Cationic surfactants have been proven to be highly effective in improving oil recovery in carbonate reservoirs with low surfactant loss due to adsorption. However, toxicity concerns and the cost of formulation have impeded their widespread usage in the oil and gas industry. Our study focuses on developing an economic and environmentally friendly solution to this challenge.
Soybean oil was used as the raw material to synthesize a surfactant that had 3 cationic sites. The resulting formulation, in conjunction with an ethanol co-solvent, was tested for emulsion and rock-fluid behavior with dolomitic reservoir rocks and oil sampled from a producing well in Morrow County, Ohio. Interfacial tension (IFT) and contact angle measurements were conducted to characterize rock-fluid behavior of the surfactant. Estrogenic and anti-estrogenic activity were evaluated to help understand its environmental impact. Finally, oil recovery was measured using spontaneous imbibition tests and the results were compared to those obtained using cationic and anionic surfactants supplied by a commercial vendor. All the tests were conducted at standard atmospheric conditions except the imbibition studies, which were conducted at reservoir temperature.
Our soy-based surfactant reduced the IFT by 60% and changed wettability from oil-wet to water-wet at concentrations lower than 3 gpt. No estrogenic or anti-estrogenic activity was detected for the surfactant at very high testing concentrations. The soy-based surfactant outperformed both the commercial anionic and cationic surfactants in imbibition tests recovering 35% of the oil originally in place (OOIP) inside the rock while the commercial cationic and anionic surfactants recovered 27% and 18% of OOIP, respectively.
These encouraging results suggest that our soy-based surfactant has the potential to provide cheap and eco-friendly solutions for improving oil recovery from tight carbonate reservoirs in addition to other potential near-wellbore performance enhancements that are currently being investigated. We believe this novel additive has the potential to solve oil recovery and near-wellbore issues at a lower cost to the operator and lesser impact on the environment compared to the products in use today.