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December, 2001

DOE Announces the Environmental Compliance Assistance (ECAS) Website

The ECAS website is designed to provide the Oil and gas industry with a tool that can do the following things:

Provides web links, phone numbers, and addresses of state and federal regulatory agencies where detailed information and forms may be obtained.

Provide guidance on preparing waste management plans, recording management, and emergency response issues.

Presents current national and NPTO events relating to the Oil and Gas Industry.

The ECAS is sponsored by the Department of Energy, the National Energy Technology Laboratory's and the National Petroleum Technology Office.

Tucumcari Basin Potential

Pennsylvanian strata within the Tucumcari basin contain good to excellent source rocks of oil and gas.  Optimum thermal maturity and total organic carbon are found in deep elevator basins in the northern part of the Tucumcari basin.

Depth to Precambrain bay exceed 12,000 feet in the deepest parts of these elevator basins.  Dark-gray to black shales that are the source rocks of gas and light oil-condensate found in the two unexploited fields located within the elevator basins.

• Excerpt from Oil & Gas Journal  Sept. 17, 2001.  Written by R. F. Broadhead, New Mexico Bureau of Geology & Mineral Resources, Socorro, NM. www.ogjonline.com

Calculation of Coalbed Methane Well Deliverability

In a paper titled "Well Deliverability of Undersaturated Coalbed Reservoir" SPE paper 71068, presented at the SPE Rocky Mountain Technology Conference, May 21st to 23rd in Keystone, Colorado, the authors, Witsarut Thungsuntonkhun and Thomas W. Engler, New Mexico Institute of Mining and Technology, present a new approach to calculate the Inflow Performance Relationship (IPR) curve for an undersaturated coal gas system. Their calculation is based on a Fetkovich-type approach that includes matrix shrinkage effects during the entire production sequence. A typical coalbed reservoir produces water until the reservoir pressure decreases below the desorption pressure when it begins to produce gas. As the coal desorbs gas, the matrix shrinks, changing reservoir permeability with time. Because of these coalbed reservoir characteristics, the authors contend that conventional methods of IPR calculation should not be applied since they may result in underestimation of IPR for a coalbed reservoir.

To model the production mechanism of coalbed reservoirs, the authors divide the production sequence into three parts; first the IPR for water is calculated as single-phase production, followed by IPR calculation for multiphase production of water and gas, and finally for single-phase gas production. Although previous work has treated the final stage single-phase gas production like a conventional gas reservoir, the authors demonstrate that because the permeability of a coalbed reservoir increases at lower reservoir pressure, coalbed reservoirs will have a greater production rate for a given well bore flowing pressure (Pwf) than conventional reservoirs.

The paper includes examples of field application of the method at the Deerlick Creek Field in the Black Warrior Basin, and Cedar Hill Field in Fruitland Coal of the San Juan Basin. In both examples, the conventional calculation underestimated the IPR while the author's method provided a much closer match of actual well performance.

• This article is reprinted with permission from the PTTC (Rocky mountain region) News letter Vol.4 3rd quarter.  This article can be viewed on the Rocky Mountain region web site. 

Basin Centered Gas in the Trinidad Raton Basin

In "Potential for a Basin-Centered Gas Accumulation in the Raton Basin, Colorado and New Mexico", U.S.G.S Bulletin 2184-b, authors Ronald C. Johnson and Thomas M. Finn and editors Vito F. Nuccio and Thaddeus S. Dyman, summarize evidence of a basin-centered gas accumulation in the Trinidad Sandstone, Vermejo Formation, and Raton Formation in the Raton Basin. The report is based on data and interpretations presented by previous authors, and re-examines this evidence in light of new understanding of how basin-centered accumulations are created and destroyed. It has long been suspected that a significant basin-centered type gas accumulation is present in Upper Cretaceous and Paleocene sandstones in the Raton Basin. Few attempts have been made to develop these resources because of the lack of gas pipelines out of the basin. Success with the current coalbed methane exploration in the basin has encouraged pipe line construction that will alleviate the transmission problem, and should lead to new attempts to develop these sandstone gas resources. Evidence for a basin-centered or continuous gas accumulation in the Raton Basin has been presented by many authors (Dolly and Meissner, 1977; Broadhead, 1982, 1991; Rose and others, 1986; and Woodward, 1987). Based on widespread reports of under-pressured gas-saturated sandstones at shallow depths, the authors suggest that a largely intact basin-centered gas accumulation still exists in the Upper Cretaceous Trinidad Sandstone and Vermejo Formation, Upper Cretaceous and Paleocene Raton Formation, and the Paleocene Poison Canyon Formation. Utilizing analogs of other Rocky Mountain basins, relatively water-free production should occur where levels of thermal maturity in the coals exceed a vitrinite reflectance value of 1.1 percent. This level of thermal maturity occurs over much of the central part of the Raton Basin. Present-day depths to the top of the Trinidad Sandstone are less than 3,500 ft throughout most of the basin. Because of the shallow depths, some of the accumulation has probably been degraded by surface water invasion. Download the full report (Acrobat Reader format): Bulletin 2184-b

• This article is reprinted with permission from the PTTC (Rocky mountain region) News letter Vol.4 3rd quarter.  This article can be viewed on the Rocky Mountain region web site.