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Why do the oil and gas resource numbers sometimes change when the USGS releases a new assessment of an oil and gas formation?

Assessments regularly change based on our understanding of geology, as well as advances in technology.  

As more is learned about the geology of a given formation, both from USGS research and from industry activity, a clearer picture of the potential recoverable oil and gas resources can be created.  

In some cases, industry activity can show that a rock formation that was previous thought to have significant quantities of oil and gas does not. In other cases, advances in research techniques and tools can show a rock formation is more likely to have the conditions necessary to produce oil and gas. 

A major source of changes in USGS assessments was the advent of production from continuous resource accumulations, such as shale and other “tight” or impermeable formations such as shale. 

Learn more: USGS Energy Assessments

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