Exploration for Natural Gas from Deeply Buried Coal Seams in Southwestern Oregon

Pappajohn, Steve¹, David May¹, Russell Ralls¹, George Hampton¹ (1) Methane Energy Corp, Coquille, OR

Exploration for natural gas reserves in deeply buried coal seams is continuing in Coos County, Oregon. The Coos Bay basin is located along the southwest Oregon coast and covers over 250 square miles. The basin contains the coal-bearing sediments of the Eocene-age Coaledo Formation. The Coaledo Formation contains multiple coal seams, many of which are saturated with natural gas. Coal beds are found in both the upper and lower Coaledo Formation.

As many as 10 individual coalbeds may be present in both upper and lower members of the Coaledo formation. Total coal thicknesses in the Lower Coaledo can reach 80 feet, with individual beds up to 20 feet. Persistent wave-dominated deltaic depositional environments during the Eocene resulted in coalbeds that can be correlated across the basin.

Coal accumulation appears to migrate from the geographic and structural center of the basin during Lower Coaledo times to southeast portions of the basin during Upper Coaledo times. Several hundred feet of marine siltstones and claystones (Sacchi Beach fm.) underlie the Coaledo formation. Volcanic deep sea marine volcanic rocks (Roseburg formation) underlie the clastic section in the basin.

Methane Energy Corporation (MEC) of Oregon is operator of an integrated exploratory drilling project in the Coos Bay basin. Based on independent analysis of gas content and related data from current drilling, over 1 trillion cubic feet of pipeline-quality gas (99% methane) are indicated in-place for Coaledo formation coalbeds. The economic viability of the project is dependent upon understanding of reservoir permeability characteristics (preferential cleat directions, stress regimes, etc.), prediction of permeability relation to depth (upper Coaledo vs. lower Coaledo), water disposal issues (underground injection zones, etc.), and gas gathering and marketing issues.