Page 31 - Shale Shakers Drilling Fluid Systems

14 SHALE SHAKERS AND DRILLING FLUID SYSTEMS

vanized iron trough. The ditch or trough leading to the screen caused by the action of the snail house springs. The action
from the well is the same width as the screen, with diamond- is very smooth at regular running speeds.
shaped wooden blocks placed just ahead of the short drop onto The vibrating screen frame should not touch the mud ditch,
the screen to insure even distribution. the constant action causing leaks under ordinary circumstances.
The screen is naturally placed immediately above the ditch The same applies to the screen frame supports. It is a simple
carrying the mud back to the pits for recirculation, the re- matter to support the screen above the ditch,
claimed fluid and that suitable for further use dropping When the installation was first made, the sand and cutting
through the screen and flowing by gravity to be picked up by were allowed to fall near the bottom of the screen. This
the pumps. The terrain is ideal at Moco 218-B for the installa- necessitated almost constant removal of these cuttings and
tion but similar layouts could be used in almost any location.
added to labor costs. The galvanized iron trough was installed
The motor and screen are kept in operation as long as circu- and enough water played on the drop at the lower end of the
lation is maintained but are stopped when the shutdown in- screen to carry the!coarse materials to a safe distance. This
volves any appreciable period. The screen gets its action from eliminated the extra labor cost. The well has the natural ad-
the belt-driven motor but its efficiency is attributed to the snail vantage of a hillside location, however, besides being far re-
house springs. The vibration is so intense when the motor has
moved from an inhabited district. It might be possible to
attained its full speed that it approaches a musical hum. The design the proper decline at any -well, the flow of water
eye cannot detect its action but a touch with the foot or hand partially governing the efficiency of the removal. When certain
gives an idea of the vibration. The heart of the cleaning action
formations were drilled through, the sand and shale cuttings
lies in the snail house springs supporting the screen frame. accumulated at a rapid rate, giving some idea of the reasons
The engineer who designed the screen for oil field use for former pump repairs and addition of fresh mud.
worked for some time to obtain an elliptical motion. This was
When this article was prepared, the installation had been
found to be the most desirable for removing the coarse par-
ticles as well as causing the mud to drop through without in use 920J/2 hours. During the time, the screen cloth had
hesitation. The four by five screen seems to be the ideal size been replaced four times. There was no further cost of re-
for an individual well. placements. The operating cost, which included chiefly power
and water, was about $2 per day. The same mud had been
The action of the screen is familiar to industrial engineers
who have used them in other industries, but the average petro- used since July 23, the date of installation, without interrup-
leum engineer has been given a chance to study the installation tion or substantial additions. No pump parts have been re-
placed during the period, while the pump had not lost suction
only during the past year. By mounting the screen frame to
the center of the snail house springs, it is obvious that a motor during drilling operations.
driving a pulley solidly attached to the frame would bring The elliptical action of the screen causes a portion of the
about the vibrating action, which might be. termed a takeoff materials not wanted in the mud to form into small balls.
from the age-old sifter action. These balls often carry a percentage of very fine sand which
Steam turbines have been used on other installations and might otherwise find its way through the screen.
may even be used on this particular layout, but the crew is A large by-pass around the vibrating screen has been in-
optimistic over the uniform action caused by the electric motor. stalled for emergenices. It empties into the ditch below the
A flat endless belt is used, but future installations will carry screen.
"V" belts. The motor is mounted on slide rails and adjust- The average cost of changing rotary drilling mud in the
ment of the belt is a simple matter. When the motor is started Maricopa district runs between 40 and SO cents per barrel;
or stopped, the screen and frame pass through critical periods so it is evident that constant reclaiming of the original mix-
of speed, vibrating vigorously for a few seconds. This is ture is a very profitable practice.

Side tnew of installation, showing mud ditch leading to sump, galvanised trough for carrying
away cuttings and sand, and by-pass