Three-dimensional seismic study of structures and salt tectonics of Eugene Island Area offshore Louisiana, Gulf of Mexico

Abstract

The Eugene Island OCS is one of the largest oil-producing areas in federally owned waters of the U.S. outer continental shelf. Fault development and salt tectonics are the most important structural features of the study area. The study is based on 200 square kilometers of three-dimensional (3-D) seismic data. The structures and the salt features are studied in the three-dimensional manner which provides more precision than the conventional two-dimensional seismic study. Four structural horizons were picked and mapped to interpret the normal faulting structures and salt features. They are from bottom to top as: Blue horizon (2.6-3.3 second), Green horizon (1.9-2.3 second), Pink horizon (1.1-1.8 second) and Red horizon (0.5-1.0 second). Also, three corresponding isochron maps are interpreted. Seismic data indicated that the study area is dominated by a single diapir which initiated as an active intrusion, developed through passive stage and is currently undergoing the reactive stage of the salt tectonics. The normal faulting system is intimately related to the development of the salt diapir. The fault pattern at different stages of the salt diapir evolution is quite different, but the general pattern consists of normal faults radiating from the salt center. Above the salt, normal faults are especially well developed suggesting that the diapir intrusion induced a significant amount of extension in the overburden. Lack of well data and paleo data makes it difficult to identify the depositional sequences and correlate the paleo horizons. Due to the salt diapir intrusion, the correlation precision is further decreased.