This paper demonstrates field application of pressure falloff testing and analysis methods to new coal degas wells in the San Juan Basin. These tests have provided absolute coalbed permeability, wellbore skin, and initial reservoir pressure. Effects due to free gas and gas desorption on pressure falloff tests are considered. The effects of sorption compressibility are shown to have a significant impact on skin but not on permeability. Influence of the duration of the injection and shutin periods on the design and analysis of coal well PFOTs is also discussed. Field examples of both pre- and post-stimulation falloff tests are presented.

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