THE ALKALI SURFACTANT/POLYMER PROCESS - EFFECTS OF SLUG SIZE, CORE LENGTH AND A CHASE POLYMER/

An experimental study was conducted to examine the effects of slug siz e, core length, and a chase polymer on the effectiveness of the alkali /surfactant/polymer (A/S/P) process in recovering waterflood residual oil. Core flood experiments were conducted with unfired linear Berea s andstone cores. The tertiary oil recovery, oil cut, pressure drop, and chemical propagation were measured for each flood. Tertiary oil recov ery significantly increased with the slug size up to 0.5 of a pore vol ume. increasing the slug size further resulted in a Smaller incrementa l increase in oil recovery. A slight increase in tertiary oil recovery was obtained when small size A/S/P slugs were followed with a chase p olymer having a viscosity higher than the slug. The lack of oil recove ry with small A/S/P slugs was due to the consumption and dilution of t he injected chemicals, especially the synthetic surfactant, due to ads orption and dispersion. Increasing the core length by a factor of 4.5 (from 9 to 40.6 cm) had no significant effect on tertiary oil recovery . Chemical propagation was found to be a function of core length (i.e. , core Peclet number) and the size of the chase polymer slug. Increasi ng core length and employing a chase polymer maintained the integrity of the A/S/P slug by decreasing the effect of dispersion and minimizin g the influence of viscous fingering at the tail of the A/S/P slug.