Abstract
The injection of CO<sub>2<sub/> into oil reservoirs is performed not only to improve oil recovery but also to store CO<sub>2<sub/> captured from fuel combustion. The objective of this work is to develop a numerical simulator to predict quantitatively supercritical CO<sub>2<sub/> flooding behaviors for Enhanced Oil Recovery (EOR). A non-isothermal compositional flow mathematical model is developed. The phase transition diagram is designed according to the Minimum Miscibility Pressure (MMP) and CO<sub>2<sub/> maximum solubility in oil phase. The convection and diffusion of CO<sub>2<sub/> mixtures in multiphase fluids in reservoirs, mass transfer between CO<sub>2<sub/> and crude and phase partitioning are considered. The governing equations are discretized by applying a fully implicit finite difference technique. Newton-Raphson iterative technique was used to solve the nonlinear equation systems and a simulator was developed. The performances of CO<sub>2<sub/> immiscible and miscible flooding in oil reservoirs are predicted by the new simulator. The distribution of pressure and temperature, phase saturations, mole fraction of each component in each phase, formation damage caused by asphaltene precipitation and the improved oil recovery are predicted by the simulator. Experimental data validate the developed simulator by comparison with simulation results. The applications of the simulator in prediction of CO<sub>2<sub/> flooding in oil reservoirs indicate that the simulator is robust for predicting CO<sub>2<sub/> flooding performance.
Highlights
During the period since 1750, CO2 concentration in the atmosphere has increased from 280 ppm to 368 ppm in 2000 and 388 ppm in 2010 (Rackley, 2010)
Based on PR equation, we developed a New State Equation (NSE) to calculate the density: P = RT −m + βm V − bm (V + bm )2 − cbm2 (15)
The Minimum Miscibility Pressure (MMP) of the CO2-oil system is 27.45 MPa, which is obtained by slim tube experiments
Summary
During the period since 1750, CO2 concentration in the atmosphere has increased from 280 ppm to 368 ppm in 2000 and 388 ppm in 2010 (Rackley, 2010). The CO2 concentration in the atmosphere is increasing at the rate of 2 ppm yearly. Depleted or mature oil fields may provide feasible sites for storing CO2 in porous and permeable reservoirs (Petrusak et al, 2009; Shtepani, 2006). Supercritical CO2 is a favorable flooding agent for EOR. Many oil fields in main oil production countries offer good opportunities for CO2 injection in oil formations for EOR purposes. The history of CO2 flooding for EOR purpose in oil fields and successful projects verifies that it can improve oil recovery to a larger extent. It may lead to the formation damages by reducing porosity and permeability (Shedid and Zekri, 2006) and have some adverse influences on production facilities such as tubing and pumps (Thawer et al, 1990; Rashid and Sultan, 2003)
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