The Impact of Shale Barriers and Injection Strategy on CO2-Flooding andSequestration Performance

摘要

In this paper the impact of stochastic shale barriers andinjection-strategy on recovery-factor and sequestrationcapacity have been investigated for secondary CO2-floods inhorizontal oil reservoirs. Permeability fields, shale size andshale fraction have been varied in several numericalsimulations and the calculated oil recovery factors have beencorrelated to a dimensionless number relating the viscous togravity forces. The results show that for relativelyhomogeneous reservoirs the impact of shale barriers can beaccounted for using an upscaled vertical permeability and thata unique relationship can be found between recovery factorand ratio of viscous to gravity forces. For layered reservoirsthe impact of shales depends very much on the vertical layerpermeability arrangement, pressure drop ratio, andoptimisation of injection strategy. Based on the best fieldcharacterisation (permeability and shale barriers), injectionstrategies aim at simulating an overall CO2 injection in alllayers, followed by an analysis of the flooding mechanisms,and ending with an optimisation of the vertical conformance.This is recommended especially for low to intermediatepressure drop ratio.