Surface Machinery and Methods for Oil-Well Pumping Page: 93

POWER-TRANSMITTING MACHINERY.

In pumping with a power the frequency of stroke generally ranges
from 10 to 20 a minute, and the length of stroke from 10 to 24 inches.
However, some powers in the Texas oil fields have a 38-inch stroke
and make 19 strokes a minute. If in pumping with a power there is
a choice between a long slow stroke and a short rapid one, the former
usually gives the better results both in work at the well and in main-
tenance of equipment.
In pumping with a power the frequency of stroke is the same at
all of the wells. In some of the older eastern oil fields, wells attached
to the same power differ widely in the time required to pump then
off. These wells may be pumped only two or three times a week, and
at each pumping there may be some that pump off in about an hour,
others in about two hours and still others in three hours or more.
These differences are sometimes due to different sizes of tubing being
used but more frequently are due to the wells differing in yield.
Under such conditions, the length of stroke can be changed at some
of the wells by using a multiplier or by changing the relative length
of the power and weight arms of the jack; then by proper adjust-
ment all of the wells on the power can be pumped off in about the
same length of time.
MOTIVE POWER FOR GROUP PUMPING.
Steam, gas, or oil engines or electric motors, of 15 to 50 horse-
power, depending on the load to be handled, are used to drive power
pumping systems. Steam engines and gas engines have been used
for years; the more recent use of oil engines and electric motors has
proved fully as satisfactory and under certain conditions has been
much cheaper. The low maintenance and smooth running of electric
motors are particularly desirable features for power pumping and
for pumping " on the beam."
POWER REQUIRED PER WELL.
As a result of the use of purchased electric current for pumping,
attention has been given the amount of power consumed. By use
of the counterbalance and balanced load, the power needed for
pumping has been materially reduced, but attempts to calculate
the amount of power required to pump a well-by means of formulas
having variables covering size of tubing, amount of fluid, length
and freqnency of stroke, gravity of oil, amount of sand in suspen-
sion, depth of well, amount of gas, and balanced or unbalanced
load-have not been at all satisfactory. Many shallow wells will
require more power than deep wells. In other ways results as to
power requirements will be obtained that do not agree with the
conditions supposed to exist at the well.

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