Delineation of Complex fault network North Slope, Alaska using seismic attributes

摘要

The North Slope, Alaska has a complex fault system in the subsurface due to different episodes of tectonics. The most producing reservoirs are fault controlled. Our study area lies in the south of the well-known Prudhoe Bay and Kuparuk River oil fields. The Triassic-aged Shublik Shale, which is the most prominent source rock, has gone through three stages of extensional tectonic activities during the Jurassic, Cretaceous, and Eocene. To understand the complex fault system, we computed an ensemble of volumetric seismic attributes, including coherence, curvature and aberrancy, and studied them along the Shublik Shale surface. In this study, we have divided the structures into three types based on seismic signature, 1. significant fault throw on vertical seismic section, 2. insignificant fault throw but clearly visible flexure, 3. insignificant fault throw and very weak flexure. We observed type 1 faults on the vertical seismic section, and seismic attributes which trends in WNW direction, these faults have large lateral extent. The type 2 faults have similar orientation as type 1. The type 2 faults are clearly visible on the curvature and aberrancy attributes. Although, the type 3 structures have no visible throw on vertical seismic, but, it can be seen as two fault lineation (which are orthogonal each other) on curvature and aberrancy attributes. Based on our attribute analysis and regional geologic understanding, we believe that, the type 1 and type 2 fault sets are of Jurassic age, whereas the two faults of the type 3 were formed in Cretaceous and Eocene with an orientation of nearly east-west and north-south orientation. These type 1 faults display cross cutting, single-tip and double-tip abutting relations with the older west-north-west striking faults.