Surface Machinery and Methods for Oil-Well Pumping Page: 96
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96 SURFACE MACHINERY AND METHODS FOR OIL-WELL PUMPING.
submergence. (2) The total vertical distance from the point of admission of
air to the point of discharge, the ratio between these two quantities repre-
senting the percentage of submergence. (3) The lift or distance from the sur-
face of the liquid to the level of discharge. (4) The air pressure. (5) The
pressure of gas in the well. (6) The gravity of the oil. (7) The percentage
of water in the oil. (8) The quantity of sand in the oil. * * *
The quantity of air should be carefully regulated, the best results being
obtained with the minimum volume of air necessary to cause the liquid to flow
in a constant stream. Owing to the extra pressure needed to overcome the
friction and inertia, the starting pressure is about double the working and cal-
culated air pressure. The variations in the level of the liquid in the well are
indicated by pressure gages on the compressor and air side of the valve that
controls the air supply.
The gas that sometimes accompanies the oil helps the action of the air
lift by diminishing the required air pressure, and in order to utilize all the
available gas pressure it is customary to place a packer between the tubing
and the casing, thus forcing the gas to flow through the discharge pipe. Wells
of the same depth may require different pressures, and in order to obtain the
best results a careful study of the special conditions will be desirable.
In most fields where the use of compressed air proves most beneficial, the
oil and water occur in somewhat well-defined layers-a lower indefinite layer
of water, an upper one of nearly pure oil, and an intermediate layer consisting
of a mixture of oil and water. In nearly all such fields the water surface stands
at a well-defined plane; below, water is obtained, above, the percentage of pure
oil increases with the distance above this plane. It is possible, therefore,
providing the necessary submergence is available, to pump either water or
oil, or, within limits, any combination of the two, by regulating the location
of the air inlet in relation to the water surface. If air is admitted to a stratum
where water and oil are mixed the churning action caused by the air has a
tendency to mix them more thoroughly and to form emulsions. This result
is avoided sometimes by pumping the water and oil in the same well separately,
using the air lift for the water and removing the oil by means of a plunger
The conditions under which the use of an air-lift pump becomes advisable
can be ascertained only after a careful and intelligent analysis of all factors
affecting the operation of the property, and usually it will be found economical
to seek the advice of a competent mechanical engineer before incurring the
necessary expense for development. The high initial cost renders the selec-
tion of compressed-air machinery of special importance, and the proper choice
and disposal of air lines and well tubing, the regulation of air pressures, and
the proper determination of the many factors involved in power-plant eco-
nomics are each problems of such importance that their solution can be best
determined by a technically trained man familar with local conditions.
In general, it may be stated that air-lift pumping in the oil fields should
be used as a last resort when the ordinary methods are no longer effective,
and should be restricted to territory where considerable water accompanies
the oil and there is ample submergence.
A number of years ago the air-lift system was much used in the
Kern River oil field, California, where conditions favored its suc-
cessful operation. The wells in the field average about 1,000 feet
in depth and produce an oil with gravity of about 14o B.; at many
wells the production is 80 to 85 per cent water. Most of the air
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George, H. C. Surface Machinery and Methods for Oil-Well Pumping, report, 1925; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc12407/m1/125/: accessed June 28, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.