HOW PETROLEUM IS PRODUCED
Time was when the engineering aspect of the production of petroleum
was practically non-existent. The ancients, and even those of the last
century, were content to resort to the most primitive means for winning
petroleum from the earth. Shallow wells were sunk or dug by hand, the
eventual securing of the oil being carried out by lowering primitive
receptacles (generally leather bottles) into the hole. It was a period
long before the advent of the Oil Age, and the methods employed were
clearly in keeping with the mode of life of that day. In practically
every oil-producing field of the world--though in this respect the
United States is almost an exception--the history records the fact that
for many years the extraction of oil from the ground was confined to
the use of the primitive methods which held sway in those days--those
associated with the operations of the hand-dug wells. In the Far East,
notably in Japan, we find the first serious attempts to obtain and
utilize petroleum, for as far back as A.D. 615, there were shallow
wells in existence, from which the “burning water,” as it was called,
was collected. In Roumania and Russia, too, the earlier attempts to
create a petroleum industry were confined to these methods.
It was only when the demand for petroleum became large and consistently
increased with the opening up of new fields, that we find other and
more practical methods were introduced for winning larger quantities
of the oil from the earth. To-day, in every branch of the industry
associated with petroleum--whether it be in producing the crude
oil, in transporting it, or in refining Nature’s product into those
numerous commodities which are part and parcel of everyday life--the
engineering aspect is one of very great importance. In fact, throughout
the petroleum industry, engineering science is the Alpha and Omega. By
its means we are now able to carefully study the nature of the ground
at depths of 6,000 feet, and to extract from the deep lying strata a
wealth of minerals; we are able, too, to transport thousands of tons of
crude oil daily across thousands of miles of continent, while is it not
the direct result of engineering science which allows over 15,000 tons
of petroleum products to be carried across the oceans of the world in
one vessel with the same ease that one would take a rowing boat from
one side of a lake to another?
Great, however, as have been the degrees of progress recorded in
connection with drilling for petroleum, the old methods, generally
speaking, and which date back to the days of early China, are still
largely copied in all pole and percussion systems of drilling, and
though steam has replaced manual labour (and electricity now bids
fair to replace steam), the operating principles to-day are the same
as then. The only exception, of course, is the advent and growing
popularity of the rotary method of drilling, to which interesting phase
of the subject I will briefly refer later.
The old Eastern method of drilling has obviously been the forerunner
of the Canadian, standard, and other systems of to-day, the wire rope
replacing the use of poles. In oil-field work, the principal types
of percussion drills used are known (1) as the Pennsylvanian cable,
(2) the Canadian pole, and (3) the Russian free-fall system, and
though from time to time many attempts have been made to introduce
modifications of these, the vast majority have been unsuccessful in
their operation.
The Pennsylvanian cable system was used for drilling the earliest
oil-wells in the United States, and doubtless took its name from the
fact that it was so largely used in that oil region. As may also be
gathered from the name, the principal feature in this system is the
cable by which the tools are suspended and connected to the walking
beam. There is no doubt that this system of drilling, which has been so
universally used in the oil-fields, gives most satisfactory results.
When first introduced in Pennsylvania, the cable system of drilling
was particularly simple, and did remarkably good work, for the reason
that the strata usually encountered was of such a nature that it did
not cave, and, as a result, the well-pipe was only lowered when the
full depth of that string had been drilled. The drilling bits were
seldom more than 4 inches thick. In order to give a rotary motion to
the bit, the continuous twisting of the cable to and fro was necessary;
but when in other fields, where deeper strata had to be explored, the
cable system was introduced, the semi-sandy nature of the strata called
for wells of larger diameter with correspondingly larger drilling
bits. As a consequence of the additional weight of the drilling bit,
it was found that the swing of the tools was sufficient to give them a
rotating movement for the drilling of a circular hole. In regions where
caving-in of the walls of the wells was liable to occur, the string of
pipe had to closely follow the tools, which, with the old Pennsylvanian
type of rig, meant frequent winding of the cable from the bull wheel,
so as to allow of the well pipes being handled.
In order to prevent the waste of time which these operations
occasioned, the calf wheel was added, by means of which the pipe could
be lowered into the hole without the removal of the drilling cable.
This cable almost invariably was of the Manila character, and in many
instances this rope is retained to-day, though wire ropes have been
introduced frequently.
The Canadian pole system, which is largely in use in oil-field
operations, is, like the first-mentioned method of drilling, of the
percussion type, the chief essential difference being that, instead of
a cable connecting the tools to the surface, poles are used. In former
times, these poles were of ash-wood, but with the extended use of the
system, iron rods took their place. The introduction of these iron rods
was a distinct advantage, for they could be welded to whatever lengths
are required, whereas the wooden poles, which were seldom more than
20 feet long, had to be spliced for practical work. The rig used with
the Canadian system is not so powerful as that for the Pennsylvanian
method, but the one great advantage of the Canadian system is that,
for the drilling of shallow oil-wells, it could be operated by men of
less experience. The success which has attended the operation of the
pole system lies in the fact that although drilling by its means is
very slow--for seldom is 250 feet per month exceeded--it is one of the
best methods of drilling through complicated strata, and, in the hands
of conscientious men, does highly satisfactory work. It might be of
interest to very briefly refer to the operations of the system when
a well is being drilled. The rig (that is, the superstructure above
ground) is quite a simple framing, 70 or more feet high, with a base
of about 20 feet. The power is usually derived from a steam engine,
with the usual means for operating the gear from the derrick; fuel
found locally, natural gas, or other form of heating agent used. One
shaft and two spools running in bearings transmit the various motions
desired, the drive being taken up by a pulley attached to the main
shaft. On this shaft are keyed two band pulleys, which communicate by
belting with two spools running immediately overhead in the upper part
of the framework. Fastened to one extremity of the main shaft is a
disc crank, which, through the medium of a connecting rod, transmits
an oscillating movement to an overhead pivoted walking beam. In all
systems of percussion drilling, the drilling bit is raised and then
dropped a distance of several feet, the result being that the strata to
be drilled are steadily pounded away. As the ground is pulverized by
the percussion tools, the debris has to be cleared away so as to enable
the drill to fall freely and to deliver clean blows to the unbroken
strata, and this work is performed by appliances known as bailers and
sand pumps. There is no need for me to go into the numerous technical
details regarding this or any other system of drilling, for my only
desire is to give a general impression as to the usual methods adopted
for the winning of petroleum.
I will therefore pass on to deal briefly with the Russian free-fall
system so much in vogue in the Russian fields. Incidentally, I may
here say that when drilling for oil in Russia, one has to recollect
several features which are not common to the development of other
oil-fields. Bearing in mind the great depth to which wells have to be
sunk to reach the prolific oil horizons in the majority of the fields
in Russia, which necessitates starting the well with a very large
diameter--frequently 30 inches--it will be easily appreciated that the
loss of a hole in the course of drilling is a very expensive affair.
The Russian free-fall system of boring necessitates patient and hard
manual labour. It is, as its name implies, of the percussion type, and
is, in fact, a modified pole-tool system which well suits the local
conditions. The clumsy drilling tools have a practically free drop,
being picked up when the walking beam is at its lowest point, and
released at the top of the stroke. When released, the tools naturally
force their way downwards in the strata, and are released only with
difficulty, although in a measure this difficulty is minimized on
account of the fact that the under-reaming (slightly enlarging the
diameter of the hole) is done simultaneously with the drilling.
After a Russian well has been started by means of a slip-hook
suspended from a haulage rope, and a depth of some 30 feet obtained,
the free-fall is added to the string of tools. This free-fall is
composed of two separate parts--the rod and the body--and these are
held together by means of a wedge working in vertical slots cut in the
sides of the body. In operating the free-fall, the handles, fixed to
the temper screw, are held by the driller. On the downward stroke these
are pushed forward from right to left, but as soon as the downward
stroke is completed, they are quickly pulled backwards. The steel
wedge enters the recess and the tools are carried to the top of the
stroke, where, by a quick forward jerk, the wedge is thrown clear of
the recess, and the tools drop freely, the momentum of the string of
tools driving the drilling bit deeper into the hole. After several feet
of the hole are drilled, the tools have to be withdrawn in order to
allow the pulverized mass of debris to be cleared away, while, owing to
the caving nature of the strata, it is necessary to case the well as
drilling proceeds.
As I have said, the system is very cumbersome, but, in the hands of
experienced men, it does its work well, if but slowly. There are many
cases on record where, when the well has assumed a considerable depth,
it has been completely spoiled by the carelessness of the operators,
but, more often than not, this has been deliberate, for the Caucasian
oil-field worker has many grievances, admittedly more or less imaginary.
[Illustration: ILLUSTRATION OF THE “OILWELL” HEAVY ROTARY OUTFIT,
SHOWING RING AND WEDGE (ON LEFT-HAND SIDE OF FOREGROUND) TO GRIP THE
CASING]
During recent years, the rotary method of drilling has been
successfully adopted, and it is in regard to this revolutionary method
of speedy drilling that I will now touch upon. The rotary method of
drilling made its début in Texas some fourteen years ago, and since
then it is not any exaggeration to say that nearly 20,000 wells for oil
have been drilled with the system, which has found popularity in all
the oil-fields of the world. Its main operation is simplicity itself: a
rigid stem of heavy pipe rotates a fish-tail drilling bit at the bottom
of the hole, cutting and stirring up the formation to be drilled. It
cuts its way through the underground formations, much in the same way
as a screw when rotated forces its way through wood. It is the essence
of speed in drilling, for, unlike the necessary principles to be
adopted in the percussion methods of drilling, the rotary drill does
not have to be lifted from the hole for the purposes of clearing. The
pulverized strata are continuously washed from the hole by a stream of
water reaching the bottom of the drill. Very frequently, a pressure-fed
mud is used, and this serves a double purpose, for in its return to
the surface it tends to plaster the walls of the well. The mud emerges
in streams of high velocity from the two apertures in the drilling bit
(for in its downward course it is carried through the drilling pipe or
stem), but naturally loses this velocity considerably in its return to
the surface. It is, however, very easy to detect the kind of stratum
being drilled through from the returned cuttings, these reaching the
surface but a few minutes after the drilling bit has entered the
formation.
From time to time various grievances have been ventilated against this
improved system of boring for petroleum, but to-day its adoption is
world-wide, and by its use wells which, with the old-fashioned method
of drilling would take many months if not two or three years, are now
got down to the producing horizons in but a few weeks. It is, in fact,
solely due to the ever-increasing use of the rotary drill that the
universally increased demands for petroleum products have been met by
an ever-increasing production of the crude oil.
Leaving the question of drilling methods, I cannot fail to mention
the interesting fact that in oil-field operations progress is now
being recorded in another direction, and that is by the increasing
utilization of electrical power in the place of steam. At the time
of writing, it is safe to say that fully 60 per cent. of the power
requirements on the oil-fields is provided for by steam plants,
with their attendant waste. Oil and gas engines, with their greater
efficiency, may claim to be operated to an extent of 35 per cent.,
while not more than 5 per cent. of the requirements are satisfied
by the use of electric motors. There is no doubt that prejudice has
had a deal to do with the very minimized use of electrical power on
the oil-fields in the past, but this is being gradually swept aside,
and, in the next few years, I have no doubt that both electrical
manufacturers and the petroleum industry generally will materially
benefit from the use of this cheap and very economical form of power.
In the past, many disastrous oil-field conflagrations have been due
solely to the use of open-fired engines in close proximity to the
wells, but with the use of electrical energy this fire danger will be
rapidly removed.
Before closing this chapter, I would say a word or two with respect to
the bringing into the producing stage of the oil-wells when once they
have been drilled. In the early history of oil-held developments,
it was not infrequent to find the crude oil ejected from the well
by natural pressure, but to-day it is the exception to find those
oil-fountains which have made the early history of the Russian
oil-fields so famous. In many of the fields, explosives are used to
promote the flow of oil, and when the well “comes in” to production,
the ordinary methods of bailing or pumping are resorted to. Compressed
air is also used for bringing about and sustaining production. The
quantity of air and the periods of admission naturally vary with
the diameters of the wells, the amount of gas present, the level of
the liquid, etc., which latter also determines the pressure of air
necessary.
The natural exhaustion of oil-wells can obviously have no remedy, but
areas conveying that impression can often be revived by methods, the
study of which is being carefully continued. As I write, I find that
the officials of the United States Bureau of Mines, who have been
studying this question of exhaustion, have arrived at the conclusion
that from 20 to as much as 90 per cent. of the crude oil remains in
the strata tapped by the well, even when it is abandoned as no longer
capable of profitable production. This conclusion opens up what may
prove some day to be a most interesting chapter in oil-field history.