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This is a continuation-in-part of previous application 08/713,604 filed Sep. 13, 1996 now issued as U.S. Pat. No. 5,996,484, and also claims benefit of provisional 60/003,781 filed Sep. 15, 1995. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The field of the present invention relates generally to the recovery of drilling fluids from discharge cuttings fluids from a drilling/production operation, more particularly, a method utilizing various types of presses for the recovery of such drilling fluids through compaction and defluidization of entrained solids in a cuttings slurry prior to such cuttings being injected into a well casing or in conjunction with other environmental distribution and/or disposal operations. 
     2. General Background 
     In oil well drilling operations, drilling fluid containing additives is circulated downwardly through the drill string to lubricate and remove cuttings from the bit. A mixture containing drilling fluid and cuttings is then returned to the surface through and annulus around the drill pipe “Adherent drilling fluid” is defined as drilling fluid adhering to the drill cuttings, and, if the drilling fluid is oil-based, the adherent drilling fluid also includes oil. 
     It is well known that the drill cuttings must be separated from the drilling fluid so that the drilling fluid can be recirculated. Additionally, solid cuttings generated in a drilling process, such as during exploration for oil or gas, which have been contaminated with adherent drilling fluid must be cleansed to remove surface contaminates prior to discharge of the cuttings to the environment. Several such methods and apparatus are disclosed by U.S. Pat. Nos. 5,361,998, 5,303786, 5,129,468, and 4,546,783. Such apparatus are particularly beneficial in laundering or cleansing of drill cuttings on offshore drill platforms so that the drill cuttings are environmentally safe for discharge into the sea. However, the loss of a portion of the adherent fluids is inevitable and is becoming more of a concern. 
     Many of the problems associated with drilling fluid recovery for onshore operations are expressed by Hart in U.S. Pat. No. 5,330,017. Hart suggests that, due to environmental concerns, much of the slurry is transported in a fluid or semi-fluid state to approved disposal sites. Such sites utilize deep wells whereby hazardous waste can be injected back into the earth or mixed with chemicals such as lye and fly ash which render the materials acceptable for land reclamation. Disposal sites may also provide centrifuges as a means of defluidizing the slurry and rely heavily on polymers added to the effluent to render the discharge liquids safe for reintroduction into the environment. 
     Many recovery and treatment apparatus utilize separate cells having low speed agitators to stir a mixture of cutting and cleansing solution called surfactants. The cuttings are transferred from one cell to the next where additional agitation and cleansing take place. Thereafter, a slurry of cleansed drill cuttings and surfactant is pumped from the cells to a vibrating screen operation whereby most of the surfactant is removed and sent back to the system. In some cases a portion of the surfactant solution, which is rich in fine drill cuttings and adherent drilling fluids, is run through one or more hydrocyclone separators which discharge the fine drill cuttings in solution separated from the larger, cleansed drill cuttings. However, it has been the practice in the past to simply pass the cuttings over one or more vibrating screens to recover the majority of the drilling additives and discharge the remainder as waste material. In any case, it is the overflow and underflow of such discharge slurries comprising surfactant solution, drilling fluid, and entrained fine drill cuttings which is the focus element of the present invention. As discussed by Lott in U.S. Pat. No. 4,546,783, hydrocyclones used in the recovery system tend to lose 4% of the surfactant solution alone in the process, which is environmentally and economically undesirable. An even greater percentage of drilling fluids are also lost in the process. Lott further suggested a process and apparatus for recovering more of the surfactant. However, Lott&#39;s use of a vacuum chamber and a drag link conveyer to clear additional shaker screens, the use of a second hydrocyclone, gas spargers and liquid spray nozzles to induce the entrained solids to rise to the surface in yet another decanter so that they can be drained off into a second decanter prior to disposal, seems to be an over-complication of the process. However, such drastic measures to recover only 4% of the surfactant, along with the drilling fluids, is indicative of the need for a more efficient method of recovery. 
     Although screw presses have been widely used in the agricultural industry to dewater fibrous slurries, such presses have not gained acceptance in the earth drilling industry for a number of reasons. Compressing earth cuttings developed from drilling operations would be difficult under most conditions, due to the volume, the abrasiveness, and nonuniformity of such materials. Dewatering screw conveyors and screen conveyor systems have been used with some success in mining operations to remove a large portion of the residual water. However, the drilling additives associated with petroleum drilling operations make defluidizing more complicated. It has been found that screw presses, such as disclosed by Eichler in U.S. Pat. No. 5,009,795, could serve as the basis for a defluidizing press in the present invention concept. However, due to the nature of the materials handled, abrasiveness, and the material&#39;s lack of compressibility, a more robust screw flighting and a much finer screen are required. A means of controlling the flow of material to form compaction is also required which will not restrict the material discharge. It is also known, according to Gloacki&#39;s U.S. Pat. No. 4,709,628, that a variable damper having a conical shape can be used to control the material discharge of such screw presses. However, Glowacki uses a plurality of flaps, which would become compacted or misshaped and impair the flow of heavy non-compressible materials such as earth cuttings. Therefore, a more rigid conical or elliptical shape would be more practical. It has therefore been found that a defluidizing type press designed specifically to handle a slurry of drill cuttings may be utilized to recover drilling fluids while defluidizing the discharge cuttings, thereby resulting in a savings of costly drilling additives and reducing the volume of discharge into the environment. Such savings are further enhanced as a result of a reduction in environmental additives, such as lime and fly ash, and other such chemicals used to neutralize the discharge waste material when being reintroduced into the environment. By defluidizing the discharge slurry, the volume of disposable material is reduced. Therefore, less chemicals are required to treat the material before introduction into the environment 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention provides a means of recovery of drilling fluids from drilling fluid slurries containing entrained solids. Such slurries are derived directly from the cascading, vibrating screens in various drill cutting processing systems. It has been found that any discharge from such systems which is considered suitable for disposal into the environment can now be cycled through a defluidizing press whereby up to 40% by volume of the remaining drilling fluids can be recovered in the defluidization process. A second defluidizing press may be used to further reduce the fluid content, thereby reducing the discharge volume. Several embodiments are disclosed which further define the process under various conditions. In addition, several types of defluidizing presses are disclosed which may prove applicable under various circumstances. It is anticipated that such defluidizing presses may be capable of replacing all or a significant part of the current processes, thus eliminating the cascading screens, hydrocyclones, and centrifuges. It should be understood that although the majority of the fluids from the cuttings are being recovered by utilizing the screw press and liquid screen as taught herein, the solids still retain a relatively high moisture content and still retain some petrochemicals. It is also desirable, in some cases, to reduce the solids to their lowest possible mass for transport and disposal into the environment. Therefore, systems also may be provided that utilize the defluidizing technology that allows the defluidized cuttings to be further processed for transport and disposal in the environment. Such systems may simply include further treatment of the defluidized cuttings with chemicals to disperse the petrochemicals and assist in the biodegradation of the solids prior to reintroduction into the environment. Other more elaborate systems as taught herein also utilize the combustible petrochemical in the cuttings to assist in drying the solids prior to mixing environmentally enhancing chemicals. 
     Defluidized cuttings may be disposed of in any number of ways as disclosed herein, such as reinduction into well casing, transported, at a reduced volume cost, for injection at processing and disposal sites, or to distillation and land reclamation farms where fewer chemicals will be required to treat the materials prior to introduction into the environment. 
     It is, therefore, an object of the present invention to provide a means of recovery of a greater percentage of drilling fluids currently being lost in the disposition process. 
     Another object is to make the use of synthetic drilling additives more economical to use due to the recovery process. 
     Still another object of the invention is to reduce the quantity of fluids being transported for disposition, thereby making transport of disposable drill cuttings more economical. 
     Yet another object of the present invention is to reduce the drilling additives in the disposable cuttings, thereby reducing the quantity of biodegradation additives generally required by land farms. 
     This summary is a concise description of the use of a press system to recover expensive drilling fluid additives and a method for achieving the objectives stated and is not intended to limit or modify the scope of the invention as stated in the claims as follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a further understanding of the nature and objects of the present invention, reference should be made to following detailed description taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein: 
     FIG. 1 is a diagram of the present invention in section view shown receiving slurry from a shaker screen system and discharging defluidized material to a well injection system, to cutting box for disposal at a hazardous waste site, or to a truck for disposition into a distillation process or the environment; 
     FIG. 2 is a partial cross section view of a system tank and the present invention mounted thereto, showing slurry material being discharged into a hopper; 
     FIG. 3 is a partial cross section view of a system tank and the present invention mounted thereto, showing an infeed screw conveyor coupled directly to the feed screw of the present invention; 
     FIG. 4 is a an isometric view of the present invention; 
     FIG. 5 is a cross sectional elevation and piping diagram of a two press system utilizing a circulating tank; 
     FIG. 6 is a cross section elevation showing the present invention discharging into a pug mill having chemical infeed capability; 
     FIG. 7 is a cross section elevation of a second embodiment of the press having hydraulic ram feed; 
     FIG. 8 is a plan view of a third embodiment showing a piston pump having defluidizing capability; 
     FIG. 9 is a side elevation of the piston pump in FIG. 8; 
     FIG. 10 is a side elevation and cross section of a screw press having means for applying pressure or vacuum to the defluidizing means; 
     FIG. 11 is a partial cross section of the screen element; 
     FIG. 12 is an illustration of a vibrator and band assembly located around the sieve screen; 
     FIG. 13 is a partial cross section view of the drive motor mounted to the screw shaft; 
     FIG. 14 is a vertical cross section view illustrating a cuttings drying system utilizing the disclosed technology; 
     FIG. 15 is a partial top view of the system illustrated FIG. 14; and 
     FIG. 16 is a vertical cross section of an alternative system utilizing the disclosed technology. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1 where the major components of the defluidization recovery system  10  starts with drill cuttings and drilling fluids in a slurry  16  collected from any source as overflow or underflow, usually from the rig&#39;s shaker screens (not shown). The slurry  16  is transported via a conveyor  18  to the screw press  20 , shown here in cross section and better seen in FIG. 2, mounted on top of a fluid recovery tank  14 , illustrating the flow path of the slurry  16  being defluidized. It is conceived that a screw press  20  or other compaction type presses depicted herein, having particular characteristics, could be mounted on or near a drilling fluids system tank  14  in which case drilling fluids contained in the overflow and underflow slurry  16  could be separated from the drill cuttings processing system prior to discharge into the environment. The slurry  16 , in most cases, contains valuable drilling additives including synthetics and/or surfactants which, after having passed through a wash system (not shown), could be fed via a screw conveyor  18  to the press  20  where the slurry  16  is defluidized. The cuttings, contained in the slurry  16 , when compacted in the press  20 , as a result of being forced through a compaction zone  25 , forces the drilling fluids  22 , which containing valuable drilling additives, to be discharged into the system tank  14  for recirculation in the drilling process. The separated defluidized cuttings residue  24  is then discharged via a discharge chute  26  to a drill cuttings injection system  28 , to a cutting storage box  30 , or to a transporting vehicle  32  for transport to a hazardous waste site for injection in a deep well  34 , or treated for environmental disposal at a land reclamation farm  36 . The slurry  16  may be conveyed to the press  20  in any accepted manner, such as screw conveyor  18 , gravity feed, or by pump. However, in most cases this is done by gravity feed or screw conveyors  18 , in which case the slurry  16  is discharged into a hopper  38  attached to the press  20  infeed portion as seen in FIG.  2 . Such screw conveyors  18  may also be coupled directly to a screw press  46  infeed screw as seen in FIG. 3, thereby eliminating the need for a separate drive mechanism  42  as shown in FIG.  2 . Any liquid overflow in the hopper  38  passes through the overflow pipe  44  attached to the hopper  38  shown in FIG.  4  and enters the system tank  14 . As indicated above, other types of presses may also be employed, such as the piston press  41  shown in FIG.  7 . However, it should be understood that alternate means for injecting materials directly into the screw press may be employed by simply closing the infeed hopper as illustrated in FIG. 10, substituting an infeed device such as a Moyno type pump. Such an arrangement further increases the press&#39;s efficiency especially when a low solids to liquid ratio is present. Still another embodiment of the piston press can also be seen in FIG. 8 and 9, whereby a dual piston pump  50  is utilized which provides a means for drawing the slurry  16  being supplied to the hopper  52  into the ram tube  54  as a result of retraction of an internal piston  56 , shown in FIG. 9 attached to the hydraulic ram cylinder  58  adjacent the ram tube  54 . Valves  60 ,  60 ′ located below the hopper  52  open alternately to allow the slurry to pass to each ram tube  54 ,  54 ′ via valve  62 . When the internal ram piston  56  is fully withdrawn an operating system reverses the piston  56  travel, whereby the valve  60  located below the hopper  52  is then closed simultaneously with valves  62 ′ being opened at the entrance to the ram tube  54 ′, juxtaposed the ram tube  54 , being filled, and sequentially opening the discharge valve  63  located between the discharge merging element  66  and the press screen  74 , the piston  56  then moves forward in the first cylinder  54 , thereby expelling the slurry  16 , while additional slurry material  16  is being taken into the second tube  54 ′ by hydraulic ram cylinder  581  and piston  56 ′ (not shown). The slurry  16  being expelled by each ram tube  54 ,  54 ′ in turn is then forced into the  30  merging connector  66 . A solids discharge zone at the end of the discharge tube  70  is essentially the same for all the presses disclosed herein. Restriction cylinders  68  are controlled remotely, thereby establishing the opening  72  between conical plug  80  and seat  82  thus providing compaction of the solids residue  24 . The slurry  16 , under pressure from the ram piston,  56  forces the slurry  16  linearly through a strainer screen  74 . As a result of compaction in the discharge tube  70 , fluids less than 50 micron are expelled through a screen sieve  74 . The expunged fluid  22  is then returned to the system tank  14  while the more dense solids residue  24  greater than 50 micron is forced through the discharge tube  70 . The system then reverses the operation for the alternate ram cylinder  58 ′, thus creating a push pull operation. Therefore, while one ram cylinder  54  is filling, the adjacent cylinder  54 ′ is being discharged. The solids residue  24  being forced through the discharge tube  70  is thereby extruded at a steady rate, controlled by the gap  72  between the elliptical plug  80  and its seat  82 . The length of the discharge tube  70  and ambient temperature further enhance compaction, thus further reducing the moisture content of the discharge material  24 . 
     The screw press  20  assembly as shown in FIG. 4 provides a better understanding of the requirement of a defluidizing press when applied to drilling fluid slurry  16  The slurry  16  is seldom consistent with respect to its volume or its density and, therefore, a positive means of controlling the restriction plug  80  is essential. Drilling fluid slurry  16  may vary in its consistency and at times may contain as little as 10% solids. Screw presses  20  have a tendency to become static when insufficient solids are present. Other press types and embodiments are disclosed herein which are capable of solving these problems. If a screw press  20  is used, it must have a more positive means of sealing between the screw flighting  90  and the cylindrical walls  92  as seen in FIG.  3 . It is also imperative that the orifices  96  shown in FIG. 11 in the screen  94  be kept open. This may be accomplished by bonding a flexible material  98  to the flighting or constructing the screw from a polymeric material which allows for constant contact between the screw flighting  90  and the cylinder wall  92 . Other methods of reducing static conditions and/or cavitation are shown in FIG. 10, wherein a valve  100  is applied between the infeed hopper  38  and the feed screen  74  and a vacuum line  101  and valve  102  are connected to the defluidizing zone  104 . This negative pressure increases flow and insures a positive flow of recovered fluid  22  through the defluidizing screens  74 . A positive pressure may also be used to increase flow through the defluidizing zone  104  through the use of air nozzles  106  located in the inflow zone  108 . It is further anticipated that a chemical, such as calcium carbonate, can he added to the slurry inflow zone from a chemical tank  110  controlled remotely by a feed valve  112 , thereby enhancing the defluidization process. As seen in FIG. 6, a screw press  20  may also he used in conjunction with a pug mill  5 , whereby chemicals  3  such as lime and fly ash are mixed with the solid cuttings residue  24  prior to discharge into the environment. As best seen in FIG. 4 press  20 , as well as in other section presses  40 ,  41  and  46 , depicted in  9 ,  7  and  3  respectively, restriction in the compaction zone  25  of the discharge portion is effected in most cases by a pair of cylinders  68  disposed parallel either side the linear axis of the discharge flange  82 . The cylinders  68  are adjusted remotely to position the conical restriction member  80  relative to the discharge flange  82 , thereby providing infinite positive control of the discharge of defluidized material  24 . The compacted solids  24  have a natural tendency to adhere to the inside diameter of the screen  74 . It has been found that a relatively small vibrator  140  can be placed on the outer diameter of the screen in the manner illustrated in FIG. 12, thus imparting a vibration over the face of the screen eliminating much of the material adhesion. 
     As seen in FIG. 4 the screw press  20  is divided into three zones,  30 : The infeed zone comprising a hopper  38  having an overflow tube  44 , the hopper  38  located above and adjacent to the screw infeed compartment  108 , a defluidizing zone  104 , a fluid discharge  22  as illustrated in FIG. 2 and 3, and a solids discharge zone  25 . The slurry  16 , containing solids and drilling additives to be separated, is conveyed to the infeed hopper  38  and thus to the screw press  20  where any excess fluid is vented off through the overflow pipe  44 . Most of the fluids in the slurry  16  are drained off through the separator strainers  74  in the defluidizing zone  104  prior to compaction. Compaction as a result of the solids being forced through the opening  72  between the restriction plug  80  the seat  82  in the compaction zone  25  by the press screw flights  90 , forces any remaining liquids  22  having a diameter smaller than 50 micron from the slurry  16  via sieve screen  74 . As seen in FIG. 4 the typical screw press of the present invention comprises a base frame  99  having vertical supports  109 ,  116 ,  118 , and  120  extending upwardly therefrom; an infeed zone comprised of a hopper portion  38  mounted to a tubular infeed housing  108 , having a flange fitting at each end, one end of which is supported inboard to vertical support  109  with the opposite end attached to one side of support  118 . The press further comprises a driver motor  42  mounted to the external flange housing  43 , shown in FIG. 4, secured to the outboard side of the vertical support  109  adjacent the infeed housing  108 . As seen in FIG. 13 the drive motor shaft  107  is coupled directly to an output shaft  111 , extending through the external flange housing  43 , and held in axial alignment by a head shaft bearing  113  located within the external flange housing  43 . The hollow screw shaft  111  is fitted with an internal spine which engages the drive motor output shaft  107 . Shaft  111  fitted with helical screw flighting  90 , shown in cross section in FIG. 11, is provided beginning in the infeed housing  108  and extending axially through the defluidizing zone  110  ending just short of the discharge flange  82  at support  116 . The shaft  111  is rotatably supported by a flange bearing  115  mounted to vertical support  116 . 
     The press further comprises a defluidizing zone  110  adjacent to the infeed zone, separator strainers  74 , a collection chamber  104  surrounding the strainers, and a fluid discharge aperture  114  below the strainer passing through the base frame  99 . The separator strainer or sieve screen  74  as illustrated in FIG. 11 comprises a 50 micron screen  94  backed by a plurality of wedged shaped, axially extending, parallel slats  97  held in an equally spaced, circumferential relationship by multiple supporting rings  93 , slats  97  having a spacing between their widest portion of precisely 0.004 of an inch for 50 micron separators used for most drilling fluid recovery systems, with larger spacing used for greater micron screening for primary or special applications. Slats are formed into a radial diameter coinciding with the inside diameter of the infeed housing. flanges corresponding to the infeed housing discharge flange are secured to each end of the wedged shaped slats, thereby defining a flanged tubular section. At least three torsion members secured to and extending axially between the flanges are attached to each of the supporting rings, providing a ridged, structural unit. Any number of these strainer sections may be connected together and utilized as necessary to provide sufficient separation of the entrained solids. The strainer flange adjacent the discharge is secured to a vertical frame member  118  having a diametrical bore equal to the flange inside diameter. 
     The screw press further comprises a discharge zone comprising a flanged reducing tubular portion  82  having an internal diameter less than an internal diameter of the strainer screen sieve  74 , the reducing flange  82  being mounted to the discharge side of the base frame, vertical support ember  120  adjacent the defluidization zone  110 , a conical disk  80 , slidable along the screw shaft  111 , operated by a pair of ram cylinders  68  connected to a collar  69  at the back side of the conical disk. 
     The screw press  20  may be driven by a drive motor  42  by direct coupling to the infeed conveyor  18  as seen in FIG. 3, or by pistons as illustrated in FIGS. 7,  8 , and  9 . In any case the slurry  16  is urged through the defluidizing zone  110  towards the discharge zone  25 . In cases utilizing rotating screw flighting  90 , such flighting ends just short of the restriction element  80 , as does the piston stroke. The elliptical restriction element  80  is slidable and rotatably fitted over the hollow feed screw shaft  111 , thereby allowing the restriction element  80  to be positioned at various positions adjacent the discharge flange  82 , such positioning being controlled by positioning cylinders  68  disposed on each side of the extension shaft  111  and attached to the elliptical restriction element  80 . The positioning cylinders may be controlled remotely or manually adjusted. Rotation of the restriction element  80  is prevented relative to the rotating screw shaft  111  by torque arresters  121 . With the restriction element  80  positioned in close proximity to the discharge flange  82 , the discharge of the semi-dry drill cuttings  24  can be innitely controlled. In this manner, the solids from the slurry  16  are compacted, thereby forcing a significant amount of the remaining fluids  22  through the screens  74 . The defluidization zone  110  defining an enclosure  104  surrounding the screen  74 , enhances the ability of the press  20  to remove fluids rapidly. It has been found that a screen sieve  74  having a 50 micron admissibility is sufficient to recover most drilling additives in the slurry  16 . It has also been found that a residue  24  moisture content of less than 40% can be achieved. It has also been found that a primary press of this nature can remove 40% by volume of the oil or water in a slurry  16  directed from the rig&#39;s cuttings shaker system, thereby reducing the moisture content of the discharge material  24  to as little as 13.4% liquid by weight. 
     A second stage press  10 ′ operation as illustrated by FIG. 5 could reduce the liquid content of the disposable cuttings  24  to less than 10% by wt. However, as illustrated, a circulating tank  27  may be necessary to maintain the slurry in solution. A system of pumps  31 ,  31 ′ and valves  33 ,  33 ′ for moving the fluids from the recirculating tank to the second stage press and from the second stage press back to the recirculating tank or system tank may also be needed. 
     As seen in FIG. 14 it is contemplated that the semidry cuttings  24  being discharged from the press  10  may also be further processed by feeding the cuttings to the feed bin  200  of a rotary kiln  202 . Where the petrochemical coated cuttings are fed into the kiln and ignited, the petrochemicals are driven off in vapors through the exhaust stack, recycled to the burner  206 , or otherwise environmentally controlled as known within the art. The dried and sterile cutting solids are then moved by conveyer  210  to a collection container for deposit into one or more of the collection and transport or distribution means illustrated in FIG. 1 or conveyed to a holding hopper  212  where the cutting are held and metered by conveyer  214  or other such metering means to a high volume fine grinder such as a mill or pulverizer prior to depositing the fines in the mixing mill  5  illustrated earlier in FIG. 6, where lime and fly ash and the like are mixed with the solids prior to transport and distribution at a land fill. A plan view of the flow path is best seen in FIG.  15 . As shown in FIG. 16, the semidry solids  24  may also be deposited directly into the fine grinder and the mixing mill  5  without drying the solids, in which case the fine solids are then combined with slurry additives which enhance flow of the solids for injection back into the earth formations through the high-pressure injection pump system  28  seen in FIG. 1 
     Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in any limiting sense.

Summary:
A press process and structure is disclosed for defluidizing earth drill cuttings, thereby extracting valuable drilling additives and returning them to the drilling system while producing a dense, drier material which may be chemically treated for distillation and/or better dissolution into the environment, thereby reducing, cost in transportation and environmental treatment chemicals thus reducing environmental contamination.