SHALE SHAKER’S DEFINITION. The purpose of a shale shaker is to remove large drilled solids from the drilling fluid. The shale shaker is the first piece of solids-control equipment to treat or condition the drilling fluid. Good shaker performance is necessary if the entire system is to function at or near design efficiency or capability. Shakers now come in a dazzling assortment of sizes, shapes, and motions. Their performance is controlled by the size(s) and shape(s) of the openings in the screen(s), the drilling-fluid properties, the amount and type of cuttings arriving at the shaker, and the general mechanical condition of the equipment.

The shaker selected for your rig may or may not be the best for the drilling at hand. Unfortunately,


if it is not, it must still be kept operational, and with intelligent, conscientious work perhaps can be made to do the job. All commercial shale shakers, however, remove cuttings—and they remove cuttings better when properly maintained and operated. Obviously cuttings cannot be removed until the drilling fluid first brings them to the surface. Solids coming off the end of shaker screens should have sharp edges. Cuttings that ‘‘roll around’’ in the borehole on the way to the surface have rounded edges. Rounded edges, or round cuttings, indicate that the cuttings are not being transported directly to the surface as fast, or directly, as they should be. The driller and/or mud engineer should be advised as to the shape of the cuttings coming over the shaker in regard to round edges. Rounded-edge cuttings indicate that there are many drilled cuttings stored in the annulus. This increases the mud weight in the annulus and the pressure at the bottom of the hole.


The excess pressure significantly decreases the drilling rate and cuttings removal from beneath the drill bit. Eight general rules to assure shale shakers will work properly and remove cuttings:

  • The shale shaker should be run continuously while circulating. Cuttings cannot be separated if the shaker bed is not in motion.
  • Fluid should cover most of the screen. If only one quarter or onethird of the screen is covered, the screen is too coarse and should be replaced with a finer screen.
  • If fluid flows through a hole or tear, cuttings are not removed. Any screen with a hole or tear should be replaced immediately. With a panel screen, the hole or tear can be plugged.
  • Shaker screen replacements should be made as quickly as possible. Minimize downtime by planning your work. Locate and arrange tools and screens before starting. If possible, get help. This will decrease the amount of cuttings being kept in the mud because the shaker is not running. If possible, change screens during a connection. In critical situations, drilling may be interrupted and the pumps stopped while the screen is replaced.
  • Dilution fluid (water or oil) should not be added in the possum belly or on the shaker screen.


    Dilution fluid should be added downstream. Dilution-fluid (even water) additions should be metered or otherwise measured.

  • Except for cases of lost circulation (when it is necessary to retain lost circulation material), the shaker should not be bypassed, not even for a short time.
  • Large cuttings should be removed from the possum belly when mud is not being circulated. If the possum belly is dumped into the sand trap just before making a bit or wiper trip, the sand trap should also be cleaned. Otherwise, when fluid circulation starts after a trip, the large cuttings dumped into the sand trap will likely move down the pit system and plug desilters or desanders.

 Note: The possum belly and/or sand trap is not always used with synthetic-based mud or some specialized fluid systems.

  • As much as possible, flow from the well (bell nipple) should be evenly distributed among all the shakers.


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