Azi-Frac vertical propped planes filled with an electric conductive permeable 8/20 calcined coke proppant are ideal for enhanced oil recovery by single or three phase electrical resistive heating. The propped inclusions are installed between horizontal wells, between vertical wells or within a single vertical well. A single or three phase alternating current passes through the inclusions, heating the proprietary proppant by resistive heating, which in turn heats the formation, heavy oil or bitumen by conduction.

Thermal reservoir simulations of the Azi-Frac Electric Resistive heating with Gravity drainage (ERG) system shows the system to be highly productive, efficient, and an environmental clean and sustainable recovery process. The ERG system is targeted to formations and leases where conventional steam assisted gravity drainage (SAGD) is not a viable recovery method, due to depth (shallow or deep), thin pay, outcrop proximity and/or lack of caprock integrity.

The proprietary ERG highly permeable proppant pack consists of differing proppants and fibers depending on the application, e.g. operating effective closure stress, pay thickness, well geometry, etc. The proppant pack can be formulated as an isotropic resistive pack, i.e. horizontal resistivity equal to vertical resistivity, or as a highly anisotropic resistive pack with up to 100:1 in anisotropy. The proppant pack is designed for a particular well layout to achieve a near uniform electric current density over the planar inclusions, thus optimizing the resistive heating of the inclusions.

Simulations conducted on a variety of ERG system well geometries, involving either horizontal or vertical wells, pay thickness, ambient oil viscosity, etc indicate that computed production rate and cumulative energy oil ratio (CEOR) show that the ERG system is both economically viable and environmentally attractive compared with conventional horizontal SAGD. Operating costs of the ERG system are expected to be similar to conventional SAGD, while capital costs are expected to be significantly less.

     Proppant/Fiber Pack Anisotropy

In a thick Athabasca bitumen deposit in the McMurray formation, an ideal layout of horizontal wells for the ERG system is for orthogonal vertical inclusions on a 50m spacing. The inclusions are first initiated and propagated at 50m spacing in the upper open-hole horizontal well. Following stimulation, the upper well is completed with a specialized slotted liner. The lower horizontal well is then stimulated open-hole, with the inclusions propagating towards and coalescing with the upper inclusions by pore pressure relief. Finally the lower well is completed with a similar slotted liner.

Graphite electrodes are placed in all wellbores, with the lower wells completed as producers with artificial lift, and the upper wells for gas injection for pressure balance and/or to assist drainage. The electrodes are excited with a single phase alternating current, which passes through the inclusions, heating the inclusions by resistive heating, and in turn heating the formation and bitumen by conduction.

Reservoir simulations of conventional SAGD can be highly unreliable due to the difficulty in estimating formation vertical permeability under steam and its significant impact on SAGD performance. The ERG system being virtually independent of formation vertical permeability, enables reservoir simulations to be conducted with a higher degree of confidence, provided the electric conductive permeable planes are installed throughout the full pay thickness.

Reservoir simulations of the horizontal ERG system in Athabasca bitumen 35m thick McMurray formation are shown along with best performing SAGD with the same reserve base. The SAGD data are from the best performing well pair in Athabasca bitumen in clean McMurray channel sand.

The ERG system outperforms the best SAGD well pair in clean McMurray channel sand by a production factor of 2. The CEOR for the ERG well has been normalized to the equivalent CSOR by equating equivalent operating cost, with the final CSOR shown being a CEOR of 76kWhr/bbl. The capital cost of an ERG system is expected to be 60-70% less than an equivalent SAGD system.

ERG - Electric Resistive Heating + Gravity