Simulation of Super-K Behavior in Ghawar by a Multi-Million Cell Parallel Simulator

Abstract

Abstract This paper describes an application of a Massively Parallel Reservoir Simulator for a Giant Carbonate Reservoir with faults, fracture and Super-K zones. It is shown that by using a multi million cell description, premature water breakthrough and complex reservoir behavior is captured with minimum up scaling of the original geological description. The new technology used in this work provides significant reduction in simulation model construction and history matching time. Super-K is a well-known phenomenon in parts of Ghawar where it provides extremely large conductivity to fluid flow. These formations are comprised of vugs, faults, fractures and stratiform dolomite rocks. They form effective flow conduits for water and impact the overall sweep. For the proper accounting of complex heterogeneities, a portion of the reservoir was simulated using a 2.5 million-cell reservoir simulation model. The fault map from the 3-D seismic was incorporated; a thin layer described stratiform Super-K layers with 70 Darcy permeability. A dual porosity type grid was imposed to handle the high permeability conduits. The fine grid in the area of interest was gradually coarsened for the proper accounting of boundary fluxes. This model with over 50 years of history and about 800 wells, was run using Saudi Aramco’s parallel simulator, POWERS1. The total execution time was 4 hours. Premature water breakthrough in the middle of the reservoir was matched closely. The phenomenon of water movement in the vertical direction was duplicated as observed in the field. This study has shown that the ability to handle extreme heterogeneities leads to a more realistic history match. State of the Art technologies enable engineers to build, execute and complete the history match in a few months.