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Mining Publication: Cross Formational Flow of Water into Coalbed Methane Reservoirs: Controls on Relative Permeability Curve Shape and Production Profile
Keywords: Methane control Water Water wells
Original creation date: March 2017
Authors: A Salmachi, CO Karacan
Peer Reviewed Journal Article - March 2017
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NIOSHTIC2 Number: 20049469
Environ Earth Sci 2017 Mar; 76(5):200
Coalbed methane (CBM) wells tend to produce large volumes of water, especially when there is hydraulic connectivity between coalbed and nearby formations. Cross-formational flow between producing coal and adjacent formations can have significant production and environmental implications, affecting economic viability of production from these shallow reservoirs. Such flows can also affect how much gas can be removed from a coalbed prior to mining and thus can have implications for methane control in mining as well. The aim of this paper is to investigate the impact of water flow from an external source into coalbed on production performance and also on reservoir variables including cleat porosity and relative permeability curves derived from production data analysis. A reservoir model is constructed to investigate the production performance of a CBM well when cross-formational flow is present between the coalbed and the overlying formation. Results show that cleat porosity calculated by analysis of production data can be more than one order of magnitude higher than actual cleat porosity. Due to hydraulic connectivity, water saturation within coalbed does not considerably change for a period of time, and hence, the peak of gas production is delayed. Upon depletion of the overlying formation, water saturation in coalbed quickly decreases. Rapid decline of water saturation in the coalbed corresponds to a sharp increase in gas production. As an important consequence, when cross-flow is present, gas and water relative permeability curves, derived from simulated production data, have distinctive features compared to the initial relative permeability curves. In the case of cross-flow, signatures of relative permeability curves are concave downward and low gas permeability for a range of water saturation, followed by rapid increase afterward for water and gas, respectively. The results and analyses presented in this work can help to assess the impact of cross-formational flow on reservoir variables derived from production data analysis and can also contribute to identifying hydraulic connectivity between coalbed and adjacent formations.
cover image for Cross Formational Flow of Water into Coalbed Methane Reservoirs: Controls on Relative Permeability Curve Shape and Production ProfilePeer Reviewed Journal Article - March 2017
Go to Web Page
NIOSHTIC2 Number: 20049469
Environ Earth Sci 2017 Mar; 76(5):200
See Also
Development and Application of Reservoir Models and Artificial Neural Networks for Optimizing Ventilation Air Requirements in Development Mining of Coal Seams
Discharge Water Handling and Treatment: Problems and Solutions at a Large Pittsburgh Seam Coal Mine
The Effects of Water Emulsified Fuel on Diesel Particulate Matter Concentrations in Underground Mines
Evaluation of the Relative Importance of Coalbed Reservoir Parameters for Prediction of Methane Inflow Rates During Mining of Longwall Development Entries
Guidelines for the Control and Monitoring of Methane Gas on Continuous Mining Operations
Managing Excess Gas Emissions Associated with Coal Mine Geologic Features
Modeling and Prediction of Ventilation Methane Emissions of U.S. Longwall Mines Using Supervised Artificial Neural Networks
Modeling the Effects of Longwall Mining on the Ground Water System
Remote Methane Sensors
Reservoir Rock Properties of Coal Measure Strata of the Lower Monongahela Group, Greene County (Southwestern Pennsylvania), from Methane Control and Production Perspectives
Page last reviewed: July 13, 2017
Page last updated: July 13, 2017
Content source: National Institute for Occupational Safety and Health, Mining Program
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