Literature Review and Experimental Observations of the Effects of Salinity, Hardness, Lithology, and ATBS Content on HPAM Polymer Retention for the Milne Point Polymer Flood

At the Milne Point polymer flood, polymer retention is dominated by illite clay. Illite and kaolinite do not delay polymer propagation but reduce effective polymer concentration and viscosity by approximately 30%, reducing oil displacement efficiency until full injected concentration is regained over several pore volumes. This work shows polymer retention on illite is insensitive to monovalent ion concentration but increases significantly with increased divalent cation concentration. Incorporating a small percentage of ATBS monomers into HPAM dramatically reduces retention. An extensive literature review reveals that polymer retention on sands and sandstones is only modestly sensitive to the presence of oil. Review of inaccessible pore volume (IAPV) literature suggests IAPV was commonly substantially overestimated, especially in rock more permeable than 500 md — which comprises the vast majority of current polymer flood targets. Bridging adsorption is proposed as the mechanism linking divalent cation concentration and retention.