ABSTRACT: Seismic Acquisition and the Environment of the People's Republic of the Congo
HANSON, REX A., Chevron Overseas Petroleum, Inc., San Ramon, CA, and RICK STOCKER, Chevron Exploration and Production Services, San Ramon, CA
From March 1989 through August 1990, the Companie Generale de Geophysique (CGG) recorded 338 km of seismic data for Chevron Overseas Petroleum, Inc., and its partners on the coastal plain of the People's Republic of the Congo. The 1179.5 sq km area under exploration, known as the Kayes A block, lies at approximately 4 degrees south latitude and 11 degrees east longitude.
Savannas dominate the terrain, but these grasslands are frequently broken by tropical forests and cut by numerous ravines and streams. The Conkouati Lagoon, a major feature of the block, divides Kayes A into northern and southern sections: the southern section composed of generally low-elevation (0-60 m), swampy terrain, and the northern section marked by its heavy forests and rapid changes in relief. The region has a humid, subequatorial climate, with heavy rain from March through May, lighter rains from October to early December, and generally dry weather for the remainder of the year.
Near-surface conditions present major difficulties in obtaining good-quality seismic data. In addition, the terrain and climate of the area pose a challenge in balancing requirements for data quality, operational safety, and environmental protection.
Evidence of the only previous seismic survey conducted in 1981 is present in the area in the form of badly eroded line and road cuts. Avoiding this kind of damage was a major priority form Chevron in its exploration of the area and was approached in two ways: (1) minimize the initial intrusion in the area, e.g., mechanized line and road clearance, and (2) repair and recontour lines and roads where necessary to avoid erosion. The second process was completed in the summer of 1991. Photographs of the areas concerned, taken before and after the contouring project, show the current state of progress.