The CO₂ Transfer And Compositional Modeling During Carbonated Water Injection

Enhanced oil recovery by carbonated water injection?CWI?has recently attracted significant attention.One of the major challenges with CWI is the numerical simulation of the complex compositional changes that take place as a consequence of the transfer of CO₂ from carbonated water to crude oil under the reservoir condition.This study presents a three-dimensional,three-phase compositional model considering CO₂ phase equilibrium between water and oil.In the model,CO₂ is mutually soluble in aqueous and hydrocarbon phases,while other components,except water,exist in hydrocarbon phases.Peng-Robinson?PR?equation of state?EOS?and Wong-Sander mixing rule with Non-Random-Two-Liquid parameters are used to calculate CO₂ fugacity in the aqueous phase.This model is validated by experimental results of CWI in our laboratory.The achievement of this paper is that it chose PR equation-of-state and Wong-Sandler mixing rule with Non-Random-Two-Liquid parameters among many other theories to calculate CO₂ transfer from carbonated water to oil.Another achievement is that it assembled a CWI?also named PR-WS?simulator based on the framework in MATLAB.The simulator includes the following modules: PVT calculation module,CWI equation module,relative permeability module,well and facility module,automatic differentiation module,and solvers for the sparse matrix.I posted the source code in my Git Hub: https://github.com/zhonglin94/ADcompsPR-WS model simulates the CWI experiment with an error of 1.2% while the conventional model overestimates the performance with an error of 4.3%.The simulation results of the study help to improve the accuracy of the numerical simulation of the oil recovery processes in which CO₂ and carbonated water injection are involved.This will,in return,improve the quality of the reservoir performance prediction and the reliability of the economic calculations.The PR-WS model is also applicable to model CO₂ flooding.One-dimensional CO₂ flooding example shows that a significant amount of injected CO₂ is dissolved in water.Our simulation displays 7% of injected CO₂ can be dissolved into the aqueous phase,which delays an oil recovery of 4%.The model also predicts that the delayed oil can be recovered after the gas breakthrough,indicating delayed oil is hard to be recovered in field application.