Planning and feasibility studies for the transportation of offshore 

 oil and gas to refinery and consumption centers onshore is initiated 

 simultaneously with the discovery and delineation of a new field. Once 

 the type, extent, and character of the reserves, and the characteristics 

 of the reservoir (porosity, permeability, water or gas pressure) are' 

 determined, from exploration drilling, production engineers can determine 

 the amounts of oil and/or gas that will ultimately be produced, production 

 rates over the life of the field, and the approximate location of 

 production platforms. With information on the production rates of 

 platforms and their approximate locations, planning for an oil and/or 

 gas transportation system can commence (See Figure 18). 



Although much of this discussion focuses on offshore operations, 

 most of the environmental impact will be incurred nearshore and onshore. 

 The major impacts from pipeline construction occur in the nearshore 

 area. The impacts from the crew, materials, construction equipment, and 

 supply boats occur onshore. 



Description 



The pipeline is constructed of steel pipe sections, usually about 

 40 feet long, joined together by advanced welding techniques. Each of 

 the "joints" or pipe sections is coated with a corrosion-inhibiting 

 mastic compound and with a concrete covering which protects the pipe_ 

 from damage that might occur during handling and laying operations; it 

 also provides weight and stability insuring that the pipe will sink. 

 Both the anti-corrosive coating and the concrete coating are applied at 

 an onshore pipe-coating yard before the pipe is transported to the "lay 

 barge" by supply boats (see Section 2.3.5). 



System : The pipeline system consists of: (1) the source of oil or 

 gas; (2) a pressure source located on the production platform or in the 

 formation; (3) intermediate pressure sources along the line (if 

 necessary); (4) a landfall site; and (5) a delivery point. The crude oil 

 or gas may come from a single production platform or from a number of 

 platforms connected by smaller pipelines. In some cases, formation 

 pressures are sufficient to drive gas onshore; in others, compressors 

 are required. Pumping equipment is always required for oil pipelines. 

 Whether intermediate pressure sources are needed is determined by the 

 length of the pipeline, the diameter of the line, the quality and type 

 of fluid being transported, the differential elevations encountered over 

 the route, and the formation pressure. 



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