BORING METHODS: ANCIENT AND MODERN
The Skill of the Ancients in Well-Boring — Present State of the
Ancient Wells — Ancient Methods of Boring — Wooden Casing —
Introduction of Machinery by Egyptian Government — Native Methods
of Boring at the Present Day — Cleaning of Wells — Divers and
their Work — Recent Boring Operations — American Steam-driven
Boring Rigs.
Olympiodorus, writing more than 1,500 years ago, remarked that
the inhabitants of the oases were celebrated for their skill in
sinking wells. Although at the present day a large proportion of
the very ancient wells are completely sanded up, or have suffered
great deterioration in respect of their flows, there are still many
examples to be met with where bores, certainly between 2,000 and
3,000 years old, are still producing strong discharges of water at
the rate of hundreds of gallons a minute by day and by night.
Although scores of the old wells have been cleaned out and repaired
in modern times, not a single instance has come under my notice
of the finding of implements used by the well-borers of ancient
times. We know, however, that the bores were in practically all cases
lined to a considerable depth with wooden casing, manufactured from
the wood of the doum-palm, date-palm, or acacia, which doubtless
were then, as now, cultivated in large numbers in the oasis. The
timber was carefully fashioned into the required lengths and fitted
together by water-tight joints. During the cleaning operations to
which many of the old wells have been subjected in modern times,
portions of the ancient casing have frequently been extracted, and
some of the examples which I have examined, especially those made of
acacia, proved to be in an excellent state of preservation. The wood
of this particular tree—‘sunt,’ as it is locally called—has
remarkably enduring qualities both in and out of water, though
not when subjected to alternations of wet and dry. Still, that it
should in some cases have retained its original qualities since
Roman times is noteworthy.
It is quite evident, from a comparison of the ancient timbering
and casing with those manufactured and used by the inhabitants of
the oases at the present day, that the methods of well-sinking in
modern times are in many respects identical with those anciently
employed. This is especially the case in sinking through the
superficial strata—_i.e._, those overlying the actual beds in
which the artesian water is held—though of the methods formerly
practised for carrying the bore through the Artesian-water Sandstones
nothing is known.
We have little, if any, information as to how the inhabitants kept
up their water-supply after the withdrawal of the Romans. Probably
there was a gradual diminution of the total output, as it is not
at all certain that any new wells were subsequently sunk—at any
rate, until after the introduction of modern hand-boring machinery
some fifty or sixty years ago. On that occasion one Hassan Effendi,
a servant of a French engineer of the name of Lefèvre, was sent
out by the Egyptian Government to instruct the inhabitants in the
use of the new machinery. Judging from their present proficiency
in sinking wells through difficult strata with the most hopelessly
worn and antiquated tackle, the natives did not take long to learn
the new system. Unfortunately, when left to themselves without
adequate supervision, they promiscuously sunk a great number of new
bores, without regard to the probable effects on the older wells
irrigating the existing palm-groves and cultivated lands, with the
result that, more especially in the oasis of Dakhla, a great deal
of harm was done. Whole districts suffered a general lowering of
water-level, many of the wells ceasing to flow altogether. This
was the direct outcome of the excessive number of new bores put
down in certain districts where the inhabitants were sufficiently
rich and influential to get and retain possession of the majority
of the newly-imported boring-rigs.
About ten years ago I studied the method of well-sinking used in
the oases, and found it to consist of a combination of ancient and
modern boring practices. Owing to the difficulty and prohibitive
cost of transporting heavy steel tubes across the desert, the use
of locally-made wooden casing could not be dispensed with, and as
casing of this description could not possibly be made of sufficient
strength to stand ‘driving,’ the upper portion of the well had
of necessity to take the form of an open shaft carried down as near
as possible to the water-bearing beds, the actual boring by means
of the drilling-plant being confined to the later stages.
The first operation consists in sinking a rectangular shaft, usually
2 metres square; this work is carried out by hand, the ordinary
native ‘fass’ being almost the only implement used. As the shaft
is cut out it is timbered with lengths of palm-wood strung one below
the other, to prevent the walls from falling in. The excavation
is carried as deep as possible, the limit generally depending on
the amount of sub-surface water met with. In the oasis of Dakhla,
where the superficial strata consist almost entirely of clays,
it can usually be continued to a depth of about 30 metres; but in
Kharga the depth varies considerably, owing to the more frequent
intercalations of water-logged sandstones. The success of the
prospective bore depends to a very great extent on the depth to
which this preliminary work is carried, as the succeeding strata,
lying between the base of the shaft and the true artesian beds,
have to be pierced by a hole unprotected by casing, and if of any
very considerable thickness, caving beds are likely to greatly
interfere with, if not prevent, the progress of the work.
On completion of the timbered shaft the wooden casing is placed
centrally in position, so as to form a vertical pipe from the base of
the shaft to the surface of the ground. The pipe may be either square
or round in section, and is usually made of acacia, though hollowed
trunks of doum-palm are sometimes used. It consists of a number of
different sections, joined together in such a way as to leave no
projecting portions either within or without, the whole length of
casing thus preserving a constant diameter from top to bottom. As
a rule, the joints are so well formed that the pipe is, to all
intents and purposes, water-tight after a short soaking. The square
variety of casing usually has an inside width of 36 centimetres,
the thickness of the wood being 4 or 5 centimetres; the circular,
and perhaps more common, variety is made with an inside diameter
of 35 centimetres, except when required for insertion within a
previously fixed string of casing, when smaller sizes have to be
used. The casing, of course, eventually forms the actual channel
through which the artesian water flows to the surface.
The space intervening between the sides of the timbered shaft and
the central pipe is then filled in with a mixture of sand and clay,
firmly packed down, so as to hold the pipe securely in position, and
prevent the escape of water should any of the joints become leaky.
Up to this point there is good reason to believe that the modern
practice is similar to, if not identical with, that anciently used;
but in the complete absence of evidence, documentary or otherwise,
we cannot conjecture how the old well-sinkers proceeded in subsequent
stages. We surmise, however, that, given sufficiency of time, they
were possessed of the requisite patience and skill to overcome
all ordinary obstacles—as has been the case for generations in
China—and it is probable that the percentage of wells abandoned
was not greater than it is at the present day in countries where
well-boring has become an art, carried out by means of scientifically
designed machinery.
The second part of the modern operations is conducted with an
ordinary percussion hand-boring outfit of European manufacture. As
the method of boring with this type of rig is essentially the same
all over the world, we only propose to describe it in brief. The
proceedings commence with the erection of a timber framework,
or derrick, immediately over the mouth of the pipe; at the summit
of the derrick is a pulley, over which passes the rope or chain
which connects on one side with the drum of the winch, and from
the end of which, on the other side, are suspended the actual tools
with which drilling is continued. The boring-rod is made up to the
required length by screwing together a number of 10-foot sections,
the terminal length being a shorter rod fitted with a chisel, auger,
or sand-pump, according to the work in hand.
The rate of progress depends to a great extent on the rapidity with
which the blows of the chisel are delivered. This, of course,
varies considerably, depending on the depth of the well and
consequent weight of the rods in use. Where the weight is great
and the formation sticky, the rods have to be lifted by means of
the winch, and not more than two or three blows a minute can be
struck. When the rods are light or working freely, as, for instance,
when drilling in sandstones, the winch can be dispensed with, and the
necessary motion conveyed by means of a lever actuated by a number
of men. In this way progress can be very much accelerated, as many
as twenty or twenty-five blows being delivered per minute. At the
best, however, the method of drilling by percussion with a solid
rod is necessarily slow, owing mainly to the fact that the terminal
tool cannot be changed or withdrawn without the entire length of
rod being taken to pieces. It is seldom, therefore, that a well of
120 to 150 metres is completed in less than five months, and the
average time taken is more like nine months or a year.
It will readily be admitted that this method of sinking wells is
in many respects well adapted to the local conditions obtaining
in such isolated localities as the oases, where time is of little
consequence to the inhabitants. The completed wells are frequently
equal in almost every respect to those put down by means of the most
up-to-date appliances; in fact, the only objections to the method
are its slowness, the limited depth to which it is applicable,
and the difficulty of fixing to the wooden casing satisfactory
appliances for regulating the discharge.
The patience and industry of the inhabitants of the oases are well
exemplified by their unceasing attempts to maintain undiminished the
water-supply on which their very existence depends. The population
must always have borne a direct ratio to the total discharge of the
wells, as on the latter depends the amount of food-supplies which
can be raised. At no period, as far as we can judge, has the output
of the wells been greater than the requirements, and it is probable
that there has always been a population somewhat in excess of that
which could be supported by local products, the surplus portion
being disposed of by emigration to the Nile Valley.
The methods of dealing with wells in which the flows have diminished
or altogether ceased are of considerable interest, as they have
given rise to a class of men called ‘ghattasin’ (divers),
which one would never have expected to find in such remote and arid
localities as the oases of the Libyan Desert.
It is seldom that the poorer inhabitants can command the use of a
hand-rig for the cleaning of their wells, so that they usually have
recourse to appliances of the most primitive description. Perhaps
the simplest form consists of a short iron rod, a sort of crowbar
or jumper, suspended from a palm-fibre rope, and with a tiny basket
attached to the lower end. In some cases the end of the jumper
is itself fashioned into the form of a cup, so that the basket of
plaited grass or palm-leaf can be dispensed with. The rod is worked
up and down in the bore, so as to stir up the sand and clay at the
bottom, which settles in the basket or cup, and is periodically
hoisted to the surface. The rope is worked over a wooden roller
fixed alongside the mouth of the well, a contrivance which enables
the up-and-down motion to be given with a minimum of energy and
friction. The process is often continued for years, the material
which can be removed in a day only amounting to a few handfuls.
The above method is only applicable to bores in which the wooden
casing is more or less intact. Where the latter has rotted and
allowed the sides of the well to collapse, a much more difficult
and complicated procedure is necessary before the discharge can
be re-established. In a case of this sort the original rectangular
shaft has to be entirely cleared of material, and a new string of
casing placed in the exact position occupied by the original pipe
of the well. Moreover, the timber of the shaft itself has generally
to be repaired or entirely renewed, as otherwise there would be
very great danger of the sides collapsing when the material from
within was removed. The process is rendered extremely difficult
and laborious by reason of the entire work having to be carried on
under water. Although a well may have stopped flowing, the passages
are never so completely blocked as to altogether prevent the water
from rising to within a few feet of the surface, and any excavation
made will always be found to become speedily filled with water. The
work can, therefore, only be carried out by men who have trained
themselves to remain and work under water, and a limited number of
these divers are found in most of the Egyptian oases.
I have frequently watched and chatted with the divers at work on
old wells, both in Dakhla and Kharga. Unlike the usual custom of
remunerating men employed on well-cleaning by shares of the resulting
water, divers are generally paid in cash at the rate of about a
shilling a day, each man receiving his food as well. The descent
is always made feet first, hand over hand down a rope stretched
from the top to the bottom. When the diver wishes to return to the
surface he signals by a motion of the rope to those at the top,
who promptly haul him up.
The rate of progress depends, of course, on the depth at which the
work is proceeding. In a well I once visited near Hindaw, in the
oasis of Dakhla, divers were working at a depth of 29 metres. Each
man descended six or seven times a day, remaining on each occasion
from two to two and a half minutes under water. Work had been in
progress here for four years, and the excavation was still 16 or
17 metres from the bottom of the shaft.
The excavated material is placed in baskets, which, when full,
are drawn up by hand. As soon as the shaft has been cleared to the
bottom the new casing is inserted, the intervening space filled in,
and the work carried on as in a new bore. Many extinct wells have
thus been put into good working order, though in some cases the
divers have been unable to overcome the difficulties encountered,
and the wells have been finally abandoned after months, or even
years, of labour.
In the reclamation operations conducted in the oasis of Kharga
during the last two or three years, both hand and steam boring rigs
have been employed, steel casing being used for all wells. The cost
per foot drilled is somewhat in favour of the hand-rigs, but the
rate of progress is far more rapid in the case of the steam-driven
machines. The method used with the hand-machines is the same in
principle as that employed by the natives and already described,
with the exception that the preliminary excavation is dispensed with,
the bore being drilled from the surface and lined with metal casing
down to the Water-bearing Sandstones. The casing is driven by means
of a heavy weight, or ‘monkey,’ attached to the boring-rod.
The steam-rigs used are of American manufacture, and of the design
usually employed in the oil-fields of the United States. The method
is a modern adaptation of a practice employed from very early times
in China, free-falling tools attached to a flexible rope being used
in place of a solid iron rod. The actual drilling tool, which is of
great weight, is suspended from a cable, and worked by steam-power in
such a way as to give a rapid succession of blows of such force as
to cut out a circular hole through the hardest of rocks. The outfit
consists essentially of a very high derrick, a large drum on which
the cable is wound, and a specially-designed engine worked by steam,
the boiler in which the latter is generated being usually placed
on a separate carriage. A second and smaller drum is provided for
a fine wire rope, which is used with various forms of sand-pump for
cleaning out the loose sand or sludge formed by the drilling tool.
[Illustration: A STEAM BORING RIG.]
[Illustration: A HAND BORING RIG.]
These steam-rigs necessitate the employment of skilled drillers,
and are, moreover, with difficulty kept in proper repair in
out-of-the-way localities. Their initial cost is high; they are
extremely cumbersome to drag from one site to another over the
soft surface of the desert, and they consume a large quantity
of fuel. These drawbacks are, however, partly, if not entirely,
counterbalanced by the rapidity with which the work can be carried
out, the average rate of progress under the conditions met with
in the oasis being 5 to 7 metres per ‘shift’ of eight or ten
hours. In the water-sandstones I have known Mr. B. F. Whiting, who
was recently my drilling superintendent in the oasis, carry a bore
down as much as 20 or 25 metres in a single shift. Breakdowns are, of
course, not infrequent with this system of boring, but the American
drillers are remarkably proficient in the recovery of lost tools.