94 SURFACE MACHINERY AND METHODS FOR OIL-WELL PUMPING.
Wells pumped on the beam seem to show the greatest variation
in power requirements. Here the requirements range from less
than 1 horsepower to more than 20 horsepower, depending upon the
depth of the well and other conditions. In many oil fields where
wells average more than 3,000 feet in depth and the oil has high
viscosity, the general power requirements seem to range from 4
to 8 horsepower when the wells are pumped on the beam and
a counterbalance is used.
Some oil-field operators estimate 2.5 horsepower as the average
power required per well when the wells are pumped by a central
power or jack plant with a well-balanced load. However, the power
requirements for this method of pumping range from less than 1 to
more than 5 horsepower per well.
The power required for bailing, swabbing, or pulling of rods
and tubing at the well is from two to three times that required for
SYSTEMS BASED UPON THE USE OF COMPRESSED AIR.
Although compressed air as a source of power for pumping is
less efficient than steam or gas engines, or electricity, sometimes its
use is warranted, as when compressed air is already used extensively
for some other purpose is available, and when efficiency can be sac-
rificed to quantity production.
The use of compressed-air pump heads and direct-displacement
pumps is an example of the former, and the air-lift system is an
example of the latter.
COMPRESSED-AIR PUMP HEADS.
On some properties at Bradford, Pa., compressed, air is piped to
each of the wells to be pumped, and there it is delivered to an air-
pump head attached to the tubing above the casing head.
The piston rod of this air cylinder also acts as the polish rod of
the well. The air enters the vertically placed cylinder below the
piston, forcing the piston to the upper end of the cylinder. This
produces the upstroke or the lifting stroke of the working valve
and rods. When the upstroke is completed, the compressed air in
the cylinder is released; then the valve and sucker rods drop and
produce the down stroke by gravity. Air is again admitted to the
lower end of the cylinder and the process is repeated.
Direct-displacement pumps displace the oil in the well by an
equal volume of air; the air pressure used corresponds to the height
of lift. This system is used extensively in connection with the
George, H. C. Surface Machinery and Methods for Oil-Well Pumping. Washington D.C.. UNT Digital Library. http://digital.library.unt.edu/ark:/67531/metadc12407/. Accessed March 1, 2015.