Numerical Simulation On CO₂ Flooding In Sandy-Conglomerate Reservoir

The Sandy-Conglomerate reservoir presents a high heterogeneity where the lithology changes so rapidly between in-depth characterizing by a rapid phase change and complex pore structures resulting in a poor oil displacement efficiency.CO₂injection is a good choice for the development of this type of reservoir with a high oil recovery factor.The method of CO₂injection should be selected and CO₂sequestration potential should be evaluated.On the basis of data collection of the target zone,types of conceptual reservoir models were constructed for the simulations.Using a computational optimization tool PVT Winprop,a selection of experimental data was collected to build and analyze the behavior of the fluid model data.The simulator GEM（Generalized Equation-of-State Model Compositional Reservoir Simulator）from CMG was used to perform optimization performance of CO₂-EOR through characterization of the fluid model,analyze of the miscibility processes with CO₂flooding and WAG process by considering a number of parameters the injection cycle,injection rate and production,WAG ratio,and slug sizes in order to evaluate the different injection strategies and injection time,in optimization of oil recovery and CO₂ storage capacity.The channeling and fingering effect become favorable as the reservoir pressure becomes lower or close to the minimum miscible pressure（MMP）.The results show that CO₂injection can increase the oil recovery factor in the sandy conglomerate reservoir.CO₂can be dissolved into the oil and decrease the viscosity of oil as the reservoir pressure in the CO₂flooding process,is slightly lower than the minimum miscible pressure.But during the WAG process,the reservoir pressure is slightly lower than the MMP thus the channeling and fingering are occurring as much as in the CO₂injection process.The CO₂injection has increased the oil recovery factor up to 70%in WAG injection with variable WAG ratios compared to the CO₂flooding method and constant WAG ratio.In addition,CO₂ can also be stored in the reservoir.