Method for Viscous Hydrocarbon Production Incorporating Steam and Solvent Cycling

Abstract

A method for producing hydrocarbons from a reservoir containing the hydrocarbon comprises a steam assisted gravity drainage (SAGD) incorporating cyclic steam, heavy (e.g. greater than C4) solvent and light (e.g. C2 to C4) solvent injection. The method involves a series of steps wherein the injection of the respective streams is varied. The method provides a significant improvement in hydrocarbon extraction efficiency as compared to a SAGD process alone and mitigates many of the drawbacks associated with typical SAGD operations.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority from U.S. application No. 61 / 173,911, filed on Apr. 29, 2009, the entire contents of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to the production of hydrocarbons, in particular viscous hydrocarbons, from petroleum deposits. More specifically, the invention relates to an improved method for producing hydrocarbons from formations, such as “oil sands”, incorporating cyclic applications of steam and solvent.BACKGROUND OF THE INVENTION[0003]Oil sand deposits are found predominantly in the Middle East, Venezuela, and Western Canada. The Canadian bitumen deposits, being the largest in the world, are estimated to contain between 1.6 and 2.5 trillion barrels of oil, so the potential economic benefit of this invention carries significance within this resource class. The term “oil sands” refers to large subterranean land forms composed of reservoir rock...

AI Technical Summary

Benefits of technology

"The invention provides an improved method for extracting hydrocarbons from a reservoir containing them using a combination of steam and heavy and light solvents. The method involves a cycle of injection and production, with the heavy solvent being injected first, followed by a pause and then the light solvent being injected. This process helps to improve the efficiency of the method and increase the amount of hydrocarbons produced."

Problems solved by technology

Bitumen is a heavy, black oil which, due to its high viscosity, cannot readily be pumped from the ground like other crude oils.

Although effective, stand alone SAGD processes have several associated inefficiencies.

Firstly, the process is very energy intensive, requiring a great amount of energy for heating the volumes of water to generate the steam used for the heat transfer process.

Further, upon releasing its heat to the formation, the injected steam condenses into water, which mixes with the mobilized bitumen and often leads to additional inefficiencies.

For example, the water must be recycled through the boilers, requiring costly de-oiling and softening processes.

In addition, the original or initial separation of the bitumen and water requires further processing and costs associated with such procedures.

Also, as common with other known active heating methods, the energy input to the deposit is often transferred to neighbouring geological structures and lost by way of conduction.

Thus, the process becomes considerably energy intensive in order to achieve sufficient heating of the target formation.

As a result, SAGD processes are typically only commercially viable for reservoirs having a minimum volume and concentration of hydrocarbons.

Finally, VAPEX methods tend to accumulate material quantities of liquid solvent within the depleted part of the reservoir.

Such solvents cannot be recovered until the end of the process thereby representing an economically significant cost for the solvent inventory.

However, both steam and solvent are injected at all times during the process.

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