Charles George Warnford Lock.

Economic mining: a practical handbook for the miner, the metallurgist and ... online

. (page 31 of 76)
Online LibraryCharles George Warnford LockEconomic mining: a practical handbook for the miner, the metallurgist and ... → online text (page 31 of 76)
Font size
QR-code for this ebook

weeks they are dry enough to be stacked or heaped up. But peat
districts are generally remarkable for a very moist atmosphere and
for a great frequency of rain. In the Highlands of Scotland and in
the Hebrides, on the average there is rain 4 days out of 6, and it r
only the months of May, June, and July that afford any continuance
of weather favourable for drying peat. Therefore the peat must all
be cut before the end of May at latest. On the other hand, if the
peat is cut during frosty weather, and becomes frozen, it crumbles to
powder when the thaw comes, and for this reason it is not safe to
commence the cutting at all before April or even May. As a rule it
might be said that the month of May is the only time available for
cutting peat. Once a skin has formed on the surface of the pieces, it
may be considered safe, whatever kind of weather follows. It maj
then remain on the ground, set up in little heaps, till the autumn,
and will get the advantage of whatever dry weather there may be^
Two men working together, one cutting and the other casting the
peat, will, in good weather, get through about one iron's work in a
day, equivalent to 10 tons of dry peat. This will still retain 20 to
30 per cent, water only separable by kiln drying. When kiln driei
peat possesses about half the calorific value of coal.

Though attempts have been repeatedlv made to produce coke from
peat, no real success seems to have attended them.

Digitized by




?(irolmm, — ^ICany theories have been advanced as to the origin of
petTolenm, bnt the most important are the chemical theory adopted
bj serend European authorities, and the organic theory favoured in
America.* llie chemical theory supposes petroleum to have been
|i:enerated by the downward passage of surface water into regions of
tlie earth's cmst where metallic iron in combination with carbon
exists in a highly heated state ; or by water containing carbonic acid
Iteiog carried down to strata where potassium and somum occur in a
laetallic state. American geologists and chemists agree that petroleum
bs resulted from the decomposition of fossils in the shales and lime-
itQnes of the Silurian, Devonian, and Lower Carboniferous rocks, chiefly
the remains of animals, but in some cases also the remains of plants ;
tbt the gas and petroleum thus formed are stored in porous sand-
(tones and limestones, and are prevented from escaping by a covering
)f impervious shale.

That the organic theory of the origin of pKBtroleum best explains
^ facts over t£e greater part of Nor& America, is beyond question.
ft probably also serves beet for most areas. But the inorganic theory
s a possible one for some regions.

As r^ards the future supply of petroleum, the question of its
Tigin is important. If it has resulted from the decomposition of
lumal or vegetable remains, the supply, however vast and seemingly
nezhaastible at present, must needs be limited, and each area will in
ime be drained. If, however, it be due to diemical action in the
Dterior of the earth, the supply may be practically ioexhaustible in
he dictricts where it is thus formed. The ^eat pressure of the gas
nd petroleum in many wells has been held to afford evidence of a
^p-seated origin; but this pressure necessarily results from the
nown geological structure of the country in many places.

The general rule in Pennsylvania,! New York, Ohio, Indiana, and
Anada, is tliat petroleum and gas are stored in porous sandstones or
mestones, where the rocks have been gently folded into anticlinal
tdges; or where, if there is a small and general dip of the strata, l^e
ip is for a space interrupted, forming a shelf of more nearly hori-
aDtal rock, after which the strata resume their normal gentle dip.
racing out the underground range of petroleum-bearing beds beyond
^ areas in which they are now productive, we find that they rise
>wards the surface, and contain water. It is the pressure of the

* B. Redwood, ' Petroleum and its Produets,' Cantor Lecture, Soo. Arts, 1886.
'. TopleY, • Sonrces of Petroleum and Natural Oas,' Jl. Soo. Arta, April 17, 1891.

t H. H. Chance, * Anticlinal Theory of Natural Gaa,' Trans. Amer. Inst Min.
t^^:^ XT. 3 ; C. A. Ashbumer, * Oeological Distribution of Natural Ghui in the
QJted States,' Trans. Amer. Inst. Min. Engs^ xv. 505 ; C. A. Ashbnroer, * Petroleum
Ml Hatoral Qas in New York State,* Trans. Amer. Inst Min^ Engs., xtL

Digitized by



water £r6m the oatcrop and the higher areas of the porous rock, acta
along and down the dip, which aooonnts for the pressure of the g
and petroleum within the prudnctiYe areas. When the porons b
oontaining gas or petrolenm is tapped bj a borehole, the contents a
forced np by the pressure of the water from the outcrop, and tl
pressure depends upon the relation between the level of me outer
and the point at which the porous bed is tapped.

According to Prof. McGhee, eveiy field in the Eastern States u
Canada is a dome or inverted trough formed by ^flexure of the rod
strata ; and in every such dome or inverted trough there is a poio
stratum (sandstone in Pennsylvania, and coarse-grained magnesL
sandstone in Ohio and Indiana) overlain by impervious shalee. The
domes or arches vary in dimensions, from a few square miles in sex
of the Pennsylvanian areas, to 2600 sq. miles in the great Indiana fie
Within each gas-charged dome are found three or more subetanc
arranged in the order of their weight; gas at the top, naphtha (if
exists in the field) and petroleum below, and finally water, which
generally salt, and sometimes a strong and peculiar bittern. Tl
order is invariable throughout each field, whatever its area, althon|
in Indiana, at least, the oils are found most abundantly about tJ
springing of each arch, while towards its crown gas immediate
overlies brine ; and the absolute altitude of the summit-level of e«
substance is generally tmiform whatever the depth beneath tl
surface. Since the volume of gas or oil accumulated in any fie
evidently depends on the area and height of the dome in which it
confined, and upon the porosity and thickness of rock in which it
contained, the productiveness of a given find may be definite
predicted after the structure and texture of die rocks have bei

In all productive fields the gas and oil are confined under pressin
When a eas ^ell is dosed, it is commonly found that the pressure i
the well head gradually increases, through a period varying from
few seconds in the largest wells to several minutes or even hours i
wells of feeble flow ; and that afterwards the pressure-gauge becoxa
stationary. This is the *' confined pressure,'' ** dosed pressure," <
" rock pressure ** of the prospector ; or, more properly, the " static pre
sure." When a well is open, and the gas escapes fredy into the ai
it is found that if the stem of a mercurial or steam gauge is introduce
a certain constant pressure is indicated. This is the '* open pressure
or '* flow pressure of the gas expert, and the capacity of the well mi
be determined from it. ■ The static pressure varies in different fidd
In Indiana it ranges from 300 to 350 lb. per sq. in., in the Findh
field it is 450 to 500 lb., and in the Pennsylvania fidd it varies froe
500 to 900 lb.

The cause of this enormous pressure is readily seen in Indian
The Cincinnati Arch (in which the gas of the great Indiana fidd
accumulated) is substantially a dome, about 50 miles across, rising i
the centre oi a stratigraphic basin fiilly 500 miles in average diamete
Throughout this immense basin the Ivaters falling on the surfiace ai
in part absorbed into the rocks, and conveyed towards its centr
where a strong artesian flow of water would prevail were the difli^

Digitized by



enoe m altitude greater ; and the light hydrocarbons floating npon
the snr&oe of this ground water, are driven into the dome, and there
nibjected to hydrostatic pressure, equal to the weight of a column of
water whose height is the difference in altitude between the water
rorfaoe within the dome and the land surface of the catchment area
ibout the rim of the enclosing basin. Accordingly, the static pressure
is independent of the absolute altitude of the gas rock and of its depth
beneath the 8urfiEu>e, except in so far as these are involved in the
relative altitudes of the gas rock and a catchment area perhaps scores
[Fr even hundreds of miles distant. Gas pressure and oil pressure
may, therefore, be estimated in any given case as readily and reliably
IS artesian water pressure ; but while the water pressure is measured
ipproximatelv by the difference in altitude between the catchment
nea and well head, that of gas is measured approximately by the
lifference in altitude between catchment area and gas rock, and that
)f oil is measured by the same difference, mtntM the weight of a column
)f oil equal to the depth of the well. It follows that the static pres-
mre of gas (as indicated at the surface) is always greater than that
»f oil, particularly in deep wells. It follows also that the pressure,
rhether of gas or oil, is not only constant throughout each field,
mt diminishes but slightly, if at all, on the tapping of the reservoir,
mtil the supply is exhausted : and* hence that pressure is no indica-
ion of either abundance or permanence of supply.

There is no uniformity in the geolo^cal ages of the strata which
rield petroleum. Even in North America the age ranges from Lower
Klurian to Tertiaiy : both gas and oil also occur in the drifts. Rocks
f Secondary age, however, with the exception of the Cretaceous, are
lot oil-bearing in North America. In Europe, only small quantities
ccur in Pabeozoio rocks. In Hanover it ranges from Trias to Cre-
i-oeoos. In Eastern Europe it is mainly Tertiary, and wholly so in
be Caucasus.

In other parts of the world the petroleum-bearing beds are, so far
B is known, rarely of older date tnan Upper Secondary. Volcanic
Kks occasionally contain petroleum, but there is good reason to
elieve that these cases are generally the result of impregnations
kto porous reservoirs of volcanic rocks from neighbouring sedimen-
iry strata.

Ingeological position, the gas and oil-bearing rocks of Pennsylvania,
ew York, Ohio, and Indiana range from Lower Silurian (Trenton
mestone) to Lower Carboniferous. Until the great stores of the
renton limestone were discovered, the Devonian and Lower Carboni-
szxKis strata were the most important sources. The oil-sands of
enango Co., Pennsylvania, are often in lenticular beds, the longer
ces of the beds ranging from north-east to south-west. In thickness
ley range frt>m a thin band up to 100 ft. Their width may be only
-2 miles, their length sometimes 20 miles. Some of the strata die^
it before reaching the outcrop, and consequently are known only
y borings. When two or more such beds occur in vertical succession,
ke lowest usually contains most oil or gas. The lenticular nature
f the sand may explain how in some cases neighbouring wells affect
v€^ Other, whilst elsewhere they may not do so. Beneath the

T 2

Digitized by VjOOQIC


Venango group, other gas or oil-bearing sands were subsequentlj
disoovered, the most important of whicn are the Warren sands
Warren Ca, and the Bradford sands of MoEean Co. The Berea
is the most important source of oil in Eastern Ohio.

In all cases these productive sands are underlain and overlain \
shales. The underlying shale is the source of the petroleum and gai
the sand is the porous reservoir in which they are stored ; the ove:
lying shale is an impervious cover which retains them in the reservd
When gas and oil are found stored in limestone, they may sometimi
have been produced in the limestone itself, but the impervious coTt
of shale is still required to retain them. The Trenton limestone,
chief source of gas and oil in Indiana, and an important source no^
in Western Ohio, is the upper member of a series of limestones whii
have been proved to a depth of 1800 ft The true Trenton *'
itself is several hundred feet thick. All this thickness of limestoi
may have produced the hydrocarbons, although they are stored
in the upper part of the Trenton, But not always so ; it is oi
when the Trenton limestone occurs in the cavernous condition that
is highly productive ; this condition is due to some of the lime havin
been removed, its place being taken by magnesia.

The storage capacity of the porous sandstone and limestone i
very great, and sufficiently accounts for the great yield of the welL
The Waterlime bed, 500 ft. thick, and with a capacity of only 0*
per cent., would contain 2,500,000 barrels of oil per square mile ; 10
sq. miles of such rock would yield the entire production of New Tor
and Pennsylvania up to January 1883. But the capacity for stora^
is offcen much more than the figures taken here. Carll has show
that some rocks can contain from iV ^ i ^^ their bulk in oiL

Referring to the natural gas wells of Indiana, S. S. Gorby *
mates that approximately 30,000 cub. ft. of gas are equii^ent
1 ton of coal as fuel. He declares that the period of exhaustion
the wells has been entered upon. The initial pressure of new w^
is now less than 300 lb., whereas it used to be 325 lb., and the ~
daries of the field are being rapidly drawn in. He estimates
probably 10 to 15 years will witness the termination of the gas fu^
supply on anything like the present scale.

There are some peculiarities which render Kentucky interesting
instructive, as a source of gas. Elsewhere the incursion of salt wai
into a gas well is the sure precursor of £Bdlure, showing that
reservoir is becoming exhausted ; but here salt water and high-pi
sure gas occur together. Some of the wells here, also, have L
lives: one, at Moreman, has been producing gas and brine since I
Salt has been manufactured here &om the brine since 1872

In California, petroleum occurs mainly in'^sandstone of T^tiai
age. The beds are generally inclined from 30° to 85°, the edges oti
cropping. High-pressure wells are consequently rare, the ou beioJ
obtained by pumping ; and the cost of wells is stated to be aboa
three times what it is in Pennsylvania, partly on account of the stee
inclination of the beds.

* Eng. and Min. JL

Digitized by VjOOQIC


Altboagh petroleum occnrs all along both flanks of the CauoasuB,*
iften in considerable quantity, the Apscheron Peninsula, on the
irestem margin of which Baku is situated, surpasses all others in value.
rbe most productive wells lie within a small area north-east of Baku,
a the Balakhany-Saboontchi district, over the crown of a low anti*
diiuJ, which is probably the easterly continuation of the great Cau-
!asns anticlinal. Another, and increasingly important prodactive
irea, is on the shores of the Oaspian, at Bibi-Eibat, south of Baku,
md about 10 miles from Balakhany.

The surface is occupied by loose sand, the rocks below being of
ite Tertiary date; beneath these probably lie the Cretaceous and
FniasBic strata, which form the main mass of the Caucasus, but it is
ioabtful if any borings have touched these rocks. The oil lies in
woiis layers of sand, separated by clay, &c. This sand is often
rery loose, and comes up in great quantities, where oil of high pres-
ure is first tapped. Enormous loss of oil often occurs when a high*
trpssnre well is first driven. The Mining Company's well in August
B87, struck oil at a depth of 790 ft., which flowed the full size of a
2-in. pipe for 69 days, 200 ft. above the derrick. The lowest esti-
mate for this well for the 69 days was 3,000,000 barrels, of which at
fiast half were lost. More sand than usual came out of this well ; an
rea of about 10 acres around the well was covered with sand from
to 15 ft. thick. 80 much sand has been carried out by the wells
liat the surface of the ground sinks, and buildings are thrown out of
lie perpendicular. Many highly productive fountains suddenly
ease ; the cause is said to be a collapse of the pipe at the bottom of
lie welL

The depth of the wells in the Baku area is gradually increasing :
1 1B82 the average depth was 350 ft. ; in 1886 it was 500 ft. Many
re now over 700 fL, and at least one is over 1000 ft

Wells sometimes continue to produce for years, especially when, as
I Nobel's works, they are seded down when not required. The
Bq)er wells as a rule produce the larger quantity and, sometimes, a
Btter quality of oil, of lower specific gravity.

There is difference of opinion as to whether wells affect the pro-
action of others in their neighbourhood. As there are several layers
r oil-bearing sand, adjacent wells may frequently draw their supplies
om 'different beds.

The most important area of the Caucasus, after Baku, in some
wpects, is that of Eouban. This lies at the north-western end of
le range. The wells here are usually of smaller depth, and are less
roductive than at Baku, although one well — as far back as 1879 — is
dd to have been bored to a depth of 1020 ft. Here, as at Baku, the
aaviest oil sometimes comes from the higher beds.

The third productive area is near ^ertch, in the Crimea. The
«lls here are not deep, and, compared with the two other districts,
1ft not highly productive.

In Boumania, petroleum lies in clays and sandstones of the '* Palu-
rne beds" ^Miocene). The oil occurs in four horizons, the lowest
idng the richest. Argillaceous beds, with thick (over 650 ft.)
* 6. Bedwood, 'BaaBian Petroleun InduBtry,' JL Soo. Ghem. Ind., Feb. 18S5.

Digitized by



deposits of salt, ooour tinder the Paludine beds. Formerly the petro-
leum was extracted by shafts more than 600 ft. deep ; abont 400 snch
shafts haTe been sank in the neighbourhood of Sarata. When drilling
was introduced, the beds were pierced to a depth of 1300 ft

Petroleum and salt are worked in Bukowina.

In Galicia petroleum occurs in the Lower Eocene beds— sometimes,
perhape^ in the Upper Oretaceous. The strata are for the moist p^rt
highly inclined, generally dipping away to the north from the Car-
pathian highlands, but the beds are often contorted. Borings now
go down over 1000 ft.; oil, sometimes with much gas, is chiefly
found in beds of sandstone.

In North-Eastem Hungary, along the southern flanks of the
Northern Carpathians, petrcSeum occurs in Neocomian, Middle Eocene,
Upper Oligocene, and in more recent stratlk. To the south-east of
Nagy-banya, in the Szatmar country, petroleum is found in a doloDiitic
limestone, underlying micanschist. In tiie Nagy-Banva basin, and
also in the Matra range, it occurs impregnating trachytic tofBi of
Miocene age.

At Oelbeim, on the east of Hanover, the oil is stored in the Gank
There seems, also, to be some in the Wealden beds, and in the Upp^
Jurassic strata. To the west are Triassic beds ; but these seem to be
mostly barren of oil, although Piedbceuf believes that the fosuliferom
Middle Trias {JAmchflikaUc) is the true source of the petroleum, whioh
has been stored in the overlying beds.

Before describing modem machinery for petroleum weU-sinking
it will be interesting to study local and rudimentary methods.

. In Japan the excavating is done by two men, one of whom
in the morning from 9 o'clock until 12, and the other from 12 until
The one who is not digging works a large blowing machine that sen
fresh air to the bottom of the welL The blowing apparatus is
wooden box about 6 ft. long by 8 ft. wide and 2 ft deep, with a boa
of the same length and width, turning in it upon a horizontal axis
the middle of each side of the box, and with a vertical division b^
the board between the two ends of the box. The workman stan^
upon the board, and walks from one end of it to the other, altera
nately depressing the ends. At his first step on each end he give6 1
smart blow with his foot, so as to close with a jerk a small v&lv^
beneath the end of the board, the valve opening by its own weighl
when the end of the board rises. The air is therefore driven to
from one end of the box, then from the other, into an air-pipe abotf
*8 ft. square, provided at the top with a small valve for eacl
end of the blowing-box. The air-pipe is made of boards in length
of about 6 ft., and is placed in one corner of the welL The ^'ei
is, besides, timbered with larger pieces at the comers, and ligtt
cross pieces, which serve also as a ladder for going up and down
though at such a time, in addition, a rope is tied round the bodj
under the arms, and held by several men above the month of tb
well. The earth or rock excavated is brought out of the well i]
rope nets, by means of a rope that passes over a wheel I ft. diaiu
hung just under the roof of a hut which covers the mouth of tft
well. The rope nets are drawn up by three men, one at eaJ

Digitized by



mer of one side of the well, and the third in a hole 2 or 3 ft deep,
d 1| ft. wide, dug along the side of the well. The wells aie about
ft aqnare, and are dug in the manner described to the remarkable
pth of 600 to 900 ft At this depth there is great difficulty in
soring sufficient light to carry on the work, and it is frequently
oaasarY for this reason to suspend work at 8 o'clock. The oil is
immed from the surface of the water, and drawn up in buckets.

Lyman is of opinion that it would be the reyerse of advantageous
introduoe the system of drilling with steam power in Japan,
account of the cost of the necessary machinery, tne heavy expense
fuel in the locality, and the difficulty of transporting machinery in
WQDtry almost wholly without wagon roads. The cost of a well in
litigo, 900 ft deep, is stated to have been <»)ly 200Z., which is little
ore than a third of the expense of drilling to that depth in England or
oerica. Moreover, a dug well can be entered for cleaning or ro-
iling, while a drilled well obvionsly cannot; besides which, the
rmer description of well necessarily exposes a larger surface for the
i to peroolate through, and is also frequently furnished with hori-
Dtal galleries extending from the bottom, wMch largely add to the
tent of sur&oe of oil-rook exposed. However, some improvements
ight advantageously be introduced into the system. Thus the only
j^t obtained is that which is reflected from a piece of yellowish
mslucent oil-paper, about 5 ft. loDg by 8) ft wide, suspended over
le well at an angle of 45^ with the horizon, across an opening
I the roof of the grass hut that covers the well ; and it would
t easy to substitute for this primitive reflector a common mirror.
! small mirror oould also be used at the bottom of the well
I reflect light into the galleries, which at present are so dark that
07 cannot be excavated to a greater length than about 12 ft A
ime cannot be used in the well as a source of light on account of the
iBtence of inflammable gas, but the incandescent electric light, if
It too costly, might be employed, and the working hours thus ex-
nded. A better system of ventilation might also be adopted ; and
te use of pumps for raising the water and oil, as well as of a water-
g:ht well-casing, which might be made of timber, to prevent the in-
IX of water, would also f^ilitate the collection of the petroleum,
ke small yi^d of the wells, however, would preclude the employ-
ent of any expensive appliances, the total yield of the wells in the
i-fields of Echigo and Shinano being only 11,000 to 12,000 barrels
ir annum.

In Burma* the wells cure dug in the. most primitive manner, a
Btive spade for loosening the soil, and a basket for removing it
MQ the weU, being the only implements used. The wells are
boot 60 ft. deep and 5 ft. square, and are planked with split timber.
We are generally 3 or 4 men employed in the work of digging,
ich (me taking his ium, and, while working in the well, having a
vpe fastened round him. Sometimes there is so much gas present
ut the digger cannot remain in the well more than a couple
f ininutes, and occasionally a man is drawn up quite insensible,
lie usual time of remaining down is about 20 minutes, and the
* J. Boll, ^Eoonomio Geology of India/ p. 124.

Digitized by




digger jerks the rope when he wishes to be drawn np. The oil i^
raised in a bucket attached to one end of a rope running over a wheel
fixed above the month of the well. The other end of the rope is
fiststened to the waist of a man or woman, who generally has two oi

Online LibraryCharles George Warnford LockEconomic mining: a practical handbook for the miner, the metallurgist and ... → online text (page 31 of 76)