Patent Publication Number: US-11643890-B2

Title: Separating solids from liquids in a drilling fluid

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional of and claims priority to U.S. patent application Ser. No. 16/879,273, filed on May 20, 2020, the entire contents of which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to separating solids from liquids in a drilling fluid. 
     BACKGROUND 
     In drilling and workover operations, drilling fluid (often called “drilling mud”) is used to keep a hydrostatic pressure within a wellbore while drilling or while work over by circulating the drilling fluid into the wellbore. For example, the drilling fluid may be circulated through a tubular work string or drill pipe and through one or more nozzles formed in the drill bit and out into the wellbore. The drilling fluid helps with well control, as well as carries cuttings removed from a subterranean formation by the drill bit during drilling the wellbore back to the surface. These cuttings can be separated from the drilling fluid to maintain an initial set of properties (for example, viscosity, density, gel strength) of the drilling fluid. 
     SUMMARY 
     This disclosure describes implementations of a shaker screen system that may be used to separate formation cuttings from a liquid in a drilling fluid that has been used and recovered from a wellbore drilling or workover operation. In some aspects, the shaker screen system includes a screen assembly that includes multiple screen sections attached or coupled together (for example, within a circular screen). In some aspects, one or more of the multiple screen sections are formed of screens with varying mesh sizes, thereby allowing cuttings of different sizes to pass through the one or more screen sections. 
     In an example implementation, a drilling fluid shaker screen system includes a screen assembly that includes a screen mounted to a funnel, the screen including a plurality of screen sections. A first screen section of the plurality of screen sections includes a first screen mesh size and a second screen section of the plurality of screen sections includes a second screen mesh size different than the first screen mesh size. The first and second screen mesh sizes are based at least in part on a size of one or more cuttings entrained in a drilling fluid used in a drilling or workover operation. The drilling fluid shaker screen system further includes a rotation assembly mounted to the screen assembly. The rotation assembly includes one or more rollers moveable to rotate the screen assembly about an axis of rotation. The drilling fluid shaker screen system further includes a motor assembly coupled to the screen assembly and configured to vibrate the screen assembly; and a housing coupled to the screen assembly and the rotation assembly. The housing includes a cuttings outlet that is fluidly coupled to a cuttings inlet formed in the screen and a liquid outlet separate from the cuttings outlet that is fluidly coupled to the plurality of screen sections. 
     In an aspect combinable with the example implementation, the screen includes a circular screen area, and each of the plurality of screen sections includes a co-equal portion of the circular screen area. 
     In another aspect combinable with any of the previous aspects, the plurality of screen sections include four screen sections that include the first and second screen sections, each of the four screen sections including a quarter of the circular screen area. 
     In another aspect combinable with any of the previous aspects, the four screen sections further include a third screen section that includes a third screen mesh size and a fourth screen section that includes a fourth screen mesh size. 
     In another aspect combinable with any of the previous aspects, each of the first, second, third, and fourth screen mesh sizes is different. 
     In another aspect combinable with any of the previous aspects, the screen is mounted to the funnel at an angle that slopes downward from a perimeter of the screen toward the cuttings inlet. 
     In another aspect combinable with any of the previous aspects, the rotation assembly includes at least one rail mounted to at least one of the screen assembly or the rotation assembly and adjacent a perimeter of the screen assembly. 
     In another aspect combinable with any of the previous aspects, the rail is configured to receive at least a portion of the one or more rollers. 
     Another aspect combinable with any of the previous aspects further includes a vibration assembly mounted to the housing and including one or more springs configured to oscillate the screen assembly based at least in part on operation of the motor assembly. 
     In another aspect combinable with any of the previous aspects, the vibration assembly is mounted to a bottom portion of the rotation assembly, and the rotation assembly is mounted to a bottom portion of the funnel. 
     Another aspect combinable with any of the previous aspects further includes a locking assembly that includes a first member attached to the screen assembly; a second member attached to the rotation assembly; a bore formed through each of the first and second members; and a pin insertable through the bore to fixedly lock the screen assembly to the rotation assembly. 
     In another aspect combinable with any of the previous aspects, the first screen mesh size is configured to allow a first cutting to pass there through, and the second screen mesh size is configured to allow a second cutting larger than the first cutting to pass there through. 
     In another aspect combinable with any of the previous aspects, the cuttings inlet includes a hole in the screen centered at a center of the screen assembly. 
     In another aspect combinable with any of the previous aspects, the housing defines an interior volume fluidly coupled to the liquid outlet. 
     In another example implementation, a method for separating cuttings from liquid in a drilling fluid includes circulating a drilling fluid that includes a liquid and a plurality of formation cuttings to a screen assembly that includes a screen, the screen including a plurality of screen sections; vibrating the screen assembly during circulation of the drilling fluid to the screen assembly; while vibrating the screen assembly, separating, with the screen assembly, the liquid from the plurality of formation cuttings; while vibrating the screen assembly, separating a first portion of the plurality of formation cuttings of a first size from the drilling fluid with a first screen section that includes a first screen mesh size; rotating the screen assembly; subsequent to rotating the screen assembly and while vibrating the screen assembly, separating a second portion of the plurality of formation cuttings of a second size different than the first size from the drilling fluid with a second screen section that includes a second screen mesh size different than the first screen mesh size; directing the separated liquid through the screen assembly to a liquid outlet; and directing at least one of the first or second portions of the plurality of formation cuttings to a cuttings outlet formed in the screen. 
     In an aspect combinable with the example implementation, the screen includes a circular screen area, and each of the plurality of screen sections includes a co-equal portion of the circular screen area. 
     Another aspect combinable with any of the previous aspects further includes further rotating the screen assembly; while vibrating the screen assembly, separating a third portion of the plurality of formation cuttings of a third size different from the first and second sizes from the drilling fluid with a third screen section that includes a third screen mesh size different than the first and second screen mesh sizes; further rotating the screen assembly; and while vibrating the screen assembly, separating a fourth portion of the plurality of formation cuttings of a fourth size different from the first, second, and third sizes from the drilling fluid with a fourth screen section that includes a fourth screen mesh size different than the first, second, and third screen mesh sizes. 
     Another aspect combinable with any of the previous aspects further includes directing at least one of the third or fourth portions of the plurality of formation cuttings through the screen assembly with the separated liquid to the liquid outlet; and directing the other of the at least one of the third or fourth portions of the plurality of formation cuttings to the cuttings outlet formed in the screen. 
     Another aspect combinable with any of the previous aspects further includes directing the at least one of the first or second portions of the plurality of formation cuttings at a downward angle toward the cuttings inlet and away from a perimeter of the screen. 
     In another aspect combinable with any of the previous aspects, vibrating the screen assembly includes operating a motor to drive a gear or wheel coupled with the screen assembly; based on driving the gear or wheel, oscillating the screen assembly with a plurality of springs coupled to the screen assembly. 
     In another aspect combinable with any of the previous aspects, rotating the screen assembly includes moving at least one roller coupled with the screen assembly on a rail; and based on moving the at least one roller, rotating the screen assembly about an axis of rotation. 
     In another aspect combinable with any of the previous aspects, the first screen section that includes the first screen mesh size is positioned to receive the drilling fluid that includes the liquid and the plurality of formation cuttings during separating the first portion of the plurality of formation cuttings of the first size from the drilling fluid with the first screen section. 
     In another aspect combinable with any of the previous aspects, rotating the screen assembly includes rotating the screen assembly to position the second screen section that includes the second screen mesh size to receive the drilling fluid that includes the liquid and the plurality of formation cuttings. 
     Another aspect combinable with any of the previous aspects further includes prior to rotating the screen assembly, unlocking the screen assembly against rotation. 
     In another aspect combinable with any of the previous aspects, directing the at least one of the first or second portions of the plurality of formation cuttings to the cuttings outlet formed in the screen includes directing the at least one of the first or second portions of the plurality of formation cuttings to the cuttings outlet that is centered at a center of the screen assembly. 
     Another aspect combinable with any of the previous aspects further includes directing at least a portion of the separated liquid through the screen assembly through the liquid outlet and to an enclosed portion of a housing that is coupled to the screen assembly. 
     Implementations of a shaker screen system according to the present disclosure may include one or more of the following features. For example, the shaker screen system may provide for multiple, different screens that each have a different screen mesh size in a single assembly. As another example, the shaker screen system may more efficiently remove unwanted fine particles as compared to conventional shaker screens, which can save cost and rig time during a drilling or workover operation. As another example, the shaker screen system may allow for switching from one screen mesh size to another without the conventional requirement of stopping operations to remove and install screens of different mesh size in the shaker screen system. As yet another example, the shaker screen system may require less time (for example, by an operator) to change to a desired screen mesh size. 
     The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of wellbore drilling or workover process that includes a shaker screen system according to the present disclosure. 
         FIG.  2    is a schematic diagram of an example implementation of a shaker screen system according to the present disclosure. 
         FIG.  3    is an exploded view of an example implementation of a shaker screen system according to the present disclosure. 
         FIGS.  4 A- 4 B  are schematic illustrations of components of an example implementation of a shaker screen system according to the present disclosure. 
         FIGS.  5 - 6    are schematic illustrations of one or more details of a screen assembly of an example implementation of a shaker screen system according to the present disclosure. 
         FIG.  7    is a schematic illustration of a locking assembly of an example implementation of a shaker screen system according to the present disclosure. 
         FIG.  8    is a partial schematic illustrations of a screen assembly of an example implementation of a shaker screen system according to the present disclosure. 
         FIG.  9    is a flowchart that describes an example method for separating formation cuttings from a liquid in a drilling fluid according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes a shaker screen system that may be used to separate formation cuttings from a liquid of a drilling fluid that is recovered to a terranean surface from a wellbore in a drilling or workover operation. In some aspects, the shaker screen system includes a rotating screen, which allows multiple size mesh to be installed in one screen to remove different size cuttings from a flow of the drilling fluid. Thus, in some aspects, the example implementations of the shaker screen system may scale efficiently and be used to separate cuttings from liquid in many different types of drilling fluid (for example, according to viscosity, density, or otherwise) as well as many different types of subterranean formations (for example, shale, sandstone, or otherwise). 
       FIG.  1    is a schematic diagram of wellbore drilling or workover process  10  (“drilling process  10 ”) that includes a shaker screen system  24  according to the present disclosure. Generally, the drilling process  10  represents a process in which a wellbore  14  is formed from a terranean surface  17  and through one or more subterranean formations  18  by a drilling rig  12 . The drilling process  10 , in this example, includes a drill bit  16  coupled to a downhole conveyance (for example, a tubular drill string, such as conventional or coiled tubing) that forms the wellbore  14  with a drilling fluid  20 . The drilling fluid  20  is provided to the drill bit  16  by, for example, the downhole conveyance, and circulates through the drill bit  16  during drilling of the wellbore  14  in order to, for example, cool the drill bit  16  and removing cuttings from the subterranean formation  18  back to the surface  17 . Thus, return drilling fluid  22  includes the drilling fluid  20  (for example, a water or foam and chemical mixture) as well as cuttings (for example, bits of rock cut from the formation  18  by the drill bit  16 ). Return drilling fluid  22 , therefore, includes liquid  28  and cuttings  26  from the formation  18 , which may be removed. 
     As shown in  FIG.  1   , the return drilling fluid  22  is circulated out of the wellbore  14  to the shaker screen system  24 . As described in more detail in this disclosure, the shaker screen system  24  separates the liquid  28  from the cuttings  26  of the return drilling fluid  22  with a screen that includes multiple screen sections. At least one of the screen sections has a particular screen mesh size (for example, a size of the holes in the screen section) that is different than another particular screen mesh size of another screen section of the screen. Thus, different sized cuttings  26  may be filtered by the shaker screen system  24 . Some cuttings  26  may be small enough to remain entrained in the liquid  28 . Other cuttings  26  may be large enough to be separated from the liquid  28  by the shaker screen system  24 . 
     As shown in the example implementation of  FIG.  1   , the liquid  28  (which may include some cuttings  26  of a size small enough to remain entrained in the liquid  28  through the shaker screen system  24 ) and the cuttings  26  are separated into two separate streams. The liquid  28  is circulated from the shaker screen system  24  in a fluid pathway  32  and into a mud tank  36 . Generally, the mud tank  36  is used to hold the separated liquid  28  and provide the separated liquid  28  as a source of liquid for additional drilling fluid  20  (in other words, to recycle back into the drilling process  10  as drilling fluid  20 ). The cuttings  26  are circulated into a cuttings pathway  30  and into one or more waste pits  34 . Generally, the waste pits  34  are pits or other enclosures that store the cuttings  26  for proper disposal. 
       FIG.  2    is a schematic diagram of an example implementation of a shaker screen system  200  according to the present disclosure. The shaker screen system  200 , in this example, may be used as the shaker screen system  24  shown in the drilling process  10  in  FIG.  1   .  FIG.  3    is an exploded view of the example implementation of the shaker screen system  200 . As shown in this implementation, the shaker screen system  200  includes a housing  212  that forms a partial enclosure with an open top. A screen assembly  202  is mounted to the open top of the housing  212  by legs  236  that insert into holes  252 . The screen assembly  202 , in this example, includes a screen  204  (for example, circular) that is comprised of multiple screen sections  206 . In this example, there are four screen sections  206  that combine to form the screen  204  in equal portions (here, quarter portions). Other implementations may include more or fewer screen sections  206 . 
     Each of the multiple screen sections  206  may have a screen mesh size that is different than a screen mesh size of the other screen sections  206 . For example, as shown in  FIGS.  2 - 3   , each of the four screen sections  206  may have a screen mesh size different than the screen mesh size of the other screen sections  206 . Thus, as the screen  204  rotates during operation of the shaker screen system  200 , a particular screen section  206  of a particular screen mesh size will remove specific cuttings  26  of a specific particle size, and as the screen  204  continues to rotate, the next screen section  206  of a different screen mesh size will remove, for example, even finer particles of cuttings  26 . During a full rotation of the screen  204  (for example, 360° about the axis  248 ), the return drilling fluid  22  may be restored to the same or similar properties (for example, viscosity, density) as the drilling fluid  20 . 
     In this example, there are four different screen mesh sizes, which allow for four differently-sized cuttings from a return drilling fluid to be separated from the liquid in the return drilling fluid. In other examples, two of the four screen sections  206  may have a particular screen mesh size and two of the four screen sections  206  may have another particular screen mesh size. In other examples, one of the four screen sections  206  may have a particular screen mesh size and three of the four screen sections  206  may have another particular screen mesh size. Other examples of different combinations of screen sections  206  and screen mesh sizes are also contemplated by the present disclosure. 
     Turning briefly to  FIG.  6   , the screen  204  is positioned at a top of a funnel  234  that includes the legs  236  that can be inserted into a rotation assembly  208  that is mounted to the housing  212  below the screen assembly  202 . The funnel  234  and screen  204  include a cuttings inlet  226  formed with a center that coincides with a centerline axis  248  of the shaker screen system  200 . Springs  238  are positioned about the legs  236  in order for the screen assembly  202  to “float” on the rotation assembly  208 . 
     Turning briefly to  FIG.  8   , this figure shows a detail of the screen assembly  202 . In this example implementation, the funnel  234  may be angled (for example, downward) at a particular angle. In this example, the angle is at or about 20°, but other angles are contemplated by the present disclosure. The screen  204  may also be angled from a perimeter  227  of the screen  204  toward the cuttings inlet  226 . In this example the screen  204  may also be angled downward at or about 20°. 
     Turning briefly to  FIG.  5   , a detail of the connection between the screen assembly  202  and the rotation assembly  208  is shown. As illustrated in this figure, the leg  236  is inserted into the hole  252  of an upper plate  250  of the rotation assembly  208 . The spring  238  buffets contact between the screen assembly  202  and the rotation assembly  209 . Once the leg  236  is positioned through the hole  252 , a cotter pin  264  may be positioned to secure the screen assembly  202  to the rotation assembly  209 , as shown. 
     Turning back to  FIGS.  2  and  3   , the rotation assembly  208  operates to provide rotation  246  to the screen assembly  202 , for example during operation of the shaker screen system  200  or between operation times of the shaker screen system  200 . In this example, the rotation assembly  208  includes one or more rails  242  (in this example, two, an upper rail  242  and a lower rail  242 ) that circumscribe an inside perimeter of the rotation assembly  208 . One or more rollers  244  are mounted to the rails  242  and are moved (for example, rotated) to rotate the rotation assembly  208  and the screen assembly  202 . 
     Turning briefly to  FIGS.  4 A- 4 B , these figures illustrate portions of the rotation assembly  208 . For example, as shown, in this example, the rails  242  are attached to the upper plate  250  and a lower plate  258  of the rotation assembly  208 . The rails  242  are aligned along the perimeters of the lower and upper plates  258  and  250 , respectively. A roller  244  is connected, in this example, to the upper plate  250  through a leg  254  to receive and ride on the rails  242  as shown. In operation, the rotation assembly  208  may be rotated in order to rotate the shaker screen assembly  202  into a position such that a particular screen section  206  (with a particular screen mesh size) is positioned to receive the return drilling fluid  22 . As described with reference to  FIG.  7   , for instance, once positioned appropriately, the shaker screen assembly  202  may be locked or otherwise held in place. If a different screen section  206  (with different screen mesh size) is desired, the shaker screen assembly  202  may be unlocked and rotated (on the rotation assembly  208 ) so that a different screen section  206  is positioned to receive the return drilling fluid  22 . 
     The example implementation of the shaker screen system  200  includes a vibration assembly  210  mounted to or in the housing  212  below a rotation assembly  208 . As shown in this example, the vibration assembly  210  include multiple springs  214  that facilitate oscillation of the rotation assembly  208  (for example, vertical oscillation), which in turn is translated to the screen assembly  202  during operation of the shaker screen system  200 . In this example implementation, a motor assembly  216  may be operated (for example, by the controller  999 ) to provide vibratory movement to initiate (and also, maintain, in some aspects) oscillation of the rotation assembly  208  (for example, vertical oscillation), which in turn is translated to the screen assembly  202  during operation of the shaker screen system  200 . 
     As shown, the motor assembly  216  includes an electric motor  232  coupled to a motor gear  218 , that in turn is coupled to a drive gear  222  through a belt or chain  220 . A control system (or controller)  999  is communicably coupled to the motor assembly  216  to control operations of the motor assembly  216 . In example implementations, the controller  999  may be a microprocessor-based, electro-mechanical, pneumatic, or hydraulic controller that may control the motor assembly  216  based on operator input and/or based on a sensed operation of the motor assembly  216 , and more generally, the shaker screen system  200 . 
     As shown in the example implementation of the shaker screen system  200 , a cuttings pathway  224  extends vertically through the shaker screen system  200 , with the cuttings inlet  226  forming an inlet to the pathway  224  and the pathway  224  having a cuttings outlet  228  formed opposite the cuttings inlet  226 . As explained in more detail later, cuttings  26  from the return drilling fluid  22  that are not small enough to be entrained with the liquid  28  are separated from the return drilling fluid  22  and move (for example, through vibration) to the cuttings inlet  226  and then through the cuttings pathway  224  for removal from the outlet  228  (for example, to one or more mud pits). In some examples, the cuttings pathway  224  is formed of a tubular that extends between the cuttings inlet  226  and the cuttings outlet  228 . Thus, once in the pathway  224 , cuttings  26  may not escape into a liquid pathway  230  of the housing  212 . 
     As further shown in this example, the liquid pathway  230  extends vertically through the shaker screen system  200  in an annulus between the cuttings pathway  224  and the housing  212 . The liquid pathway  230  includes an inlet  231  located under the screen  204  in order to receive the separated liquid  28  from the return drilling fluid  22 . In this example, the liquid pathway  230  include an outlet  240  to direct the liquid  28  to, for example, one or more mud tanks  36 . As explained in more detail later, liquid  28  (and small cuttings  26  entrained in the liquid  28 ) from the return drilling fluid  22  is separated from the return drilling fluid  22  and falls through the screen  204  into the liquid pathway  230 . In some examples, the liquid pathway  230  is formed of a tubular that extends between the inlet  231  and a bottom of the housing  212 . Thus, once in the pathway  230 , liquid  28  may not escape into an inner volume of the housing  212  or into the cuttings pathway  224 . 
     Turning to  FIGS.  4 B and  7   , these figures illustrate an example implementation of a locking assembly  268  of the shaker screen system  200 . For example, during non-operation of the shaker screen system  200  or, for example, to lock a particular screen section  206  (with a desired screen mesh size) at a desired location, the rotation assembly  208  may be locked against rotational movement, thereby also locking the screen assembly  202  against rotational movement. As shown in this example, the locking assembly  268  includes a plate  260  attached to the upper plate  250  and a plate  260  attached to the lower plate  258 . Each of the plates  260  includes a bore  262  there through. When the plates  260  are aligned, the bores  262  of the plates  260  are aligned to accept a locking pin  266  through the bores  262 . The locking pin  266 , once inserted through both bores  262 , locks the upper and lower plates  250  and  258  against rotational movement, thereby preventing rotational movement of the rotation assembly  208 . 
       FIG.  9    is a flowchart that describes an example method  900  for separating formation cuttings  26  from a liquid  28  in a return drilling fluid  22 . The example method  900  is described with reference to the shaker screen system  200  shown in the figures. Method  900  may begin at step  902 , which includes circulating a drilling fluid of liquid and formation cuttings to a screen assembly that includes a screen of multiple screen sections. For example, return drilling fluid  22  may be circulated to the screen assembly  202  of the shaker screen system  200  shown in the figures. The return drilling fluid  22  is comprised of liquid  28  and cuttings  26 . As shown in  FIGS.  2 - 3   , the screen assembly  202  includes multiple screen sections  206  of the screen  204 . In some aspects, the screen sections  206  have differing screen mesh sizes to allow for different sizes of the particles in the cuttings  26  to fall through the mesh. 
     Method  900  may continue at step  904 , which includes vibrating the screen assembly during circulation of the drilling fluid to the screen assembly. For example, as shown in  FIGS.  2 - 3   , the motor assembly  216  (for example, with electric motor  232  or other prime mover) may be started (and controlled by the controller  999 ) to vibrate the shaker assembly  200 . The motor  232  drives the motor gear  218 , which in turn drives the gear  222  through belt or chain  220 . As the gear  222  rotates, the shaker screen assembly  202  vibrates. For example, oscillation of the rotation assembly  208  (and likewise the screen assembly  202 ) may occur based on the operation of the motor assembly  216  to initiate vibration and also the springs  214  mounted below the rotation assembly  208 . In some aspects, initial operation of the motor assembly  216  may be sufficient to begin (and maintain) oscillation of the assemblies  208  and  202  by the springs  214 . In some aspects, continual operation of the motor assembly  216  may be needed to begin (and maintain) oscillation of the assemblies  208  and  202  by the springs  214 . In some aspects, the oscillation may be eccentric. 
     Method  900  may continue at step  906 , which includes which includes separating, with the screen assembly, the liquid from the formation cuttings. For example, as the return drilling fluid  22  is circulated to the screen  204 , the liquid  28  may be separated by failing through the screen sections  206 . The separated liquid  28  falls into the liquid pathway  230  and exits the housing  212  of the shaker screen system  200  at the outlet  240  (for example, to the mud tank  36 ). In some aspects, a portion of the cuttings  26  may also be entrained in the liquid  28  and fall through the screen sections  206  into the liquid pathway  230 . For example, one or more particular screen sections  206  may be selected based on or include a screen mesh size that allows certain size particles to stay entrained with the liquid  28 . As the screen assembly  202  rotates and the particular screen sections  206  receive the circulated return drilling fluid  22 , such smaller particles may pass through these screen sections  206 . 
     Method  900  may continue at step  908 , which includes separating a first portion of the formation cuttings of a first size from the drilling fluid with a first screen section of a first screen mesh size. For example, particles larger than those entrained with the liquid  28  may remain in the return drilling fluid  22  on the screen  204  until such particles are moved (for example, by vibration) to a first screen section  206  with a mesh size that allows the particles of the cuttings  26  to fall there through (to the cuttings pathway  224 ). Other, larger particles of the cuttings  26  may remain on the screen  204  as they do not fall through the first screen section  206 . 
     Method  900  may continue at step  910 , which includes directing the separated liquid through the screen assembly to a liquid outlet. For example, the separated liquid  28  falls into the liquid pathway  230  and exits the housing  212  of the shaker screen system  200  at the outlet  240  (for example, to the mud tank  36 ). In some aspects, of course, steps  908  and  910  may be performed simultaneously or substantially simultaneously. 
     Method  900  may continue at step  912 , which includes rotating the screen assembly. For example, in some aspects, the first screen section of the first screen mesh size may be desired to separate the formation cuttings of the first size from the liquid. But as the return drilling fluid may change consistency (for example, with different sized formation cuttings due to, for instance, a different rock formation). Thus, in some aspects, another screen mesh size (in a second screen section) may be desired at some point during method  200 . In some aspects, rotating the screen assembly includes unlocking the rotation assembly  208  to allow rotation of the rotation assembly  208 , and thus the shaker screen assembly  202 , to move the desired shaker screen section  206  to receive the return drilling fluid  22 . Once rotated, the shaker screen assembly  202  may be re-locked into position, for instance, by re-locking the rotation assembly  208 . 
     Method  900  may continue at step  914 , which includes separating a second portion of the formation cuttings of a second size different than the first size from the drilling fluid with a second screen section of a second screen mesh size that is different than the first screen mesh size. For example, the larger particles that do not fall through the first screen section  206  of step  908  may nonetheless be moved (for example, through vibration) to a second screen section  206  with a larger mesh size (in other words, larger holes in the screen section) relative to the first screen section  206  of step  908 . Once the larger particles of the cuttings  26  are moved to the second screen section  206 , such particles may then fall through the second screen section  206  to the cuttings pathway  224 . In additional aspects of method  900 , steps  912  and  914  may be repeated for each different screen mesh size of the different screen sections  206  of the screen  204 . 
     Method  900  may continue at step  916 , which includes directing the separated liquid through the screen assembly (the second screen section) to the liquid outlet. For example, the separated liquid  28  falls into the liquid pathway  230  and exits the housing  212  of the shaker screen system  200  at the outlet  240  (for example, to the mud tank  36 ). In some aspects, of course, steps  914  and  916  may be performed simultaneously or substantially simultaneously. 
     Method  900  may continue at step  918 , which includes directing at least one of the first or second portions of the formation cuttings to a cuttings inlet formed in the screen. For example, once the particles of the cuttings  26  fall through one of the first or second screen sections  206 , such particles may then enter the cuttings pathway  224  and exit the housing  212  to the waste pits  34 . 
     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, example operations, methods, or processes described herein may include more steps or fewer steps than those described. Further, the steps in such example operations, methods, or processes may be performed in different successions than that described or illustrated in the figures. Accordingly, other implementations are within the scope of the following claims.