A comparison of foam stability at varying salinities and surfactant concentrations using bulk foam tests and sandpack flooding

Abstract

Two conventional approaches for foam screening are core/sandpack flooding and bulk foam stability tests. The former is more accurate, but requires expensive equipment and long test duration. For initial screening, the faster and cost-effective bulk foam stability tests are used to narrow down the selection to a few surfactants, which are then further tested using corefloods/sandpacks. The bulk foam stability tests have been historically used for surfactant selection at a fixed salinity and fixed surfactant concentration. The foam generated in bulk foam stability test was observed to be quite homogeneous, whereas foam generated through porous media is more heterogeneous; hence, a modification to the bulk foam test was made in that a small quantity of quartz river sand was placed at the bottom of the test tube for generating foam that simulates porous media. To evaluate the use of bulk foam and modified bulk foam stability tests for screening and optimizing salinity and surfactant concentrations, sandpack flooding tests were conducted at a range of salinities, and surfactant concentrations and results were compared. Bulk foam stability tests results were found to be compatible with sandpack results for surfactant concentration optimizations, but showed significant deviation for salinity optimization. The modified bulk foam stability tests, however, showed better agreement with sandpack results in both salinity and surfactant concentration tests.