Bureau of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
AAPG Annual Convention, Houston, Texas, April 9–12, 2006
Application of Seismic Forward Modeling of Detailed Outcrop Data in Improving Sub-Surface Interpretation
The ability to directly compare outcrops with seismic objects has the potential to aid the training of seismic interpreters, where the scales involved can often lead to misinterpretation. One of the first steps to delineating a reservoir is the interpretation of sub-surface stratigraphy and depositional elements using seismic data. Exploration seismic data is typically acquired with a peak frequencies varying from 30 to 60 Hz, giving average vertical stratigraphic resolution of between ~23 m (30 Hz) and 11 m (60 Hz) in siliciclastics and ~60 m (30 Hz) and 30 m (60 Hz) in carbonates.
Many stratigraphic architectural elements are typically at higher resolution, and their interpretability on seismic profiles is limited. Seismic forward modeling of outcrops helps to address this problem, enabling the examination of known stratigraphy and depositional elements at various scales. We present results from six deep-water clastic and carbonate outcrops from the Brushy Canyon and Victorio Peak Formations of West Texas. High-resolution 3-D outcrop profiles were acquired using a Lidar scanner. Stratigraphic surfaces and architectural elements investigated using traditional methods were interpreted directly onto the digital data, similar to seismic interpretation, providing a truly 3-D outcrop interpretation. These outcrop-constrained stratigraphic data were used to construct reservoir models. Petrophysical properties for producing analog reservoirs of similar depositional geometry were assigned to lithofacies zones. Seismic forward modeling of each reservoir model was carried out at several peak frequencies; the results, draped back onto the outcrop profile, allow an immediate comparison between outcrop architecture and its seismic image. This comparison can not only improve our seismic interpretation skills but also enable us to quantify the loss of resolution inherent within the seismic method.