National Supply Builds
15,000-Psi Subsea BOP
And Wellhead System
National Supply Company has
shipped to British Petroleum Ltd.
a unique 15,000-psi subsea well-
head system to be used in the
North Sea.
The BOP stack and individual
components were successfully
tested in December at National's
Houston Wellhead Plant and
shipped on schedule for subsea
installation.
11" X 13H "
15,000 PSI
UPPER BODY
CASING
"straightforward" development of
the concepts used in the com-
pany's present designs. It used
two 15,000-psi double-ram pre-
venters for the main BOP assem-
bly and a 10,000-psi annular pre-
venter for the lower riser package.
This 11-inch, 15,000-psi well-
head design concept is the first
application on a National Sea
King 13-5/8-inch, 10,000-psi well-
head. This design can be utilized
in all other sizes of National's
10,000-psi Sea King wellhead
equipment.
The key advantage to this sys-
tem is the flexibility it provides
the customer. It allows him to up-
grade his National equipment to
higher ratings when required.
National Supply developed the
industry's first underwater prod-
uct unit, placed in Lake Erie in
1957, and designed the first sub-
sea production unit to go into
operation in the North Sea.
A division of Armco Steel Cor-
poration, National Supply Com-
pany manufactures the most
complete line of oil-field drilling
machinery and related equipment
in the industry.
For additional information on
the 15,000-psi subsea wellhead
system, write to William Marmac,
National Supply Co., Division of
Armco Steel Corporation, 1455
West Loop South, Houston, Texas
77027.
How crossover to 15,000 psi was per-
formed is demonstrated in this drawing.
Components shown in white were devel-
oped to allow 15,000 psi completion
within existing 10,000-psi-rated equip-
ment, shown shaded in drawing.
The new National system fea-
tures a unique "crossover" that
allows a 15,000 psi completion
within existing 10,000-psi-rated
equipment. This approach offers
the customer the higher rated
equipment at considerable savings.
BP engineers came to National
Supply for assistance after run-
ning into unexpectedly high pres-
sures in the North Sea. No subsea
wellhead system then available
was rated for more than 10,000
psi. Without properly rated equip-
ment, the potential of the discov-
ery could not be properly assessed.
National's engineers designed
the new 15,000-psi BOP stack
and wellhead equipment to be
used with existing 10,000-psi-
rated equipment.
The advantages to this ap-
proach are:
• The well could be drilled in
and established with readily avail-
able equipment.
• Use of standard National
wellhead components saves on well
costs.
• The system requires fewer
new components.
• The system could be used
with BP's existing National equip-
ment.
The BOP stack is a relatively
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July 15, 1977 9
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