For an operation where a drill ship or work ship is not available 
in a timely manner, a barge or other available vessel could be outfitted 
for the specific operation with (1) a leased oil well rig including 
pipe, crew and accessories, (2) a leased portable concreting plant and 
materials storage and handling systems, (3) mooring, positioning and 
other systems to suit the given operation, and (4) crew accommodations 
and work space. 
This approach has the disadvantage of having to provide and shake- 
down the marine and ocean systems as well as the pipe, concreting and 
materials systems. Advantages are that in some instances, perhaps in a 
remote area, it would be faster, or more cost effective, to use a locally 
available platform. 
Positioning Systems and Operations Monitoring Systems. Both position 
determination and position control systems are required at the surface 
and at the seafloor for the horizontal and vertical directions. The 
positioning and monitoring systems used for a given concreting operation 
will depend on the specific needs of that operation and on the capabilities 
of the drill ship or other surface vessel. 
The position determination system furnishes information on the 
horizontal and vertical location of three objects: the surface platform, 
the sub-sea object, and the lower end of the pipe string. These objects 
are located relative to each other and to some frame of reference such 
as geographic coordinates or a nearby taut buoy. Surface position 
determination systems include traditional navigational methods as well 
as more precise location systems such as satellite navigation, ship's 
radar, electronic distance measurement systems and horizontal angle 
measurement systems such as theodolites and lasers. Water column and 
seafloor navigation and position determination systems include short and 
long baseline acoustic transponder systems, load mounted sonar and TV, 
taut wireline to seafloor, and pipeline inclination measurement systems. 
Vertical position may be determined by fathometer, load mounted sonic 
altimeter, and measurement of the length of pipe or wireline inside the 
pipe. Television is useful for target acquisition and initial approach 
to the seafloor as well as for post-operation observations, but will not 
be useable during concreting due to turbidity. 
The primary function of the position control system is to place and 
maintain the discharge end of the pipeline at the desired horizontal and 
vertical position at the seafloor relative to the target location. 
Position will be controlled by a combination of maneuvering and station 
keeping of the surface ship for the gross position control, and the use 
of guidance devices (guidelines, posts, funnels, and cones) and subsea 
motive systems (attached near the lower end of the pipeline) for the 
local fine position control at the seafloor. Horizontal surface position 
is controlled by single or multiple point mooring systems in water 
depths to 2,000 feet or so, or by dynamic positioning to maintain the 
vessel at the desired surface position. Propeller and jet thrusters 
have been proposed for the attachment to the lower portion of a pipe 
string for its horizontal position control near the seafloor. These 
methods have been found to be unnecessary in many cases in actual 
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