Integrated Modeling of Fracture System and Evaluation of its Impact on Carbonate Heavy Oil Reservoir Performance

Abstract

In the Usinsk field located in the Timano-Pechora region of Russia, heavy oil is produced from vuggy-fractured carbonate Permian-Carboniferous reservoir. It has a more than 30 years history of operations and has produced mostly by natural water drive and in some pilot areas by hot water and steam injection. The presence of fractures highly affects the reservoir performance and is critical for current and new pilot projects of steam injection efficiency. This study presents an integrated approach to characterize and model the fractures, and assess their dynamic impact in the south-west (SW) sector with 85 wells where new steam injection pads are being organized. The approach included the detailed analysis of available core data, FMI logs, 3 D seismic, production data, well testing, etc, fully integrated by a unique advanced technology. The obtained results of the characterization allow developing the discrete fractured model of the SW sector which takes both into account the effect of seismic faults and several sets of diffuse fractures related to the fold structure of the reservoir. The fracture model was then tuned and verified using the well test results to match KH and pressure responses. The end product was a 3 D model of the equivalent fracture parameters (permeability, porosity, and matrix block size) directly usable for the dual - porosity dual - permeability model reservoir simulation. The conducted simulation runs confirmed the significant improvement of the history matching process using the created model and its applicability to clarify the effect of the fracture system on natural water flooding and steam injection results in the SW sector of the reservoir.