Fluvial Facies Delineation Through 3D True Volume Interpretation
McCANN, CECILIA BINIG, and GEORGE A. ALCORN, JR.
The Oligocene Frio Formation holds its greatest allure to oil and gas
prospectors in the elusive meandering fluvial channels. 3D seismic true volume
interpretation techniques are used in this study to pursue these subtle
features. Using value thresholds, automatic tracking delineated subvolumes from
the full volume which could not have been isolated by conventional horizon based
approaches.
Compartmentalized bodies which cut down through older rocks such as the Frio channels defy chronostratigraphic surface delineation. Visualization of the connected and nonconnected units establishes the spacial and genetic relationships of depositional facies tracts without surfaces. Associated fluvial facies identified in the study include distributary channels, levees, crevasse splays, and point bars. These features as well as depositional axes are labeled in the study volume. This presents an enhanced subsurface model shifting the paradigm from traditional geometric block diagrams.
True volume isopach displays are superimposed at depth with land information which was previously constrained to surface projection Likewise borehole penetrations are reviewed and planned with greater structural accuracy by using true volume visualization. Optimal well positioning for maximum sand penetration in the frio fluvial channels is shown in the semi transparent seismic volume space.
Geologists and geophysicists have long been able to communicate subsurface concepts through laborious and insufficient mapping techniques. Now however these complex stratigraphic and structural models can be illustrated more efficiently to greater audiences with greater understanding.