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This document provides technical guidance to Partners of the CCAC Oil and Gas Methane Partnership (OGMP). It is one in a series describing a core source of methane emissions from oil and natural gas production operations. The guidance documents introduce suggested methodologies for quantifying methane emissions from specific sources and describe established mitigation options that Partners should reference when determining if the source is “mitigated.”
The source described here is well venting for liquids unloading. Over time, gas production naturally declines in non-associated gas wells as the reservoir is depleted. Initial flow (gas velocity) from a gas well is usually sufficient to entrain produced liquids as droplets and carry them through the wellhead and to a separator. However, as flow declines, the gas velocity may be insufficient to lift the produced liquid, and liquid may accumulate in the wellbore. As liquid accumulates in non-associated gas wells, the pressure of the liquid becomes greater than the gas velocity and eventually stops the flow of gas to the sales line. These gas wells therefore often need to remove or “unload” the accumulated liquids so that gas production is not inhibited. Well liquids must be managed on an ongoing basis and adapted to the changes in wells’ flow characteristics as wells move through their lifecycle.