Gas is piped to a gas processing facility, the shore destination, 

 on line between the landfall site and the market transmission line. Oil 

 is piped to one of two shore destinations, a nearby refinery or a marine 

 terminal, for transshipment to a refinery. 



Site Requirements 



The most important factor of the pipeline project is the selection 

 of the pipeline corridor. The major object is to minimize the total 

 capital and operating cost of getting the oil or gas from offshore to 

 the desired location onshore. Minimizing the transport cost of oil 

 usually, but not always, requires minimizing the length of the offshore 

 pipeline, because marine pipeline construction is considerably more 

 expensive than most onshore construction (pipelines through wetlands may 

 be as expensive as offshore). 



Particular physical and environmental offshore obstacles to be 

 avoided include: deep trenches parallel to or crossing the shoreline, 

 heavy surf zones, soft bottom sediments, sediments subject to lique- 

 faction, extremely hard and rough bottoms, strong bottom currents, sand 

 waves, areas of seismic activity, live reefs, and heavy fishing areas. 

 This may cause a pipeline corridor to deviate from the shortest straight 

 line to the shore. 



The Corridor : The preliminary technical assessment of potential 

 pipeline corridors by industry is begun after the size of the prospective 

 pipeline is determined. A number of corridors are selected which 

 originate in the offshore field and terminate at various shore locations 

 which are either feasible locations for transshipment terminals or 

 places where the pipeline can join an onshore pipeline. Each corridor 

 is assessed by developing a preliminary profile from hydrographic charts 

 and estimating the soil conditions and currents along the route. 



From this preliminary study, the corridors being considered are 

 narrowed to several options to be considered in detail. Field recon- 

 naissance investigations examine the feasibility of each of the corridors. 

 Sidescan sonar is used to determine the presence of obstacles, debris, 

 and live bottoms. Hydrographic studies determine water depths and 

 bottom topography. Seismic surveys determine the near surface geology 

 and identify potential difficulties along each of the corridors. From 

 these reconnaissance surveys, a construction corridor is chosen by the 

 pipeline company. 



The information developed during a reconnaissance survey, even 

 though allowing the final selection of a corridor, is insufficient 

 either to precisely position the pipeline during construction or to 

 develop engineering design and construction criteria. To provide this 

 information, a much more thorough survey is necessary; significant 

 financial commitments are made, and, as a result, location options begin 

 to be foreclosed. 



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