Method for producing heavy oil

Abstract

A method is provided for production of heavy oil from a reservoir containing heavy oil, the method including the steps of: providing a plurality of wells into the formation; injecting into the plurality of wells a mixture comprising steam and a solvent; ceasing injection of the mixture; producing a mixture of heavy oil, solvent and condensed steam from the plurality of wells after injection of steam has ceased: and after production of the mixture of heavy oil, solvent and condensate from at least one of the plurality of wells has declined to a predetermined rate, injecting into the at least one well a stream consisting essentially of steam while at least one other well continues to operate as a producing well.

Description

RELATED CASES[0001]This application claims the benefit of U.S. Provisional Application No. 61 / 894,681, filed on Oct. 23, 2013, which is incorporated herein by reference.BACKGROUND[0002]The invention relates to a method for producing heavy oil from a formation by co injection of steam and solvent.[0003]Reservoirs of heavy oil can be challenging to produce because heavy oils can have viscosities, at the ambient temperatures of the reservoirs, that render the oils essentially immobile. To produce the heavy oils, the oils may have been heated using, for example, steam injection. A thermal drive process for producing heavy oils typically employs an injection well and a production well. A hot fluid, typically steam, is introduced into the formation through the injection well. The injected steam heats the heavy oil, reducing its viscosity, and drives the heavy oil toward the production well. This process is problematic because the injected steam does not contact a large portion of the heav...

AI Technical Summary

Benefits of technology

The patent describes a method for producing heavy oil from a reservoir containing heavy oil using a mixture of steam and solvent. The method takes steps to increase the amount of heavy oil produced from the reservoir, while minimizing the amount of asphaltenes. The process involves injecting the mixture of steam and solvent into a formation and producing a mixture of heavy oil, solvent, and condensed steam. The method can be repeated until communication is observed between adjacent wells. The technical effects of the invention are an increase in heavy oil production with reduced asphaltenes content.

Problems solved by technology

Reservoirs of heavy oil can be challenging to produce because heavy oils can have viscosities, at the ambient temperatures of the reservoirs, that render the oils essentially immobile.

This process is problematic because the injected steam does not contact a large portion of the heavy oil, and the ambient temperature heavy oil is a very effective barrier to flow.

Initial injection periods are relatively short because the formation will not accept very much steam, and injection pressures are limited to prevent the steam from fracturing the formation to the extent the steam escapes from the near-wellbore region.

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