Phase Boundaries and Copolymerization of Acrylic Acid+ Butyl Methacrylate + Carbon Dioxide under High-Pressure Single-Fluid Initiation (oral presentation)

JUAN MANUEL MILANESIO

Los Cocos

Conferencia; VI Iberoamerican Conference on Supercritical Fluids (PROSCIBA 2023); 2023

IPQA y Universidad Nacional de Córdoba

In recent years, the oil industry has demonstrated increasing interest in Enhanced Oil Recovery (EOR) of exhausted reservoirs using several techniques. Polymer flooding is one of the most extended technologies and partially hydrolyzed polyacrylamides (HPAMs) are the most frequent polymer used for this operation. The incorporation of hydrophobic groups into water-soluble polymers (Wever et al., 2011) is a chemical modification of HPAMs with the aim of increasing the viscosity of their aqueous solutions. This strategy has shown promising results, as the addition of hydrophobic monomers enable macromolecules to tolerate harsh reservoir conditions, including high temperature and high salinity in the formation water (Scott et al., 2020). To achieve this objective, it is imperative for the polymer to exhibit high viscosity at low concentrations and endure the varied pH, temperature, and salinity conditions prevalent in the reservoir (Juárez Data et al., 2020). The synthesis of these water-soluble polymers for EOR is commonly carried out by solution or precipitation techniques, utilizing aqueous or organic solvents such as ethyl acetate or toluene (Nazaripour et al., 2012). It is important to note that products obtained from these polymerization methods often require a separation process after the reaction, involving one or several steps (MOJPS 33).The use of pressurized fluids in precipitation polymerization offers the advantage of minimizing or even completely eliminating the need for a separation process, allowing to obtain the polymer by simply depressurization of the system (Bin et al., 2004). Supercritical carbon dioxide (scCO2) is the main pressurized fluid used in the industry due to its low critical temperature and pressure conditions (Tc = 31.1 °C) (Ferro et al., 2012) (10.1016/j.supflu.2020.104787). scCO2 can dissolve several vinyl monomers such as acrylic acid (AAc) and acrylic acid and methacrylic acid esters. Robert and colleagues discovered that scCO2 acts as an inert solvent for chain transfer reactions, producing high molecular weight polymers (10.1002/pola.20728, 10.1016/j.ces.2005.11.052). This study is focused on the synthesis polymers using scCO2 as the reaction medium. The polymers synthesized were poly(acrylic acid) (PAA) and two copolymers: acrylic acid-co-butyl methacrylate (BMA) (PAA-co-BMA), and acrylic acid-co-lauryl methacrylate (LMA) (PAA-co-LMA), with varying comonomer concentrations. These comonomers act as hydrophobic association point on the polymer chain, potentially augmenting inter- and intrachain interactions, and consequently, enhancing the viscosity of the polymer's aqueous solutions in comparison to analogous PAA solutions. The viscosity of the solutions was determined through rheometry in water under various salinity and pH conditions. The incorporation of BMA and LMA into the polymer chain was analyzed using spectroscopic techniques such as FTIR and 1H-NMR.The results revealed that increasing the BMA incorporation in the copolymer from 4% to 8% w/w does not affect the solubility of the macromolecule obtained in water, nor under the measured pH and salinity conditions. However, it does result in an increased viscosity due to a higher number of inter- and intrachain polymer interactions. On the other hand, LMA exhibited a greater viscosity increment in the resulting polymer compared to its BMA counterpart, even with a lower proportion of comonomer incorporated into the polymer chain, ranging between 1% and 4%. This viscosity increment is attributed to the larger aliphatic chain of LMA compared to its BMA counterpart, resulting in a higher number of inter- and intrachain interactions in the solution, which leads to an augmented viscosity.