DRILLING THE OIL WELL
Methods of well drilling differ in various regions in accordance with
the special problems to be encountered and perhaps no other industry
furnishes more examples of mechanical ingenuity in the solution of
physical difficulties. Drake went about the business of drilling
the first well by using the traditional methods of boring for salt.
Improvement was inevitable, however, and the Canadian wells of Western
Ontario, which came into existence almost contemporaneously with those
of Pennsylvania, were fruitful of inventions which have influenced
drilling practices in many parts of the world. If we go back to the
origins of oil and salt drilling mechanisms we find ourselves in China
centuries before the Christian era. The Chinese used an auger attached
to a pole that was held in a vertical position from a cross pole
supported on a post. The end of the cross pole was fastened to a lever
while a driller guided the cable to which an auger or boring tool was
attached. Several coolies jumped from a platform on to the reverse side
of the board, so that the tool would be jerked up and would plunge
down and thus deepen the hole with each stroke. The deeper the hole
became, the more coolies required for the task of “kicking down.”
Jumpers were not a part of the staff of an oil-drilling organization
in America in the early days but foot power was sometimes employed for
the same purpose of driving the drilling tools into the ground. To-day
labour-saving machinery plays as great a part in well drilling as in
other branches of industry.
Let us suppose then that an oil company, or an individual with the
requisite capital at his back, has advanced through the preliminaries
which must precede drilling operations; the geologists have made a
favourable declaration as to the prospective site; the leases and
royalties have been arranged and the title is secure. When it is
decided to start drilling, roads are built, water lines laid, and the
lumber, casing machinery and other equipment are hauled to the location
(often under very primitive and difficult conditions). The apparatus
most commonly installed under these circumstances is the Pennsylvania
cable system, which consists of a standard derrick or rig, built
of wood or steel, about eighty feet in height, having a twenty-foot
base and a four-foot top. The strength of the derrick is conditioned
entirely by the size and depth of the well the operator wishes to
drill, for nowadays nothing is left to chance. The size of the hole
necessary in starting a well depends upon the physical formation. If
it is soft, it is necessary to start with a hole of large diameter, to
overcome the disabilities produced by caving. It sometimes happens that
soft formations cave so much that it is necessary to insert several
columns of casing before the required depth is reached. A hole with a
large diameter is also used in deep drilling.
[Illustration: The Drader Well in the Moreni field, Roumania. This well
was producing 20,000 barrels daily when it caught fire]
[Illustration: Burkburnett in northern Texas, showing development since
August, 1918]
The drilling equipment is called by the oil workers a “string of
tools.” It consists of a rope socket, a stem or sinker about thirty
feet long and five inches or more in diameter, depending on the size
of the hole to be drilled, with a bit at the bottom. Attached to a
string of tools is a set of what are known as “jars,” which take their
name from their function of enabling the driller to jar the sinker
loose. Manila or wire cable is wound upon a large reel known as the
“bull wheel” which is placed in the base of the derrick and a section
of this cable passes over a crown pulley at the top of the derrick
and is fastened to the rope socket and “string of tools.” The drilling
movement is created by a power-driven walking beam which is a heavy
timber working on an axis. This walking beam rocks up and down, with
a stroke of three or four feet; thus the tools are raised and dropped
at regular intervals, their great weight giving them a stroke equal
in force to a steam hammer. The power used is ordinarily steam and
the cable is connected with the walking beam by a temper screw, which
enables the driller to lower the tools and handle them with ease and
accuracy.
Another method of growing importance is the rotary system, perfected
within the present century in the Gulf Coast field of Texas and
Louisiana and which in many sections is coming into common use. Its
special advantage is speed in soft or caving formations. It consists
of a perforated fish-tail bit screwed to a string of drill pipe, which
projects up through the derrick platform and is rotated at the rate
of about two hundred revolutions per minute by a turn-table. The top
or “grip” joint of the pipe is usually made square, or hexagonal,
to supply a good bearing surface for the turn-table. The tools are
suspended by means of a swivel at the top of the grip joint. This
swivel also has a hose connection through which thin mud is pumped down
to the bottom of the hole. The circulation of this mud carries out the
cuttings made by the fish-tail bit, and also serves to plaster up the
side of the hole and thus prevent caving. The column of mud in the
hole exerts a hydrostatic pressure which absolutely prevents quicksand
from running in and causing the hole to collapse. A rotary appliance
has been known to drill two hundred feet or more in twelve hours, but
usually so high a rate of speed is impossible, since the pipe stem has
to be pulled out at frequent intervals and the bit replaced. The fact
that the delicate fish-tail bit grows smaller with wear creates this
necessity.
Another periodical process that must be carried on in the intervals of
drilling is that of lining the hole with casing, in order that water
and caving strata may be cased off before the oil sands are reached.
After a well is operating, the lower part of the casing may rust
through, causing leakage. To meet this difficulty an inner casing is
put in place with a casing shoe, on the outside of which is lead or
other soft material which expands under pressure from above to make a
snug fit. Not infrequently, it is necessary to decrease the size of
the hole with packers in this way four or five times, though it is kept
as large as is practicable all the way down.
When oil is struck it is sometimes suddenly driven to the surface by
imprisoned gas, and another gusher, a comparatively common phenomenon
in Mexico, is recorded. But if this condition does not arise,
tubing and pump are inserted and the oil is drawn to the surface.
Not infrequently, however, the oil sands at the outset do not yield
an adequate flow and in a great number of cases what is known as
“shooting” with nitro-glycerine, an interesting and once dangerous
process, is resorted to. In the early days before oil production had
been reduced to scientific formulas the obtaining of crude was often
attended with serious hazards to life. Ignorance of the properties of
petroleum also created imaginary dangers for the pioneers. In 1860
the people of Western Pennsylvania were thrown into a panic by the
proposal of a stranger, claiming to be a European scientist, to shoot
a white-hot bolt into the bowels of the earth through an iron pipe
driven to a great depth for the purpose. By the ignition of inflammable
gases thought to exist in the great cavities beneath the earth’s crust
the promoter expected to produce a sufficient explosion to lay bare
the subterranean reservoirs of oil. The Pennsylvania populace, instead
of viewing this proposal with the apathy usually accorded to the
first essays of inventive minds, possessed sufficient imagination to
picture the possible results, and were so convinced that the alleged
scientist minimized the possibilities of his project that they selected
a small but determined committee to lynch him. Because he threatened to
undermine not merely the foundations of society but the ground on which
society subsisted, he was taken into custody by the authorities and
solemnly warned to desist.
Less than a year afterward nitro-glycerine was being exploded in large
quantities down deep in the earth to shatter the oil-bearing rock and
make wells flow, without noticeable public or physical disturbance.
Any one who has watched farmers blow up tree stumps with dynamite may
imagine what effect eighty quarts of nitro-glycerine would produce
at the bottom of a deep eight-inch well. The “oil-shooters” are
necessarily men of steady nerve and extreme caution. A shot will vary
from ten quarts to as much as three hundred quarts, as the well to be
treated may seem to require. For this purpose the nitro-glycerine is
contained in tin tubes or shells five feet long and two inches or more
in diameter, pointed at the lower end and having bail handles at the
top. From five to fifteen shells, as the case may be, are lowered into
the hole with extreme delicacy, and then the “go-devil”--a five-pound
pointed shell--is released point downward. Nowadays, it is customary
to use a nitro-glycerine squib wound with a long fuse more often
than a “go-devil,” since the lowering of the cans of explosives may
loosen earth which forms a cushion above the shells. An example of the
presence of mind of a well shooter was provided a few years ago. Just
after the first shell had been lowered, the rope suddenly slackened.
This could only mean that the well had unexpectedly begun to flow and
that in the space of a few seconds the shell containing six quarts of
deadly explosive would be hurled from the well mouth. There was no time
to run and the only thing that could be done this “well shooter” did.
Bracing himself directly over the well he grasped the shell as it came
to the surface, and although the impetus with which it had ascended
threw him across the derrick and dislocated his shoulder, he held it
free from contact and saved the lives of the entire crew.
Under the careful arrangements now made, a well is controlled with no
more loss of oil than the driller thinks necessary to flush out the
dirt and debris caused by the explosion.
The early or flush production of a well is usually of considerably
greater volume than its normal or settled flow after it has been in
operation for a few weeks. This decline in production is often as much
as 50% in the first 30 days. Where wells do not flow naturally, various
devices can be used to stimulate the output. Gas pressure has much to
do with the problem. As a general rule the well of low gas pressure
must be pumped from the beginning. The “gusher” which is the result
of high gas pressure usually recedes rapidly in the matter of flow
and becomes what is known as a “pumper,” the name given to wells when
pumping is resorted to.
The minimum of flow at which a well ceases to be profitable varies
according to location, and is fixed by many conditions of which
transportation and quality are the most important. Thus, in Mexico,
a well yielding only fifty or one hundred barrels per day is usually
abandoned as uncommercial, whereas in Pennsylvania and West Virginia,
where the facilities for handling are better, there are thousands of
old “pumpers” in operation producing a superior grade of oil, many of
which supply only one-fourth of a barrel per day.
The production of the first well drilled on a new location fixes the
policy to be pursued with regard to the rest of the acreage under
lease. After it has been tested and proven to be satisfactory the
remainder of the property is drilled as quickly as possible. If the
field is shallow and the wells are all “pumpers,” a central power
station operated by gas or gasoline is sometimes installed which
may provide the energy for pumping as many as a dozen wells. The
shackle-rods spread out over the field like a spider’s web, and the
rhythmical “chug-chug” is music to the ears of the oil man and also to
the farmer who has leased the oil rights to him--for the song of the
pumping plant symbolizes fat royalties.
It will be clear to the reader that even in the initial process the
production of crude petroleum under modern standardized processes
which eliminate, so far as possible, waste of labour or of product,
involves a considerable capital expenditure. The cost of a well in a
new district, where the depth is likely to be in the neighbourhood
of three thousand feet, may amount to considerably more than $50,000
and a year may pass in the process of drilling. In the case of deep
wells a permanent derrick is built, but in earlier days, for shallower
holes a portable drilling machine was used, and with good fortune oil
was often reached within a short time and the cost kept well within
a margin of $5,000. It will be remembered that in the original Drake
well at Titusville, oil was struck at sixty-nine and a half feet and
that it took seven months to drill the well; a concrete illustration
of the improvement in methods which has transpired in sixty years. But
the days of cheap drilling have passed into the limbo of half-forgotten
things and there is practically no oil production at the present time
which does not represent a very considerable initial outlay.