Optimization of closed-cycle oil recovery: a non-thermal process for bitumen and extra heavy oil recovery

Abstract

Energy from unconventional resources includes bitumen and extra-heavy oil that represent two-thirds of the known resources in the world. Extra-heavy oil and bitumen are currently recovered using thermal processes having a large carbon footprint and significant environmental impacts on water resources. A novel process is proposed: closed-cycle oil recovery (C-COR). C-COR is a greener alternative to provide energy from these unconventional resources with minimal water consumption. C-COR relies on recovering oil solubilized within a single-phase microemulsion, eliminating the need for viscosity reduction to both mobilize heavy oil or to transport it. Proof-of-concept work was conducted using conventional phase behavior experiments with extracted oil and surfactant formulations to develop a surfactant formulation for oil recovery using C-COR. As a part of process development and scale-up, we conducted flow experiments presented in this paper. We learned that a high degree of surfactant adsorption, which negatively impacted the C-COR process, resulted at low pH levels. These findings required modifying traditional static batch tests (phase behavior studies) using actual oil sand instead of the extracted oil. These unorthodox tests revealed that surfactant adsorption caused low oil solubilization and that alkali can be used to reduce adsorption, improving oil solubilization. In addition, unique flow experiments were designed to optimize the delivery and recovery process and are presented in this paper. The unique batch tests and flow experiments were conducted using oil sands from Canada to optimize the process. The proposed optimized approach would employ intermittent flow (soaking) that would result in the fastest recovery of about one-third of the OOIP, followed by continuous injection to recover an additional 10% OOIP, ending with thermal enhancement to recover another 25% OOIP for a total of 61%.

Fig. 1. Photographs showing the effects of open-pit mining of oil sands in Canada. Photo credit: Peter Essick.

Fig. 2. Conceptual diagram of closed-cycle oil recovery.

Fig. 3. Flow diagram of the field implementation of closed-cycle oil recovery.

Fig. 4. Surfactant adsorption onto solids with respect to sodium carbonate concentration; note the inflection point at 2 wt% sodium carbonate.

Fig. 5. Concentration profile for bitumen in dynamic test 1; concentrations are normalized by the highest concentration, approximately 30 000 mg L⁻¹.

Fig. 6. Concentration profile for bitumen in dynamic test 2, concentrations are normalized by the approximate highest concentration (37 700 mg L⁻¹).

Fig. 7. Dynamic test 2 sand pack: top – original sand sample; bottom left – inlet sand sample after test, and; bottom right – outlet sand sample after test.

Fig. 8. Comparison of the cumulative oil recovery for the five methods used to implement CCOR. The soaking method resulted in the fastest recovery of over 36% OOIP. Note that each method was terminated once the oil concentration in produced microemulsion.

Fig. 9. Comparison of the cumulative oil recovery per produced volume for the five methods used to implement CCCOR shows that the soaking method results in the highest.

Fig. 10. Cumulative recovery of the proposed, optimized approach begins with soaking followed by continuous flow and ending with thermal enhancement of injected fluids.

Fig. 11. Cumulative recovery per volume produced of the proposed, optimized approach (soaking, continuous flow, and thermal enhancement).