F. Subsea Operations 
1. Potential Advantages and Philosophy 
The potential advantages of having an under- 
water operating capability are: 
—Extension of production capabilities to greater 
depths than those for which fixed platforms are 
economical. Fixed steel platforms (similar to 
Figure 41) can be designed for very deep water, but 
there is an economic and technical limit to their 
maximum height. Moreover, to emplace them is 
extremely risky, particularly when the site is far 
from available fabrication sites. 
—Removal of operations from the often turbulent 
surface environment to avoid loss of platforms in 
hurricanes or damage from severe storms and 
shifting foundations. 
—Elimination of navigation hazards. 
—Additional operational options in such hazardous 
ice areas as Cook Inlet. 
Figure 41. Two derrick barges installing section 
of fixed platform. Equipped with 500-ton ca- 
pacity revolving cranes, barges are erecting a 
650-ton crude oil storage deck on permanent 
drilling and production platform in Gulf of 
Mexico. (Brown and Root photo) 
VI-172 
The fact that the industry is buying leases in 
ever deeper waters implies that the bidders expect 
that it will become economically and technically 
feasible to produce in deep water. 
Any discussion of subsea operations must be 
preceded by qualification of the type of field 
involved. Each field is different in water depth, 
size, and product nature; in closeness to shore; and 
in many other factors which must be taken into 
account. 
The requirement for collection, storage, or 
transportation a few miles off Santa Barbara, 
California, is not expected to resemble those in 
areas distant from shore as in the Gulf of Mexico. 
In the Santa Barbara area a simple pipeline 
without underwater separation facilities may suf- 
fice, while in the latter, production and storage 
facilities may be necessary for intermittent de- 
livery to shuttling tankers. In each case, however, 
it is possible that employment of some subsea 
completion, production, and maintenance features 
may enhance the system’s economic appeal. It is 
difficult to predict which system will ultimately 
prove most practical, but it is likely that several 
different techniques will be employed. 
In conclusion, future economical production in 
deep water will depend on a choice among surface, 
completely underwater, or some hybrid technol- 
ogy. It is reasonable to assume that the industry 
will continue in prototype technical work to: 
—Make the best economical estimates of these 
options. 
—Take maximum advantage of deep water oppor- 
tunities found by exploration. 
—Select an option that can be used side by side 
with its more familiar surface technology. 
2. History 
The first subsea wellheads were installed on gas 
wells by divers on the shallow bottom of the Great 
Lakes in 1959. The first oil well was completed in 
1960 in the Gulf of Mexico in 55 feet of water. 
Underwater wells in the Santa Barbara Channel 
have been producing since 1964 in waters more 
than 250 feet deep. There are presently between 
50 to 100 subsea completions throughout the 
world. They are still considered experimental in 
