Improving squeeze scale inhibitor adsorption and flow back characteristics with surfactants

Abstract

The most common method for preventing downhole scale deposition is by the use of a scale inhibitor in a scale squeeze treatment. The process consists of injecting a scale inhibitor down a producer well into the near wellbore formation. It is believed that a change in the rock wettability will enhance the scale inhibitor adsorption to the rock, hence increasing the treatment lifetime. This master thesis discusses the effect of a surfactant preflush on scale inhibitor lifetime and also flow back characteristics.

Particular attention is given to laboratory corefloods tests, where the field conditions of an oil field reservoir are simulated, in an attempt to give the most accurate and relevant results. Six coreflood tests were completed using Berea sandstone core plugs, five of them with more oil wet characteristics and one core plug with water wet conditions to use as base line.

The study clearly shows an improvement in the potential squeeze lifetime when a surfactant/ solvent is used as a preflush. The results also show that the change in the wettability is not the only factor influencing the treatment lifetime. This is validated by data showing the product with the biggest change in wettability is not the showing the largest improvement in the treatment lifetime.