--> ABSTRACT: Three-Dimensional Geometry of Fluvial Reservoir Sands: Steam-Drive Case Study, by John G. McPherson and Donald D. Miller; #91022 (1989)

Datapages, Inc.Print this page

Three-Dimensional Geometry of Fluvial Reservoir Sands: Steam-Drive Case Study

John G. McPherson, Donald D. Miller

The three-dimensional geometry of fluvial sands in South Belridge heavy oil field was investigated as part of an Enhanced Oil Recovery study. It was shown that only close-spaced well data are sufficient to define the sand-body geometries and heterogeneities of multichannelled fluvial systems. Reservoir flow-unit patterns cannot necessarily be correctly delineated by isolated vertical sequence analysis. Wireline logs from 19 wells and conventional cores from seven wells in a 10-ac (660 ft × 660 ft) pattern were correlated in detail, using additional input from sedimentology, steam-flow patterns, and reservoir flow-unit continuity.

The three sand-rich zones under investigation form the principal reservoirs of the Pleistocene upper Tulare Formation in the southern portion of South Belridge field, Kern County, California. The sands are unconsolidated, immature lithic arkoses of high reservoir quality (porosity = 35%; permeability = 3,000 md). They are fine to coarse grained, moderately to poorly sorted, and contain abundant intraclast lags, large-scale cross-stratification, parallel lamination, and ripple cross-lamination. Fining-upward cycles are common.

The sands are mostly fluvial channel fill from a mobile channel-belt system. Both coarse-grained (sand-rich) and fine-grained (mud-rich) channel-belt systems are present. The two uppermost zones are of the coarse-grained system, consisting of a multilateral, amalgamated sequence of smaller individual channels, each with an erosive base containing intraclasts. Vertical and lateral communication between the smaller individual channels is high, and the sand zones have sheetlike flow-unit geometries. Recognition of individual depositional units is of no consequence to the reservoir performance.

The lowermost zone is more mud rich and is a composite of small individual sand channels commonly encased in mud. Individual channel dimensions are consistent with the range of calculated values obtained from paleohydraulic reconstructions. The average thickness is 10 ft, width is 500 ft, and length is several thousand feet. Vertical and lateral communication between sands is poor because of their limited interconnectedness. Accordingly, lateral flow-unit geometries are restricted in the lowermost sand zone.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.