a central collecting point where it is pumped 
ashore via a large pipeline or stored for loading 
onto a barge or tanker. In some cases, portable 
storage facilities are installed near the platform to 
allow production to begin before the pipeline is 
completed. 
In the production phase, the offshore oil 
and gas industry is largely a single industry. 
Historically, additions to the gas reserves have 
come chiefly via the oil producers. Only in recent 
years has the search for gas as an independent 
commodity begun in offshore areas. The principal 
activity of the gas industry in the oceans has been 
related to pipelines. All offshore gas is brought 
ashore by pipelines. 
1. Laying Techniques 
Most offshore pipelines are laid using either of 
two methods: a long stinger stretching from the 
lay barge to or close to the bottom or a short 
curved stinger in conjunction with tensioning 
apparatus. Both have limitations. Figure 39 shows 
a conventional pipelaying barge with a long stinger 
which allows the pipe to follow a gentle slope to 
the bottom during the laying operation. 
a. Long Stingers Unless efficient locating and 
control instruments are developed, the usefulness 
of the long stinger is limited, especially under 
adverse tide and weather conditions as in the Cook 
Inlet or North Sea. Frequently the stinger is 
dropped to the bottom during severe weather. In 
the Cook Inlet operation, shutdowns accounted 
for more than half the elapsed time. 
b. Short Curved Stingers The use of a short 
curved stinger with tensioning devices is an alterna- 
tive having the principal advantage of reducing 
laying stresses. The advantage of tension declines 
as pipe diameter increases, since the effect of 
tensioning is to lessen normal laying stresses which 
increase in proportion to the square of the pipe’s 
diameter. 
2. Present Status and Problems 
Offshore contractors have developed methods 
of laying 12-inch diameter pipelines in depths up 
to 340 feet. Lengths of pipe are joined aboard 
specially designed barges. The joints are welded, 
x-rayed, primed, wrapped, and concrete-coated as 
the pipeline is fed off the end of the barge. An 
estimated 5,000 miles of pipe, ranging in size from 
small diameter flow lines to 26-inch trunk lines, 
now traverse the sea floor in the Gulf of Mexico; 
large-diameter lines have been installed in the 
Persian Gulf (to 48 inches) in depths of about 100 
feet. Figure 40 shows a novel reel barge which was 
developed to lay up to six-inch diameter flow lines 
at high rates. Rollers straighten the pipe as it is 
laid. The tide-swept Cook Inlet has presented the 
toughest problem, and installation costs in this 
area have reached $500,000 per mile even for 
relatively small-diameter pipe. 
Figure 39. Conventional pipe-laying barge with 
a floating stinger allowing pipe to assume a 
gentle slope to bottom during laying operation. 
(Shell Oil photo) 
VI-170 
Figure 40. Barge laying small-diameter pipe 
from reel at a high rate. Rollers straighten pipe 
as it ts laid. (Shell Oil photo) 
