# US 4,391,327 A · Solvent foam stimulation of coal degasification well

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- Number: US 4,391,327 A
- Document ID: US4391327A
- Status: Granted
- Kind: A
- Application number: 06/262,575
- Filed: 1981-05-11
- Granted: 1983-07-05
- Earliest claimed: 1981-05-11
- Assignees: Conoco Inc.
- Inventors: Leonard J. De Carlo
- Web page: https://patentgrep.com/patent/US4391327A

## CPC

- E21B 43/295: Gasification of minerals, e.g. for producing mixtures of combustible gases (E21B43/243 takes precedence)
- E21B 43/255: {including the injection of a gaseous medium as treatment fluid into the formation}
- E21B 43/27: by use of eroding chemicals, e.g. acids
- E21F 7/00: Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21F: SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS

## Abstract

A foamed fluid containing a coal solvent is injected into a coal seam to improve the gas permeability of the coal.

## Claims

### Claim 1

A method for improving the gas drainage characteristics of a coal seam comprising:
(a) injecting into said coal seam a foamed fluid comprised of a liquid solvent selected from the group consisting of toluene, pyridine, xylene, tetralin, anthracene, coal tar and mixtures thereof, a foam-producing surfactant and a high pressure gas, said foamed fluid containing an amount of said solvent effective to partially dissolve coal contacted by said foamed fluid;
(b) maintaining said foamed fluid in contact with said coal seam for a period of time sufficient for said solvent to partially dissolve coal contacted therewith thereby improving the gas drainage characteristics of said coal seam; and
(c) recovering injected material and naturally occurring gas from said coal seam.

### Claim 2 (depends on 1)

The method of claim 1 wherein said foamed fluid is injected into said coal seam at a pressure less than its fracturing pressure.

### Claim 3 (depends on 1)

The method of claim 1 wherein said foamed fluid is injected through an injection well extending into said coal seam, after said fluid is injected said well is shut in for a period of at least 0.5 hours, and said well is then opened for flow from said coal seam.

### Claim 4 (depends on 1)

The method of claim 1 wherein said foamed fluid contains a solvent diluent selected from the group consisting of alcohols having from 1 to 4 carbon atoms.

### Claim 5 (depends on 1)

The method of claim 1 wherein said gas is selected from the group consisting of inert gases and air.