Coal bed pretreatment for enhanced carbon dioxide sequestration

Abstract

A method is claimed for enabling storage of greater volumes of carbon dioxide for sequestration while simultaneously enhancing methane recovery from the coal bed. The process is implemented by injecting hydrogen into a coal bed, such as a depleted underground coal deposit, at a temperature below about 800 degrees Centigrade (10); extracting the hydrogen together with methane from the deposit (20); separating the hydrogen from the methane (30); delivering the methane as a product of the process (40); reinjecting the separated hydrogen into the deposit to continue the process until sequestration of carbon dioxide is desired (50); optionally producing hydrogen from methane (60) and optionally injecting carbon dioxide for sequestration (70).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Pursuant to 35 U.S.C. section 119(e), the present invention claims the benefit of the filing date of United States provisional application No. 60 / 597,447 filed 02 Dec. 2005, the text of which is hereby incorporated by reference herein.FIELD OF INVENTION [0002] In the field of carbon dioxide sequestration, a coal bed pretreatment process using hydrogen for increasing the storage potential of an underground coal deposit and enhancing production of methane. DESCRIPTION OF PRIOR ART [0003] Methods for adjusting the porosity and permeability of an underground coal bed have been practiced using the injection of fluids. However, none propose the use of hydrogen alone as a fluid displacing methane from the pores of an underground coal bed to enhance the carbon dioxide storage capability of the coal bed. [0004] Enhanced coal bedded methane recovery is currently under development using carbon dioxide injection prior to carbon dioxide sequestratio...

AI Technical Summary

Benefits of technology

"The patent describes a process for storing more carbon dioxide while also increasing the recovery of methane from a coal bed. This is achieved by injecting hydrogen into the bed, extracting the hydrogen and methane, separating the hydrogen from the methane, and delivering the methane as a product. The separated hydrogen is then reinjected into the bed to continue the process until carbon dioxide sequestration is desired. Additionally, the patent suggests the option of producing hydrogen from methane and injecting carbon dioxide for sequestration. The technical effect of this process is the ability to store more carbon dioxide while also increasing methane recovery from coal beds."

Problems solved by technology

However, none propose the use of hydrogen alone as a fluid displacing methane from the pores of an underground coal bed to enhance the carbon dioxide storage capability of the coal bed.

However, this yield quickly drops off because the carbon dioxide tends to swell the coal and tends to block the passage of the methane out of the coal deposit.

The '411 patent does not teach the use of hydrogen to displace methane and is confined to an oil well to produce oil by a chemical process, namely hydrogenation.

This separation process consumes energy and generally, the larger the difference in the molecular weight of the gases being separated, the lower the energy consumption.

Water can be an environmental pollution problem in coal bedded methane recovery, but may not be a significant effluent in some sites.

In traditional enhanced methane recovery process using carbon dioxide, the problem is that carbon dioxide is relatively soluble in the water especially under pressure and it forms carbonic acid.

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