'Mosul Question, Lausanne 1922-1923 and after - Papers, despatches, speeches - Hotel de la Mer at Lausanne - Correspondence about oil' [‎217v] (432/501)

206
OIL ENGINEERING AND F
February 17, 1923.
THE CALCULATION OF THE
THICKNESS OF WATER CASING IN
OIL WELLS.
For a water casing to be effective, it is necessary
that there should be an hermetic seal between it and
the wall of the well, and that the casing should be
able to withstand the maximum pressure to which it
may be subjected. The failure of water casings can
not, as is sometimes erroneously supposed, be caused
by the formation of a vacuum, or by pumping the
water out of the bore too rapidly, nor is it to be avoided
by the introduction of a protection casing, except in
the case that the well has reached the oil horizon with
the same casing that has served to exclude the water,
in which case the protection casing is necessary to
afford protection against the erosion of sand and the
friction of the baling rope, etc. The maximum
pressure to which the water casing will be subjected
should be ascertained by calculation, and the casing
made of a corresponding thickness to withstand it. In
the case of a well in which the water has been cased
off at a depth of h metres from the surface, and in
which the water has been pumped out to a depth of x
metres from the surface, the pressure at x metres from
the surface which the column must bo able to with
stand is P : =(X“y)/10 atm. The column supports
this pressure from the depth of x metres down to its
shoe, or respectively, down to h metres from the sur
face. The pressure at any point h metres from the
surface is h/10 atm. The pressure, being zero at the
f
Rom
surface, gradually ' id creases with increasing depth,
being greatest at the bottom. To calculate the
pressure to be resisted, it is necessary to suppose that
the well is entirely empty of water, and that the space
behind the casing is full of water. It must also be
borne in mind that the gravity of the liquid may ex
ceed that of water, owing to the presence of suspended
matter, and the factor of safety used must provide for
this contingency. Professor Stewart found that the
collapsing pressure of such tubes as are employed in
casing = Pt = 1,0(M) (1 - V 0 - 1600 t 2 ld~), Pt being the
collapsing pressure in lbs. per sq. in., d external
diameter of tubes in inches, and t thickness of tubes in
inches. This formula applies to cases where P is less
than 581 or when t /d is less than 0.023. When these
values are greater the formula applicable is Pt =
86,670 i/d—1,386. The corresponding formulae for
the metric system are Pt=70.3 (1 — -vAl -- 1.600 t-/d-)
and Pt^ 6,094 tld — ^lAh respectively, w T here Pt is
expressed in kgr. per sq. cm. and the diameters are
in mm. The first formula applies when P is less than
41, or t/d is less than 0.023, and the second when these
values are greater. By these formulae the thickness of
tubes may be calculated, a coefficient of safety of 2
being sufficient. On the basis of these figures the
accompanying sketches show the necessary thickness
of casing tube for various depths and the weight of
tube per unit of length, both in the English and metric
systems.—(By J. T. Hayward and E. C. Masterson.
Moniteur du Petrols Roumain, January 1st, 1923.)—
P. J. M.
BOLIVIAN TRADE CONDITIONS.
January, 1923, stands out as the peak month in
Bolivia, commercially speaking, since the beginning
of the dull period of 1920, says the American Consul
at La Paz, in a cable to the Department of Commerce.
A continuous rise in the price of tin is reported, with
consequent general improvement over the country.
Exports were the first to feel the effects of the better
price and although official figures for December are
not yet obtainable it is known that a notable increase
in shipments has occurred. The average price of tin
for 1922 was ;£158, as compared with ^185, which is
the price now prevailing. The opening of many tin
mines is anticipated as a result of the continued high
prices.
Improvement is not confined to Bolivia’s principal
product, but includes others of her minerals. A
general betterment in copper mining is noticeable, and
increased silver production is expected.
Considerable work has been done by an American
oil company under its concession, and the location of
about 4,000,000 hectares of petroleum has now been
concluded. The Backus petroleum concession has
recently been transferred to a large British oil com
pany. With one exception all of the important manu
facturing plants are reported prosperous.
Railway construction work on the Atocha Vil-
lazon Railway is progressing satisfactorily. At the
present time rails are being laid on two new sections
of the road. This line will connect La Paz with
Buenos Aires and will form the last link in a new trans
continental route. The Government is building the
railroad from La Paz to the Yungas region and it is
progressing slowly.
Certain European capitalists are said to be in
terested in the proposed Cochabamba-Santa Cruz line.
After considerable deliberation the Government
has decided to build a railroad from Potosi to Sucre
under its own management.
WHAT
“Oil Engineering & Finance”
will cost in 1923.
Subscription to “OIL ENGINEERING
& FINANCE ’’ published weekly at 1/-.
12 Montks. 6 Months. 3 Months.
Including all Including all Including all
Special Nos. Special Nos. Special Nos,
52/- 26/- 13/-
DE LIVER ED FREE BY POST.
No Oil Man can afford to be without this Journal-

'Mosul Question, Lausanne 1922-1923 and after - Papers, despatches, speeches - Hotel de la Mer at Lausanne - Correspondence about oil' [‎217v] (432/501)

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