Underground Wastes in Oil and Gas Fields and Methods of Prevention Page: 26
iii, 3-28 p. : ill. ; 25 cm.View a full description of this report.
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26 UNDERGROUND WASTES IN OIL AND GAS FIELDS.
column of mud-laden fluid is maintained behind the casing, and the
operator, if he so desires, can usually unseal a sand by removing the
fluid, provided the rock pressure is great enough to force the mud out
of the sand after the restraining pressure of the column of fluid has
been taken off. By means of this system, any oil, gas, or water-
bearing sand penetrated by the well can be sealed off, whether of
immediate value or not, and preserved for use. Furthermore, danger
from corroded casing is lessened and the danger from the unsys-
tematic use of either casing or packers, is eliminated.
ADVANTAGE OF MUD-LAI)EN FLUID M'ETIIOD.
The cost of applying the method, which must be added to the first
cost of drilling the well, can be kept low and is compensated by the
probably greater cost of satisfactory alternative methods of drilling,
more casing can be recovered after the well is finished, and casing left
in the hole is protected from corrosion by water. The method 'is
simple and is easily applied; it can be used under almost any condi-
tions, the materials for making the mud can in most places be
obtained near the well, and little extra equipment is necessary. The
formations penetrated can be permanently sealed off; ordinarily a
formation can be unsealed if so desired, and all strata are sealed in
whether they are of value at the time of drilling or not.
The method is self-testing; that is, if mud-laden fluid is placed
behind a casing and a defect develops, it makes itself evident at
once, and the operator can always know whether the hole is in good
condition or not. In this respect the method has an especial advan-
tage over other methods and in particular over sealing with packers.
The mud-laden fluid will not work through loosely screwed joints
in the casing as readily as water, which will not only seep through,
but will enlarge the leak and weaken the joint by rusting the threads.
All danger from unsystematic casing or the use of packers is elimi-
nated, and the field is left more nearly as it was before development
than by any other system; that is, practically as a sealed reservoir.
If it is desired to drill a well through an oil or gas sand, the lower
part of which carries water not separated by a break or parting from
the oil or gas, drilling with mud-laden fluid is usually the only way
to protect the sand. For drilling into a sand containing gas under
high pressure, the mud-laden fluid is often the only method that can
be employed to drill in and complete the well without first reducing
the rock pressure by permitting the gas to waste either into the
atmosphere or into porous underground formations. Furthermore,
the well can be handled with less danger, expense, waste, or chance
of losing control. In no other way now known can a well be drilled
through a gas sand without waste or damage. By the use of mud
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McMurray, William F. & Lewis, James O. Underground Wastes in Oil and Gas Fields and Methods of Prevention, report, July 1916; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc66456/m1/30/: accessed April 20, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.