Development and Evaluation of a Novel Sulfonated Phenol-Formaldehyde Resin with High Dispersion Stability

Sulfonated phenol-formaldehyde (SPF) resin used as a cross-linker for petroleum reservoir conformance control was synthesized under alkaline conditions. The reaction process of SPF resin was evaluated by measuring the solution's viscosity with respect to phenol-formaldehyde (PF) resin. The molecular structure of SPF resin was characterized by both FTIR and HPLC-MS/MS. The influence of the formaldehyde/phenol molar ratio (F/P) and the sodium formaldehyde sulfoxylate/phenol molar ratio (S/P) on the properties of SPF were analyzed in terms of the storage time, coagulation value, molecular size, and zeta potential. The results indicate that the presence of formaldehyde sodium bisulfite could slow down condensation reaction. Phenol rings were connected by methylene bridges in the position of o-p, and sulfonated SPF resin molecules all had one sulfonate group on the oligomer structure. The storage time decreased from 87 to 6 days, and the zeta potential decreased from -3.02 to -7.70 mV with the increase in F/P (1.2-2.0). Meanwhile, the sedimentation value and the diameter increased from 3.291 × 10⁴ to 5.045 × 10⁴ mg/L and from 2.7 to 5.3 nm, respectively. Sulfonation could significantly increase the storage time and dispersion stability. With the increase in S/P (0.1-0.35), the storage time increased from 15 to 86 days, the sedimentation value increased from 1.927 × 10⁴ to 5.269 × 10⁴ mg/L, and the diameter decreased from 6.3 to 3.0 nm. This paper can present new ideas for improving the storage stability and salt tolerance of phenol-formaldehyde resin and further improving the range of its applications, which has essential reference significance.