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Abstract: Examples of Cased Reservoir Analysis in the Ventura Basin, California

ODOM, RICHARD, Computalog Research

A reevaluation of how logs are conventionally used to make maps resulted in several significant changes in data utilization and mathematical procedures. Standard techniques typically average log responses over each interval of interest to produce map parameters such as sand thicknesses, porosities, and water saturations. Averaging large numbers of log responses from each well into individual parameters greatly reduces the quantity of inputs for maps. An alternative is to eliminate invalid log responses and continuously process the remaining relative abundance of data for more detailed maps. Conventional averaging techniques often produce graceful rounded map contours that contrast with the abrupt angularities that are commonly observed in sedimentary systems. Continuous processing of log responses can produce plots with complex shapes that much more closely resemble well-known sediments.

Advanced mapping techniques were developed to fully utilize large quantities of continuous data. Current and wave equations modeled water current and wave sedimentation processes. Appropriate depositional dispersion directions and distances were derived for common clastics. More exacting plots became possible to make extended sedimentation patterns. Components of recreated bays, islands, channels, lakes, and deltas are closely compared to satellite photographs of complex modern equivalents.

More detailed maps have reconciled differences between conventional geologic maps and production engineering data maps. Also, the advanced techniques have revealed permeability barriers and undrained areas with high sand contents in old fields. Additional successful wells were drilled.

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California