There are currently two main categories of processes for in situ—i.e., underground, without mining—thermal recovery of bitumen and heavy oil: steam injection and combustion. Thermal recovery reduces bitumen viscosity, and allows it to flow to the surface.

• In the steam injection process (steam-assisted gravity drainage, SAGD), the heat from injected steam reduces the viscosity of bitumen and, consequently, reduces the flow resistance of bitumen through porous media, increasing the cumulative recovery and production rate.

• For in situ combustion (“fire flood”), the heat is generated and propagated along the reservoir by igniting a part of the original heavy oil-in-place. This heat subsequently reduces the viscosity of the unburnt bitumen, thereby improving its flow.

The high energy intensity and huge amount of water consumption, especially for the SAGD process, as well as the low quality of the produced bitumen through the in situ thermal recovery processes pose challenges for future deployment of the current technologies. Therefore, it is necessary to search for new ideas or alternatives in the field of in situ recovery to improve current technologies and make them environmentally sound and cost-effective.

In situ upgrading of bitumen or heavy oil is an innovative environmentally friendly approach and recently is attracting considerable attention. This approach uses the reservoir as a high-temperature reactor, and it is based on integrating the catalytic hydrogenation reaction with thermal recovery methods. The idea of the underground refinery project is to use porous media as a chemical reactor with a series of chemical reactions (i.e., hydrocracking, hydrotreating, etc.) to improve the quality of produced heavy oil and bitumen.

—Hashemi et al.

Successful underground upgrading requires:

• presence of catalyst in formation or an appropriate zone near production well;

• mobilization of reactants including heavy oil and co-reactants such as steam or hydrogen; and

• creation of necessary processing conditions to achieve reasonable degree of upgrading (i.e., sufficient temperature and pressure).

Several important underground heavy oil recovery and upgrading processes have been reported, which are implemented at the pilot plant and field scales, the University of Calgary authors noted. These include steam distillation and in situ upgrading processes; conventional fireflood field projects and dry combustion; solvent-based in situ processes and propane de-asphalting; thermal upgrading and visbreaking of heavy oil; in situ hydrogenation and hydroprocessing; toe-to-heel air injection (THAI) process; aquathermolysis; and in situ combustion (ISC).

The main mechanism of the in situ recovery and upgrading processes is to decrease bitumen viscosity and enhance the liquid quality, which subsequently improve the productivity index of the producer well.

—Hashemi et al.

The University of Calgary study is aimed at developing a catalytic-enhanced oil recovery method for Athabasca bitumen recovery through the viscosity reduction mechanism with the aid of trimetallic (W, Ni, and Mo) nanoparticles.

They conducted a series of experiments at a pressure of 3.5 MPa, residence time of 36 h, and temperatures from 320 to 340 °C in an oil sands packed bed column. Obtained experimental results showed that the recovery curve for vacuum gas oil injection without nanocatalysts was at a plateau. Further observations proved that adding a certain percentage of pentane enhanced the recovery performance of injection tests. The third phase of experiments was conducted in the presence of the trimetallic nanocatalysts in emulsion with vacuum gas oil. Results showed the effectiveness of nanocatalysts for enhancing the recovery performance compared with the cases of no nanoparticle implementation.

This work is a continuation of our previous studies, and it aims at experimentally investigating the effect of UD nanocatalysts on the recovery enhancement of Athabasca bitumen in a one-dimensional (1D) continuous flow oil sands packed bed column. The present work holds great promise for in situ heavy oil upgrading and recovery. It should be noted here that the effect of nanocatalyst content in the porous media and temperature on the extent of Athabasca bitumen upgrading and subsequent liquid quality improvement shall be communicated in another study.

—Hashemi et al.

Resources

• Rohallah Hashemi, Nashaat N. Nassar, and Pedro Pereira Almao (2013) Enhanced Heavy Oil Recovery by in Situ Prepared Ultradispersed Multimetallic Nanoparticles: A Study of Hot Fluid Flooding for Athabasca Bitumen Recovery. Energy & Fuels doi: 10.1021/ef3020537