Why have some estimates of undiscovered technically recoverable oil or gas changed so much from previous estimates?

Petroleum geologists have long known that oil and gas resources were present in “tight” or impermeable formations such as shale. But there was no feasible way to extract that oil and gas, so they were not “technically recoverable” and were not included in USGS assessment results.

Thanks to new technologies, oil and gas can now be extracted from “tight” formations, so they can be counted in assessments of undiscovered technically recoverable resources.

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How and where do drillers dispose of waste hydraulic fracturing fluid?

Most of the water and additives used in hydraulic fracturing (or “fracking”) remain deep underground in the geologic formation from which the oil or gas is being extracted. But some of the fluid, mixed with water or brine from the formation, returns through the well to the surface and is referred to as “produced water”. After a well is brought on-...

Are other countries using hydraulic fracturing for oil and gas extraction?

Yes, hydraulic fracturing is being used extensively in Canada and is increasingly being used in countries in Asia, Europe, and South America.