The in-situ behavior of a Thermally Activated Polymer (TAP) was investigated through laboratory work on a high permeability core (7.5 D) and was interpreted by refined simulation. The experiment, carried out in a 100% water saturated core, aimed at determining the adsorption of the non-activated TAP and the activated TAP Residual Resistance Factor (RRF). The experiment and simulation results led to three observations impacting economic evaluation of TAP/gel treatment.
Firstly, unswollen TAP adsorbed, even if the significant values measured (130 µg/g of rock) may be overestimated due to the nature of the sand or to the fact that no residual oil was present in the porous medium. Secondly, in such high permeable sand, the main mechanism for mobility control of the swollen TAP was found to be the viscosity increase of the TAP solution. Indeed, in such high permeability material, permeability reduction estimated after 8 Pore Volumes (PV) of chase water was low (1.3). Refined history matching of the chase water injection in TAP evidenced that the fingering of the chase water through the high viscosity TAP slug should be expected. Therefore, rate variations and a high volume of chase water are required to evaluate the permeability reduction generated by TAP, and not to overestimate it. Finally, the injection of a slug of TAP in a quarter of five spot pattern was simulated with core scale grid blocks. Sensitivities were performed to quantify the dilution of the TAP slug. Results confirmed that the adsorption of the non-activated product and the viscosity of the injected solution affect the TAP distribution. The authors believe that these three observations should be included in the design of TAP treatments, and more generally, for in-depth gel treatments.