Methods of Dipmeter Processing and Interpretation in California's Productive Facies

Mike Mulhern, Harold Sugden, Jim Vohs

Dipmeters from the major petroleum-producing facies of California have been computed using INCLINE, a commercially available program. Computational quality control and conformity of results from logs from different areas and logging companies are required to complete multiwell fracture analysis and stratigraphic studies. The flexible program allows the geologist to test processing parameters to obtain optimal results for the objectives of the analysis.

High-angle dips, for example, common in deformed Monterey Formation strata and in fault-induced drag zones, require proper search angles and step distances and can be masked by conventional filtering routines. These rocks are best studied with oriented microconductivity and eccentricity anomaly plots to analyze fracture zones. The strike of dominant and subordinate fracture trends and strike and dip of faults can be used to construct a structural model. Also visible are soft-sediment deformation and slump features, corroborated by microscanner images. Shale drape over fractured metamorphics indicates direction of structurally higher basement in another example. Dip statistical data have proven a valuable Monterey producibility index input, with excellent correlation to production.

In Sacramento Valley turbidites, stratigraphic computations reveal sediment transport and channel thickening directions for step-outs. Larger patterns on structural computations locate and orient submarine canyon or "gorge" fill unconformities, indicating truncation or subcrop traps as well as gorge thickening direction.

In nonmarine (Chanac) and shallow marine (Etchegoin and Temblor Formations) sediments of the San Joaquin Valley, example wells demonstrate directional permeability related to cross-bedding and suggest injection pattern designs to avoid premature steam breakthrough.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.