PBS a Great Success!

Title: PBS a Great Success!
Author: Mark Longman
Publication: The Outcrop, December 2003, p. 1, 6-7

RMAG’s 2003 Piceance Basin Symposium was held in conjunction with the AIPG Annual Meeting in Glenwood Springs, Colorado, October 4 to 6. Almost 50 people participated in the sold-out field trip, which brought together representatives of all the major companies actively developing the Upper Cretaceous gas reserves that are so widespread in the basin. Also well represented were various state and government agencies including the Colorado Geological Survey, and the ranks of consultants. Perfect fall weather combined with great outcrops and lively discussions to create an enjoyable time for all.

In the foreground is the uppermost part of the Williams Fork Formation, overlain by the steeper cliffs and pinnacles of the Ohio Creek interval and capped by the darker colored conglomerates of the lowermost Wasatch Formation. Field trip co-leader Rex Cole is standing directly behind the white van. Photo provided by Tom Carpenter.

Field trip leaders Rex Cole (Mesa State College) and Steve Cumella (Williams Production RMT Company) must have spent months preparing a beautifully illustrated and very detailed 63-page guidebook for the field trip. Only a limited number of the guidebooks were printed for the field trip, but the whole guide is included in RMAG’s recently released CD-Rom entitled “Piceance Basin 2003 Guidebook.” The CD-Rom, edited by Kristine Peterson, Terrilyn Olson, and Donna Anderson, contains 460 pages of text and color figures divided into 19 chapters (papers) prepared by 42 authors. Many of these papers were presented in the one-day Piceance Basin technical session, either as talks or posters. Topics covered ranged from source rock analyses to reservoir characterization, fracture distribution and significance, borehole imagery, and nahcolite mining. The CD also contains a 77-page bibliography of Piceance Basin references arranged by subject (coalbed natural gas, Dakota-Cedar Mountain formations, fractures, geochemistry, etc.) that was compiled from GeoRef, Petroleum Abstacts, and the Gas Technology Institute’s database by Ann Priestman.

On the two field trip days, Rex and Steve did a great job showing off and discussing the world-class outcrops that surround much of the Piceance Basin. The focus of the trip was on the coastal marine sandstones of the Corcoran, Cozzette, and Rollins members of the Iles Formation, and the overlying thick (1500+ ft) section of fluvial channel sandstones and shales that form the Williams Fork Formation. Numerous cliff faces many hundreds of feet high and miles long along Coal and Plateau Creek canyons on the southwest side of the basin, and at Rifle Gap on the east side, were examined up close and from afar through binoculars to reveal facies relationships in these sections.

Trip leaders Steve Cumella and Rex Cole present a panorama of Mesaverde exposures. Photo by Tom Carpenter.

The exposures at Coal Canyon reveal five types of shale-encased fluvial channel sandstones in the lower Williams Fork, which is about 600 ft thick. The various types of channel sands range in average thickness from 2.8 to 13.8 ft, and in exposed width from 98 to 815 ft. Similar small channel sands form many of the reservoir zones in the Piceance Basin gas fields such as Rulison, Grand Valley, Mamm Creek, and Parachute. Considering the size of the channels, it is no surprise that well spacing in these fields has been shrinking through the years from 160 acres to 40, then 20, and now down to as little as 10 acres in parts of Rulison Field.

The upper 800 ft of the Williams Fork Formation on the southwest side of the Piceance Basin is much richer in sandstones than the lower part. From a distance many of the fluvial sandstones in this part of the section appear blanket-like, but close examination reveals coalescing channels that form “braid plains.” Unfortunately, these sandstones are locally so continuous that they have failed to trap gas and are now water bearing, particularly in the shallower parts of the Piceance Basin.

The audience dons 3-D glasses for a better view of some of James Howe’s maps during his presentation of “Digital Elevation Models for Terrain Visualization, Structural Analysis, and Petroleum Exploration in the Piceance Basin Region” at the Sunday technical session. Photo by Tom Carpenter.

Another highlight of the symposium for some was a Sunday afternoon excursion to visit Glenwood Cavern, located in the Leadville Limestone about 1200 ft above Glenwood Springs on Iron Mountain. The cave has become a major tourist attraction since a gondola was built earlier this year and is well worth a visit. Cavers Harvey DuChene, Hazel Barton, and Fred Luiszer provided a detailed discourse on the formation of the cave (it formed mainly from about 1.69 to 1.34 Ma) and the varied deposits formed by its past and present microbial inhabitants. Most dissolution responsible for forming the cave resulted from carbonic acid in warm waters comparable to those now flowing from Yampah Hot Springs, but the presence of gypsum locally in the upper levels of the cavern suggests that part of the cave was modified by sulfuric acid related to hydrogen sulfide gas.

Steve Cumella, one of the Mesaverde field trip leaders, describes the geology of Rulison Field. Photo by Tom Carpenter.

In conclusion, those responsible for originally proposing the Piceance Basin Symposium (Susan Landon), organizing the CD-Rom guidebook (Kristine, Terrilyn, and Donna), and putting together the outstanding field trip (Rex and Steve) deserve praise and thanks from RMAG members. The synergy provided by the diverse group of participants, the support of numerous companies who contributed financially to the success of the guidebook and meeting, and the wealth of ideas presented by individuals in the 3 days of discussions at the PBS will be hard to duplicate in the near future.

Harvey DuChene gives an overview of the geology of Glenwood Caverns with Glenwood Canyon in the background during the Sunday afternoon field trip to the caves. Photo by Tom Carpenter.