PITTSBURGH (AP) — Federal energy experts say Marcellus Shale natural gas production has hit an all-time high.

The U.S. Energy Information Administration says Tuesday that production from Pennsylvania and West Virginia totaled about 15 billion cubic feet per day in July. That’s more than seven times the 2010 production.

The Marcellus Shale generally lies about a mile or more underground, and is the most productive natural gas field in the U.S. At current rates the total yearly production is the energy equivalent of about 800 million barrels of oil.

EIA says it expects that Marcellus production will continue to grow.

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