Microemulsification-based method enables field-deployable quantification of oil in produced water

Abstract

The oil and gas industry involves the generation of a large amount of produced water (PW), which incorporates chemicals of ecological concern such as petroleum compounds (oil) that further imply deleterious effects to its recovery rate and safety of operation. As limitation, the monitoring of oil in PW (OiW) samples at onshore and offshore wells is challenging as the currently available methods usually require the use of benchtop equipment and laborious experimental routines. Using the microemulsification-based method (MEC), which was introduced by our group in 2014, here we describe a cost-effective, user-friendly, fast, and scalable strategy for the on-field determination of OiW. The analysis is based on the monitoring of the minimum volume fraction of amphiphile needed to thermodynamically stabilize cloudy dispersions, thus forming transparent microemulsions. Applying the own sample as oil-water phases, Tween-80 25% v/v in acetone as amphiphilic phase, and a handheld turbidimeter, the assays are performed in less than 5 min with a limit of detection of ∼6 ppm. The latter is lower than the maximum average (OiW 29 ppm per month) that is limited by the Brazilian environmental agency. In addition to showing high robustness facing changes in salinity, it is noteworthy that the method enabled the determination of OiW in real samples with accuracies ranging from 95.7% to 105.6%. Our results are a significant step towards the on-field quantification of OiW. The oil and gas industry may benefit from this method for translating useful solutions into the real world to support the making/management of decisions aiming to minimize ecological and operational side effects.