Abstract:
Systems and methods for de-watering waste drilling fluid. In some embodiments, the de-watering system includes a drilling fluid reclamation system receiving the waste drilling fluid from a wellbore and removing at least some solids from the waste drilling fluid, a manifold combining the waste drilling fluid from the drilling fluid reclamation system and organic polymers, whereby an aggregated mixture of solids in the waste drilling fluid and water are formed, and a centrifuge receiving the aggregated mixture and separating the solids from the water in the aggregated mixture, whereby solid drilling fluid waste and substantially colloidal-free water are formed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. provisional application Ser. No. 61/095,532 filed on Sep. 9, 2008, and entitled “System and Method for De-Watering Waste Drilling Fluids,” which is hereby incorporated herein by reference in its entirety for all purposes. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       BACKGROUND 
       [0003]    The present disclosure relates generally to systems and methods for de-watering drilling fluid. More particularly, the present disclosure relates to systems and methods for de-watering waste drilling fluid by conditioning the fluid with organic polymers. 
         [0004]    A key element of any drilling process is the use of drilling fluid, or mud. The drilling fluid serves several purposes. The density, or weight, of the drilling fluid prevents formation fluids and gases from entering the wellbore, and thus controls formation pressures. The drilling fluid also suspends and carries drilled cuttings from the bottom of the wellbore to the surface. Solids control equipment at the surface enable the drilling fluid to re-circulated continuously, and/or deposited into earthen pits, also called reserve pits, located adjacent drilling rig mud tanks. 
         [0005]    Prior to drilling a well, the drilling operator was required to construct and line a reserve pit to contain the amount of drilled cuttings and thousands of barrels of water-based drilling fluid waste expected to be generated from solids control equipment discharge and dumping of drilling fluid waste to maintain optimum fluid properties, cement displacement, and rig tank cleaning prior to rig moves. Since most of the drilling rigs using traditional practices did not utilize specific types and efficient solids control equipment, it was common that a “dump and dilute” approach was followed to control mud density, viscosity, and solids content to help improve bit penetration rates and prevent drill pipe sticking tendencies. The “dump and dilute” approach meant that large volumes of water would be consumed to reduce the concentration of colloidal solids and reformulated with chemical additives to bring the optimum drilling fluid properties back in line. Meanwhile, the reserve pit continued to contain greater volumes of drilling fluid waste as a result of the periodic dumping. The traditional drilling operation has been phased out as a result of governmental regulatory agencies, citizens, rig locations, drilling costs, well complexity, and drilling fluid performance. 
         [0006]    In order to provide bit lubrication and cooling, cuttings removal and well control, the properties of drilling fluid must be carefully controlled. As cuttings build up in drilling fluid, the weight and viscosity of the drilling fluid increases, which in turn, increases drag forces on the drill bit slowing the rate of penetration (ROP), increases the thickness of wall cake on the borehole wall, and makes control of the well pressure more difficult. To control the drilling fluid weight and viscosity, and thus prevent loss of well control, reduced ROP, and/or a drilling component from becoming stuck in the borehole due to increased wall cake thickness, water is added to the reclaimed drilling fluid to condition it prior to re-injection. 
         [0007]    To reduce the costs associated with disposing waste drilling fluid, transporting clean water to the well site, and site restoration, a variety of techniques have been developed for de-watering waste drilling fluid. These de-watering techniques enable water to be reclaimed from waste drilling fluid and subsequently combined with unused or recycled drilling fluid prior to injection into the drill string. After water is separated from waste drilling fluid, the remaining solid waste is smaller in volume and lighter in weight, as compared to that of the waste drilling fluid prior to de-watering, and can be transported from the well site and disposed of at significantly less expense. 
         [0008]    The conventional means of solids control equipment used on a drilling rig begins as drilling fluid exits the borehole at the flow line. The drilling fluid passes through a linear motion shaker capable of handling 100% of the mud pump flow while removing coarse sized solid particles between 320 to 75 microns, depending upon the screen mesh size being used. The drilling fluid then passes through de-sander and de-silter hydrocylclones for further removal of fine and silt sized drill solid particles ranging in size between 20 to 74 micron at a process rate of approximately 110% of the mud pump flow rate. Finally, the fluids are processed by a high speed solids control decanter centrifuge to remove ultra-fine drill solid particles greater than 5 micron at an average process rate of approximately 20% of the mud pump flow rate. 
         [0009]    Studies have shown that the colloidal content a water base drilling fluid, the faster the drill bit rate of penertion. Minimizing colloidal solids help lower the plastic viscosity of drilling fluid, contributing to greater horsepower at the bit. However, removing colloidal solids becomes difficult if not impossible, if they are allowed to accumulate and further degrade when continuously re-circulated in the drilling fluid. Colloidal solids with particle sizes greater than 5 micron and larger are removed from the drilling fluid waste by particle charge destabilization with a high cationic charged/low molecular weight organic polymer and aggregated together to form a “Hard Floc” with the addition of a varying anionic charged/high molecular with organic polymer. 
         [0010]    To further increase the overall efficiency of these conventional de-watering processes, inorganic polyelectrolytes or polymers are often added to the drilling fluid prior to entering the centrifuge. Drilling fluid is a suspension of various sized solids generated from the ground or commercially produced, and water. The solid particles carry an electrical charge that causes them to repel one another, thereby enabling the solids to be suspended in the water. Due to these repulsive forces and the concentration of colloidal/ultra-fine solids, the drilling fluid would require such a significant amount of time as to make this natural process an impractical means of de-watering. To accelerate the de-watering process, the drilling fluid is treated with inorganic coagulant prior to conveying the drilling fluid through the centrifuge. Typically, an inorganic coagulant, such as aluminum sulfate, polyaluminum chloride, ferric chloride, calcium hydroxide, or acid, is first added to the drilling fluid to de-stabilize the suspended solids of the mixture. As used herein, de-stabilization refers to the process of neutralizing the electrical charge of solids suspended in the colloidal mixture, or drilling fluid, so as to reduce or breakdown their repulsive forces. 
         [0011]    After de-stabilization of the solids, an organic flocculant is added to the drilling fluid to aggregate the de-stabilized solids so that when the drilling fluid passes through the centrifuge, the de-stabilized and subsequently aggregated solids do not break apart and cause the centrate, or reclaimed water, to become highly turbid and discharge wet cake solids. The organic flocculant has an electrical charge that attracts the de-stabilized solids, causing the solids to attach themselves to the flocculant. Attachment of the de-stabilized solids to the organic flocculant forms an aggregated network of de-stabilized solids called flocs. By de-stabilizing and subsequently aggregating the solids into flocs, the solids and water of the colloidal mixture, or drilling fluid, may be more easily and effectively separated in the centrifuge, thereby increasing the overall efficiency of the de-watering process. 
         [0012]    Inorganic coagulants are used in conventional de-watering techniques primarily because these substances are by-products, or waste, produced by other common chemical processes, and thus are relatively inexpensive. Even so, their use is not without disadvantages. First, some inorganic coagulants, such as acid, are ineffective de-stabilizers. When used as the sole de-stabilizing coagulant, the de-watering process yields water that still contains a significant level of colloidal solids. Second, inorganic coagulants will not react with suspended solids in a colloidal mixture if the pH level of that mixture is too high. Drilling fluid, such as mud, typically has a high pH level. Therefore, in order to de-stabilize drilling fluid using an inorganic coagulant, the drilling fluid must first be treated with acid to lower the pH level of the mixture to a range where the inorganic coagulant, when added to the treated mixture, reacts with the suspended solids in the mixture. The addition of acid in this manner increases the overall expense of the de-watering process. Third, the addition of inorganic coagulants to a colloidal mixture, like drilling fluid, causes the creation of solids within the mixture that are difficult to filter, de-water and are often corrosive. Further, the use of inorganic coagulants introduces chlorides to the water contained in the drilling fluid. This requires the treatment of that water with additives, such as sodium hydroxide, to adjust the pH level of the water prior to re-use. Finally, inorganic coagulants added with organic flocculants produce a small to medium sized aggregated de-stabilized solids, or flocs, that are fragile and sensitive to shear rate and may break apart within the centrifuge and become again suspended in the colloidal mixture. To prevent this, it may be necessary to reduce the feed rate to the centrifuge, which in turn, slows the de-watering production rate. 
         [0013]    Embodiments of the present disclosure are directed to de-watering systems and methods that seek to overcome these and other limitations of the prior art. 
       SUMMARY OF THE PREFERRED EMBODIMENTS 
       [0014]    Systems and methods for de-watering waste drilling fluid. In some embodiments, the de-watering system includes a drilling fluid reclamation system receiving the waste drilling fluid from a wellbore and removing at least some solids from the waste drilling fluid, a manifold combining the waste drilling fluid from the drilling fluid reclamation system and organic polymers, whereby an aggregated mixture of solids in the waste drilling fluid and water are formed, and a centrifuge receiving the aggregated mixture and separating the solids from the water in the aggregated mixture, whereby solid drilling fluid waste and substantially colloidal-free water are formed. 
         [0015]    In some embodiments, the de-watering system includes a manifold with a de-stabilizing zone and an aggregating zone downstream of the de-stabilizing zone. The de-stabilizing zone is adapted to combine organic coagulant and the waste drilling fluid, whereby solids suspended in the waste drilling fluid are de-stabilized and a de-stabilized mixture of the de-stabilized solids is formed. The aggregating zone is adapted to combine organic flocculant and the de-stabilized mixture, whereby the de-stabilized solids are aggregated to form a plurality of flocs and an aggregated mixture of the flocs and water is formed. 
         [0016]    Some methods for de-watering waste drilling fluid flowing at a preselected flowrate include rotating a sample of the waste drilling fluid in a container to form a vortex, adding a quantity of organic coagulant to the sample until coagulation of the sample occurs, wherein solids contained in the sample are de-stabilized, adding a quantity of organic flocculant to the sample until aggregation occurs, wherein a plurality of flocs are formed, calculating a flowrate of the coagulant as a function of the quantity of the coagulant added to the container, the quantity of the waste drilling fluid added to the container, and the preselected waste drilling fluid flowrate, and calculating a flowrate of the flocculant as a function of the quantity of the flocculant added to the container, the quantity of the waste drilling fluid added to the container, and the preselected waste drilling fluid flowrate. 
         [0017]    Thus, the embodiments of the invention comprise a combination of features and advantages that enable substantial enhancement of couplings. These and various other characteristics and advantages of the invention will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention and by referring to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    For a more detailed understanding of the preferred embodiments, reference is made to the accompanying Figures, wherein: 
           [0019]      FIG. 1  is a schematic representation of a de-watering system in accordance with the principles disclosed herein; 
           [0020]      FIG. 2  is a schematic representation of the de-stabilizing and flocculating manifold of  FIG. 1 ; 
           [0021]      FIG. 3  is a method for quantifying the optimum volumetric flowrates of organic coagulant and organic flocculant to be added during de-watering of waste drilling fluid; 
           [0022]      FIG. 4  depicts an embodiment of a human-machine interface (HMI); 
           [0023]      FIG. 5  depicts the control module for drilling fluid flow within the HMI of  FIG. 4 ; 
           [0024]      FIG. 6  depicts the control module for acid flow within the HMI of  FIG. 4 ; 
           [0025]      FIG. 7  depicts the control module for organic coagulant flow within the HMI of  FIG. 4 ; and 
           [0026]      FIG. 8  depicts the control module for organic flocculant flow within the HMI of  FIG. 4 . 
       
    
    
     NOTATION AND NOMENCLATURE 
       [0027]    Certain terms are used throughout the following description and claims to refer to particular system components. This document does not intend to distinguish between components that differ in name but not function. Moreover, the drawing figures are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form, and some details of conventional elements may not be shown in the interest of clarity and conciseness. 
         [0028]    In the following discussion and in the claims, the term “comprises” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    Referring now to  FIG. 1 , a schematic representation of a drilling fluid reclamation system and a de-watering system in accordance with the principles disclosed herein is shown. Drilling fluid reclamation system  100  includes a screen shaker  105 , a desander and desilter hydrocyclone  110 , and a decanter centrifuge  115  coupled by a piping system  180 . Waste drilling fluid  135  reclaimed from a well bore at a well site is conveyed through piping system  180  to screen shaker  105  and the components of reclamation system  100  downstream of screen shaker  105 . Upon exiting reclamation system  100 , waste drilling fluid  135  is stored in a waste drilling fluid storage tank  140 . In some embodiments of reclamation system  100 , excess drilling fluid may also be conveyed to and stored in tank  140 . 
         [0030]    Each of screen shaker  105 , hydrocyclone  110 , and decanter centrifuge  115  is configured to remove solid particles within a prescribed size range from waste drilling fluid  135  as waste drilling fluid  135  passes therethrough. In this exemplary embodiment, screen shaker  105  removes solids having dimensions in the range 75 to 320 microns. Hydrocyclone  110  removes relatively smaller solids having dimensions in the range 20 to 74 microns. Decanter centrifuge  115  removes particulates having dimensions greater than 5 microns, while high-speed centrifuge  125  removes smaller particulates. Thus, as waste drilling fluid  135  passes through each of these respective devices  105 ,  110 ,  115 , more solids are progressively removed from waste drilling fluid  135 , thereby decreasing the concentration of solids suspended in drilling fluid  135 . 
         [0031]    De-watering system  190  includes a de-stabilizing and flocculating manifold  120  and a de-watering centrifuge  125 , both connected in series by a piping system  130 . Reclaimed waste drilling fluid  135 , contained in a storage tank  140 , is conveyed by a pump  145  through piping system  130  to manifold  120  and de-watering centrifuge  125 . In this exemplary embodiment, pump  145  is a progressive cavity feed pump. However, in other embodiments, pump  145  may be another equivalent type of pump known in the industry. 
         [0032]    De-watering centrifuge  125  applies centrifugal force to waste fluid drilling  135  passing therethrough. The centrifugal force creates a pressure load exerted on waste drilling fluid  135  causing water contained therein to be forced from waste solids also contained in drilling fluid  135 . In some embodiments, de-watering centrifuge  125  removes particulates having dimensions less than 5 microns. To promote the ease and effectiveness at which high-speed de-watering centrifuge  125  removes particulates from waste drilling fluid  135  passing therethrough, waste drilling fluid  135  is treated or conditioned within coagulation and flocculation manifold  120  with organic polymers  150  prior to entering de-watering centrifuge  125 . 
         [0033]    Turning now to  FIG. 2 , manifold  120  includes a de-stabilizing zone  200  and an aggregating zone  205 . Waste drilling fluid  135  is conveyed via pump  145  from drilling waste storage tank  140  first into de-stabilizing zone  200  of manifold  120 . Within de-stabilizing zone  200 , an organic coagulant  210  is introduced to waste drilling fluid  130  to de-stabilize solids remaining suspended in waste drilling fluid  135  and to subsequently form bridges between the de-stabilized solids to form a colloidal web. The colloidal web is an essential building block for developing a hard floc that maintains retention, i.e., does not break apart, regardless of shear stress and shear rate experienced when passing through manifold  120  and de-watering centrifuge  125 . 
         [0034]    Organic coagulant  210  has an electrical charge that acts to neutralize the electrical charge of solids suspended in the drilling fluid  135  and a low molecular weight. In some embodiments, organic coagulant  210  is cationic and has a molecular weight in the range 1000 to 1 million. The positive charge of organic coagulant  210  neutralizes the electrical charge of solids suspended in the drilling fluid, and thus reduces or breaks down their repulsive forces relative to each other. In other words, organic coagulant  210  de-stabilizes the solids in the drilling fluid. The low molecular weight of organic coagulant  210  enables faster de-stabilization of the solids and a lower viscosity of the water remaining in waste drilling fluid  135 , as compared to that provided by the conventional use of inorganic coagulants. Organic coagulant  210  may be in powder, emulsion or liquid form, and in some embodiments, is a polyamide coagulant, such as “Color-Katch-7” manufactured by Kem-Tron, Inc. 
         [0035]    Due to the organic nature of coagulant  210 , waste drilling fluid  135  need not be pre-treated, for example, with acid to lower its pH level prior to introduction into de-stabilizing zone  200 . Unlike inorganic coagulants, organic coagulant  210  reacts with solids suspended in a high pH fluid. Thus, organic coagulant  210  is an effective de-stabilizer of high pH fluids, like waste drilling fluid  135 , and need not be pre-treated to enable a reaction of organic coagulant  210  with solids in drilling fluid  135 . Also in contrast to inorganic coagulants, after de-stabilizing solids in drilling fluid  135 , organic coagulant  210  promotes the formation of a network of meshed, de-stabilized solids which is more easily separated from water remaining in drilling fluid  135  during processing in de-watering centrifuge  125 . The ability of organic coagulant  210  to promote the formation of such a colloidal web of de-stabilized solids increases the overall efficiency of de-watering system  190 . 
         [0036]    After the solids remaining in waste drilling fluid  135  are de-stabilized, drilling fluid  135  passes from de-stabilizing zone  200  into aggregating zone  205  of manifold  120 . Within aggregating zone  205 , an organic flocculant  215  is introduced to waste drilling fluid  135  to aggregate the de-stabilized solids contained therein to form a plurality of large, rounded flocs. Aggregating the de-stabilized solids enables the solids to withstand shear forces imparted to them during processing in high-speed centrifuge  125  without breaking the solids apart and causing the solids to become again dispersed or suspended in the water of waste drilling fluid  135 . 
         [0037]    Organic flocculant  215  has an electrical charge that attracts the de-stabilized solids within drilling fluid  135  and a high molecular weight. The electrical charge of organic flocculant  215  causes the de-stabilized solids to attach themselves to organic flocculant  215 , thereby creating large, rounded flocs of aggregated de-stabilized solids. The high molecular weight of organic flocculant  215  allows the large, rounded flocs of de-stabilized solids to withstand shear forces imparted to the flocs during processing by high-speed centrifuge  125 . In some embodiments, organic flocculant  215  has a molecular weight in the range 13 million to 15 million. Further, the organic nature of flocculant  215  enables larger, harder and more rounded flocs of de-stabilized solids, as compared to smaller, rougher flocs achievable with the use of conventional inorganic flocculants. By increasing the floc size, the flocs are more resistive to shear forces and thus less likely to break apart in high-speed centrifuge  125 . As such, there is less of a need to slow the speed of centrifuge  125  to ensure the flocs remain intact during processing in centrifuge  125 . Further, the rounded configuration of the flocs promote re-aggregation of the solids should some of them break apart in centrifuge  125 . Thus, the larger, more rounded flocs promote the overall efficiency and production rate of de-watering system  190 . 
         [0038]    Organic flocculant  215  may be in powder, emulsion or liquid form, and in some embodiments, is a polyacrylamide flocculant, such as “K-Floc,” “Kan-Floc,” or “Kat-Floc” manufactured by Kem-Tron, Inc. Additionally, in some embodiments, organic flocculant  215  is a blended polyacrylamide flocculant, which includes a quantity of flocculant, e.g., “Kan-Floc”, having a particular charge density mixed with another quantity of the same flocculant but having a different charge density. For example, organic flocculant  215  may include an equal blend, by volume, of Kan-Floc having a charge density of 2% and Kan-Floc having a charge density of 23%. As used herein, charge density refers to the percentage of sites along a polymer chain given an electrical charge. For instance, 2% charge density means that 2% of the sites along a polymer chain are given a negative or anionic electrical charge, while the remaining 98% of the sites have no electrical charge. Testing has indicated that a blended polyacrylamide flocculant is more effective than an unblended polyacrylamide flocculant having a charge density approximately equal to an average of the two charge densities included in the blend. In other words, and continuing with the example above, a blended polyacrylamide flocculant having equal amounts by volume of 2% charge density Kan-Floc and 23% charge density Kan-Floc is more effective than the same volume of 14% charge density Kan-Floc. 
         [0039]    After aggregation of the de-stabilized solids remaining in waste drilling fluid  135 , drilling fluid  135  passes from aggregating zone  205  into de-watering centrifuge  125 , where, as described above and illustrated in  FIG. 1 , the water remaining in drilling fluid  135  is forced from the flocs of de-stabilized solids in fluid  135  under pressure from centrifugal force applied to fluid  135 . Upon completion of processing in high-speed centrifuge  125 , two products exit centrifuge  125 : a colloidal-free or clear water  155 , which may be re-used, for example, to condition drilling fluid prior to injection downhole, and a cake-like solids  160 , which may be transported from the well site for disposal. 
         [0040]    The de-watering systems and methods disclosed herein, including de-watering system  190 , enable the production of colloidal-free or clear water  155  at faster production rates than possible with conventional systems and methods. Further, the use of an organic coagulant in the de-watering process yields colloidal-free or clear water that may be reused without the need to treat it, such as to alter its pH, prior to reuse. In other words, the use of organic coagulant  210  does not alter the pH level of water in waste drilling fluid  130  such that, once separated from the solids suspended in fluid  130 , the water requires treatment or conditioning prior to reuse. This is in contrast to conventional de-watering systems and associated methods utilizing inorganic coagulants that produce water having higher levels of colloidal solids. Such “grey water” often must be treated to lower its pH prior to reuse, a practice that increases drilling time and expense. Furthermore, cake-like solids  160  produced by de-watering systems and methods disclosed herein, including de-watering system  190 , have lower water content than that produced by conventional de-watering systems and methods. By reducing the water content, solids  160  are lighter by weight and occupy less volume that they would otherwise, allowing them to be transported from the well site and disposed of at lower cost, comparatively speaking. 
         [0041]    While the use of organic polymers in de-watering of waste drilling fluid  135  offers the improvements and benefits described above, the de-watering methods disclosed herein may be further improved, even optimized, by careful control of the relative quantities of organic coagulant  210  and organic flocculant  215  introduced during de-watering. Turning to  FIG. 3 , a method of quantifying the optimum volumetric flow rates of organic coagulant  210  and organic flocculant  215  required to de-water a given volumetric flow rate of waste drilling fluid  135  is depicted. This method  300 , referred to herein as “the Reardon Vortex Beaker Test” or simply “the Test,” enables optimization of de-watering system  190  and related methods illustrated by  FIGS. 1 and 2 . 
         [0042]    Test  300  begins by measuring the density in lbs/gallon, viscosity in sec/qt, pH, chloride level, and hardness of a well-mixed quantity of drilling fluid  135  for which de-watering is desired (step  305 ). If the measured density exceeds 9.2 lb/gal and the measured viscosity exceeds  40  sec/qt, a 100 mL sample of well-mixed drilling fluid  135  is deposited into a container, such as but not limited to a beaker (step  310 ). In some embodiments, the volume of the beaker is 400 mL. Alternatively, if the measured density is less than 9.2 lb/gal or the measured viscosity is less than 40 sec/qt, a 150 mL sample of well-mixed drilling fluid  135  is deposited into the beaker (step  315 ). 
         [0043]    For reasons presented below, the volume in mL of drilling fluid  135  added to the beaker in either step  310  or step  315  is identified symbolically herein as V DF . 
         [0044]    Depending on the pH level measured in step  305 , the drilling fluid sample may require acid treatment to adjust its pH. If the measured pH level exceeds 11.5, a small quantity of acid is added to the drilling fluid sample deposited in the beaker (step  320 ). The drilling fluid sample is then stirred and its pH level measured using a pH meter (step  325 ). This process, meaning steps  320  and  325 , are repeated until the pH level of the drilling fluid sample is approximately 8.5. 
         [0045]    Next, a first quantity of organic coagulant  210  and a second quantity of organic flocculant  215  are drawn into a first syringe and a second syringe, respectively (step  330 ). In some embodiments, these quantities are 3 cc and 10 cc, respectively. If the chloride and hardness levels, both measured in step  320 , exceed 2500 ppm and 400 mg/L, respectively, a high molecular weight organic flocculant  215  should be selected for step  330  and all subsequent steps. As the organic polymers are drawn into their respective syringes, any air that becomes entrapped in either syringe is forced from the affected syringe before drawing additional polymer therein. 
         [0046]    The beaker, with the drilling fluid sample contained therein, is then rotated to cause the drilling fluid sample to form a vortex within the beaker (step  335 ). As the beaker is rotated in this manner, organic coagulant  210  contained in the first syringe is gradually added to the drilling fluid sample contained in the beaker (step  340 ). Once the drilling fluid sample slightly thickens, indicating coagulation of the drilling fluid sample, the addition of organic coagulant  210  ceases, and the total volume in milliliters (cubic centimeters) of organic coagulant  210  added to the beaker, V OC , is recorded. The vortex formed by rotation of the beaker promotes the ability to see coagulation of the drilling fluid sample contained in the beaker. 
         [0047]    As rotation of the beaker continues, organic flocculant  215  contained in the second syringe is slowly added to the now-coagulated drilling fluid sample contained in the beaker (step  345 ). When large, smooth flocs of drilling fluid form, each approximately ⅜″ to ¾″ in diameter and having the ability to slide around the beaker without breaking apart, the addition of organic flocculant  215  ceases, and the total volume in cc&#39;s of organic flocculant  215  added to the beaker, V OF , is recorded. At this point in test  300 , the beaker contains large, smooth flocs of aggregated, de-stabilized drilling fluid solids substantially separated from water also contained therein. 
         [0048]    If the size and strength of flocs and/or water clarity obtained in step  345  are not as desired, or more organic flocculant  215  is added in step  345  than desired, steps  305  through  345  should be repeated. During repeat of steps  305  through  345 , a different amount, either more or less, of organic coagulant  210  should be added at step  340 . Steps  305  through  345  may repeated until the desired size and strength of flocs and water clarity is obtained (step  350 ). 
         [0049]    Upon satisfactory completion of steps  305  through  345 , the optimum volumetric ratios of organic coagulant  210  and organic flocculant  215  have been identified for the given sample of drilling fluid  135 . These ratios may be determined from the volumes of organic coagulant  210 , organic flocculant  215 , and drilling fluid  135  required to satisfactorily complete steps  305  through  350 . Next, this information is converted into volumetric flowrates indicating the rate at which organic coagulant  210  and organic flocculant  215  should be added to a specified volumetric flowrate of drilling fluid  135  during de-watering of fluid  135  to provide optimum production of colloidal-free or clear water  155  ( FIG. 1 ) and solid drilling fluid waste  160  ( FIG. 1 ). 
         [0050]    For a specified volumetric flowrate of drilling fluid  135  in gal/min, FR DF , pumped through a de-watering system, such as de-watering system  190  ( FIG. 1 ), organic coagulant  210  and organic flocculant  215  should be added to drilling fluid  135 , such as in de-stabilizing zone  200  ( FIG. 2 ) and aggregating zone  205  (also  FIG. 2 ), at volumetric flowrates, FR OC , and FR OF , respectively, as follows (step  355 ): 
       Standard De-watering without Emulsion Polymer Make-down Units 
       [0051]    
       
      
       FR 
       OC 
       =V 
       OC 
       /V 
       DR 
       *FR 
       DR  
      
     
         [0000]        FR   OF   =V   OF   /V   DR *2.5* FR   DR    
       Standard De-watering with Emulsion and Liquid Polymer Make-down Units 
       [0052]      FR OC   =V   OC   /V   DR   *FR   DR    
         [0000]        FR   OF   =V   OF   /V   DR *2.0* FR   DR    
         [0000]    Should the volumetric flowrate of drilling fluid  135 , FR DF , through the de-watering system change, or may be expected to change, the volumetric flowrates of organic coagulant  210 , FR OC , and of organic flocculant, FR OF , should be adjusted in accordance with the above equations to continue to provide optimum de-watering of drilling fluid  135  (step  360 ). 
         [0053]    While the Reardon Vortex Beaker Test is described above in the context of quantifying optimum organic coagulant  210  and organic flocculant  215  flowrates for a defined flowrate of waste drilling fluid  135 , the Test may also be used to determine similar information regarding inorganic coagulants, inorganic flocculants, and/or other additives which may be introduced during de-watering of waste drilling fluid  135 . In other words, the Test applies to organic as well as inorganic de-watering additives. 
         [0054]    Adjustment of the volumetric flowrates of organic coagulant  210 , FR OC , and organic flocculant  215 , FR OF , as well as other parameters of a de-watering system, like de-watering system  190  ( FIG. 1 ), may be achieved by the use of an interface configured to receive input from a human operator and generate a signal(s) which adjusts components of the de-watering system in accordance with the input.  FIGS. 4 through 8  depict a human-machine interface (HMI) which is operable to define, control and adjust the volumetric flowrates of drilling fluid  135 , FR DR , organic coagulant  210 , FR OC , and organic flocculant  215 , FR OF , introduced to a de-watering system, as well as other parameters. 
         [0055]    Turning to  FIG. 4 , HMI  400  is a computerized interface that allows a human operator to input desired flowrates  405  and other parameters affecting a de-watering process via a computer monitor having a touchsensitive display. The input is then converted into signal(s) which modify the affected subsystem(s)  410 . In this exemplary embodiment, HMI  400  enables control of the volumetric flowrates  500 ,  600 ,  700 ,  800  of drilling fluid  135 , FR DR , acid, organic coagulant  210 , FR OC , and/or organic flocculant  215 , FR OF , respectively, through the de-watering system, as illustrated by  FIGS. 5 ,  6 ,  7  and  8 , respectively. A human operator may adjust these flowrates  500 ,  600 ,  700 ,  800  as needed during de-watering. In some embodiments, his or her adjustments are in accordance with the Reardon Beaker Test described with reference to and illustrated by  FIG. 3 . Furthermore, in some embodiments, HMI  400  may include a computer storing an executable program that generates signals to automatically adjust these flowrates  500 ,  600 ,  700 ,  800  in accordance with instructions defined within the stored program. The computer program is stored in non-volatile storage, e.g., a hard disk drive, volatile memory, e.g., random access memory, or combinations thereof. The instructions may be either a supplement to or replacement of input provided by an operator. 
         [0056]    While various preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings herein. The embodiments herein are exemplary only, and are not limiting. Many variations and modifications of the apparatus disclosed herein are possible and within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.