Polymer viscosifier systems with potential application for enhanced oil recovery: a review

Abstract

Due to the growing demand for oil and the large number of mature oil fields, Enhanced Oil Recovery (EOR) techniques are increasingly used to increase the oil recovery factor. Among the chemical methods, the use of polymers stands out to increase the viscosity of the injection fluid and harmonize the advance of this fluid in the reservoir to provide greater sweep efficiency. Synthetic polymers based on acrylamide are widely used for EOR, with Partially Hydrolyzed Polyacrylamide (PHPA) being used the most. However, this polymer has low stability under harsh reservoir conditions (High Temperature and Salinity – HTHS). In order to improve the sweep efficiency of polymeric fluids under these conditions, Hydrophobically Modified Associative Polymers (HMAPs) and Thermo-Viscosifying Polymers (TVPs) are being developed. HMAPs contain small amounts of hydrophobic groups in their water-soluble polymeric chains, and above the Critical Association Concentration (CAC), form hydrophobic microdomains that increase the viscosity of the polymer solution. TVPs contain blocks or thermosensitive grafts that self-assemble and form microdomains, substantially increasing the solution’s viscosity. The performance of these systems is strongly influenced by the chemical group inserted in their structures, polymer concentration, salinity and temperature, among other factors. Furthermore, the application of nanoparticles is being investigated to improve the performance of injection polymers applied in EOR. In general, these systems have excellent thermal stability and salinity tolerance along with high viscosity, and therefore increase the oil recovery factor. Thus, these systems can be considered promising agents for enhanced oil recovery applications under harsh conditions, such as high salinity and temperature. Moreover, stands out the use of genetic programming and artificial intelligence to estimate important parameters for reservoir engineering, process improvement, and optimize polymer flooding in enhanced oil recovery.

Behavior study of a thermo‐responsive hydrophobically associative water‐soluble terpolymer in laboratory test with heavy crude oil

“…Indeed, they explained that the addition of salt caused a decrease in the associative temperature of related polymer which conducted to an increase in viscosity of the polymer solution due to the formation of hydrophobic micro domains from the thermos‐responsive moieties giving rise to both hydrophobic and intermolecular interactions between polymer chains 49 . In addition, variations in the salinity of aqueous polymer systems led to an increase in the viscosity of thermo‐associate polymer solution at early exposure time as reported by Wang et al 50 …”

“…On the other hand, researchers demonstrated the influence of the addition of salt on the increase in the viscosity of the thermo-viscosifying polymer at temperature below 90 C. Indeed, they explained that the addition of salt caused a decrease in the associative temperature of related polymer which conducted to an increase in viscosity of the polymer solution due to the formation of hydrophobic micro domains from the thermos-responsive moieties giving rise to both hydrophobic and intermolecular interactions between polymer chains. 49 In addition, variations in the salinity of aqueous polymer systems led to an increase in the viscosity of thermo-associate polymer solution at early exposure time as reported by Wang et al 50 Prior to the evaluation of the polymeric solution in the presence of a heavy crude oil sample from a high salinity carbonate well located in southern Mexico, the latter was first characterized with the aim to know its physical properties. Data from viscosity measurement crude oil sample carried out at 25 C showed a zero-shear viscosity of 2.26 Pa s. The API gravity was also determined to have a better point of view on the crude oil sample before the evaluation with the synthesized terpolymer.…”

Synthesis and salt resistance of non-ionic polymer P (AM/ APEG400/NVP/SM)

“…Hydrophobically associating polymer [8][9][10], as a new type of water-soluble polymer with a small number of hydrophobic groups introduced into the macromolecular chain of the polymer, has become one of the hot spots in the research of polymer materials in the past 30 years. With the deepening of research and the practice verification, it has successfully applied in the pilot test and large-scale application of EOR in oilfield chemical flooding, and has excellent potential in EOR application [11][12][13]. At present, many studies on the synthesis and salt resistance of hydrophobically associating polymers with different molecular structures have been reported.…”

Can Supramolecular Polymers Become Another Material Choice for Polymer Flooding to Enhance Oil Recovery?

“…Zou et al [ 44 ] synthesized a cyclodextrin-based polymer and proposed a mixed flooding of host–guest system and surfactant, which not only reduces the interfacial tension of rock–oil–water but also fully controls the oil–water mobility ratio and improves the oil displacement efficiency of mixed flooding. A large number of studies [ 39 , 45 , 46 ] have shown that the modified polymers have specific application requirements in terms of structure and properties, and they have different effects in improving oil recovery. The study of supramolecular chemical systems in petroleum has played an important role in promoting the supramolecular system in improving oil recovery.…”