24 



Table 2. Effects on the marine environment which may occur as a result of the development of an 

 offshore oil and gas field (adapted from Neff et al. 1987). 



ACTIVITY 



POTENTIAL EFFECTS 



Platform installation 



Drilling 



Completion 



Platform servicing 



Separation of oil and 

 gas from water 



Offshore emplacement of 

 storage and pipelines 



Transfer to tankers 

 and barges 



Pipeline operations 



Seabed disturbance resulting from placement and 

 subsequent presence of platform 



Discharges of drilling fluids and cuttings; risk of blowout 



Increased risks of spills 



Discharges from vessels 



Chronic discharges of petroleum and other 

 pollutants 



Seabed disturbance; effects of structures 



Increased risk of oil spills; acute and 

 chronic inputs of petroleum 



Oil spills; chronic leaks 



A considerable body of data has already been collected from areas where OCS oil and gas activities have 

 occurred in the past or may occur in the future. This includes rig and platform monitoring studies in the 

 Atlantic, Pacific, and Gulf of Mexico OCS Regions supported and administered by the MMS' Environmental 

 Studies Program (e.g., Table 3), as well as studies sponsored by other federal agencies (e.g., Environmental 

 Protection Agency/National Marine Fisheries Service, Buccaneer Gas and Oil Field Studies; Environmental 

 Protection Agency drilling fluid studies) and private industry. 



While most research agrees that the short-term or "acute" effects resulting from the operation of an oil and gas 

 platform or rig on the OCS are localized and ephemeral, there is less certainty regarding chronic, long-term 

 stresses (National Research Council 1985; Boesch and Rabalais 1987; Aurand 1988). As early as 1981, the 

 National Marine Pollution Program Plan (Inter-agency Committee on Ocean Pollution Research, Development, 

 and Monitoring) concluded that the most significant unanswered questions for offshore oil and gas development 

 are those regarding the effects on ecosystems of chronic, low-level exposures resulting from discharges, spills, 

 leaks, and disruptions caused by development activities (Boesch et al. 1987). 



The effects on the marine environment which may "potentially" result from the development of an OCS oil and 

 gas field are listed in Table 4. By no means is this list complete, rather, it is intended to stimulate and focus the 

 discussions to follow. For example, the possible long-term effects of chemically dispersed oil may also wish to 

 be considered. A review of the use of oil spill dispersants has recently been completed by the National Research 

 Council (NRC) (U.S.) Committee on the Effectiveness of Oil Spill Dispersants (NRC 1989). Logistically, what 

 are the criteria for selecting an individual platform, complex of platforms, or an entire lease block for study and 

 how long should the "impacts" be examined/monitored before they are judged as "significant" against natural 

 variability? 



In order to provide a means to assess the long-term, ecological effects of pollutant influx, the identification of 

 the processes of bioaccumulation and biomagnification of contaminants introduced to the shelf also needs to be 



