Insights Into Bitumen Viscosity Reduction Using Ultrasound-Assisted EOR

Abstract

Abstract The present work clarifies the mechanisms associated with bitumen viscosity reduction during ultrasound sonication. A Canadian (CDN) and Nigerian (NGR) bitumen, selected for this study, have a respective viscosity of 2,617 and 12,043 cP at room temperature. Two series of ultrasound sonication experiments were performed using an ultrasonic generator and the submersible traducer. A series of experiments at 28, 38 and 200 kHz under ambient (air)-environment revealed that sonicating the oil continuously for 3 h at 200 kHz reduced NGR viscosity from 12,043 to 2,079 cP and the asphaltene content from 3.21 to 1.14 wt.%. Under the same conditions, CDN viscosity reduced from 2,617 to 486 cP and its asphaltene content increased from 5.72 to 8.11 wt.%. A reverse trend was observed at 38 kHz. For an average of 70% viscosity reduction, asphaltene content increases to 7.94 wt.% for NGR and decreases to 1.03 wt.% for CDN. On the other hand, bitumen sonication at 38 kHz under nitrogen (N2), and carbon dioxide (CO2) environment showed that irradiating NGR for 3 h under an N2 environment resulted in the lowest oil viscosity of 3,274 cP. However, the asphaltene content increases to 16.3 wt.%. Changing the gas environment to CO2 and air could reduce the viscosity to 4,415 and 9,773 cP, respectively. The asphaltene content decreases to 15.1 and 2.37 wt.%, concurrently. No direct relation between asphaltene content and viscosity reduction was established. Nevertheless, the viscosity reduction is influenced either by the applied frequency or gas environment. The minimum energy required to initiate the flow increased with the applied frequency and was fairly altered by the change in the gas environment.