Enhancing hydrocarbon recovery

Abstract

Recovery of hydrocarbon fluid from low permeability sources is enhanced by introduction of a treating fluid. The treating fluid may include one or more constituent ingredients designed to cause displacement of hydrocarbon via imbibition. The constituent ingredients may be determined based on estimates of formation wettability. Further, contact angle may be used to determine wettability. Types and concentrations of constituent ingredients such as surfactants may be determined for achieving the enhanced recovery of hydrocarbons.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is related to commonly-assigned and simultaneously-filed U.S. patent application Ser. No. ______, entitled “Method of Hydrocarbon Recovery”, incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The Invention is generally related to hydrocarbon recovery from low permeability sources.BACKGROUND OF THE INVENTION[0003]Recovering hydrocarbons such as oil and gas from high permeability reservoirs is well understood. However, recovery of hydrocarbon resources from low permeability reservoirs is difficult and less well understood. Consequently, operators have until recently tended to bypass low permeability reservoirs such as shales in favor of more conventional reservoirs such as sandstones and carbonates. A shale reservoir typically includes a matrix of small pores and may also contain naturally occurring fractures / fissures (natural fractures). These natural fractures are most usually randomly occurring o...

AI Technical Summary

Benefits of technology

[0011]The Invention is predicated in part on recognition that in low permeability sources the conditions which favor release of oil due to imbibition differ from the conditions which favor release of gas due to imbibition. Further, the interfacial tension between oil and water is much lower than the interfacial tension between a gaseous phase and water. In accordance with an embodiment of the Invention, a method for enhancing hydrocarbon recovery from a low permeability source comprises: causing treating fluid to contact the source such that the treating fluid is imbibed by the source, thereby increasing hydrocarbon recovery. In accordance with another embodiment of the Invention, apparatus for enhancing hy

Problems solved by technology

However, recovery of hydrocarbon resources from low permeability reservoirs is difficult and less well understood.

In a shale gas reservoir, this presents a problem because the pore matrix contains most of the hydrocarbons.

However, according to Katsube the storage pores do not contribute to the migration of fluids through the rock formation.

Despite a favorable mobility ratio, the authors point out that entrapment of the non-wetting gas phase is likely due to high surface tension.

It is widely believed that water imbibition into a reservoir from a well that will be used for production is deleterious in several ways.

Imbibed water increases the water saturation and is thought to become trapped and to block hydrocarbon flow.

If imbibed water is fresher than formation water, it may affect fresh water sensitive expanding clays.

Furthermore, imbibition of water into formations such as shales during drilling may be responsible for spalling and wall collapse.

On a relative permeability basis, in general, the greater the value of the initial trapped fluid saturation, the less original reserves of gas in place are available for production, and also the lower the initial potential productivity of the matrix.

This often results in significant reductions of the original reserves of gas in place in the porous media, and may also result in a very low or zero effective permeability to gas, as the gas saturation may be at or near the critical mobile value, and hence it will exhibit limited or no mobility when a differential pressure gradient is applied to the formation during production operations.

In situations where exceptionally low matrix permeability is present in a gas-producing reservoir, unless a sub-irreducibly saturated original condition is present, the reservoir will exhibit insufficient initial reserves / permeability to be a viable gas-producing candidate.

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