Use of organoclay as a stabilizer for water-in-oil emulsions under high-temperature high-salinity conditions

Abstract

Emulsified polymer gels are used in near wellbore applications for water shut-off treatment to control produced water in oil and gas reservoirs. The emulsified gels are expected to separate into oil and water phases at reservoir conditions. The stability of emulsified gels, as measured by the separation time, is influenced by the emulsifier type, salinity of the mixing water, and temperature. Although a range of commercial surfactants is used as emulsifiers, their toxicity and high cost are significant drawbacks. Nowadays, various nanomaterials have been developed for quite a few applications in different fields of endeavors, due to their low cost, availability, high surface area, and most prominently environmental-friendly. The proposed alternative organoclay (OC) has been shown to enhance emulsion stability with increasing OC concentration. The total separated volume reduced by a factor of 4.8, due to the decrease in the interfacial tension, when the OC (Cloisite 15A) concentration was increased from 600 to 1000 ppm. The stability of an emulsion prepared using a 6 vol% polyethylene glycol-2 ether (PEG-2E) enhanced by a factor of ∼2 when the concentration of Cloisite 15A was increased from 300 to 1000 ppm. The separation time can be controlled by controlling the OC dose, depending on the application. A chelating agent can be used to reduce the effect of salts on emulsion stability. The OC materials have the potential to be used as cost-effective emulsifiers for PAM/PEI at high temperature (>100 °C) and high salinity (>200,000 ppm). The OC materials can be used as standalone emulsifiers or co-surfactants to enhance the performance of commercial emulsifiers.