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The reconnaissance phase entails the identification of basins that may contain BCGAs. In direct systems, identification of source rocks is critical. For example, the identification of humic, gas-prone coal beds is the most obvious source rock for direct BCGAs; in nearly every country with coal reserves, there are some published data concerning geographic distribution, rank, and thickness. The rank of coal beds must be greater than high-volatile C (greater than [[vitrinite reflectance]] values of 0.6% R<sub>o</sub>) to initiate thermal generation of gas.<ref name=Hunt_1996>Hunt, J. M., 1996, Petroleum geochemistry and geology, 2nd ed.: New York, W. H. Freeman and Co., 743 p.</ref>
 
The reconnaissance phase entails the identification of basins that may contain BCGAs. In direct systems, identification of source rocks is critical. For example, the identification of humic, gas-prone coal beds is the most obvious source rock for direct BCGAs; in nearly every country with coal reserves, there are some published data concerning geographic distribution, rank, and thickness. The rank of coal beds must be greater than high-volatile C (greater than [[vitrinite reflectance]] values of 0.6% R<sub>o</sub>) to initiate thermal generation of gas.<ref name=Hunt_1996>Hunt, J. M., 1996, Petroleum geochemistry and geology, 2nd ed.: New York, W. H. Freeman and Co., 743 p.</ref>
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The existence of reservoirs with appropriate quality is another important aspect to consider during the reconnaissance phase. In most cases, coal-bearing intervals are associated with interbedded sandstones that have low porosity and permeability, especially at diagenetic stages commensurate with thermal maturity levels greater than 0.6% R<sub>o</sub>. Sandstones deposited in alluvial plain, coal-bearing environments typically have poor reservoir properties. High porosity and permeability in reservoirs are not desirable attributes for the development of a BCGA. In basins where some drilling activity has occurred, gas shows are also very helpful.
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The existence of reservoirs with appropriate quality is another important aspect to consider during the reconnaissance phase. In most cases, coal-bearing intervals are associated with interbedded sandstones that have low porosity and permeability, especially at diagenetic stages commensurate with thermal maturity levels greater than 0.6% R<sub>o</sub>. Sandstones deposited in [[alluvial]] plain, coal-bearing environments typically have poor reservoir properties. High porosity and permeability in reservoirs are not desirable attributes for the development of a BCGA. In basins where some drilling activity has occurred, gas shows are also very helpful.
    
===Confirmation phase===
 
===Confirmation phase===

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