3.3.4. Highlights of Important Results

The DOE effort was aimed mostly at defining the size and recoverability of the resource base as well as the use of natural gas associated with active coalmine operations.

The DOE CBM resource assessments established that a large, 400-Tcf natural gas resource was contained in coal seams. Fifty-three field tests were conducted in 10 geologic areas. Efforts focused on successfully collecting and analyzing coal samples for determination of gas content and performing geophysical logging to determine coalbed depth and thickness. Drill stem tests were conducted at six test wells. Gas content analyses were obtained from more than 300 samples taken from more than 50 sites in 10 basins: Arkoma, Green River, Illinois, Northern Appalachian, Piceance, Powder River, San Juan, Warrior, Western Washington and Wind River. A similar report was prepared for the Richmond Basin of Virginia.

Basin reports were completed and published and estimated of gas-in-place determined for eleven basins: Arkoma, Greater Green River Region, Illinois, Piceance, Powder River, San Juan, Raton Mesa, Warrior, Western Washington, Uinta and Wind River. The total estimated CBM gas-in-place was determined to be between 45 and 259 Tcf.

A water jet directional drilling system designed to enhance production from vertical wells without the use of fracture treatments was built and field tested.

The feasibility of increasing the permeability of coal by igniting an explosive gas mixture within the natural fracture system of the coal seam was assessed and determined to be ineffective due to coal “fines” production.

Significant research was conducted to better understand the mechanisms controlling fracture initiation and propagation, leading to the confirmation that: in the absence of confining stresses, fractures will propagate along bedding planes, and that natural shale layers (stringers) within the coal have a definite influence on fracture toughness.

A drill cuttings desorption technique was tested to facilitate the determination of commercial quantities of methane during drilling without the need for coring procedures.

Production technology development efforts included the design, application and/or evaluation of 40 fracture treatments in six basins. These tests helped to demonstrate:

• Technical feasibility of completing a well in multiple coal seams from a single wellbore,
• Economic production could be achieved from a multiple completion in spite of low methane content of individual seams,
• Predrainage of methane by drilling long, horizontal holes from within a mine is compatible with longwall mining operations,
• Drilling of long, horizontal holes can be accomplished without a complicated guidance system if operators are trained to distinguish between the drill string’s response to drilling coal versus roof or floor rock,
• Methane collection systems can be properly designed to safely collect gas from a number of boreholes and transport it to the surface using polyethylene pipe,
• Nitrogen-generated foam appears to be suitable for stimulating coalbeds, and
• Use of coalbed methane to provide fuel sources for onsite power generation, process heat and coal drying is technologically viable.