What is Tight Gas?

The demand for natural gas has grown over time.

Sealed gas is natural gas that is difficult to access due to the nature of the rock and sand surrounding the deposit. Because this gas is much more difficult to extract than natural gas from other sources, companies need a big financial incentive to go after it; as energy prices rise, so does the interest in extracting it. Several global oil and gas companies control significant restricted gas reserves, and some have also invested substantial resources in learning more about how to extract it more efficiently.

Normally, natural gas is fairly easy to access. When a deposit is identified, a well can be dug, and the gas naturally flows into the well, making it easier to pump to the surface and distribute it from there. This is because natural gas is normally surrounded by porous rock deposits, with many small holes for the gas to seep through. Sometimes the gas almost literally pumps.

In the case of tight gas, the sandstone, shale or other surrounding rock is not as permeable, appearing much denser in cross section. The lack of permeability locks the gas underground, making it difficult to drill a profitable well. This gas is also found trapped in coal deposits. To achieve it, it is necessary to find a “sweet spot” where a large amount of gas is accessible, and sometimes to use various means to create a pressure vacuum in the well that pulls gas from the surrounding rock.

Historically, these deposits were written off as “unrecoverable,” but as demand for natural gas grew, many companies rethought that assessment, pushing to see if the deposits could be accessed. While extracting tight gas is expensive, higher gas prices can make the expense worthwhile, especially if the gas has a distillation-friendly composition, allowing the company to extract multiple valuable fractions from a single well.

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Most restricted gas deposits date to the Paleozoic era, meaning they are at least 251 million years old. The advanced age of such deposits is presumably responsible for their inaccessibility; in other words, the gas is tight because the surrounding rock has had more time to become dense. These deposits can also be deeper than ordinary gas deposits, presenting additional challenges. Tight gas companies use a variety of research tactics to identify potential sources of gas and pinpoint the best drilling locations.

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