Low Pressure Dehydration Unit Process Selection and Operating Successes for Coal Bed Natural Gas

摘要

Coal bed natural gas (CBNG) wells typically operate at low volume, low pressure and are saturated with water vapor at wellhead conditions. In Wyoming and other cold climates this results in water vapor condensing in the pipelines that cause operating problems including higher pressure drops due to drip liquids, freezing, and water disposal. This paper provides a description of the benefits of using low-pressure dehydration to decrease pigging frequency, lower pipeline pressure drop, and decrease overall compression costs. In addition, a review of the process selection study that evaluated low pressure dehydration technologies, including condensation, triethylene glycol absorption, methanol injection, glycol injection, regenerative adsorption system (activated alumina), and non-regenerative adsorption system (calcium chloride), is provided. While triethylene glycol (TEG) absorption is typically considered a high-pressure process to remove water vapor to pipeline specifications (4-7 lbs water vapor per MMscfd natural gas), this technology was selected for a demonstration unit, as it held the best potential for positive operational and economical impacts on production. This paper provides insights on the design and operation (including capital costs, operating costs, and economic justification) of the demonstration unit for coal bed natural gas in the Powder River Basin.