Abstract: A 3-D Physical Modelling Approach to Fault Identification, Peace River Arch, Alberta, Canada: Implications for Reef Development

Darran J. Edwards

Keg River Formation patch reefs or bioherms of the Middle Devonian are the principal reservoir facies in this active exploration area, and have largely developed on, or above, prominent Precambrian basement structures. Such anomalous structural highs are thought to be areally closed, a pattern consistent with the idea of a surface fractured by conjugate pairsets of faults. Erosion of these uplifted fault blocks produced coarse-grained basal clastic or granite wash detritus in adjacent margins. It can be shown that direct detection of such basement faulting on 2-D seismic data is difficult, probably due to the limited offset, sub-vertical nature, and strong strike-slip component of these displacements. Such a scenario is used as a template for 3-D physical model construction.

The study presented involves a 3-D survey shot using the physical modelling facilities at The University of Calgary. The main objective was to analyze the potential for imaging directly the faulting commonly found beneath carbonate buildups in this area. Through the examination of both vertical and horizontal sections, this problem of fault resolution can be further attributed to a transparent, shadow-zone effect observed beneath the reefs. However, timeslice investigation does allow the areal extent of the basal clastic fault block to be well imaged away from, and beneath, the reef margins. It is then possible to extrapolate these preferred trends, thereby indirectly inferring the presence of faulting beneath reefs.

This modelled dataset has significant economic implications when applied to a real 3-D survey recently shot in the eastern Peace River Arch area. If a direct relationship between reef morphology and fault movement can be shown to exist for a particular hydrocarbon-rich area, it may be possible to predict other possible plays by extrapolation of proven basement trends. Such reactivated structures may have created conduits for hydrocarbon migration into a suitable reef reservoir, improved by fracture-related secondary porosity. There is great potential using exploration philosophies oriented toward such a basement-reef tectonic control model.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994