Digital Outcrop Models - Leading to New Insights into Characterization and Modeling of Carbonate Reservoirs
Stratigraphic solutions to subsurface data sets are non-unique and, as a consequence, subsurface exploration and reservoir characterization require constant improvement of input data and geostatistical modeling concepts. Data-rich digital outcrop models of end member carbonate systems (DOMs) identify geologic heterogeneity (resolution, architecture, continuity, correlation, facies juxtaposition) and provide concepts and strategies that can be incorporated into less-constrained subsurface-based models
Lower Jurassic outcrops representing end member carbonate systems that serve as analogs in the Caspian Basin, Middle East and elsewhere were studied in the High Atlas of Morocco. They yield insight into facies and stratigraphy for 1) the platform top and steep slopes of a 34 by 6 km isolated carbonate platform (Djebel Bou Dahar) that is characterized by extensional tectonics, margin retrogradation, fracturing, and tidal flat deposits, and 2) facies partitioning along a 35 km mixed clastic-carbonate ramp system (Amellago) as a result of sea level, post-rift tectonic subsidence, and changing depositional environments in a dip direction.
DOMs were generated by integrating traditional geology with LIDAR, RTK DGPS data, and terrestrial, airborne and/or satellite imagery which provided exact and quantitative information on properties like stratal anatomy, spatial lithofacies trends, sedimentary body shapes, and facies juxtaposition rules. Lithofacies types were simulated using both static modeling (MPS/FDM) and forward modeling (Dionisos) techniques. MPS/FDM allows global conditioning to hard data and simulates both depositional and diagenetic shapes, trends and spatial associations between rock types at variable resolution scales (i.e. exploration to reservoir). Dionisos provides spectra of end-member solutions with limited conditioning but serves as a powerful tool for regional exploration, training and communication.
The “outcrop-to-subsurface” workflow yielded a digital library with morphometric data on the grand-scale and smaller (reservoir) scale in two end member carbonate settings, helped to identify the impact of data density on the preservation of geological heterogeneity, and provided fundamental learnings in geostatistical modeling concepts Future steps include generating flow models in such hydrocarbon reservoir systems and simulating diagenetic facies using MPS/FDM and Reactive Transport Modeling (RTM).
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009