Performance of thermophilic strain on the reduction of viscosity of crude oil under high pressure and high temperature conditions: Experiments and modeling

Abstract

The matured reservoirs all over the world leads on the way to highly viscous crude oil. The heavy and waxy oil would act as an alternative to conventional reserves, only with the application of a technology to reduce the viscosity. This study aims to analyze the microbial activity on crude oil, and the synergetic effect of microbial interaction, pressure and temperature on viscosity. The reports on application of microorganisms on the viscosity reduction of crude oil are very rare at high temperature and high pressure environment. The application of Bacillus subtilis , a thermophilic bacterium for improving the flow properties of waxy crude oil is investigated at various temperatures and pressures in a high pressure cell. This study has been carried out to simulate the microbiological phenomenon occurring in the reservoir, when a bacteria is introduced for viscosity reduction. Bacillus subtilis could grow well from 0.1 to 5 MPa, and less growth was observed at 10 MPa. The maximum 52.1% of viscosity of crude oil was reduced at the pressure of 1 MPa, temperature of 50 °C, and at the shear rate of 1000 s −1 by microbial interaction. The implicit correlations as a function of pressure, temperature, and shear rate has been developed to predict the viscosity of crude oil during the microbial treatment. This work also proposed a new model incorporating the thermodynamic and microbial kinetics to estimate the viscosity of crude oil during the process of microbial degradation. The proposed model has provided satisfactory predictions when compared with the experimental values of degradation. All these findings demonstrate the influence and suitability of Bacillus subtilis in crude oil production and transportation. • Suitability of Bacillus subtilis at high temperature and pressure was explored. • Interaction of crude oil and Bacillus subtilis were examined for viscosity reduction. • Analyzed the synergetic effect of pressure and temperature on viscosity reduction. • Viscosity of crude oil was reduced by 52.1% at 1 MPa, 50 °C, and 1000 s −1 . • Proposed a model to predict viscosity during microbial degradation of crude oil.