need exists for a power unit in the intermediate 
range between the trickle chargers and the large 
stationary units on land. 
e. Acoustics Remote control and monitoring by 
a physical link to the surface have been described. 
However, there are obvious advantages of having 
no hard wire link, relying instead on a coded 
underwater acoustic link to command the subsea 
system to activate a particular valve mechanism. 
An acoustic interrogator could be used to monitor 
valve position, read pressure, and obtain other 
desired data. One acoustically controlled, isotope- 
powered wellhead was installed recently in the 
Gulf of Mexico. 
Acoustic links also may find an important role 
during the drilling operation itself in conjunction 
with blowout preventers used to control the 
tremendous pressures in deep formations encoun- 
tered during drilling. Figure 44 shows an under- 
water blowout preventer. 
Acoustics also have been used with bottom- 
mounted transponders in water depths to 5,000 
feet to enable a drilling ship to pinpoint the 
precise location of a subsea wellhead when 
returning to it for hole re-entry. 
Figure 44. Underwater blowout preventer. 
(Shell Oil photo) 
f. Floating Production Station A floating pro- 
duction station moored over a submerged platform 
or subsea wellhead could be used instead of a fixed 
platform. 
4. Underwater Drilling and Storage 
Some petroleum operators foresee a time 
when drilling and collecting oil in water depths to 
3,000 feet or more will be common. Indeed, 
recent reports suggest the possibility of petroleum 
deposits on the continental margin in waters as 
deep as 15,000 feet. Not everyone in the industry 
agrees on the direction in which the required 
technology will proceed. The large power require- 
ments of the drilling rigs (several thousand horse- 
power) and the advances made in mobile rigs make 
the economics of underwater drilling controversial. 
Some feel that total underwater drilling will not be 
economically justified except for large, highly 
productive fields. 
The French have developed a subsurface coring 
rig, remotely operated from a tender ship, which 
possibly could be extended to deep coring. A 
submarine drilling rig design of the late 1950's 
proposed an automatic drilling rig mounted in a 
submarine which would carry the necessary 
drilling mud, drill pipe, casing, and supplies to drill 
fullscale wells. Aside from the formidable prob- 
lems of generating power for such a rig, the overall 
economics were so unfavorable that it was never 
seriously considered. It is possible that future 
coring rigs could be controlled acoustically; how- 
ever, it is more likely that some type of hydraulic- 
mechanical control will be employed similar to 
that used by the French rig. 
Nevertheless, various ambitious conceptual de- 
signs are being examined. At least one oil company 
is studying the feasibility of housing both the 
drilling equipment and crews in structures on the 
ocean floor One concept envisions an entire 
undersea community. The habitat, as described at 
a recent offshore oil conference, would enable 50 
men to live and work in depths to 1,000 feet for 
extended periods. 
The problem of oil storage arises when the 
pipeline investment becomes too high. One solu- 
tion is to store the oil on or near the production 
platform and transport it to shore in barges later. 
In very shallow and well protected waters, barges 
often provide both storage and transportation. 
VI-175 
