Installation and maintenance of lines. 



Activity sequence 



Lines associated with gas and oil activity may be separated into 

 three groups - supply lines, flowlines, and transportation lines. 

 The activity levels necessary for their placement range from minor 

 to major. 



Water, gas, and other lines bringing supplies to the wellsite are 

 usually laid on the surface, typically parallel to an access road or 

 access canal. If a line route does not parallel wellsite access 

 routes, a survey crew must enter the marsh by foot or marsh buggy 

 and stake the pathway. Trucks or barges supply the pipe; if the 

 route crosses unmodified marsh, a marsh buggy will be used to carry 

 pipe. The lines are small and are usually connected and placed by 

 hand. 



Flowlines span the distance between the wellhead and the production 

 facilities, usually less than five km (three mi). If an 

 access road has been constructed through the marsh, the flowlines 

 will be placed on the levee or the adjacent marsh surface. In 

 dredged locations, flowlines are placed on the marsh surface or 

 supported slightly above the surface. Marsh buggies are used to 

 stake and clear the route. When crossing canals, flowlines are 

 buried deep enough to avoid problems with maintenance dredging; 

 draglines or jetting barges are necessary for this procedure. 

 Crossing nonnavigable canals often requires the driving of piles for 

 pipe supports. 



Long-distance transportation of well products is accomplished by 

 large buried pipelines which vary from 20 to 150 cm (8 to 60 inches) 

 in diameter. Pipeline locations must be surveyed and staked. Since 

 pathways tend toward straight-line orientations between facilities, 

 they must span existing surface features. Dredges and draglines are 

 most frequently used in crossing a salt marsh; marsh buggies are 

 employed as auxiliary equipment. The push method requires a special- 

 ized barge (located in a dredged slip) to assemble and push the 

 pipeline into a canal; the pipe is supported on floats and guided by 

 a marsh buggy. A dragline is used to excavate this straight canal 1 

 to 2 m (4 to 6 ft) deep and about 3 m (8-10 ft) wide. Spoil may 

 be placed on one or both sides of the canal. The area affected is 

 about 10 m (30 ft) wide for small lines (20-cm, or 8-inch, diameter); 

 wider areas are disturbed for larger pipes. In some cases the marsh 

 vegetation and upper soil layers can be separated from the lower 

 portions of the substrate during excavation. After the pipeline is 

 in place and the canal refilled, the upper soil and vegetation is 

 replaced. This "double ditching" technique facilitates revegetation 

 of the disturbed area. In some instances the pipeline canal is not 



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