Preparation and Performance Evaluation of a Temperature and Salt Resistant Hydrophobic Associative Weak Polymer Gel System

Abstract

We targeted high-temperature and highly saline old oil fields, whose environmental conditions could be attributed to the significantly high heterogeneity cause by long-term water flooding. The Huabei Oilfield was chosen as the research object. We developed a hydrophobic functional monomer–polymer with temperature and salt resistance by introducing the temperature-resistant and salt-resistant monomer NVP and a hydrophobic functional monomer into the main chain for copolymerization. We used a crosslinking agent with phenolic resin to prepare a weak gel system that showed temperature and salt resistance and investigated its temperature and salt resistance, infective property, plugging performance, liquid flow ability, micropore throat migration, and plugging characteristics. The results obtained using the infrared spectroscopy technique revealed the successful preparation of the phenolic resin crosslinker. The weak gel exhibited good temperature and salt resistance when the polymer concentration was 2000 mg/L, the cohesion ratio was 1:1.5, the additive concentration was 2000 mg/L, the reservoir temperature was 120 °C, and the injected water salinity was 40,300.86 mg/L. The average viscosity retention rate of the 90-day weak gel reached more than 80% and its microstructure was examined. The coreflow experiment results revealed that the weak gel system was characterized by good infectivity. After plugging the weak gel, the effect on the direction of the liquid flow was evident and the flow rate of the low permeability layer increased to a maximum of 48.63% under conditions of varying permeability levels. A significant improvement in the water absorption profile was achieved. The plugging was carried out through a sand-filling pipe under varying permeability conditions and the pressure measuring points in the sand-filling pipe were sucessfully pressurized. The migration ability of the weak gel was good and the blocking rate was >85%.

Study on Water-Soluble Phenolic Resin Gels for High-Temperature and High-Salinity Oil Reservoir

“…Xu et al [23,24] chose AM-AMPS copolymer as the gel-forming agent and studied the plugging performance of a water-soluble phenolic resin gel system under the conditions of a salt concentration of 41,110 mg/L and a temperature range of 80-90 • C. Qu et al [25] presented a gel with gelation time of 26-34 h at 55 • C using polyacrylamide, chromium acetate and water-soluble phenolic resin for the purpose of controlling water coning. In 2023, Zhi et al [26] prepared a weak gel that demonstrated excellent resistance to temperature and salt by utilizing a crosslinking agent in conjunction with the phenolic resin when the salinity was 40,300.86 mg/L at 120 • C. From the above studies, it can be found that during the preparation of gels, most of the water-soluble phenolic resins are used at temperatures between 70 • C and 90 • C, and the reservoir salinity is usually lower than 4 × 10 4 mg/L. It is because water-soluble phenolic resins would precipitate and stick to walls in high salinity water, resulting in poor stability and unsatisfactory gelling properties.…”

“…Qu et al [ 25 ] presented a gel with gelation time of 26–34 h at 55 °C using polyacrylamide, chromium acetate and water-soluble phenolic resin for the purpose of controlling water coning. In 2023, Zhi et al [ 26 ] prepared a weak gel that demonstrated excellent resistance to temperature and salt by utilizing a crosslinking agent in conjunction with the phenolic resin when the salinity was 40,300.86 mg/L at 120 °C. From the above studies, it can be found that during the preparation of gels, most of the water-soluble phenolic resins are used at temperatures between 70 °C and 90 °C, and the reservoir salinity is usually lower than 4 × 10 4 mg/L.…”

Preparation and Performance Evaluation of Temperature-Resistant and Salt-Resistant Gels

“…A comparative analysis between a watersoluble phenolic resin and a phenolic composite cross-linking agent revealed that the use of water-soluble phenolic resin can lead to cost reduction and enhance the strength of the gel system. Zhi et al [20] developed a weak gel system by cross-linking a hydrophobic association polymer with a cross-linking agent based on phenolic resin. After 90 days of aging, the average viscosity retention rate of this system exceeded 80%.…”

Preparation and Performance Evaluation of Self-Cementing Nanoscale Polymeric Microspheres with Salt and Temperature Tolerance

“…After long-term water injection in oilfield development, the presence of reservoir heterogeneity and unfavorable fluid mobility ratios often leads to the formation of dominant channels in high-permeability reservoirs, resulting in inefficient or ineffective cycling in low-permeability reservoirs, thereby impacting overall field development and ultimate recovery [ 1 , 2 , 3 , 4 , 5 ]. Practice has shown that profile control technology has become an important means to improve water flooding in oilfield development, laying a solid foundation for stable production and increased oil recovery in domestic and international water-flooded reservoirs [ 6 , 7 ].…”