Abstract:
Methods and systems are disclosed employing a quad-tier shale shaker for processing a mixture of drilling fluid and solids which solids include, in one aspect, lost circulation material (and/or material of size similar to the size of the lost circulation material). This abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims, 37 C.F.R. 1.72(b).

Description:
BACKGROUND OF THE INVENTION 
     1. Field Of The Invention 
     The present invention is directed to drilling fluid processing systems; shale shakers; to methods for using these things; and, in certain particular aspects, to the separation of lost circulation material from used drilling fluid. 
     2. Description of Related Art 
     In the oil and gas industries, shale shakers use screens to treat drilling fluid contaminated with undesirable solids. Typically such apparatuses have a basket, deck, or other screen holding or mounting structure mounted in or over a receiving receptacle or tank and vibrating apparatus for vibrating one or more screens. Material to be treated is introduced to the screen(s) either by flowing it directly onto the screen(s) or by flowing it into a container, tank, or “possum belly” from which it then flows to the screen(s). Often, the screen or screens used to treat material is sealed in place on a screen deck, in a screen basket, or on screen mounting structure. 
     In the past it has been common to use multiple screens at multiple levels in a shale shaker to process drilling fluid, e.g., screens at one, two or three levels. 
     “Lost circulation” of drilling fluid occurs when, in drilling a wellbore, the circulation of drilling fluid to and then away from the drill bit ceases due to the porosity of the formation and/or due to fracturing of the formation through which the wellbore is being drilled. When lost circulation occurs, drilling fluid is pumped into the fractured formation rather than being returned to the surface. Often circulation is lost at some specific depth where the formation is “weak”, and that the fracture extends horizontally away from the borehole. Expressions used to describe rocks that are susceptible to lost returns include terms like vugular limestone, unconsolidated sand, “rotten” shale, and the like. 
     A wide variety of “lost circulation materials” (“LCM”) have been pumped into wellbores to fill or seal off a porous formation or to fill or seal off a wellbore fracture so that a proper route for drilling fluid circulation is re-established. Often lost circulation materials are generally be divided into fibers, flakes, granules, and mixtures. 
     Often it is also desirable to recover and retain the lost circulation material in the drilling mud system during continuous circulation. Screening the drilling mud for removal of undesired particulate-matter can also result in removal of the lost circulation material and, therefore, require continuous introduction of new lost circulation material to the drilling mud downstream of the mud screening operation. 
     The addition of lost circulation material compounds the separating problems because it, like the drilling fluid, is preferably cleaned and recirculated. Exiting the well is the drilling fluid of small size, the lost circulation material of a large size, and the undesirable material of a size therebetween, with the largest and smallest of the materials to be recirculated. One proposed solution to this separation problem is a conventional two step screening process as shown in U.S. Pat. No. 4,116,288. There the exiting mixture of drilling fluid, lost circulation material and undesirable material is first subjected to a coarse screening to separate the lost circulation material from the drilling fluid and undesirable material which drops to a second finer screen therebelow to separate the drilling fluid from the undesirable material. The drilling fluid and lost circulation material are then reunited for recirculation into the well. This system is susceptible to height restrictions and fine screen problems. The lost circulation material can be coated with undesirable material which will not go through a first screen, moves over and exits off of the top side of the first screen, and is circulated back into a well. 
     There are a variety of known drilling fluid processing systems, shale shakers, and methods for recovery of lost circulation material; including, for example, but not limited to, those in U.S. Pat. Nos. 6,868,972; 6,669,027; 6,662,952; 6,352,159; 6,510,947; 5,861,362; 5,392,925; 5,229,018; 4,696,353; 4,459,207; 4,495,065; 4,446,022; 4,306,974; 4,319,991; and 4,116,288 (all said patents incorporated fully herein for all purposes). 
     In certain prior systems, problems have been encountered with systems for screening out lost circulation material when undesirable material of the same size is also screened out. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention discloses, in certain aspects, methods and systems for processing drilling fluid to recover components thereof and, in one particular aspect for separating lost circulation material (or lost circulation material along with solids of similar size) from used drilling fluid. In certain aspects, the separated lost circulation material is recovered and used. 
     In certain particular aspects, such methods and systems employs a novel shale shaker according to the present invention with screening apparatus below an initial scalper screen apparatus for separating lost circulation material (and/or material of similar size) from used drilling fluid. 
     A vibratory separator or shale shaker, in one embodiment according to the present invention has a screen or screens at separate levels as described herein according to the present invention. In one particular aspect, two lowermost screens can receive flow from a higher screen in parallel or in series. The present invention, in certain embodiments, includes a vibratory separator or shale shaker with a base or frame; a “basket” or screen mounting apparatus on or in the base or frame; screens at three or four different, spaced-apart distinct levels according to the present invention; vibrating apparatus; and a collection tank or receptacle. Such a shale shaker can treat drilling fluid contaminated with solids, e.g. cuttings, debris, etc.; and drilling fluid with lost circulation material (and/or material of similar size) therein. Such a shale shaker, in certain aspects, provides a separate exit stream from a second screening level which is primarily lost circulation material (and/or material of similar size). 
     Accordingly, the present invention includes features and advantages which are believed to enable it to advance the processing of drilling fluid with lost circulation material (and/or material of similar size) therein. Characteristics and advantages of the present invention described above and additional features and benefits will be readily apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments and referring to the accompanying drawings. 
     Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures, functions, and/or results achieved. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention. 
     What follows are some of, but not all, the objects of this invention. In addition to the specific objects stated below for at least certain preferred embodiments of the invention, other objects and purposes will be readily apparent to one of skill in this art who has the benefit of this invention&#39;s teachings and disclosures. It is, therefore, an object of at least certain preferred embodiments of the present invention to provide the embodiments and aspects listed above and: 
     New, useful, unique, efficient, nonobvious drilling fluid processing systems; shale shakers; and methods of the use of these systems and shakers; and 
     Such shale shakers with screens at four levels according to the present invention with the last two screens operating in series or in parallel; and 
     New, useful, unique, efficient, nonobvious drilling fluid processing systems and shale shakers; and methods of their use for separating and recovering lost circulation material (and/or material of similar size) from spent drilling fluid. 
     The present invention recognizes and addresses the problems and needs in this area and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one of skill in this art who has the benefits of this invention&#39;s realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of certain preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent&#39;s object to claim this invention no matter how others may later attempt to disguise it by variations in form, changes, or additions of further improvements. 
     The Abstract that is part hereof is to enable the U.S. Patent and Trademark Office and the public generally, and scientists, engineers, researchers, and practitioners in the art who are not familiar with patent terms or legal terms of phraseology to determine quickly from a cursory inspection or review the nature and general area of the disclosure of this invention. The Abstract is neither intended to define the invention, which is done by the claims, nor is it intended to be limiting of the scope of the invention or of the claims in any way. 
     It will be understood that the various embodiments of the present invention may include one, some, or all of the disclosed, described, and/or enumerated improvements and/or technical advantages and/or elements in claims to this invention. 
     Certain aspects, certain embodiments, and certain preferable features of the invention are set out herein. Any combination of aspects or features shown in any aspect or embodiment can be used except where such aspects or features are mutually exclusive. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       A more particular description of embodiments of the invention briefly summarized above may be had by references to the embodiments which are shown in the drawings which form a part of this specification. These drawings illustrate certain preferred embodiments and are not to be used to improperly limit the scope of the invention which may have other equally effective or legally equivalent embodiments. 
         FIG. 1  is a schematic view of a system according to the present invention. 
         FIG. 1A  is a perspective view of a shale shaker according to the present invention. 
         FIG. 2A  is a side view, partially in cross-section, of a shale shaker according to the present invention. 
         FIG. 2B  is a cross-sectional view of the screens and related structure of the shale shaker of  FIG. 2A . 
         FIG. 2C  is a cross-sectional view of a shale shaker according to the present invention. 
         FIG. 3A  is a side cutaway view of a shale shaker according to the present invention. 
         FIG. 3B  is a side cutaway view of a shale shaker according to the present invention. 
         FIG. 4A  is a perspective exploded view of a system according to the present invention. 
         FIG. 4B  is a schematic side view of the system of  FIG. 4A . 
         FIG. 5A  is a perspective exploded view of a system according to the present invention. 
         FIG. 5B  is a schematic side view of the system of  FIG. 5A . 
     
    
    
     Presently preferred embodiments of the invention are shown in the above-identified figures and described in detail below. Various aspects and features of embodiments of the invention are described below and some are set out in the dependent claims. Any combination of aspects and/or features described below or shown in the dependent claims can be used except where such aspects and/or features are mutually exclusive. It should be understood that the appended drawings and description herein are of preferred embodiments and are not intended to limit the invention or the appended claims. On the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims. In showing and describing the preferred embodiments, like or identical reference numerals are used to identify common or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness. 
     As used herein and throughout all the various portions (and headings) of this patent, the terms “invention”, “present invention” and variations thereof mean one or more embodiment, and are not intended to mean the claimed invention of any particular appended claim(s) or all of the appended claims. Accordingly, the subject or topic of each such reference is not automatically or necessarily part of, or required by, any particular claim(s) merely because of such reference. So long as they are not mutually exclusive or contradictory any aspect or feature or combination of aspects or features of any embodiment disclosed herein may be used in any other embodiment disclosed herein. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a system S according to the present invention which includes a derrick  1  that extends vertically over a wellbore  2 . A tubular work string  3  extends into the wellbore  2 , and extends from the earth&#39;s surface to a desired depth within the wellbore. A flow line  4   a  is connected to the tubular work string  3 . A flow line  4   b  is connected to annular space  5  formed between the outer surface of tubular work string  3  and the inner surface of wellbore  2 . 
     Drilling fluid (or “mud”) for the system in a mud pit  6  is circulated through the overall mud system via a mud pump  7 . During typical drilling operations, fluid is pumped into the tubular work string  3  by the mud pump  7  through the flow line  4   a , circulated out a bottom end  3   a  of the tubular work string  3  (e.g., but not limited to, out from a drill bit  9 ), up an annulus  5  of the wellbore  2 , and out of the annulus  5  via the flow line  4   b.    
     Spent (or used) fluid mud exiting the wellbore annulus  5  through the flow line  4   b  includes drilling fluid, drill cuttings, lost circulation material (and/or material of similar size), and other debris encountered in the wellbore  2 . Accordingly, the spent drill cuttings mixture leaving the well is directed to a separation device, such as one or more shale shakers  8  according to the present invention. The combined mixture of drilling fluid, added material (e.g. solids and/or lost circulation material, etc.), debris, and drilled cuttings are directed to the shale shakers  8 . Liquid drilling fluid passes through screens  8   a ,  8   b ,  8   c ,  8   d  which are at four different levels of the shale shakers  8  and is directed into the mud pit  6  (or the two lowermost screens are at the same level each receiving a portion of flow from the screen  8   b ). Drill cuttings and other solids pass over the screens  8   a - 8   d  of the shale shakers  8  and are discharged (arrows  8   e ,  8   f ,  8   h ). With the proper selection of screen mesh for the screen  8   b , lost circulation material (with some material of similar size, if present) is separated by and discharged from the top of the screen  8   b  (see arrow  8   f ). The recovered lost circulation material (and/or material of similar size) flows and/or is pumped to a reservoir or to a further processing apparatus  8   k . Optionally, the shale shakers  8  are like any other shale shaker disclosed herein according to the present invention. 
     Referring now to  FIG. 1A , a shale shaker H according to the present invention has screens A 1 , A 2 , A 3 , A 4 , each of which is, according to the present invention, at one of four different levels (with screen or screening cloth or mesh as desired). The screens are mounted on vibratable screen mounting apparatus or “basket” B. The screens A 1 , A 2 , A 3 , A 4 , according to the present invention, may be any suitable known screen or screens, with the screen A 2  (or the screens A 2  and A 3 ) used to separate lost circulation material (and/or material of similar size). The basket B is mounted on springs C (only two shown; two as shown are on the opposite side) which are supported from a frame D. The basket B is vibrated by a motor and interconnected vibrating apparatus E which is mounted on the basket B for vibrating the basket and the screens. Elevator apparatus F provides for raising and lowering of the basket end. Fluid passing through the screens A 1 , A 2 , A 3 , A 4  flows into a receptacle R beneath the bottom screen A 4 . In certain aspects screen A 1  has the coarsest mesh of all the screens and acts as a scalping screen and the screens A 3  and A 4  provide fine screening. The exit feeds from the top sides of the screens A 1 , A 3 , A 4  may go to disposal or may be directed as described below for any embodiment of the present invention. The lost circulation material recovered from the top of the screen A 2  (or, optionally, from the tops of the screens A 2  and A 3 ) may be flowed, processed and treated as described for any embodiment of the present invention. As shown, the screens A 3 , A 4  operate in series, i.e., the underflow from the screen A 3  flows down to the screen A 4 . Optionally, the screens A 3 , A 4  may be operated in parallel with each receiving a portion of screen A 2 &#39;s underflow. 
       FIGS. 2A and 2B  show a system  10  according to the present invention which includes a shale shaker  12  with a base  14  and a screen-supporting basket  16 . A vibrator apparatus  18  vibrates the basket  16  and screens mounted in it. 
     Four spaced-apart screens  21 - 24  are mounted in the basket  16  at different levels (e.g. spaced-apart six to eight inches) or put another way, at four different heights in the basket. In one particular embodiment the screen  21  is a scalping screen which, in one particular aspect removes relatively large pieces of material, e.g. with mesh sized so that pieces ⅛″ and 1/64″ is used. In one aspect, the screen  21  has a mesh size such that pieces greater than 1/16″ are removed (and pieces of, among other things, solids and/or lost circulation material that are 1/16″ or smaller in largest dimension pass through the screen  21  (e.g., but not limited to graphite ball lost circulation material that are 1/16″ in largest dimension or slightly smaller). 
     The screen  22  has a mesh size as chosen for removing material of a certain largest dimension or larger, including, but not limited to solids, debris, drilled cuttings, desirable additives, and/or lost circulation material. In one aspect the mesh size is chosen in cooperation with the mesh size of the screen  21  so that the screen  22  removes lost circulation material (and solids or pieces of similar size) and, in one particular aspect the mesh size is chosen so that lost circulation material of a largest dimension of 1/16″ or greater does not pass through the screen  22  and flows from the top thereof In one aspect such lost circulation material is graphite balls. 
     The screens  23  and  24  further filter out solids from the flow through the screen  22  and, in certain aspects, the screens  23  and  24  act as typical standard fine screening screens used to process a mixture of drilling fluid and solids. 
     The exit streams from screens  21 ,  23 , and  24  exit from the tops of their respective screens and flow down to a container, system or apparatus  20  for storage and/or further processing. Drilling fluid flowing through the screens flows down to a sump or container  26  and from there to a reservoir or in one aspect, back to an active rig mud system. The exit stream from the screen  22 , in particular aspects, has wet lost circulation material (or wet lost circulation material along with solids of similar size) of at least 50% by volume; and in one particular aspect at least 75% lost circulation material by volume (in one example, the output is 50% lost circulation material and 50% solids of similar size). In certain aspects, screen mesh size is chosen so that a relatively large percentage of the flow off the top of the screen is lost circulation material, e.g. by volume, up to 50%, 75%, or up to 90%. 
     Fluid with some solids therein (including the lost circulation material of a certain size, if present) that flows through the screen  21  is directed to the screen  22  by a flowback barrier (or plate)  31 . Optionally, the flowback barrier  31  is eliminated. The material (including lost circulation material of a certain size, if present) that exits from the top of the screen  22  is transferred to a reclamation system  40  (which, in one aspect, is, has or includes an auger apparatus  42  for moving solids to and/or from the reclamation apparatus). 
     Fluid with solids that flows through the screen  22  is directed to the screens  23  and  24  by a flowback barrier or plate  32 , a flow channel  32   a , and a weir  32   b . Fluid with solids that flows through the screen  23  is directed to the sump  26  through a channel  51  by a flowback barrier  33  and a channel  33   a . When the level of fluid (with material therein) exceeds the height of the weir  32   b , part of the flow from the screen  22  flows into the flow channel  50  bypassing the screen  23  and flowing to the screen  24  (thus, the screens  23 ,  24  in this manner operate in parallel). Fluid flowing through the screen  24  flows into the sump  26 . Optionally, the screen  21  includes an end weir  21   w  and fluid and material on top of the screen  21  in a pool  21   p  that exceeds the height of the weir  21   w  bypasses the screen  21  and flows to the screen  22  via a channel  17 . The flowback barriers extend under substantially all of the surface of the particular screens under which they are located. Any one, two, or three of the flowback barriers can, optionally, be eliminated. 
     The screens  21 - 24  are at typical screen tilt angles, e.g. between 6 degrees to 12 degrees from the horizontal and in one aspect, about 8 degrees. 
     A shale shaker  10 a shown in  FIG. 2C  is like the system  10 ,  FIG. 2A  (and like numerals indicate like parts). Two screens, the screens  22  and  23 , are used in the shale shaker  10   a  to remove LCM material (and/or material of similar size) . The two screens  22 ,  23  act in parallel with flow from the upper screen  21  flowing both to the screen  22  and, over a weir  22   w , to the screen  23 . Fluid flowing through the screen  22  flows to a channel  50   a  and then down to the screen  24  as does fluid flowing through the screen  23 . 
       FIGS. 3A and 3B  show a shaker system  10   b  like the system  10 ,  FIG. 2A  (like numerals indicate like parts). The shaker  10   b  has a collection chute  60  which receives material from top of a screen  21   a  (like the screen  21 ,  FIG. 2A ) and from which the material flows down to a cuttings ditch, pit, or collector  19 . An auger system  70  receives material from the top of a screen  22   a  (like the screen  22 ) and augers the material into a conduit  70   a  from which it flows to storage or further processing apparatus  70   b . The flows from the tops of screens  23   a  (like screen  23 ) and  24   a  (like screen  24 ) flow to the cuttings ditch (etc.)  19 . Fluid flowing through the screens flows to a sump  26   a  (like the sump  26 ). In one aspect, the screen  22   a  is used to recover LCM (and/or material of similar size), optionally, as in  FIG. 2C , both screens  22   a  and  23   a  are used to recover LCM (and/or material of similar size). 
     Material recovered from the top of a second screen in systems according to the present invention (e.g. from the top of the screen  8   b ,  21  or  21   a ) can, according to the present invention, be sent to additional treatment apparatus for further processing; including, but not limited to, a sprinkle-wash system for solids recovery, centrifuge(s), hydrocyclone(s), and/or magnetic separation apparatus. This material from the tops of these screens is, in one aspect, lost circulation material. In one aspect, considering the totality (100%) of the lost circulation material in a drilling fluid mixture fed to a top scalping screen of a system according to the present invention, about 97% of this lost circulation material flows to the second screen and about 95% (95% of the original totality of the material) is recovered from the top of the second screen; or optionally, a combination of similar sized material, including both LCM and other material is recovered. 
       FIGS. 4A and 4B  illustrate a quad-tier system  100  according to the present invention which has screen decks  101 ,  102 ,  103 , and  104 . A feed  105  of a drilling fluid mixture is fed onto a first deck  101  with a plurality of screens  101   a ,  101   b ,  101   c  (may be any suitable number of screens). Drilling fluid (with some solids) flowing through the screens  101   a - 101   c  flows to a chute  106  and from there down to the deck  102 . Overflow  107  from the deck  101  flows over a weir  108  (of a pre-determined height) down to the deck  102 . Oversized material  109  flows off the top of the screen  101   c.    
     Drilling fluid with some solids flowing through screens  102   a  (four shown; may be any suitable number of screens) flows to chutes  116  and from there to the deck  103 . Oversize material  119  flows off the tops of screens  102   a . A weir  118  prevents any overflow from the top of the screens  102   a  from flowing down to the deck  103 . 
     Drilling fluid with some solids flowing through screens  103   a  (size shown; may be any number) of the deck  103  flows to a diverter  126  and from there to a collection structure, e.g. a tank, sump or receptacle. Overflow from the top of the screens  103   a  flows to a channel apparatus  128  and from there to a channel apparatus  138  which directs this flow to the top of the deck  104 . Oversized material  129  flows off the tops of end screens  103   a.    
     Drilling fluid flowing through screens  104   a  (four shown; any number may be used) flows down to chutes  136  and then to the tank, sump, or receptacle. Oversized material  139  flows off tops of end screens  104   a.    
     The oversized material flows,  109 ,  119 ,  129  and  139  flow to typical collection sump, pit tank, or receptacle or storage apparatus and/or to subsequent processing apparatus. 
     In one particular aspect of the system  100 , the deck  101  is a coarse screening deck (e.g. but not limited to the screen  8   a , screen A 1 , screen  21  or screen  21   a ); the deck  102  is a medium mesh screening deck (e.g. but not limited to, like the screen  8   b , screen A 2 , screen  22 , or screen  22   a ); the deck  103  is a medium or fine screening deck (e.g., but not limited to, like the screen  8   c , screen A 3 , screen  23  or screen  23   a ); and the deck  104  is a fine screening deck (e.g., but not limited to, like the screen  8   d , screen A 4 , screen  24  or screen  24   a ). 
       FIGS. 5A and 5B  illustrate a system  200  according to the present invention which is, in some ways, like the system  100 ,  FIG. 4A . In the system of  FIG. 4A  underflow from the deck  102  flows to both the deck  103  and the deck  104 . In the system  200  flow from the deck  101  flows to both the deck  102  and the deck  103 , with underflow from both of these decks flowing to the deck  104 . 
     Drilling fluid with some solids (underflow from the deck  101 ) flows from the deck  101  down to the deck  102 . Overflow from the deck  102  flows via the channel apparatus  128   a  and channel apparatus  204  to the deck  103 . Underflow from the deck  102  flows to the chutes  116  and is diverted to the deck  104  by a diverter  202  (with handles  203 ) and via a channel apparatus  206  and a channel apparatus  208  to the deck  104 . In one aspect the diverter  202  is connected to the channel apparatus  204  (indicated by the wavy lines on both). 
     Underflow having passed through the deck  103  and chutes  116   a  (like the chutes  116 ) is diverted by a diverter  202   a  (like the diverter  202 ) to the deck  104 . Underflow having passed through the deck  104  flows to the chutes  136  and then to collection, storage, tank, or receptacle. 
     The various chutes, diverters, and channel apparatuses in the systems  100  and  200  are interchangeable, in one aspect, so that series or parallel flow to and from one or more selected decks is facilitated. In certain aspects, the chutes, diverters and channel apparatuses are made of metal, plastic, or composite material. 
     In the system  100 ,  FIG. 4A , the channel apparatus  128  has three flow passages  128   a ,  128   b ,  128   c . The diverter  126  has two flow passages  126   a ,  126   b . The channel apparatus  138  has flow passages  138   a ,  138   b ,  138   c . In the system  200 ,  FIG. 5A , the channel apparatus  128   a  has flow channels  128   c ,  128   d . The channel apparatus  204  has flow passage  204   a ,  204   b . The channel apparatus  206  has flow passages  206   a ,  206   b . The channel apparatus  208  has flow passages  208   a ,  208   b.    
     The present invention, therefore, provides in at least certain embodiments, a system for processing a mixture of drilling fluid and solid material to separate at least one component of the mixture by size from the mixture, the system including a vibratable basket; a sump at a bottom of the basket; a plurality of spaced-apart screens including a first screen deck, a second screen deck positioned below the first screen, a third screen deck positioned below the second screen deck, and a fourth screen deck positioned below the third screen; the screens mounted in the vibratable basket and vibratable therewith; the first screen deck having screen mesh of a first size to remove from a top of the first screen deck solids from the mixture with a largest dimension equal to and larger than a first dimension so that material with a largest dimension smaller than the first dimension is passable down through the first screen deck; the second screen deck having screen mesh of a second size to remove from a top of the second screen solids from the mixture passing to the second screen deck from the first screen deck which have a largest dimension equal to or larger than the second size so that material with a largest dimension smaller than the second size is passable down through the second screen deck, material and fluid passing through the second screen deck comprising a secondary flow; diversion apparatus connected to the basket positioned for providing at least a portion of the secondary flow to the third screen deck and, selectively, a portion of the secondary flow to the fourth screen deck; the third screen deck having screen mesh of a third size, and the fourth screen deck having screen mesh of a fourth size for removing solids from the secondary flow on the top of the third screen deck and from the top of the fourth screen deck; and drilling fluid flowing through the first screen deck, the second screen deck and one of the third screen deck and fourth screen deck flowing down into the sump. Such a system may have one or some, in any possible combination, of the features and aspects described above for any system according to the present invention. 
     The present invention, therefore, provides in at least certain embodiments, a system for processing a mixture of drilling fluid and solid material to separate at least one component of the mixture by size from the mixture, the system including: a vibratable basket; a sump at a bottom of the basket; a plurality of spaced-apart screens including a first screen deck, a second screen deck positioned below the first screen, a third screen deck positioned below the second screen deck, and a fourth screen deck positioned below the third screen; the screens mounted in the vibratable basket and vibratable therewith; the first screen deck having screen mesh of a first size to remove from a top of the first screen solids from the mixture with a largest dimension equal to and larger than a first dimension so that material with a largest dimension smaller than the first dimension is passable down through the first screen deck; the second screen deck having screen mesh of a second size to remove from a top of the second screen solids from the mixture passing to the second screen deck from the first screen deck which have a largest dimension equal to or larger than the second size so that material with a largest dimension smaller than the second size is passable down through the second screen deck, material and fluid passing through the second screen deck comprising a secondary flow; diversion apparatus connected to the basket positioned for providing at least a portion of the secondary flow to the third screen deck and, selectively, a portion of the secondary flow to the fourth screen deck; the third screen deck having screen mesh of a third size, and the fourth screen deck having screen mesh of a fourth size for removing solids from the secondary flow on the top of the third screen deck and from the top of the fourth screen deck; drilling fluid flowing through the first screen deck, the second screen deck and one of the third screen deck and fourth screen-deck flowing-down into the sump; wherein the first screen deck is a scalping deck; wherein the screen mesh of a second size is suitable for removing solids the size of lost circulation material, said solids including pieces of lost circulation material and pieces of material other than lost circulation material; the drilling fluid mixture introduced to the system to be treated by the system includes a first amount of lost circulation material; the second deck is able to remove a second amount of lost circulation material; the second amount at least 75% of the first amount; and reclamation apparatus for receiving the lost circulation material. 
     The present invention, therefore, provides in at least certain embodiments, a method for treating a mixture of drilling fluid and solid material to separate at least one component of the mixture by size from the mixture, the method including: feeding the mixture to a vibratable basket of a system, the system as any described herein according to the present invention, and the method further including flowing drilling fluid through a first screen deck, a second screen deck and one of a third screen deck and a fourth screen deck of the system down into a sump; or flowing drilling fluid through a first screen deck, and one of a second screen deck and a third screen deck flowing down into a sump. 
     In conclusion, therefore, it is seen that the present invention and the embodiments disclosed herein and those covered by the appended claims are well adapted to carry out the objectives and obtain the ends set forth. Certain changes can be made in the subject matter without departing from the spirit and the scope of this invention. It is realized that changes are possible within the scope of this invention and it is further intended that each element or step recited in any of the following claims is to be understood as referring to the step literally and/or to all equivalent elements or steps. The following claims are intended to cover the invention as broadly as legally possible in whatever form it may be utilized. The invention claimed herein is new and novel in accordance with 35 U.S.C. §102 and satisfies the conditions for patentability in §102. The invention claimed herein is not obvious in accordance with 35 U.S.C. §103 and satisfies the conditions for patentability in §103. This specification and the claims that follow are in accordance with all of the requirements of 35 U.S.C. §112. The inventors may rely on the Doctrine of Equivalents to determine and assess the scope of their invention and of the claims that follow as they may pertain to apparatus not materially departing from, but outside of, the literal scope of the invention as set forth in the following claims. All patents and applications identified herein are incorporated fully herein for all purposes. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function. In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.