STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

654 Drilling and Well Completions
RPM SETTING
Figure 4-107. Typical flow curve of mud using a direct-indicating viscometer.
API Filtration. A filter press is used to determine the wall building characteristics
of mud. The press consists of a cylindrical mud chamber made of materials
resistant to strongly alkaline solutions. A filter paper is placed on the bottom of
the chamber just above a suitable support. The filtration area is 7.1 ( fO.l) in.2.
Below the support is a drain tube for discharging the filtrate into a graduate
cylinder. The entire assembly is supported by a stand so that a 100-psi pressure
can be applied to the mud sample in the chamber. At the end of the 30-min filtration
time volume of filtrate is reported as API filtration in milliliters. To obtain
correlative results, one thickness of the proper 9-cm filter paper, Whatman No. 50,
S&S No. 5765, or the equivalent, must be used.
Thickness of the filter cake is measured and reported in t of an inch. Also,
the cake is visually examined and its consistency reported using such notations
as “hard,” “soft,” tough,” “rubbery,” or “firm.”
Sand Content. The sand content in mud is determined using a ZOO-mesh sieve
screen 24 in. in diameter, a funnel to fit the screen, and a glass measuring tube.
The measuring tube is marked for the volume of mud to be added to read
directly the volume percent of sand on the bottom of the tube.
Sand content of the mud is reported in percent by volume. Also reported is
the point of sampling, e.g., flowline, shaker, suction, pit, etc. Also, solids other
than sand may be retained on the screen (lost circulation material, for example)
and the presence of such solids should be noted.
Liquids and Solids Content. A mud retort is used to determine the liquids
and solids content of the drilling fluid. Mud is placed in a steel container and
heated until the liquid components have been vaporized. The vapors are passed
through a condenser and collected in a graduated cylinder, and the volume of
liquids (water and oil) is measured. Solids, both suspended and dissolved, are
determined by volume as a difference between mud in container and distillate
in graduated cylinder.
Specific gravity of the mud solids Ss is calculated as
lOOS, -(vw +O.~V,,)
s, = (4-44)
vs