  coupled to the shaft coupler  363 . In certain embodiments, the second agitation unit  120  may be a homogenizer. The second motor  361  may provide power to the second agitation unit  120 . The upper and lower impellers  364  and  365  may be smaller in size compared to the impeller  304  of the first agitation unit  110 , and they may be rotated at speeds sufficient to provide intense high-shear zones near the impellers  364 ,  365  for quickly homogenizing materials that are prone to cause fish eyes. High intensity shear zones may also rapidly eliminate suspended gelled particles and drastically reduce apparent viscosity of highly thixotropic fluids. In  FIG. 3 , the upper impeller  364  and the lower impeller  365  may be identical and of a rotor-stator type, where the outside rotor has teeth that create high shear when rotated around a stationary inter-stator that has slots. The upper and lower impellers  364  and  365  may include a variety of configurations. The present disclosure is not limited to a specific number of impellers, rotor teeth, stator slots, diameter, shape, or positioning of impellers, or length of rotor teeth. For example, the number and the diameter of the upper and lower impellers  364  and  365 , the number and length of the rotor teeth, and/or the number of stator slots may be varied within the scope of the present disclosure. 
     Still referring to  FIG. 3 , powders or liquids that are prone to encapsulate and form fish eyes when added into a fluid in a low-shear zone may be added directly to a high-shear zone created by rotating upper impeller  364 . The funnel  352  in conjunction with the valve  353  and feed line  384  may be used to transfer powders and liquids directly into the fluid vessel  102  near the upper impeller  364 . The capability to directly add certain powders and liquids to a high-shear zone inside of the fluid vessel  102  reduces or eliminates the formation of undesired fish eyes. The ability to add powders and liquids with encapsulating tendencies directly to the fluid vessel  102  without causing excessive fish eye formation eliminates the need for a separate inline hopper/blender and thus greatly simplifies the system  300  and results in skid systems that are easier to transport, easier to set up, and require less ground or deck space at the drill site. 
     Still referring to  FIG. 3 , the system  300  may further include the third agitation unit  130  mounted such that it is at least partially disposed in the fluid vessel  102 . The third agitation unit  130  may include a third motor  370 , a shaft coupler  371  coupled to the third motor  370 , and upper and lower impellers  372  and  373  coupled to the shaft coupler  371 . In certain embodiments, the third agitation unit  130  may be a dispersion mixer. The upper and lower impellers  372  and  373  may be of a variety of configurations. For example, the upper and lower impellers  372  and  373  may be identical and shaped to create a dispersion mixing action as shown in  FIG. 3 . The third agitation unit  130  may be designed to create moderate shear zones as well as rapid radial and vertical acceleration of fluid within the fluid vessel  102 . The impellers  372  and  373  may be an angled turbine type, a hydrofoil type, or any other impeller type known to those of skill in the art having the benefit of this disclosure. The shear zones may become smaller as the apparent viscosity of the fluid increases. The present disclosure is not limited to a specific number of impellers, impeller style, diameter of impellers, or shape, length, or positioning of the impellers. For example, the number and diameter of the impellers and/or the design of the impellers may be varied. 
     Each agitation unit  110 ,  120 , and  130  may include a first, second, and third agitator seal  345 ,  346 , and  347 . The agitator seals  345 ,  346 , and  347  may each function as a barrier assembly located where each agitation unit passes through the wall fluid vessel  102 . Each agitator seal  345 ,  346 ,  347  may allow the respective shaft coupler  303 ,  363 , and  371  to rotate without allowing materials to leak out of or into the fluid vessel  102  even when the fluid vessel  102  is operated at positive or negative pressures with respect to ambient pressures. 
     As described above, the first agitation unit  110 , the second agitation unit  120 , and the third agitation unit  130  each include a separate shaft coupler ( 303 ,  363 , and  371 , respectively), and are each coupled to a separate motor ( 301 ,  361 , and  370 , respectively). Therefore, the first, second, and third agitation units  110 ,  120 , and  130  may be controlled independently. The first, second and third motors  301 ,  361 , and  370  may be any suitable type of motor such as, for example, electric, hydraulic, pneumatic, or of any other type known to those in the art having the benefit of this disclosure. An electric motor with an acceptable hazardous zone classification is preferred. The first, second, and third agitation units  110 ,  120 , and  130  may also be directly coupled to a reciprocating diesel, gasoline, or natural gas engine. The first, second, and third motors  301 ,  361 , and  370  may be capable of operating at variable speeds. Options for providing variable speed agitations include, but are not limited to, variable frequency drives (VFD), variable speed DC motors, gear couplers, pulleys/belts, and hydraulic or pneumatic speed control devices. 
     Thus, in operation of the system  300 , the first, second, and third agitation units  110 ,  120 , and  130  may be operated independently, such that they may be run one at a time, concurrently, or in any combination. For maximum blending and mixing intensity, all three agitation units  110 ,  120 , and  130  may be operated concurrently at maximum rotational speed settings. Operation of all three agitation units  110 ,  120 , and  130  concurrently creates a triple action agitation system within a single fluid vessel  102 . It is advantageous to have triple action within the fluid vessel  102  as it may create significant synergies with regards to blending and mixing over a wide range of apparent viscosities and solid concentrations. Triple action mixing capability allows for preparing, storing, and/or deploying a wide range of difficult to handle fluid compositions. Triple action agitation systems within a single fluid vessel  102  may also reduce or eliminate the need to use several different vessels or unit operations when processing or blending complex compositions, resulting in simplicity of operation and reduced equipment-related costs. The system  100  provides greater flexibility at the drill site to prepare, store, and deploy a wide range of different types of pills in an optimal manner without the disadvantages of additional specialized equipment as compared to previous systems in the art. 
     In further operation of the system  100 , the first, second, and third agitation units  110 ,  120 , and  130  may provide different blending and mixing actions that may include high-shear homogenizing, dispersion mixing, and slow-speed blending. The first, second, and third agitation units  110 ,  120 , and  130  may be configured to operate at variable speeds. The first, second, and third agitation units  110 ,  120 , and  130  may be equipped with a soft-start feature to help prevent excessive stress that may form on each agitation unit  110 ,  120 , and  130  when breaking a gel. The impellers on each agitation unit  110 ,  120 , and  130  may be custom-designed to achieve each different type of mixing action. For example, the upper and lower impellers  372  and  373  on the third agitation unit  130  may be disposed at an angle in order to achieve dispersion mixing. The upper and lower impellers  364  and  365  on the second agitation unit  120  may be configured as a rotor-stator in order to provide homogenization. The impeller  304  on the first agitation unit  110  may be configured as an anchor in order to provide bulk blending. 
     The control panel  121  may include an interface to couple with the first, second, and third agitation units  110 ,  120 , and  130 , each of which may have variable speed and programmable capabilities. For alternating electric powered systems, the variable speed drives may change the frequency of the currents that feed the first, second, and/or third motors  301 ,  361 , and  370  and thus control the rotational output of each motor. Such drives may be referred to as a variable frequency drive (VFD). The control panel  121  may be communicatively coupled to the VFDs (not shown) that control the rotational speeds of the agitation units through a wired or wireless communication network. In order to meet hazardous area ratings, three separate VFDs may be used to control the rotational speeds of the first, second, and third motors  301 ,  361 , and  370  and the pump drive  117 . These VFDs may be housed in sealed boxes that are rated for hazardous locations that are mounted on a skid (not shown), located in a modular building rated for hazardous locations (not shown), or located in an area outside of the hazardous location. Locating the VFDs in a modular building rated for hazardous locations or in areas outside of the hazardous zone may offer many design, operational, cost, and maintenance advantages especially when more than one skid system is operated inside of the same hazardous area. The control panel  121  may be a programmable logic controller (PLC) or any other type of automatic control system known to those in the art having the benefit of this disclosure. The control panel  121  may provide a user interface permitting a user to manipulate the operation of the first motor  301 , the second motor  361 , and the third motor  370 . For instance, a user may set the control panel  121  such that the variable speed drive in the first motor  301  may operate the first agitation unit  110  at variable speeds and may automatically change the speed over time. When exposed to static conditions, some fluids may form strong gels that may stress mechanical components if any of the agitation units are started-up abruptly. For this reason, the agitation units  110 ,  120 , and  130  may be programmed to increase their rotational speeds slowly during their initial start-up in order to prevent excessive stress on mechanical components. When preparing pills, the mixing action and intensity of the mixing provided by each agitation unit may be varied throughout the preparation process. For example, maximum mixing intensity of all three agitation units may be needed when adding powders that may form fish eyes or when shearing highly thixotropic pills before discharging them from the fluid vessel  102 . The first agitation unit  110  may be operated at low speeds over extended time periods when storing pills that may experience the slow settling of solids such as barite or when heat transfer to prevent freezing is advantageous. 
     The rotational shaft speeds of the first, second, and third agitation units  110 ,  120 , and  130  may each be communicated to the control panel  121  via an interface. Thus, feedback loops to the respective first, second, and third motors  301 ,  361 , and  370  may be created. Specifically, the first, second, and third motors  301 ,  361 , and  370  may each be communicatively coupled to the control panel  121  through a wired or wireless communication network. Communications may be sent from each of the first, second, and third motors  301 ,  361 , and  370  to the control panel  121  regarding the rotational speed of the each respective agitation unit so that the speed of the respective motors may be adjusted if it is not the same as the input speed. Using these control loops, the revolutions per minute of each agitation unit may be automatically controlled and varied. 
     The electrical power for all electric motors (such as the first, second, and third motors  301 ,  361 , and  370  and the pump drive  117 ), instrumentation, electric powered valves, control panels (not shown), communication devices, lights (not shown), and other such electrical apparatuses included in the system  300  is supplied through a generator  118  (not shown in  FIG. 3 ; shown in  FIG. 1 ). The generator  118  may be of several different types including, but not limited to, a rig site generator, a local-skid mounted generator set, and a generator set mounted on a separate modular. Backup power for critical safety systems may be supplied by batteries  140  (shown in  FIG. 1 ). 
     As shown in  FIGS. 1 and 3 , the fluid vessel  102  may be coupled to the pump  116  so that fluid may be selectively removed from the fluid vessel  102  as needed at the drill site. The pump  116  may be any pump suitable for transferring highly-viscose sludge and slurries that may have a high concentration of solids. The pump  116  may not require a high net positive suction head (NPSH). Suitable pumps for highly-viscose fluids include, but are not limited to, progressing cavity pumps (PCP), gear pumps, triplex-style plunger pumps, piston pumps, and diaphragm pumps. Pumps that have a minimum pressure pulse or no pressure pulse are preferred for directly transferring fluid from the fluid vessel  102  into a rig drilling fluid pump, cement unit pump, or into a downhole work string. The pump  116  may have valves or be valve-free such as PCP and S-tube piston pumps. As discussed above with respect to  FIG. 1 , the pump  116  may be coupled to the pump drive  117 . The pump drive  117  may be an electric, hydraulic, pneumatic, motor, a reciprocating diesel, gasoline, or natural gas engine, or any other suitable means of power known to those in the art having the benefit of this disclosure. An electric motor drive correctly rated for the area hazards is preferred. 
     In the embodiment shown in  FIG. 3 , the pump  116  may be a PCP. The rotational speed output of the pump  116  may be controlled by the pump drive  117 . The pump drive  117  may be an electric motor capable of variable speed operation. Therefore, the pump drive  117  may be mechanically or communicatively coupled to the control panel  121 . The pump drive  117  may be operable to vary the rotational shaft speed of the pump  116  to control the volumetric discharge rate of a fluid and to control the discharge pressure of the pump  116 . A Coriolis mass flow meter  376  may be coupled to the pump  116  and may operate to regulate the flow of fluids being pumped out of the fluid vessel  102 . Additionally, a pressure transmitter  377  may be coupled to the pump  116  and may operate to measure and transmit the amount of pressure in a pump discharge pipe  378  through which fluid is being pumped out of the fluid vessel  102 . A pressure relief valve  379  may also be coupled to the pump  116 . The high-pressure relief valve  379  may operate to reduce pressure in the pump discharge pipe  378 . The control panel  121  may receive input from the Coriolis mass flow meter  376  and/or the pressure transmitter  377 . Utilizing this control loop, the rotational speed of the pump  116  may be automatically flow-controlled and/or pressure-controlled. Deadhead protection of the pump  116  may be provided by a high-amp switch (not shown) located on a power line to the pump drive  117 , the high-pressure relief valve  379 , and/or a high-pressure shut-down based on output from the pressure transmitter  377 . In addition, a minimum flow indicator  380  may be coupled to the pump  116  to shut down the pump  116  if operated without adequate flow over a pre-set time period. 
     As shown in  FIG. 3 , the system  300  may further include the drain valve  115  disposed on the bottom of the fluid vessel  102 . A preferred type of drain valve  115  may be a ram/piston design that is resistant to clogging by viscose sludge and slurries. Ram/piston drain valves allow full port discharge when opened, and the valve piston extends into the bottom of the fluid vessel  102  when the drain valve  115  is closed. During the closing operation, the piston serves as a ram that pushes residual fluid from the valve body back into vessel. The pump suction line  382  couples the drain valve  115  to the pump  116  and may be at least four inches in diameter and without constrictions. A minimum net positive suction head (NPSH) at a pump inlet is necessary for a pump to function correctly. In order to maintain adequate NPSH when discharging difficult to handle pills, the pump  116  may create suction at the pump inlet, and the fluid vessel  102  may be pressurized with air to help establish and maintain flow into the pump inlet. A pressure transmitter  381  may be coupled to the pump suction line  382  to verify adequate NPSH when discharging pills from the fluid vessel  102 . 
     The system  300  may be equipped to provide a high turn-down ratio to allow the preparation, storage, and discharge of smaller volume pills without changing out or making major adjustments to equipment. A volumetric turn-down ratio may be defined as the maximum pill volume divided by the minimum pill volume that can be effectively blended, sheared, and mixed using all three agitation units  110 ,  120 , and  130 . A system operable to produce a higher turn-down ratio that may be used to prepare, store, and deploy a variety of pills at a drill site during different drilling and completion intervals offers significant advantages. Specifically, this type of system prevents having to change out agitator shafts or move impellers to different locations on the shafts at the drill site. Changing or moving equipment in the fluid vessel  102  at the drill site may require cleaning, isolating, opening, adjusting, and closing the fluid vessel  102 . Such activities may require considerable non-productive time, delay operations, contribute to temporary labor storages, increase the volume of waste to dispose of, and increase labor costs. 
     The three agitation units  110 ,  120 , and  130  may operate before and throughout the discharge process to maximize the recovery of small and/or difficult to handle pills. To achieve the desired turn-down ratio, at least one impeller on each agitation unit may be located in the lower section of the fluid vessel  102 . For example, in  FIG. 3  impellers  304 ,  365 , and  373  are located in the lower section of the fluid vessel  102  and may stay submerged at lower fluid levels, thus allowing adequate mixing of smaller pills. In some embodiments, and as shown in  FIG. 3 , the second agitation unit  120  and third agitation unit  130  may include multiple impellers to increase the pill volume turn-down ratio. By installing two impellers each on the second agitation unit  120  and the third agitation unit  130  as illustrated in  FIG. 3 , a turn-down ratio of up to 6:1 is expected. Thus, the system  300  as shown in the illustrative embodiment of  FIG. 3  has a turn-down ratio of up to 6:1. By substituting a conical-shaped vessel bottom for a dished shape vessel bottom, the turn-down ratio may be increased to up to 10:1. A user may vary the size of the fluid vessel  102  in accordance with the desired maximum allowable pill size and practical transportation limitations. Based on practical considerations such as common drilling and completion pill applications, ground transport regulations, and the maximum lifting capacity available at the drill site, the preferred range of maximum allowable pill volume for a single vessel system may range from 15 to 50 barrels of fluid (assuming 42 gallons per barrel of fluid). Based on a 6:1 turndown ratio, a single vessel system with a 50 barrel maximum allowable pill volume may be operated with a minimum pill volume of 8.5 barrels and a single vessel system with a 15 barrel maximum allowable pill volume may be operated with a minimum pill volume of 2.5 barrels. These pill volumes are listed as examples of the flexibility of the systems and methods disclosed herein and are not intended to limit this disclosure. As discussed previously, the fluid vessel  102  may vary in size without departing from the scope of this disclosure. 
     In the embodiment shown in  FIG. 3 , the system  300  may be rated for both vacuum and pressurized service. It is advantageous to have vacuum and pressurized service because this service may provide, for example, lower emissions from a closed operating system, lower risk of spills and splashes from a closed operating system, ability to provide the pump  116  with a higher NPSH, ability to apply a partial vacuum to transfer any flowable fluids from rig pits or transport containers into the system  300  instead of using pressure, a higher acceptable temperature range of operation when some solvents, including water, are present, and the ability to apply a partial vacuum while adding powders to the fluid vessel  102  through the funnel  352 . The advantages of using a partial vacuum to pull in powders through funnel  352  include less risk of plugging, less risk of back flow, and higher addition rates. Another operational benefit of applying a partial vacuum to the fluid vessel  102  is that materials may be charged into the fluid vessel  102  by sucking out of external containers into fluid line  362 , through the valve  363 , into the feed line  385 , and then into the fluid vessel  102 . Transferring flowable materials into the fluid vessel  102  by creating a partial vacuum in the fluid vessel  102  eliminates the need for portable pumps and the associated limitations, set-up time delays, safety hazardous, cleanup, and environmental hazardous of these pumps. For example; materials from drums, pails, Intermediate Bulk Containers (IBC), Iso-tanks, Marine Portable Tanks (MPT), and totes may be transferred out of these containers into the fluid vessel  102  by applying a vacuum instead of setting up portable diaphragm, metering, or centrifugal pumps. 
     The risk of accidental releases is reduced when negative pressure is applied to the transfer lines or flexible hoses instead of positive pressure when transferring materials. The vent system  390  includes a vent to atmosphere  388 , a pressure regulator  386 , a line to a compressed air supply  387 , which is coupled to the pressure regulator  386 , and a line to vacuum system  389 . The compressed air supply  387  may supply compressed air to the fluid vessel  102  in order to pressurize the fluid vessel  102 . The vent to atmosphere  388  may be engaged in order to change or release the pressure in the fluid vessel  102 . The vacuum system  389  may be engaged to create a negative pressure inside the fluid vessel  102 . 
     In order to prepare a variety of pills at the drill site, a broad range of materials such as reactive powders, non-reactive powders, solids, gels, viscose fluids, slurries, sludge, non-volatile fluids, and volatile fluids may be transferred into the fluid vessel  102  from rig pits, other process vessels, rig silos, drums, sacks, totes, intermediate bulk containers, marine portable tanks, ISO-tanks, tank trucks, and other types of transport containers. During filling operations, materials may be pumped, gravity fed through piping, dumped, or sucked into the fluid vessel  102  through the fluid addition line  362 , the funnel  352 , and the hatch  350  into the fluid vessel  102 . Materials may be fed into the fluid vessel  102  as an open system or as a closed system. When adding materials to the fluid vessel  102 , the weight of the materials contained in the fluid vessel  102  may be monitored gravimetrically by the strain gauge load cells  114 . The strain gauge cells  114  may also be utilized to gravimetrically monitor the weight of pill removed from the fluid vessel  102  during discharge operations. Whether during filling or discharge of the fluid vessel  102 , the capability to monitor changes in vessel content weight is advantageous. Direct gravimetric measurement is particularly advantageous when operating a closed system. 
     In certain embodiments, the system  300  may be equipped for use in a cool climate and thus may be insulated or insulated and heated (not shown in  FIG. 3 ). A rapid increase in viscosity as temperature decreases is a common property for many pill formulations. As the fluid temperature drops, the pill may transition into a gel or semisolid fluid that may be very difficult to handle. In addition, pills formulated with water as a major component are common when the drilling fluid at the drill site is a water-based mud (WBM) or when the drilling operation switches to completion brines. Lower ambient temperatures tend to cool pills over time and may eventually cause processing and handling problems associated with high viscosities, salt precipitation, or freezing unless insulation and/or heating is employed. Therefore; some pills cannot be built, stored, and deployed unless the fluid is kept at or above a minimum temperature. An insulated and heated system may include one or more of the following components: an insulating material coupled to the fluid vessel  102 , a heat transfer fluid, a heat transfer device in fluid communication with the fluid vessel  102 , a heat supply coupled to the heat transfer device, and a temperature sensor  346  coupled to the fluid vessel  102 . The heat transfer device may include, but is not limited to, a fuel burner or an electric heater. The heat transfer device may include any combination of the following: one or more external jackets, one or more external coils, tracing, and one or more internal coils. The heat transfer device may be coupled to the fluid vessel  102  by one or more lines and/or vessels. The lines and vessels may be traced with electric elements or heat transfer fluid tubes. The heat transfer fluid may be circulated through the coils, jackets, and tracing tubes. The heat transfer fluid may be a treated fresh water solution referred to as tempered water, a brine, or oil. The composition of tempered water may contain an antifreeze and/or one or more micro-biocides. In some embodiments, a steam vapor may be used as the heat transfer fluid. The desired physical properties of an oil-based heat transfer fluid may include low viscosity and low vapor pressure. The piping systems, nozzles, and vessels may also be insulated. These types of insulation systems are known to those with skill in the art having the benefit of this disclosure. 
     In certain embodiments, the system  300  may include a variety of other connections and features, which are not shown in  FIG. 3  for the sake of clarity. For example, the system  300  may include a chain hoist or a hydraulic lift system coupled to the top head (not shown) of the fluid vessel  102 . Such a system may allow for the rapid removal of the top head for quick clean-out between pill batches or may allow for the changing out of vessel internal components such as impellers. 
     Further, it may be advantageous to couple two or more modular fluid vessels together into an integrated system for preparing, storing, and/or deploying multiple pills. Turning now to  FIG. 4 , a front view of a mobile three-vessel integrated system for preparing, storing, and/or deploying pills in accordance with an illustrative embodiment of the present disclosure is denoted generally with reference number  400 . The system  400  includes vessel bays  402   a,    402   b,  and  402   c.  Modular vessel skids  404   a,    404   b,  and  404   c  may be mounted on the vessel bays  402   a, b, c.  The modular vessel skids  404   a, b, c  may include fork truck slots and crane lift eyes for safe lifting. Fluid vessels  406   a, b, c,  may be mounted on the vessel skids  404   a, b, c.  For multiple vessel integrated systems, the fluid vessels  406   a, b, c  may be of different sizes, shapes, and configurations. In some embodiments, each fluid vessel  406   a, b, c  may be used for a different purpose. For example, pills may be prepared in fluid vessel  406   b,  transferred to fluid vessel  406   a  for storage, and transferred back to fluid vessel  406   b  for destruction of all gelled globular particles before being pumped downhole. The system  400  also includes a work deck  407  positioned adjacent to the vessel bays, a pump and power bay  408  that may be positioned below the work deck  407  adjacent to the vessel skids  404   a, b, c,  and a safe access ladder  409  coupled to the work deck  407 . The vessel skids  404   a,    404   b,  and  404   c  and the pump and power skid (not shown in  FIG. 4 ) may each be coupled to the rack skid  410 . The rack skid  410  may be configured to accommodate combinations of various types of fluid vessels  406   a, b, c  that may conform to the dimensions of the vessel bays  402   a, b, c  thus providing flexibility in terms of capabilities and cost. The three modular vessel skids  404   a, b, c,  the rack skid  410 , and the pump and power skid (not shown) included in the system  400  may be transported to the drill site separately or in any combination that road weight regulations and available lift equipment weight limitations allow. Once at the drill site, the rack skid  410  allows the components of the system  400  to be arranged such that deck space or ground space requirements are minimized. Two or more rack skids  410  of various functionalities may be coupled and stacked to form an integrated system that minimizes the ground or deck space occupied. For example, the system  400  may be expanded into a six-vessel integrated system by stacking two rack skids  410 . The stacked skid configuration may be operated as one integrated system and does not require additional drill site deck or ground space. The modular skid systems may be an integral part of an overall pill delivery system and may increase the value of such systems at the rig site by increasing the overall number of pills and pill volumes that can be prepared, stored, and deployed. For certain operations such as displacements, prepared and stored spacer pills may be rapidly deployed downhole in succession without interrupting the circulation of the wellbore. 
     Turning now to  FIG. 5 , a mobile power and pump skid for preparing, storing, and/or deploying pills in accordance with an illustrative embodiment of the present disclosure is denoted generally with reference number  500 . The system  500  may include a pump  516 . The pump  516  may be specified for high viscosity fluids. A pump drive  575  may be coupled to the pump  516 . The pump drive  575  may be specified for variable speed and hazardous locations. The pump drive  575  may be any suitable pump including, but not limited to, an electric pump drive. A generator  518  may provide power to the pump drive  575  and to the agitation units shown in  FIGS. 1 and 3 . The generator  518  may be coupled to a reciprocating engine  519 . The generator  518  and reciprocating engine  519  may be specified for hazardous locations. The generator  518  may be sized to meet all anticipated loads and provide 230 volt, 3 phase power. The reciprocating engine  519  may be diesel, gasoline, natural gas, or dual fuel. The batteries  540  may be coupled to and designed for starting reciprocating engine  519  and providing critical uninterruptable power. A control panel  521  may be communicatively coupled to the pump drive  575  and the generator  518 . The control panel  521  may be housed with monitoring screens and a VFD in some embodiments. The control panel  521  may house all electrical components that are not rated for hazardous locations or need protection from the environment. The pump  516  may provide several different types of transfers, including fluids between skid vessel, pills to drilling operations, and waste fluids to containers or discharge points. The system  500  may be configured and specified for lifting by fork truck and crane, transport by land and marine, operation on land and offshore, and to be placed into a rack skid as part of an integrated system. The pump  516  may be coupled to a first transfer line  507  and a second transfer line  508 . The first transfer line  507  provides fluid communication between the suction of pump  516  and the fluid vessel (not shown). The second transfer line  508  provides fluid communication between the discharge of pump  516  and drill site operations (not shown). The system  500  may be configured to allow integrated pill preparation, storage, and deployment systems with minimum reliance on rig personnel and utilities. 
     EXAMPLE 1 
     The following example is included to help illustrate the present disclosure. 
     A barrier fluid pill may be prepared for tripping out of wellbore during managed pressure drilling operations. Once placed in the wellbore under static conditions, the purpose of the barrier pill is to prevent a higher density mud cap that may be placed in an upper portion of the wellbore from mixing with the less dense drilling fluid in a lower portion of the wellbore. This highly thixotropic pill may be prepared, stored, and deployed by following the given step sequence as shown in  FIG. 6  using a single vessel process apparatus as depicted in  FIG. 3 . Turning now to  FIG. 6 ; sequential steps for preparing, storing, and/or deploying a pill in accordance with illustrative embodiment of the present disclosure are shown, and references are made to the system  300  depicted in  FIG. 3 . At step  602 , fresh water may be added to the fluid vessel  102  through the fluid addition line  362  at atmospheric pressure until a desired fluid weight set point is detected by the load cells  114 . After proper isolation of the fluid vessel  102  from the atmosphere, a partial vacuum is applied and controlled by the vacuum system  389  at step  604 . At step  606 , the first agitation unit  110 , the second agitation unit  120 , and the third agitation unit  130  are started and set to maximum rotational speed settings to create high-intensity triple action mixing. At step  608 , a powder additive used to create viscosity and suspension capability may be added to the fluid vessel  102  through the funnel  352  by opening valve  353  and transferring through line  384 . The funnel valve  353  may then be closed, followed by continuation of high-intensity mixing for approximately an additional 20 minutes to insure complete hydration of the powder additive. At step  610 , the second agitation unit  120  may be turned off, the third agitation unit  130  may be adjusted to a medium speed, and the first agitation unit  110  may remain on high speed. At step  612 , the partial vacuum may be broken through the vent line  388  and atmosphere pressure inside of the fluid vessel  102  is confirmed by the pressure transmitter  342 . At step  614 , the hatch  350  is opened, desired fluid viscosity is confirmed, and barite powder is added until the fluid density specification is reached. At step  616 , a sample of the thixotropic pill is withdrawn through the hatch  350  and quality control analysis as related to density and rheological properties are performed. At step  618 , all three agitation units  110 ,  120 ,  130  are turned off or confirmed turned off, the hatch  350  is closed, the finished highly thixotropic pill is allowed to form a strong semisolid gelled mass, and the finished pill is stored in the fluid vessel  102  until needed. At step  620 , to prepare for deployment by breaking gel, the hatch  350  is opened, the fluid gel structure is broken by soft starting the first agitation unit  110  and the third agitation unit  130  and adjusting both of these agitation units to medium speed. At step  622 , to prepare for deployment, hatch  350  may be closed, air may be added from the compressed air system  387  to pressurize the fluid vessel  102 , and the second agitation unit  120  may be turned on at medium speed. The vessel discharge pump  116  and the transfer lines  382  and  378  may be prepared. At step  624 , to deploy the pill, the first, second, and third agitation units  110 ,  120 , and  130  are adjusted to maximum speed. The bottom vessel discharge valve  115  may be opened, the vessel discharge pump  116  may be turned on, and the speed of the discharge pump  116  may be adjusted. The desired pill volume transferred by monitoring load cells  114  may be confirmed. Then, the vessel discharge pump  116  may be shut down, the bottom discharge valve  115  may be closed, and the first, second, and third agitation units  110 ,  120 , and  130  may be turned off. Finally, the vent to atmosphere  388  may be opened to relieve pressure from the fluid vessel  102 , and the hatch  350  may be opened. 
     Therefore, the present disclosure is 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 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 or modified and all such variations are considered within the scope and spirit of the present disclosure. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. 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.