order. Because accidents happen even then, it is advisable to avoid 

 drilling at sites that would significantly imperil nearby ecologically 

 vital or other critical areas. 



The disposal of drill cuttings and drilling mud during drilling 

 is a matter of some concern. If the platform site is not in a vital 

 area, these problems are greatly simplified. The drill cuttings 

 tend to pile up under the platform and to dissipate \/ery slowly. 

 Where they do accumulate, they temporarily eliminate bottom life. 

 The mud may cause local turbidity and contamination from any heavy 

 metals they may contain. Federal OCS orders (issued by USGS) nor- 

 mally require that any drilling muds or drill cuttings containing 

 significant amounts of free hydrocarbons not be disposed of in the 

 sea. Biocides used during drilling may also affect nearby aquatic 

 resources. 



Production Operations : The major problems in the production period, 

 other than oil spills, are disposal of "formation water", which may be 

 briny and sulfurous wastes that are separated from the oil stream on the 

 platform in a process called "free water knockout" (gravity separation). 

 Emulsions of water remaining in the oil stream are removed by heat or 

 chemical treatment. 



Producing wells require safety measures to lower the risk of blowouts 

 and accidental spills. In wells "capable of flowing oil and gas", storm 

 chokes, or down-hole surface-actuated safety devices, are required to 

 prevent accidental leaks from a well that goes out of control [165]. Still, 

 there is the chance that mechanical defect or operator negligence can cause 

 failure. 



Abandonment : The principal ecological concern involving abandonment 

 of wells (including exploratory wells) is that they be properly plugged 

 to avoid any leakage of hydrocarbons or other toxic substances into the 

 sea. This plugging (15 feet below the surface) is required by USGS 

 regulations . 



The removal of an existing platform will eliminate the "artificial 

 reef fish concentration area" created during its existence on site. Much 

 public opposition may be encountered as rigs are abandoned and moved. The 

 responsibility of leaving a structure and its maintenance after well 

 abandonment are unresolved legal questions. 



4.19 MARINE TRANSPORTATION SYSTEMS'- SUBPROJECT 19 



Marine shipment of oil and gas is a subject of environmental 

 controversy because of possible oil spills, bilge cleaning activities, 

 and release of highly flammable liquefied natural gas (LNG). Oil and 

 gas may escape into the environment at many points from wellhead to des- 

 tination on land. In the transportation system, small-volume spillage occurs 

 routinely, particularly at transfer points. Accidents, human errors, and 



186 



