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 After several feet of the hole are drilled, the tools have to be withdrawn in order to allow the pulverized mass of debris to be cleared away, while, owing to the caving nature of the strata, it is necessary to case the well as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 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.