(283a) Phenol Formaldehyde Gels: Studies on the Gel Formation at a High Temperature and at Different pH

A phenol-formaldehyde gel system with different mole ratios and different percentage of phenol is tested at a high temperature of 140 deg C in laboratory for the formation of gel. It is experimentally found that a phenol-formaldehyde based monomer gel system with 3.0 % phenol solution in water and phenol-formaldehyde mole ratio 3.5 is best suited to adopt for formation of gel at a temperature within the range of 135 ? 140 deg C. The gel formation is strongly dependent on the pH. At this elevated temperature phenol reacts with formaldehyde to form a significant amount of tri-methylol derivative which then act as monomer for network formation. Such network formations are studied. An explanation for the gelling behavior is presented which is based on an optimum ion concentration of Na+ to initiate the methylol formation that leads to the formation of tri-methylol derivatives. Subsequent gel formation begins when concentration of tri-methylol phenol attains a minimum threshold value. The observed dependence of gelling time has been explained. The kinetics studies provide rationale for the proposed hypothesis. Findings of gel formation in such monomer system can be used for near-welbore profile modification in oil recovery very efficiently.

Keywords: Phenol-Formaldehyde Monomer System, Methylolation, Gelation, Gelling-zone, High temperature gelling.