Recovery of hydrocarbons using electrical stimulation

Abstract

A method of recovering hydrocarbon such as heavy oil or bitumen from an underground oil-rich reservoir formation such as oil sand or oil shale is provided. One or more substantially vertical wells are drilled into the formation so that the bottom portion of each well extends into the formation and, preferably, below the bottom of the formation. The bottom portion of each well may be enlarged relative to the rest of the well. The bottom portion of the well is substantially filled with conductive liquid, sealed at the surface and high voltage power of up to 72,000 Volts or more is applied via an electrical conductor having an electrode submerged in the conductive liquid. The resulting current flow increases the formation temperature, causing the heavy oil or bitumen to flow from the formation into the bottom portion where it can be removed from the well.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority benefit from U.S. Provisional Patent Application No. 60 / 596,390 filed Sep. 20, 2005.FIELD OF THE INVENTION [0002] This invention relates generally to a method of recovering hydrocarbons such as bitumen from underground formations. More particularly, this invention relates to a method of recovering hydrocarbons by drilling one or more substantially vertical wells in the formation and applying high voltage electrical power directly to the formation via said wells to increase the temperature and / or pressure in the formation. The heated hydrocarbon such as bitumen readily flows to a production cavity in the well and is elevated to the surface through the well using the high pressure created within the formation. BACKGROUND OF THE INVENTION [0003] Over the past several years, there has been much advancement in thermal processes applied for recovering heavy, viscous oil (e.g., bitumen) from subterranean reserv...

AI Technical Summary

Benefits of technology

[0037] substantially sealing the top of each well to maintain a sufficiently high pressure in each well to prevent evaporation once saturation temperature is reached and to force the heated heavy oil or bitumen to flow into the bottom portion of the well and through the well to the surface of the well.

[0069] Sixth, “Off-Peak” power, not mentioned in electrical in-situ power comparisons, can be used at a price reduction of 20-40% for much of the energy needs. This is possible because of the large heat sink created within the formation. Power may be cut off and easily restored as desired by the power company, thereby allowing “Peak-Power” periods to be bypassed. This feature alone makes electrical power cheaper than SAGD steam energy.

Problems solved by technology

However, there are several problems that one encounters when employing SAGD for bitumen extraction.

Steam injection disturbs the formation, causing silt and sand washout; 8.

Contaminated water disposal is an environmental issue; 11.

SAGD methods are believed to be limited to about 2000 ft in the depth from which recovery may most economically be realized.

However, problems were also encountered with this method, including: 1.

Energy losses through the pipe casing, which conducted the electrical current from the surface to the formation, caused much of the energy to be absorbed by the pipe before it got to the formation.

This reduced energy efficiency.

It also limited the quantity of power reaching the formation; 5.

There is a misconception within the industry that electrical energy created from steam could not be as efficient as using steam directly to heat the formation thereby limited electrical effort using electrical power as the main heat source; 7.

Low voltages used to date could not viably transmit the required large power needs into the formation without using closely spaced, numerous drill holes, making such installations uneconomical.

Low voltage needs high current to transmit large power loads into the formation, a limiting factor in earlier experiments; 8.

There is a problem with sand / silt accumulations seriously interfering with bitumen extraction through SAGD pipes; and 9.

The overall electrical efficiency from the electrical energy methods tried in past proved to be less efficient than that achieved using steam.

Images