The Tiffany Unit N2 - ECBM Pilot: A Reservoir Modeling Study
In October, 2000, the U.S. Department of Energy, through contractor Advanced Resources International, launched a multi-year government-industry R&D collaboration called the Coal-Seq project. The Coal-Seq project is investigating the feasibility of CO{sub 2} sequestration in deep, unmineable coalseams, by performing detailed reservoir studies of two enhanced coalbed methane recovery (ECBM) field projects in the San Juan basin. The two sites are the Allison Unit, operated by Burlington Resources, and into which CO{sub 2} is being injected, and the Tiffany Unit, operating by BP America, into which N{sub 2} is being injected (the interest in understanding the N{sub 2}-ECBM process has important implications for CO{sub 2} sequestration via flue-gas injection). The purposes of the field studies are to understand the reservoir mechanisms of CO{sub 2} and N{sub 2} injection into coalseams, demonstrate the practical effectiveness of the ECBM and sequestration processes, demonstrate an engineering capability to model them, and to evaluate sequestration economics. In support of these efforts, laboratory and theoretical studies are also being performed to understand and model multi-component isotherm behavior, and coal permeability changes due to swelling with CO{sub 2} injection. This report describes the results of an important component of the overall project, the Tiffany Unit reservoir modeling study. The Tiffany Unit is located in the northern portion of the prolific San Juan basin (in Southern Colorado). The study area consists of 34 methane production wells and 12 nitrogen injection wells. The field originally began production in 1983, and N{sub 2} injection operations for ECBM purposes commenced in 1998. Nitrogen injection was suspended in 2002, to evaluate the results of the pilot. In this study, a detailed reservoir characterization of the field was developed, the field history was matched using the COMET3 reservoir simulator, and future field performance was forecast under various operating conditions. Based on the results of the study, the following major conclusions have been drawn: (1) The injection of N{sub 2} at the Tiffany Unit has resulted in incremental methane recovery over estimated primary recovery, in approximate proportion of one volume of methane for every 0.4 volumes of injected nitrogen on a net basis. In the swept areas, an incremental methane recovery of approximately 20% of original-gas-in-place resulted from N{sub 2}-ECBM operations. (2) At the prevailing gas prices at the time the project was implemented ({approx}2.20/Mcf), and not considering any tax credit benefits, the pilot itself was uneconomic. However, with today's gas prices of {approx}$4.00/Mcf, N{sub 2}-ECBM appears economically attractive. (3) Performance predictions of future injection suggests CO{sub 2} sequestration can be accomplished at a slight profit. Economic performance is enhanced by adding some N{sub 2} to the injectant.
- Research Organization:
- Advanced Resources International, Incorporated
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC26-00NT40924
- OSTI ID:
- 923257
- Country of Publication:
- United States
- Language:
- English
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