Relevance. In recent years, polymer flooding technologies have been widely used in exploitation of oil and gas fields, especially in the later stages of field development. However, when operating reservoirs with elevated temperature of more than 70-80 °C and a high de8 gree of salinity of formation water, many polymeric oil8displacing agents undergo rapid degradation, which leads to decrease in the le8 vel of hydrocarbon production. In this regard, one of the important problems is the creation and development of thermo8 and salt8re8 sistant polymeric materials and compositions based on them to increase the production of hydrocarbons in the oil and gas fields. The main aim of the research is to investigate the effect of formation water salinity on the physicochemical and filtration characte8 ristics of polymer solutions and gels to enhance oil recovery. Methods. Viscosity of the polymer solutions and polymer gel were determined on Brookfield DV8II viscometer; shape and size of the po8 lymer particles and polymer gel were studied on Hitachi S8400N scanning electron microscope; polymer size of molecular tangle Dh was measured on a wide8angle dynamic/static light scattering system Brookhaven BI8200SM (Brookhaven Instruments Cop., USA); physical modeling of fluid filtration at reservoir conditions was carried out on the filtration unit; determination of viscoelasticity and rheological properties of polymer solutions and gels was studied using a rheometer Harke 10. Results. The degree of mineralization of formation water has a significant effect on the viscosity of polymer solutions. Due to the fact that calcium and magnesium ions were preliminarily removed in partially demineralized water, the polymers have good solubility and the ability to increase the viscosity of the solutions. With increasing concentration of displacing agent, the viscosity of the solutions increases. Destructive effects of salts of formation water on polymers cause a significant decrease in viscosity of solutions of displacing agents. Due to the high degree of mineralization of partially demineralized water, a large amount of sodium chloride ions surround the molecu8 lar skeleton of the polymer of the displacing agent. The macromolecules of polymer P81 have a predominantly two8dimensional network structure. The macromolecules of polymers P82 and P83 have a predominantly spatial three8dimensional network structure, in which some polymer molecular chains are broken and the network structure of polymers is defective. Compared with polymer P83, the three8dimen8 sional network structure of the polymer molecular aggregate P84 has a clearer spatial structure. Comparing the physico8chemical pro8 perties of polymers P81, P82 and P83, it follows that the coefficient of resistance and the coefficient of residual resistance for polymer P81 are greater than for polymers P82 and P83. This is due to the fact that the salt8resistant polymer P81 forms aggregates of the network structure due to intermolecular association, which leads to poor compatibility with core pores, and the resistance coefficient and residu8 al resistance coefficient for polymer P84 are the greatest the polymer mixture underwent reactions of intramolecular crosslinking of po8 lymer molecules and Cr 3+ cations, which led to a significant increase in the retention of the polymer solution, filtration resistance, injec8 tion pressure and to enhance oil recovery.
|Number of pages||10|
|Journal||Bulletin of the Tomsk Polytechnic University, Geo Assets Engineering|
|Publication status||Published - 1 Jan 2019|
- Molecular coil size
- Polymer gel
- Resistance coefficient.
- Rheological properties
ASJC Scopus subject areas
- Materials Science (miscellaneous)
- Fuel Technology
- Geotechnical Engineering and Engineering Geology
- Waste Management and Disposal
- Economic Geology
- Management, Monitoring, Policy and Law