Page 108 - Shale Shakers Drilling Fluid Systems

CHAPTE R TW O

The Role of Shale Shakers

Shale shaker is a general term for a vibrating from statistical data the size and number of shale
device used to screen solids from a circulating shakers required to drill a particular well, as well
drilling fluid. Many configurations have been used, as the mesh size of the shaker screens used for
including: any portion of any well. However, due to the large
number of variables involved, these data simply
• A square or rectangular screening area with do not exist. Many shale shaker manufacturers,
drilling fluid flow down the length because of customer demand, publish approximate
• Revolving, nonvibrating, cylindrical screens flow charts that indicate their shakers can process
with longitudinal flow down the center axis a certain flow rate of drilling fluid through certain
• Circular screens with flow from the center to size screens. These charts are usually based on
the outside general field experience with a lightly treated,
water-base drilling fluid and should be treated as
The majority of shale shakers flow the drilling approximations at best.
fluid over a rectangular screening surface. Larger Rheological factors, fluid type, solids type and
solids are removed at the discharge end, with the quantity, temperature, drilling rates, solids/liquid
smaller solids and drilling fluid passing through the interaction, hole diameters, hole erosion, and other
screen(s) into the active system. All drilled solids variables dictate actual flow rates that can be pro-
above 74 microns are considered especially undesir- cessed by a particular screen. Drilling fluid with-
able in any drilling fluid. For this reason, 200-mesh out any drilled solids can pose screening prob-
(74 microns) screens are extremely desirable on lems. Polymers that are not completely sheared
shale shakers. Weighting materials that meet API tend to blind screens and/or appear in the screen
specifications may still have 3% by weight larger discard. Polymers that increase the low-shear-rate
than 74 microns. Screens this size may remove large viscosity or gel strength of the drilling fluid also
quantities of barite, which may significantly impact pose screening problems. Polymers, like starch,
the drilling fluid cost, but may decrease well cost. that are used for fluid-loss control are also diffi-
Shale shakers are the most important and easi- cult to screen through a fine mesh screen (such
est to use solids removal equipment. In most cases, as 200 mesh). Oil-base drilling fluids without
they are highly cost-effective. However, if shale adequate shear and proper mixing are difficult
shakers are used incorrectly, the remaining solids to screen, as are oil-base drilling fluid through
removal equipment will not perform properly. screens finer than 100 mesh without sufficient oil-
A shale shaker can be used in all drilling wetting additives.
applications where liquid is used as the drill- Screen selection for shale shakers is dependent
ing fluid. Screen selection is controlled by the on geographical and geological location. Screen
circulation rate, shaker design, and drilling combinations that will handle specific flow rates
fluid properties. Variation in drilling fluid proper- in the Middle East or Far East, for example, will
ties control screen throughput to such a large not necessarily handle the same flow rates in Nor-
degree that shaker capacities are not included in way or the Rocky Mountains. The best method to
this handbook. select shale shaker screens and/or to determine the
Most operations involved in drilling a well can number of shale shakers for a particular drilling site
be planned in advance because of experience and is to first use the recommendations of a qualified
engineering designs for well construction. There- solids control advisor from the area. Screen use
fore, well planners expect to be able to determine records should be established for further guidance.

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