--> ABSTRACT: Integrated Multidisciplinary Reservoir Characterization of a Deltaic System - 2: Developing a Petrophysical Model for Reservoir Simulation Using Data From the Ferron Sandstone, Utah, by Steve Snelgrove, Craig Forster, Joe Koebbe, Rich Jarrard; #91020 (1995).

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Integrated Multidisciplinary Reservoir Characterization of a Deltaic System - 2: Developing a Petrophysical Model for Reservoir Simulation Using Data From the Ferron Sandstone, Utah

Steve Snelgrove, Craig Forster, Joe Koebbe, Rich Jarrard

Geological, petrophysical, and geophysical studies underway at outcrops of the Cretaceous-age Ferron Sandstone, East-Central Utah provide an integrated basis for developing 3-dimensional geological and petrophysical models of a deltaic reservoir system. The results of outcrop surveys carried out on 3 sides of a cliff-bounded plateau complement data from 5 coreholes located on the plateau in a five-spot pattern with 40-acre spacing. Outcrop studies include detailed and regional-scale geologic mapping (see companion paper in this session by Adams et al.), gamma ray surveys, core plugging transects, in situ mini-permeability tests, and shallow seismic surveys. The vertical transects of permeability, petrophysical properties, and gamma-ray variations can be used to tie petrophysi al units observed in outcrop to those observed on a more detailed vertical scale in the adjacent drillcore and geophysical logs. Distinct differences are found when comparing results of both vertical permeability transects and gamma ray surveys performed at distal and proximal positions within the delta parasequence. Detailed lateral transects of permeability data document characteristic permeability variations within several different lithofacies found within a delta parasequence.

Cliff-face geological mapping performed within "windows" approximately 60 m by 17 m (180 ft. by 50 ft.) provides detailed geometric observations needed to scale up the fine-scale petrophysical data to produce suitable grid-block parameters for input to a reservoir simulator. A homogenization method is applied that computes representative grid-block properties using averages of fluid flux vectors computed within a fine-scale modeling domain. Geometrical and petrophysical properties of characteristic bedform types are simulated and homogenized at a series of scales to obtain representative parameters for grid blocks that range in size from 1 m by 1 m (3 ft. by 3 ft.) to 3 m by 3 m (10 ft. by 10 ft.) and larger. The results of the combined field studies and numerical simulations will ult mately lead to construction of a 3-dimensional reservoir model that preserves the inherent character of the deltaic systems found within outcrops of the Ferron Sandstone.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995