Rheological study of polymeric fluids based on HPAM and fillers for application in EOR

Abstract

Partially hydrolyzed polyacrylamide (HPAM) is the most widely used polymer in the chemical method of enhanced oil recovery (EOR). However, it is not recommended for reservoirs with high salinity and high temperature, due to its weak stability under these conditions. Therefore, in this work we prepared and evaluated fluids containing HPAM and two reinforcement fillers, SiO2, and coal fly ash (CFA), mainly seeking to increase the thermal stability of HPAM. Rheological analyses were performed of the fluids, with or without the presence of these fillers, to determine their injectivity in petroleum reservoirs at 30 °C and their stability at temperatures of 30 °C (ambient) and 85 °C (typical of reservoirs), during 60 days at the latter temperature, in the absence or presence of oxygen. We also evaluated the rock-fluid interaction and conducted filtration tests of the most promising fluids. The results showed that all the fluids prepared had viscosities suitable for injection in reservoirs and stability at 30 °C. At 85 °C, the HPAM fluids with fillers presented smaller viscosity variation in relation to the counterpart fluids without filler, and the presence of oxygen diminished the stability of these fluids. The fluid-rock contact angle changed very little with the addition of the fillers, with the rock being slightly more wettable by the polymeric fluid with higher filler concentrations. Finally, the filtration tests showed that the fluids containing the fillers SiO2 and CFA are suitable for injection under typical reservoir conditions, with those containing CFA being recommended only for reservoirs with greater rock pore volume.