Abstract
Commonly used surfactants exhibit cloud point or salting out phenomena in a high ionic environment. These phenomena were interpreted in the literature with configurational aspects of surfactant molecules such as functional groups and ionic nature. This paper presents a non-configurational interpretation of this behavior of surfactants and set a parameter for their selection to be used in that environment to avoid treatment failure, previously not reported in the literature.
The power water injectors in carbonate reservoir in field Q were left stable after drilling using a diesel based completion fluid. The flowback of the completion fluid was not allowed due to presence of hydrogen sulfide gas in high concentrations. Formation damage was expected due to injection of the completion fluid into the formation.
These injectors were planned to be treated by using surfactants that are compatible with high salinity formation and injection waters. Thorough lab investigations were conducted on the formation damage induced by the completion fluid by conducting return permeability tests on reservoir cores and compatibility tests. Various treatment fluids containing surfactants and mutual solvents and combinations of these were prepared. Use of surfactants with low electrochemical properties resulted into sudden precipitation of salts. This behavior of surfactants has been discussed in detail in this paper.
