Annular Gas Flow

Definition - What does Annular Gas Flow mean?

Annular gas flow can be defined as the formation gas flow in the concentric space between a casing and a wellbore wall, which is also known as annulus. The formation gas flows through the annulus during the phase when there is inadequate hydrostatic pressure. If there is enough hydrostatic pressure in the annulus, it can halt the flow of the gas. Usually, annular gas flow can happen in both the cemented as well as the uncemented sections of the oil wellbore. There are different additives used in the base slurry or cement slurry to prevent the annular gas flow during the drilling phase.

Petropedia explains Annular Gas Flow

When an oil wellbore is drilled, a casing, which is a steel pipe is installed in the wellbore in a vertical position. This pipe is fixed in the well by cementing it using a base slurry, also known as cement slurry, which seals any spaces between the case string and the wall of the oil well. During the drilling operation, when natural gas seeps through these spaces, also called annulus, it is referred to as annular gas flow. The gas can easily flow through the spaces which aren’t sealed. However, the flow isn’t limited to just the unsealed annulus; it can also occur in the cemented sections.

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