EVALUATION OF NITROGEN-FOAM FLOODING IN MULTILAYERED HETEROGENEOUS RESERVOIR

Abstract

Most oil reservoirs yield early high water cut due to heterogeneity, resulting in poor sweep efficiency and consecutively inefficient oil recovery. Selection of proper Enhanced Oil Recovery (EOR) technique is therefore top priority and prime concern is to control mobility of water and gas. Foam flooding is one of the techniques that can increase macroscopic sweep efficiency in heterogeneous reservoir. In this study, injection of nitrogen-foam is performed in multi-layered heterogonous reservoir. Reservoir model is built using black oil reservoir simulator and reservoir heterogeneity is quantified by Lorenz coefficient. Nitrogen-foam is created by co-injecting of anionic surfactant solution and nitrogen gas. Simulation results show that co-injection of surfactant solution and nitrogen gas with proper adjustment of operational parameters yields positive results compared to conventional waterflooding. Nitrogen-foam flooding with proper adjustment of operational parameters yields recovery efficiency up to 0.59. Finalized base case is performed at fluid injection rate 1,000 rb/day, production-injection ratio 1.5, gas-liquid ratio 2.0 and slug size 0.25 PV. Foam generated under these parameters helps displacing light oil efficiently in multilayered heterogeneous reservoir. Study of interest parameters shows that high vertical permeability tends to reduce oil recovery factor due to solution gas liberation and also bypassing of chasing water. Formation with oil-wet condition gains benefit from nitrogen-foam flooding since surfactant can increase a gap of recoverable oil during flooding mechanism. However, time required to recover oil is higher in oil-wet rock and hence, high water production cannot be avoided. Foam advancement obtains benefit from higher thickness due to smaller formation pressure in top layers. Injecting foam in multi-slug does not yield great benefit since thinner slug could result in bypassing of chasing water. Lorenz coefficient higher than 0.35 might yield low oil recovery since foam cannot control mobility effectively.