CHINA MINERAL
RESOURCES OF THE UNITEDSTATES
1891
Annales des Mines, vol.
xix, 1891, describes in detail the brine and
gas wells of the province of Sze Chuen, in western
China.
This produces annually, as nearly as can be estimated, there being no
regular
statistics, about 812,000 tons of salt, which is entirely derived from
borings, the salt being accompanied in places by petroleum and natural
gas, the latter being utilized for boiling down the brine.
The most important centers of production are in a district about 80
square
miles in extent, about 25 miles northwest of the town of Fou
Chonen.
The geological structure of the district appears to be somewhat
complicated,
but, according to the author, a complete succession from Cambrian up to
Tertiary and post-Tertiary strata, which is recognizable in the
following
order:
Stratigraphy of the Sze Chizen gas fields,
China. Meters.
Yellow sandstone Tertiary 38 to 100
Red
sandstone--------------------------------------------------------
Gray
limestone-------------------------------------------------------
200
Ferruginous oolite, often with bituminous springs at
Blue and yellow sandstone, Lias 270
At this level gas is found sometimes in small
quantities.
Bluish gray marl 330 to 600
White limestone, Permian
These strata yield brine of a yellowish color and medium
saturation
(10 to 15 % of salt)
Sandstone and limestone with coal Carboniferous.
Brown shining shale Silurian.
Green schist Roofing slates.
Dark colored brine, of the
higher strength of 15 to 28 percent of salt,
is found below the last mentioned strata at depths varying from 930
meters
to 1,100 meters, as well as the most important gas springs. As a rule,
the upper yellow brine bearing beds are not found in these deep
borings.
The
system of boring is percussive, the cutting tool
and sliding
piece weighing from 200 pounds to 300 pounds, being suspended by a
rope,
and lifted about 2 feet at a stroke, by a lever worked by groups of
coolies
acting as dead weight. According to the depth, from two to eight
men are required to lift the tool from twelve to fifteen times a
minute,
the gangs being relieved at intervals of ten minutes. The cutting tool
has eight steel-faced teeth, but without grooves, so that the, detritus
accumulates at the bottom of the hole. This is removed by a sludger,
consisting
of a cylinder of wood covered with deep notches arranged ladder wise,
which
is lowered into the hole and moved about by a jerking motion on the
rope
until the grooves are filled with the sludge.
Usually a pit is sunk by
hand to a depth of about 100 feet from the surface, and lined with
blocks
of stone before the actual boring is commenced. The diameter adopted is
from 9 to 12 inches, which may be contracted to 6 or 7 inches when it
is
necessary to life the hole through loose ground.
The grating tubes are
either large bamboos bored out or are built up of half trunks of
cypress
trees fitted together by swallow tailed joints, which are covered by
hempen
cloth, water proofed with a paste of lime and oil. This first covering
is
protected by a close serving of cord, with a thicker layer of the
cement
over all, the total thickness of the structure being but little less
than
the diameter of the hole. According to the nature of the ground,
the length of these casing tubes may vary from 10 to 300 feet; but when
more than 20 feet are required in one length, the high derrick must be
provided. This is made up of two of timber 40 feet to 50 feet high,
with
two diagonal struts, and a multiplicity of guy ropes, the use of iron
being
restricted to a minimum.
As may be imagined, the
progress of the work is very slow, varying from
a few feet per day in loose ground to an inch or less on very hard
rock.
Some of the deeper wells have taken from twenty to forty
years in sinking,
and have ruined several sets of adventurers in succession.
The
deepest
actual boring, 1,160 meters, has never yielded anything.
Some three or four holes are above 1,000 meters deep, but the greater
number are between 530 and 930 meters, in the Tsze-liu-tsing group. In
the Kong-tsin group they vary from 330 to 660 meters as the most
general
depth, the shallowest being about 200 meters.
The accidents to which the
borings are liable and the method of remedying
them are treated at length by the author, with illustrations of the
tools
employed from Chinese drawings. These are generally similar to those
adopted
in Europe; but the construction is very different in principle, bamboo
and string entering very largely into their composition instead of
metal.
As a last resource, the
method of pulverizing a lost tool is adopted
and carried out with incredible patience. The removal of a tool
weighing
300 pounds, in this manner, required about five years continuous work,
night and day, of thirty-two men, at a cost of about Y, 3,000.
The brine is brought to the
surface by tubular buckets of bamboo, with
a foot valve varying from 2 to 6 inches inside diameter, and from t6 to
140 feet in length.
For the latter size, used in the deepest wells, derricks for 90 to
120 feet are required, the highest in use being 164 feet. These are
built
up of beams of timber lashed together with bamboo ropes, and cost from
Y8OO to Y1,000.
The bucket is lowered and
lifted by a flat rope 20 millimeters and 5
millimeters thick, formed of slips of bamboo united by hempen cords
winding
upon a gin which is usually drawn by buffaloes, two, four, or six of
these
being required, according to the depth of the well; but in the
shallower
ones the lifting is sometimes done by a windlass worked by from two to
six men treading fashion. The load upon the rope in the deeper wells in
some cases exceeds 30 hundred weight, corresponding to a stress of 9
1/2
tons per square inch.
The quantity of brine raised
at each lift varies from 116 liters (250 1/2
gallons) with the smallest bamboos, to between 620 and 950 liters (136
to 200 gallous) with the larger ones, and under the most favorable
conditions
from two to four lifts may be made per hoar, according to the depth.
When
the bamboo is raised to the surface, a cover is pushed over the top of
the bore hole, the valve is lifted by the ladder with an iron hook, and
the brine runs into a reservoir.
The product of the deep
wells is very dark-colored, and often emits
suphuretted hydrogen in sufficient quantity to be dangerous to the
workmen
about the top of the pits if it is incautiously inhaled. In addition to
salt, some of the wells yield petroleum and gas in variable quantity;
the
former is skimmed off from the surface of the water after it has been
allowed
to settle in the reservoirs.
The product varies in
quality from a pure white-burning oil to yellow,
greenish, and black kinds of low illuminating power and giving much
smoke.
All are, however, burned, as the Chinese have no knowledge of petroleum
refining.
The wells being generally
away from the salt works, the brine is carried
to the latter either by hand, when the journey is short, or by conduits
made of bamboos, with chain and bucket-lifting wheels for overcoming
intermediate
differences of level, when a greater distance has to be traversed.
The boiling down is
done in shallow cast-iron pots about 4 feet in diameter, and 1.7 inch
deep
in the center. The thickness varies from 11 inch in the center to
1 inch at the edges, and the weight is about 1,000 pounds. The
heating
may be done by straw, wood, coal, or natural gas.
The operation lasts from twelve to twenty-four hours, according to the
intensity of the fire, and yields about 100 pound,; of salt.
In
the district of Fou Chouen, where natural gas
wells are principally found, from 600 to 1,200 pans may be heated by a
single well. The principal supply is obtained from depths of not less
than
670 meters. It is manly marsh gas, being less carburized than that
obtained
at shallower levels, which burns with a tolerably white flame, but is
only
got in small quantities.
The top of the well is enclosed
to a depth of 10 feet by a wooden casing, as nearly tight as possible
and
the gas is led by bamboo pipes into cemented reservoirs with dented
roofs
formed by inverted salt parts. From these reservoirs, the distribution
of the gas is effected by means of bamboos leading to the pans, a short
length of iron pipe being attached to the end of each line.
The actual burner is a perforated
block of stone of a conical form about 1 foot high; the gas is
introduced
by a lateral pipe at the bottom, and mixing with air is burned at the
top
of the block over which the pan is placed.
The whole arrangement is
very primitive and imperfect, nothing of the
nature of a stop valve being displayed anywhere on the line of
pipes.
When the workman wishes to extinguish the flames, he places a brick on
the top of the burner; but the gas continues to flow without
interruption,
and disperses in the atmosphere. As, however, the work is done
under
open sheds, there is not much danger of explosions; but the smell of
the
gas is very prejudicial to the health of the workmen.
The saltpans are presently
built by the proprietors of the gas wells,
who leases them to salt makers at a rental of about Y(L?) 32 per
annum.
The yield to the proprietors is therefore large, but the duration of
the
gas is very uncertain.
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