Abstract

P.T. Caltex Pacific Indonesia has developed a novel work process for building structural and stratigraphic frameworks employing 3D seismic attribute data within a volume interpretational system.

Former structural and stratigraphic frameworks were typically developed by interpreting exaggerated 2D time inlines and crosslines using a single 3D volume attribute. Conventional work processes: a) leads to incorrectly picked surfaces, faults and channels; b) extends reservoir sands laterally beyond their actual limit; and c) produces inadequate structural models of deeper trap geometries. Technological achievements in hardware and software permit interpreters to simultaneously utilize multiple seismic volumes such as acoustic impedance, amplitude and high resolution EDGE attributes. Application of these seismic volumes with sound work processes to identify faults, channels, subtle incised valleys as well as lateral 4^th order discontinuities within pay intervals will reduce the overall interpretation cycle time while increasing accuracy.

Structural frameworks are derived from fault interpretations that use two 3D attribute volumes simultaneously. The work process uses two workstation monitors, one monitor displays an inline or crossline view of an amplitude volume while the second monitor displays Chevron's proprietary EDGE (Edge Detection of Geologic Events) amplitude difference or multi-attribute volume timeslice. Actual fault picking is conducted at a true 1:1 scale along both inline and crossline views within an amplitude volume; while, high resolution amplitude difference timeslices act as templates for locating faults thus reducing interpretational bias. The fault surfaces act as boundaries for 3D voxel picking of horizons, channels, clinoforms, fluid contacts (oil/water, steam, etc.). To achieve optimal interpretation of stratigraphic events, an amplitude volume is interpolated and trimmed to the area of interest or structural compartment. Like the EDGE volume, the acoustic impedance volume depicts lateral discontinuities within pay intervals and acts as a guide for the interpreter during 3D picking of stratigraphic events. This same work process is completed until all of the structural compartments are picked and the 3D earth architecture is characterized for each respective reservoir, attic location or prospect.