In situ process to recover heavy oil and bitumen

Abstract

An in situ reservoir recovery process consisting of a horizontal injection well and a horizontal production well to extract bitumen or heavy oil from a reservoir. The process consists of a first phase operated at high-pressure in which steam, hydrocarbon solvent and non-condensable gases are injected into the reservoir and a second phase in which the injected fluids are transitioned to a high content of solvent and non-condensable gas and a reduced amount of steam to maintain a warm zone in the neighbourhood of the injection and production wells. The steam injection is sufficient to promote vapor transport of the solvent into the vapor depletion chamber and maintain the process at elevated temperatures in order to maintain low fluid viscosities in the production wellbore and to achieve preferred phase behaviour of the solvent hydrocarbon and the heavy oil or bitumen. The operating pressure of the process is controlled to prevent losses of the solvent hydrocarbon to the formation and to aid in solvent production to the production well in order for future re-cycling.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method to improve heavy oil and / or bitumen recovery from a hydrocarbon reservoir. The invention, in particular, relates to a process in which steam, solvent and non-condensable gas injection rates and pressure into an injection well are phased throughout the process to achieve improved thermal efficiency, mobilization of heavy oil and / or bitumen within the hydrocarbon reservoir and improved solvent recovery. BACKGROUND OF THE INVENTION [0002] There are many methods that are used to recover in situ heavy oil or bitumen from oilsands reservoirs. Typically, in situ methods are used in heavy oil or bitumen deposits that are greater than about 70 m deep where it is no longer economic to recover the hydrocarbon by current surface mining technologies. Depending on the operating conditions of the in situ process and the geology of the heavy oil or bitumen reservoir, in situ processes can recover between about 25 and 75% of the...

AI Technical Summary

Benefits of technology

[0018] In one embodiment of the invention, a method is provided to extract heavy oil or bitumen from a reservoir located underground. The reservoir is penetrated by a horizontal wellpair that comprise a top injection well and a bottom production well both being substantially parallel to each other. In the method, steam, solvent, and non-condensable gas are injected through the injection well into the reservoir over time while reservoir fluids are produced through the production well. The injected fluids enter a vapor chamber that surrounds and extends above the injection well. In the present invention, the injection rates and injection pressure are controlled in order to minimize heat losses to the overburden and maximize the action of the solvent in reducing the viscosity of the heavy oil and / or bitumen. Additionally, the operating pressure is controlled together with the relative amounts of steam, solvent, and non-condensable gas to maximize the solvent recovery from the process. The partial pressure of the solvent is controlled in the vapor chamber as the process is evolved.

[0020] The recovery method may include the additional step of adjusting the injection pressure and relative amounts of steam, solvent, and non-condensable gas to control the vapor chamber temperature to enhance the solubility of solvents.

[0022] A further object of one embodiment of the present invention is to provide a method for recovering heavy hydrocarbons from an underground reservoir containing heavy hydrocarbons, an injection well and a production well, comprising injecting steam into the reservoir, to form a steam vapor chamber, co-injecting predetermined quantities of steam, hydrocarbon solvent and non-condensable gas into the steam vapor chamber to maximize the solubility of the solvent in the heavy hydrocarbons, recovering produced hydrocarbons through the production well, adjusting the volume of steam injected into the vapor chamber to be subordinate to the volume of hydrocarbon solvent and non-condensable gas whereby partial pressure of the steam in the chamber is reduced and hydrocarbon solvent solubility is elevated in the heavy hydrocarbons, and recovering further produced hydrocarbons through the production well.

Problems solved by technology

Typically, in situ methods are used in heavy oil or bitumen deposits that are greater than about 70 m deep where it is no longer economic to recover the hydrocarbon by current surface mining technologies.

The steam loses its latent heat to the cool heavy oil or bitumen at the edges of the steam chamber and as a result raises the temperature of the heavy oil or bitumen.

The major capital and operating costs of SAGD involve the facilities to generate steam and re-cycle produced water back to the steam generators.

At present, it remains unclear what the optimal amount of non-condensable gas that should be added to the injected steam.

There are two issues about this process: first the process uses high solvent to hydrocarbon ratio and second the solvents are typically more valuable than the produced hydrocarbon.

Both of these issues adversely impact process economics.

Also there are unresolved issues on how to prevent significant solvent losses to the reservoir which will be vitally important for economic success of the process.

Additionally, the operating pressure range of VAPEX is limited because of required condensation of the injected gaseous solvent at the edges of the vapor chamber.

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