Loseth, Tore M.1, Jan C. Rivenæs1, John B Thurmond2, Ole J.
(1) Norsk Hydro Research Centre, N-5020 Bergen, Norway
(2) University of Texas at Dallas, Richardson, TX
ABSTRACT: The Value of Digital Outcrop Data in Reservoir Modeling
Digital three-dimensional outcrop models were collected from the Eocene AinsaII Turbidite System, Spanish Pyrenees. The geometry of outcrop surfaces was measured by GPS-positioned laser scanners with decimeter resolution. Digital photos were then accurately draped over the triangulated surfaces, resulting in three-dimensional outcrop models with stunning verisimilitude. The scanning and textural draping are carefully coordinated so each pixel in the digital photograph is positioned in real-world coordinates to sub-decimeter accuracy.
These fully digital geological outcrop data were used to build a quantitative high-resolution reservoir model. A zone-model was constructed by digitizing points on the virtual outcrops and data from four cores collected behind the outcrops. The orientation of the resulting modeling grid follows both the geological bedding and the structure of the area. A facies model was built by incorporating measured sections and facies maps made in the field. Petrophysical properties were assigned to each facies using data from analogous hydrocarbon-producing fields and using different upscaling approaches.
The goal of constructing such a detailed reservoir model was to compare it to a typical model built for a less constrained subsurface reservoir. A second lower-resolution model was constructed, by using only the large-scale geometrical data and the four cored wells, to simulate the typical level of detail available in the subsurface. Both models were simulated for hydrocarbon production and compared directly to each other, providing insights into the importance of various modeling parameters in typical subsurface reservoirs. The comparison clearly illustrates the importance of accurately capturing the true heterogeneity in reservoir models.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.