Chemical Gels for Diverting CO2: Baseline Experiments

Abstract

ABSTRACT Large-scale reservoir heterogeneities, such as fractures, channels, or high-permeability streaks, can cause early breakthrough of injected CO2 which will reduce oil recovery efficiency. This paper describes the first part of a multiple-part study on the effect of some commercial gelants on the reduction in CO2 permeability. A methodology is presented of testing gelants in vial tests, core tests, and with two-dimensional flow visualization studies in high-pressure micromodels. Test conditions were selected to match some west Texas/southeast New Mexico reservoirs: 1500 psi and 105°F (CO2 MMP ≈ 1200 psi). The gelants used included some commercially available crosslinked polymer systems. In the core tests, gel stability and polymer-gel interactions were assessed by monitoring the permeability of repeated water/CO2 WAG cycles. The high-pressure micromodel studies were valuable in assessing the mechanisms responsible for permeability reduction at the pore level.