Evaluation of Terpolymer-Gel Systems Crosslinked by Polyethylenimine for Conformance Improvement in High-Temperature Reservoirs
A terpolymer-gel system using low toxic polyethylenimine (PEI) as the crosslinker was developed for conformance improvement in high-temperature reservoirs. Suitable gelation time (GT), gel strength, and thermal stability could be obtained by selecting PEI molecular weight and adjusting terpolymer concentrations. With the increase of terpolymer concentration, GT decreases and the gel strength increases. However, in this research, the effect of PEI concentration on the gelation performance was much less obvious than that of the polymer concentration. Very low concentrations of sodium chloride (NaCl) can slightly shorten the GT. After critical concentrations were reached, the authors determined that the ions will delay the crosslinking reaction. Moreover, the addition of sodium carbonate (Na2CO3) can also lengthen GT. The gel systems were able to maintain thermal stability at 150°C. Uniformly distributed 3D network microstructures and the small size of the gel-grid pores made the network structure maintain thermal stability. The use of the terpolymergel- system gelation mechanism crosslinked by PEI can help petroleum engineers better understand and apply this terpolymer-gel system.
D. Zhu et al., "Evaluation of Terpolymer-Gel Systems Crosslinked by Polyethylenimine for Conformance Improvement in High-Temperature Reservoirs," SPE Journal, vol. 24, no. 4, pp. 1726 - 1740, Society of Petroleum Engineers (SPE), Aug 2019.
The definitive version is available at https://doi.org/10.2118/194004-PA
Geosciences and Geological and Petroleum Engineering
Center for Research in Energy and Environment (CREE)
Keywords and Phrases
Crosslinking; Gelation; Sodium Carbonate; Sodium chloride; Thermodynamic stability, Critical concentration; Crosslinking reaction; Gelation mechanisms; High temperature reservoirs; Low concentrations; Network structures; Polymer concentrations; Sodium chloride (NaCl), Petroleum reservoir evaluation
International Standard Serial Number (ISSN)
Article - Journal
© 2019 Society of Petroleum Engineers (SPE), All rights reserved.
01 Aug 2019
This work was supported by the National Science and Technology Major Projects (Nos. 2016ZX05014-004-004 and 2017ZX05009-004), the Science Foundation of China University of Petroleum, Beijing at Karamay (No. YJ2019A01001 and RCYJ2017A-01-001), the open research project of the Ministry of Education Key Laboratory for Petroleum Engineering on the development and application of new sealing systems for carbon dioxide (CO) flooding processes, and the China Scholarship Council (No. 201606440051).