Laboratory evaluation of phenol—formaldehyde/polymer gelants for high-temperature applications

Polymer gels are attractive tools for stopping unwanted fluid production from oil and gas wells, but conventional gelant formulations become increasingly difficult to apply at higher formation temperatures. In contrast phenol—formaldehyde cross-linked polymer gelants remain viable to at least 140°C. Choice of polymer composition permits control of the gelation delay, and the gelants display good injectivity even when the residence time approaches the gelation time. Cross-linking occurs over a wide range of pH and is insensitive to lithology. Although retention of the gelant components on formation rock is negligible, phenol strongly partitions into oil phases contacted by the gelant. Experiments and numerical modelling show that a preflush of phenol is an effective method of compensating for phenol partitioning in the formation.