- Copyright © 2004 Society of Exploration Geophysicists
The Thunder Horse North discovery is a part of the greater Thunder Horse complex in Boarshead Basin, which is in the south-central part of the Mississippi Canyon protraction area of the Gulf of Mexico. The area is very complicated due to abundant salt bodies that overlie and obscure major structures of interest. Resolving this structural complexity through adequate seismic imaging is key to any successful exploration and development program.
3D ray-trace modeling played a critical role in understanding many imaging issues in this area. Modeling results showed that 3D speculative seismic data acquired in the E-W direction would not resolve the structural details and, hence, some key elements of the Thunder Horse North prospect. This led to acquisition in the N-S direction of an additional small 3D survey over the prospect area using the same crew and survey parameters as the spec survey.
The prospective reservoir section and associated seismic attributes are clearly evident in the N-S data but not visible in the E-W data. Accordingly, the N-S data were used for prospect evaluation and planning the first exploration well. The well, drilled in 2000, discovered an oil accumulation in the reservoirs only imaged by the specially designed N-S seismic data.
Since exploratory wells in deepwater are very expensive, appropriate understanding of structural complexity through adequate seismic imaging should be achieved before drilling. This is the reason that more and more exploration programs are demanding 3D seismic coverage along with specialized processing before committing to drill any well.
However, 3D seismic coverage, if not acquired properly, may not be able to resolve structural details in this area and in many instances may not even be superior to 2D seismic data in preferred orientations. It is important to examine existing 2D coverage, if any, to gain understanding of the structural complexity …