Remobilized Sands: Integrating Field Techniques and Seismic Modeling

A. M. Robinson
Cardiff University, Dept. of Earth Sciences, Cardiff, Wales, UK

Postdepositional processes of liquefaction and fluidization that remobilize sandstone reservoirs have only recently become appreciated, and many aspects of this process are far from understood. Remobilization of Eocene sandstones in the Faeroe-Shetland Basin form a central theme of my research, based on 3-D seismic interpretation, calibrated by only a small number of wells. Sandstone injection features seen here occur as layered complexes or as conical sills. The aim of this proposal is to undertake a field mapping study of analogues to these subsurface examples to validate the seismic interpretation, and providing realistic geometries for synthetic seismic modeling. Fieldwork is to be conducted on Miocene intrusions in Santa Cruz, California, and Mid-Cretaceous intrusives in the Sisteron region, SE France. These two areas are well known from previous studies, and this proposal will build on those studies by focussing mainly on constraining the 3-D geometry of injected bodies.

Samples will be taken for petrographic analysis to calibrate representative rock properties, and structural data will assist in developing a model for sandstone intrusion. The modeling will investigate how thickness variation of the injected body affects the geophysical response. The field data will additionally be used to suggest processdriven models of emplacement.

This proposal has significant implications for the petroleum industry: Many producing hydrocarbon provinces have accumulations reservoired in remobilized sands (e.g., Alba, North Sea). By quantifying the size/shape of these bodies using geophysical models, it will be possible to build more accurate reservoir models and plan development wells more effectively.

AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid