Method of hydrocarbon recovery

Abstract

A method is given for treating a wellbore to increase the production of hydrocarbons from a subterranean formation penetrated by a wellbore, involving a period of injecting into the formation an aqueous injection fluid having a different chemical potential than the aqueous fluid in the formation. If there is water blocking, an osmotic gradient is deliberately created to cause flow of water into the injected fluid; hydrocarbon is then produced by imbibition. If the pore pressure in the water-containing pores in the formation is too low, an osmotic gradient is deliberately created so that water flows from the injected fluid into the water-containing pores, increasing the pore pressure and facilitating hydrocarbon production by imbibition. The method may be repeated cyclically. A semipermeable membrane may be created to enhance the osmosis. Wetting agents may be used to influence imbibition.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is related to commonly-assigned and simultaneously-filed U.S. patent application Ser. No. 12 / 253,406, entitled “Enhancing Hydrocarbon Recovery”, incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]The invention relates to the recovery of hydrocarbons from subterranean formations. More particularly, it relates to methods of using osmotic pressure effects to increase the rate and / or amount of hydrocarbon that flows to producing wells.[0003]Hydrocarbons (gas, supercritical fluid, condensate, and oil) are typically found in the pores of subterranean rock formations. Although occasionally hydrocarbons flow naturally to a producing well at a commercially acceptable rate and extent due to inherent hydraulic forces, normally some means must be employed to increase the rate and / or extent of this flow. Methods include pumping, which will not be discussed further, stimulation, and enhanced recovery. Stim...

AI Technical Summary

Benefits of technology

[0006]One embodiment of the Invention is a method of producing hydrocarbon from a subterranean formation penetrated by a wellbore. The method includes a period of injecting into the formation an aqueous injection fluid having a higher chemical potential than the aqueous fluid in the formation. Water in the injection fluid flows into the formation fluid by osmosis, there is an increase in pressure in the formation, and a portion of the hydrocarbon flows to the wellbore. This flow may be by co-current and / or counter-current imbibition (hereinafter referred to collectively simply as “imbibition”). The injection fluid may contact, for example, at least one quarter of the practical wellbore drainage volume. The period of injection may be followed by a period of production without injection. The period of production without injection may be followed by a second period of injection. The method may additionally include injecting a semipermeable-membrane forming material in an amount sufficient to form a semipermeable membrane. The injection fluid may, for example, include a formate. The injection fluid may also include an agent that increases the contact angle of the formation with water. The injection fluid may alternatively include an agent that decreases the contact angle of the formation with water. In the method, the osmotic pressure may generate fractures in the formation.

[0007]Another embodiment of the Invention is a method of producing hydrocarbon from a subterranean formation penetrated by a wellbore involving injecting into the formation an aqueous injection fluid having a lower chemical potential than the aqueous fluid in the formation. A portion of the water in the formation fluid flows into the injection fluid by osmosis, phase trapping is reduced, and a portion of the hydrocarbon flows to the wellbore. This flow may be due to imbibition. The injection fluid may contact, for example, at least one quarter of the practical wellbore drainage volume. The period of injection may be followed by a period of production without injection. The period of production without injection may be followed by a second period of injection. The method may additionally include injecting a semipermeable-membrane forming material in an amount sufficient to form a semipermeable membrane. The injection fluid may, for example, include a formate. The injection fluid may also include an agent that increases the contact angle of the formation with water. The injection fluid may alternatively include an agent that decreases the contact angle of the formation with water. In the method, the osmotic pressure may generate fractures in the formation.

[0008]Yet another embodiment of the Invention is a method of producing hydrocarbon from a subterranean formation penetrated by a wellbore that involves injecting into the formation an aqueous injection fluid having the same chemical potential as the aqueous fluid in the formation. No osmotic pressure gradient is created, but a portion of the hydrocarbon flows to the wellbore. This flow may be due to imbibition. The injection fluid may contact, for example, at least one quarter of the practical wellbore drainage volume. The period of injection may be followed by a period of production without injection. The period of production without injection may be followed by a second period of injection. The method may additionally include injecting a semipermeable-membrane forming material in an amount sufficient to form a semipermeable membrane. The injection fluid may, for example, include a formate. The injection fluid may also include an agent that increases the contact angle of the formation with water. The injection fluid may alternatively include an agent that decreases the contact angle of the formation with water. Osmotic pressure may be used in a separate step to generate fractures in the formation.

Problems solved by technology

In the method, the osmotic pressure may generate fractures in the formation.

This flow may be due to imbibition.

In the method, the osmotic pressure may generate fractures in the formation.

This flow may be due to imbibition.

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