Polymer/Surfactant Effects on Generated Volume and Pressure of CO₂ in EOR Technology

Dense phase gases (carbon dioxide, nitrogen, light hydrocarbons, etc.) are used to develop miscibility with crude oil in enhanced oil recovery processes. Due to the certain reasons, carbon dioxide (CO₂) flooding is considered the fastest-growing improved oil recovery method. However, due to the low viscosity of dense CO₂, displacement front instabilities and a premature CO₂ breakthrough is observed in many cases. An alternative scheme to the traditional methods of oil recovery by injection of carbon dioxide gas is the technology developed by the NMT, IGDFF and IMM, which proposes in-situ CO₂ generation as a result of the thermochemical reaction between water solutions of the gas-forming (FG) and gas-yielding (GY) chemical agents injected to the productive horizons. This technique excludes CO₂ injection from surface communication systems and does not require expensive delivery equipment. This process allows avoiding many negative consequences of CO₂ injection technology. Based on the in-situ CO₂ generation concept, several new technological schemes were developed in order to provide an integrative effect on the productive horizons. In this paper we present the results of the experimental studies on effect of polymer and surfactant additives on generated CO₂ miscibility. The solutions of gas-yielding (GY) agent with different concentrations of surfactants and polymer additives were used as a reacting agent in these laboratory studies. Within the limits of the experimental conditions stochiometric reactions between gas-yielding (GY) and gas-forming (GF) water solutions were simulated. The tests were conducted on the experimental set up designed and built for these purposes. In the first series of experiments a polyacrylamide was added to the gas-yielding (GY) agent in the concentrations 0.1, 0.25 and 0.5 wt.%. A dynamics of the pressure changes during stoichiometric reaction was recorded. It is shown that the pressure of the generated CO₂ gas significantly depends on concentration of the polymer additive and, as a consequence, on viscosity of the water solution. It slightly depends on the concentration of the surfactant added to the GY reactant.