Environmental Hazards: Considerations For Outer Continental Shelf Development
Authors: Teleki P.G. , Garrison L.E. , Hampton M.A. 
Published: October 2008

Expansion of offshore petroleum operations into unknown frontier areas, deeper waters, and more hostile environments has increased industry's and the Government's awareness about environmental hazards on the Outer Continental Shelf (OCS). Data on environmental exposure are absent in the public domain although these data (1) are needed to test engineering concepts for the design of offshore structures, (2) are factors in leasing on the OCS, and (3) govern economic decisions on petroleum exploration and production. The summary of environmental hazards on the U.S. Continental Shelf presented shows much variability in the hazard potential among OCS areas and complex interactions among various types of hazards within a single area. The U.S. Geological Survey is actively studying the stability and properties of marine sediments, extreme wave conditions, earthquake induced ground motion, and arctic sea ice and permafrost to improve its understanding of the processes governing the existence and behavior of these hazards.

INTRODUCTION

In 1947, when the first steel oil and gas platform was installed in less than 6 m water depth, 12 miles out in the Gulf of Mexico by Kerr-McGee, little thought was given to the hazards posed by the marine environment other than to make the structure heavy and stiff as possible in the face of storm waves. Sixteen 24-inch pilings, penetrating 104 feet into the seabed, served as its foundation. This was obviously an effective design because that platform still stands and produces oil and gas. It does not, however, represent economical construction methods. In contrast, during the 32 years that this structure has been standing, other platforms were lost or irreparably damaged that were larger, more sophisticated, and much more expensive.

As the offshore industry moves steadily seaward into increasingly severe environments, hazards become increasingly crucial in design plans, risk calculations, and platform operations. Necessarily, our knowledge of the environmental processes that produce loads on offshore structures needs continual refinement.

This refinement in the definition and understanding of environmental forces has arisen for economic as well as safety reasons. The survival of Kerr-McGee's pioneer platform is based simply on overdesign whereby excess strength replaced more precise design force calculations. Since 1947, such excess safety factors have been largely responsible for the low incidence of catastrophic failures of fixed platforms, however, as the size of platforms and the cost of construction continue to increase, the concept of overdesign will need reconsideration.

Statistics for the 28-year period from 19471974 (Marshall and Bea, 1976, Moan, 1978) show that until, now the U.S. industry has operated in relatively benign environmental conditions. The environment of the relatively shallow and protected waters of the Gulf of Mexico and the Santa Barbara channel are quite unlike conditions in other recently leased are on or at the edge of OCS (Outer-Continental Shelf) areas.