Coal as a Conventional Source of Methane: Review and Analysis of a 31-Well Production Area in the Mary Lee Coal Seam, Tuscaloosa County, Alabama
- Bill W. Dunn (Enhanced Energy Resources, Inc.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- January 1985
- Document Type
- Journal Paper
- 157 - 162
- 1985. Society of Petroleum Engineers
- 5.1.5 Geologic Modeling, 1.6 Drilling Operations, 3 Production and Well Operations, 2.4.3 Sand/Solids Control, 4.2 Pipelines, Flowlines and Risers, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 4.6 Natural Gas, 1.1 Well Planning, 5.8.3 Coal Seam Gas
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This paper presents a review of the actual production, sales, and economicdata from a 31 well production area developed by a joint coal industry/gasindustry effort owned equally by Jim Walter Resources, Inc. (JWR), a subsidiaryof Jim Walter Corporation of Tampa, Florida and Enhanced Energy Resources, Inc.(EER), a subsidiary of Kaneo Services, Inc. of Houston, Texas. The uniquereservoir characteristics of the coal environment are described in brief, acomparison of actual methane production from coal with computer modelpredictions is production from coal with computer model predictions ispresented, and the capital and operating costs are presented, and the capitaland operating costs are discussed with specific emphasis on the economicresults.
This information differs from similar previous work in that economicvitality is now apparent whereas previous inquiries , were essentiallyrestricted to the technical reservoir engineering characteristics and thephysical capability of coal to desorb (produce) methane. There are a number ofpublished papers on this important technical aspect, several of which arereferences for this presentation.
Production Area 1 (31 well production area) has been generating an operatingprofit for the past 15 months. Profits have increased substantially in the pastseven Profits have increased substantially in the past seven months as a resultof the completion of an 3" transmission line and reduced operating costs.Initial production commenced in late 1979. A five well pilot project wasevaluated for approximately two years before commercial development commencedin late 1981. A total of 31 wells were drilled by mid-1982. First salescommenced in February of 1982.
The economic viability is demonstrated based on actual operating profitsover the past fifteen months and current experience with respect toimprovements in operational techniques and costs. These data are applied to thecomputer forecasts of long term deliverabilities for projections of expectedeconomic performance. projections of expected economic performance
Although coal has been used as an energy source since prehistoric times, thevast coal reserves in the United prehistoric times, the vast coal reserves inthe United States (approximately 26 percent of the worlds known coal reserves)have taken on added significance as a clean energy source with the successfulextraction of methane from coal seams through vertical well bores.
During the process of coalfication considerable quantities of gases areevolved from the indigenous carbonaceous material. These gases include methaneand heavier hydrocarbons, carbon dioxide, nitrogen, oxygen, hydrogen, andhelium. The primary constituents are methane and carbon dioxide. These gaseshave been observed in coal mines and the emmission of methane from coal bedshas created problems in mining since the inception of the industry. In manycases the presence of methane can cause the cessation of mining operations.Regardless of the range of severity, methane presence in coal mines isdetrimental to safety, increases mining costs, and reduces efficiency of mineproduction. Quantities of methane and air in proper proportions (5 to 15%present methane) result in explosive mixtures. It is the ignition of thesemixtures that cause the disastrous explosions in coal mines. Concurrently,however, methane being the principal constituent of natural gas offers apotentially large supply of energy for traditional residental, commercial andindustrial markets.
Historically, mines are engineered to vent as much methane as possible.According to the U.S. Department of Energy (DOE) estimates, in excess of 250million cubic feet (MMcf) of methane gas is vented daily as a routine safetymeasure for underground mining operations. However, this vented methane fromactive mines is only a small percentage of the potentially producible methaneavailable from properly developed vertical well programs. An alternate toventing is to reduce the coal extraction rate. Both solutions are expensive andwasteful.
The nation's resource of gas trapped in coal is extremely large (See Figures17 and 18). According to the DOE the amount exceeds 700 trillion cubic feet(Tcf). Of this 700 Tcf it is estimated that approximately 300 Tcf isrecoverable; this is the equivalent of a ten-to-twenty-year supply based on1981 U.S. consumption rates.
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