Polymer Chemical Structure and its Impact on EOR Performance

Abstract

Polymer flooding is a mature EOR technology that has seen an increasing interest over the past decade. Co-polymers of Acrylamide (AMD) and Acrylic Acid (AA) have been the most prominent chemicals to be applied, whereas sulfonated polymers containing 2-Acrylamido-tertiary-butyl sulfonic acid (ATBS) have been used for higher temperature and/or salinity conditions. The objective of this study was to generate guidelines to aid in the selection of appropriate polyacrylamide chemistry for each field case. Our main focus was in sandstone fields operating at the upper end of AMD-AA temperature tolerance, where it needs to be decided whether sulfonation is required. The performance of the polymer throughout the whole residence time in the reservoir was considered since the macromolecule can undergo some changes over this period. Several key properties of nine distinct polymer species were investigated. The polymers consisted of AMD-AA co-polymers, AMD-ATBS co-polymers and AMD-AA-ATBS ter-polymers. The polymers were studied both in their original state as they would be during the injection (initial viscosity, initial adsorption and in-situ rheology) as well as in the state which they are expected to be in after the polymer has aged in the reservoir (i.e. in a different state of hydrolysis and corresponding viscosity retention and adsorption after ageing for various time periods). We note that the combination of viscosity retention and adsorption during the in-situ ageing process has not been typically investigated in previous literature, and this is a key novel feature of this work. Each of the above parameters has an impact on the effectiveness and the economic efficiency of a polymer flooding project. The content of ATBS was limited to 15 mol%. Buff Berea sandstone was applied in the static and dynamic adsorption experiments. The majority of the work was carried out in seawater at temperature, T = 58°C. Under these conditions AMD-AA samples showed maximum viscosity and lowest adsorption when the content of AA was moderate (20 mol%). When the AMD-AA polymers were aged at elevated temperature, the AA content steadily increased due to hydrolysis reactions. When the AA content was 30 mol% or higher, the viscosity started to decrease, and adsorption started to increase as the polymer was aged further. Thermal stability improved when ATBS was included in the polymer structure. In addition, sulfonated polyacrylamide samples showed increasing initial viscosity yields and decreasing initial adsorption with increasing ATBS content. For most of the samples, the maximum observed apparent in-situ viscosity increased when the bulk viscosity and relaxation time of the sample solution increased. The information generated in this study can be used to aid in the selection of the most optimal polyacrylamide chemistry for sandstone fields operating with moderate/high salinity brines at the upper end of AMD-AA temperature tolerance.

Molecular Dynamics Simulation of Polyacrylamide Adsorption on Calcite

“…The polymers can be easily synthesised and hydrolysed with different copolymers to improve the adsorption performance [ 14 ]. Some examples include hydrolysed polyacrylamide (HPAM) and sulfonated polyacrylamide (SPAM), which SPAM has a bulkier copolymer of deprotonated 2-acrylamide-tertiary-butyl sulfonic acid and exhibit higher thermal stability as a polymer flooding agent [ 13 , 15 ]. There is a well-established guideline for the evaluation and selection of these water-soluble polymers in different operating conditions [ 16 ].…”

Acrylamide-Based Active Quadripolymer as an Efficient and Robust Foam Enhancer for Gas Mobility Control

“…Nevertheless, the stability of polymers is inferior under severe conditions. It has been observed that copolymers can significantly enhance the temperature and salt tolerance of monomer polymers. − Extensive investigations have been performed to explore the fundamental mechanisms of polymer-enhanced foam (PEF) flooding, and the results demonstrated that polymers could extend the longevity of the foam mainly in two ways. , One of the noticeable advantages of applying polymer was to viscosify the foam lamella, as it was reported that the drainage time of the foam lamellae was directly proportional to its viscosity . Second, the thickness of foam lamella stabilized by polymers could be dramatically increased, which inhibited the bubble coarsening and collapse .…”

Investigating the Effect of Water Softening on Polymer Adsorption onto Carbonates through Single-Phase and Two-Phase Experiments

“…Recent technological advances have triggered the development of novel acrylamide-based polymers that contain unique monomers, such as N-vinylpyrrolidone and sodium ATBS, which provide stability at high-temperature and -salinity conditions (Jabbar et al 2018;Beteta et al 2020). However, the field applications of these polymers are limited due to their high production costs.…”