with oil), if found in large enough quantities to justify the construction of 

 a pipeline, is transported ashore for further processing and to recover 

 liquifiable hydrocarbons. 



In some cases the entire well stream is piped ashore. There is a tradeoff 

 here, however, between using the larger pipe size needed to carry the in- 

 creased volume (because of free water) versus the use of valuable platform 

 space for water separators. Emulsified water is usually separated out of the 

 wellstream onshore because equipment necessary for this process is relatively 

 complex. Both free and emulsified water must be treated before discharge. 

 The siting considerations and impacts of onshore oil and gas processing and 

 treatment facilities are shown in Tables 9 and 10. 



Refineries 



A modern oil refinery physically or chemically alters all or part of 

 crude oil to produce a number of petroleum products. The three major types of 

 refineries are market refineries built to serve a particular market, resource 

 refineries built on or near major oil fields, and swing refineries built to 

 balance supply and demand. The market refinery is the preferred type of 

 refinery because shipping bulk crude oil is less costly than shipping several 

 refined products. Refineries are not usually constructed to accommodate OCS 

 production area unless a relatively large demand is located nearby. 



Refineries usually are parts of complexes that also include storage 

 tanks, administration and maintenance facilities, water treatment facilities, 

 and laboratories. The entire complex is usually surrounded by a buffer zone. 

 Transportation systems including rail, road, pipelines, and marine terminals 

 also are required. Siting considerations and impacts associated with refin- 

 eries are given in Tables 9-10. 



Platform Fabrication Yards 



Offshore OCS oil and gas drilling and production are conducted from plat- 

 forms that are constructed of steel or concrete. The main body, or jacket, 

 supporting the platforms is constructed almost entirely of tubular steel that 

 is fabricated onshore at a waterfront location, placed in the water and towed 

 to the installation site, and set in place on the ocean floor. Decks, drill- 

 ing rigs, living quarters, and other rig components also are constructed 

 onshore and towed to the offshore site. Several types of platforms are 

 constructed depending upon depth, sea bottom type, weather trends, the mix and 

 type of oil and gas in the find, and other factors. 



Platform fabrication yards are large marine facilities usually consisting 

 of fabrication shops, welding racks, pipe mills, concrete mixing plants, and 

 cement storage silos (if concrete platforms are used), and administrative 

 facilities (Tables 9-10). 



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