In a previous study, we developed a synthetic hydrophobically modified hydroxyethyl cellulose (HEC) using bromododecane (BD), which we denote as BD-HMHEC. In this work, we continually investigate the rheological properties and its oil displacement efficiency in PuTao well area in Daqing oilfields, China. Results show that BD-HMHEC solution has good viscosification, thermal-resistance, salt-tolerance, shear resistance, and acid/alkali resistance. The storage modulus (G’) and the loose modulus (G”) of the BD-HMHEC solutions increase significantly with increasing BD-HMHEC concentration, and the solution becomes viscoelastic at a sufficiently high BD-HMHEC concentration. The core flooding results showed BD-HMHEC flooding improves oil recovery by 7–14% in comparison with HEC flooding at concentrations of 4,000 mg/L under equivalent conditions. Moreover, BD-HMHEC flooding improves oil recovery by 7–8% after conducting water and hydrolyzed polyacrylamide (HPAM) flooding. The oil displacement mechanism of BD-HMHEC solutions is discussed based on a visual evaluation. The results indicate that BD-HMHEC flooding is a feasible means for improving oil recovery after water/HPAM flooding.

To model foamy-oil flow in the development of heavy oil reservoirs, three depletion experiments were conducted with foamy oil treated as a pseudo-single-phase flow. In this pseudo single phase, dispersed bubbles are viewed as a part of the oil, and the redefined effective permeability varies with the changes of pressure depletion rate, oil viscosity, and gas saturation. A mathematical expression for the effective permeability was developed based on experiments, where the viscosity of foamy oil is assumed to be approximately equal to the saturated oil under equivalent conditions. The compressibility coefficient of foamy oil is treated as a volume-weighted compressibility coefficient of that of oil and gas phases. A new mathematical model for foamy-oil flow was proposed with consideration of foamy-oil supersaturation. To validate the mathematical model, the oil recovery and the production gas-oil ratio (GOR) calculated by the new model, conventional black oil model, supersaturation model and pseudo-bubble-point (PBP) model were all compared with those of the experimental data. The new model provided a substantially improved fit to the experimental data compared with the rest three models, which verifies the suitability of the mathematical model presented for simulating foamy-oil flow in the development of heavy oil reservoirs.

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