all the way to the wellsite location, which has a different shape and dimensions 

 from those of the channel. After dredging is finished, the equipment is moved 

 out of the area. Depending upon siltation rates, redredging may occur once 

 every six months to every five yr. 



Nichols (1959) reported that 19.8-m (65-ft) wide canals with 9-m (30-ft) 

 berms separating spoil piles on both sides of the canal actually encompassed a 

 width of 93 to 104 m (306 to 340 ft) when measured from the outer edges of the 

 spoil piles. Thus a marsh area as wide as five to six times the canal width 

 may be directly affected by the petroleum canal (KcGinnis et al., 1972). In 

 this case, for each meter of channel length, 100 m^ of marsh may be affected. 

 By extension, each km of canal length may directly affect 0.1 km of marsh, 

 converting the area into canal, berm, and spoil deposit. 



Gagliano (1973) described changes in surface environments in two Louisiana 

 oil fields. Comparing the total amount of area of channels, canals, and spoil 

 banks to the total canal length, the ratio of area directly affected per unit 

 length of canal may be calculated. A figure of 0.153 km per km of canal 

 length is derived by combining the figures for both areas and sampling periods. 

 This agrees closely with the estimate from Nichols (1959). 



Relatively few attempts are made to vegetate the spoil banks. In many 

 areas there are opportunistic species that will colonize a new bank rapidly, 

 though planting may be desirable to maximize stabilization. If the well is dry 

 or only marginally productive, the site may be abandoned. Natural siltation 

 may tend to fill the channel, though plugging the canal is more desirable in 

 areas where drainage or saltwater intrusion may cause problems. 



Planning access canals for field development. The petroleum industry 

 often makes a distinction between exploration and development drilling. Explora- 

 tion is usually thought to be the drilling of a "wildcat" - an oil or gas well 

 drilled in territory not known to be productive. A development well is drilled 

 in a proven field to increase the production and percent extraction from that 

 field. 



When an exploratory well is planned in a marsh area that can be accessed 

 only by canal, the petroleum exploration company will try to reach the wellsite 

 economically, weighing cost, environment, and other factors. If commercial 

 quantities of gas or oil are found, the company will want to develop the field. 

 This involves determining the spatial extent of the deposit and placing wells 

 in an optimum arrangement to maximize the mineral extraction while minimizing 

 costs. Until the spatial extent of the resource is known, little planning of 

 access routes can be done. 



Other wells may be drilled to aid in determining the extent of the resource. 

 On the basis of test results from drilling, seismic work, etc., the field can 



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