State-of-the-Art Laboratory Methods for Chemical EOR

Abstract The objective of this paper is to present a critical review of best practices for conducting laboratory experiments to evaluate chemical EOR. Some legacy methods and procedures are outdated and need to be updated to address their inherent flaws. This paper presents the reasons improvements are necessary and serves to introduce or highlight better methods, while providing a good resource to review past studies. Common laboratory methods and procedures used to evaluate chemical EOR are critically reviewed and discussed for polymer flooding, surfactant-polymer flooding, alkaline-surfactant-polymer flooding, alkaline-co-solvent-polymer flooding specifically but also apply to similar processes. The laboratory methods for evaluating chemical EOR include surfactant phase behavior, coreflooding, chemical adsorption and retention measurements, polymer residual resistance factor measurements, polymer transport, polymer filtration ratio measurements, polymer stability. The best methods and procedures for these and other measurements should take into account how the laboratory measurements will be used for making field-scale performance predictions, the type of oil reservoir, the chemical EOR process and many other factors. Conducting corefloods with a low residence time is an example of a common mistake. New or improved methods are introduced or highlighted to bring best practices to the forefront. New methods that are highlighted include Residence Time Distribution Analysis to determine polymer retention and IPV, polymer transport in cores with two-phases present, and the addition of solvents/pre-shearing for improved polymer transport. The state-of-the-art laboratory methods and procedures discussed herein yield more accurate, more scalable data that are needed for reservoir simulation predictions and field-scale applications of chemical EOR. The recommended best practices will provide a better understanding needed to help select the appropriate chemicals and to determine the optimal chemical mass for field applications of chemical EOR.