The use of water-in-oil emulsions (w/o) to deploy scale inhibitors has been reported in the literature as an alternative to water-based squeeze treatments. The non-aqueous nature of these emulsions has the advantage to prevent water blocking, which adversely affects oil production in aqueous squeeze treatments. Placing the scale inhibitor in a w/o or "invert" emulsion has shown in some cases the additional advantage of enhancing treatment lifetime. However, results from the literature seem contradictory and highlight a poor understanding of this technology.
The present paper aims at providing further insight on emulsified scale inhibitor placement in porous media. Preliminary experiments, using a low molecular-weight biopolymer as scale inhibitor, showed low adsorption/retention in aqueous solution. Re-formulation of the product under invert emulsion was investigated to enhance inhibitor retention.
Results from coreflood experiments, in well-characterized silicon carbide (SiC) packs provided preliminary evidence of aqueous droplet adsorption as the main retention mechanism in porous media. This was expected considering the average droplet size of 0.3 μm. The mother formulation of the w/o emulsion is a concentrate, containing 80% weight of water phase and 8% weight of active scale inhibitor. It can be diluted down to 2% water phase adding the desired oil phase without loosing stability or increasing the droplet size.
These results are a promising first step towards the development of a technically and commercially viable, environment-friendly scale inhibitor technology based on w/o emulsions.