--> ABSTRACT: Stratigraphic Methods Used to Explore and Exploit Fruitland Formation Coal-Bed Gas, San Juan Basin, New Mexico and Colorado, by William B. Hanson, Robert G. Kemp, Bradley L. Steer; #91002 (1990).

Datapages, Inc.Print this page

ABSTRACT: Stratigraphic Methods Used to Explore and Exploit Fruitland Formation Coal-Bed Gas, San Juan Basin, New Mexico and Colorado

William B. Hanson, Robert G. Kemp, Bradley L. Steer

Since 1985, coal beds of the Upper Cretaceous Fruitland Formation have become a major producer of natural gas. In the northern half of the San Juan basin, these coal beds are organized as five complex but generally seaward-stepping imbricate regional lenses as a result of deposition on successively prograded coastal plains. Coal beds are thickest far landward (about 15 mi southwest) of the coeval Pictured Cliffs Sandstone foreshore. Seaward edges of these coal-bed reservoirs are commonly thin, laterally continuous, and draped over a broad subsided platform of marine sandstone. Penecontemporaneous channelfill sediments and splays deposited on Fruitland peat created their own local accommodation space by compaction of the underlying peat. As a result, spectacular splits and differential compaction complicate geometries and may, to the uninitiated, obscure the great lateral continuity of the major Fruitland coal beds.

Classical stratigraphic methods such as correlation by stratal continuity, position in sequence, marker beds and isochronous layers, characteristic wireline log profiles, and distinctive lithology or fluid content, provide the framework necessary for application of numerous advanced technologies. Many tonstein layers record volcanic ash falls into areally extensive paludal environments. These isochronous layers as confirmed in cores and mines are easily identified by high-resolution wireline logs and therefore are powerful stratigraphic tools. Stratigraphic analysis is required for quantification of in-place gas, for delineation of the first-order flow-capacity architecture, and for detailed mapping of structural form and discrete coal-bed reservoirs and their internal quality.

AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990