The Energy Information Administration (EIA) said Jan. 21 that its updated maps and geologic information for the Eagle Ford Shale help characterize the formation's structure, thickness and surface area. The updated materials also define the gas-oil ratio (GOR) of the shale's producing wells from January 2000 to June 2014.

“This information provides a better understanding of recent production within the context of key geologic parameters,” the EIA added.

Source: U.S. Energy Information Administration, DrillingInfo. Inc., Texas Natural Resources Information, U.S. Geological Survey, University of Texas Bureau of Economic Geology

By mapping the initial GOR, the mixture of oil and natural gas production by well is shown. High initial GORs are gas-rich while lower initial GORs are oil-rich, the EIA said.

Deeper wells (up to 15,000 feet) in the southeast have higher initial GORs, or a relatively greater share of natural gas, while the shallower wells in the northwest (below 6,000 feet) have lower initial GORs, or a relatively greater share of oil.

The eastern half of the Eagle Ford, with wells reaching between 5,000 feet and 12,000 feet, has initial GORs of 6,000 cubic feet per barrel (cf/bbl) or less, producing more oil than gas. The western half, with wells “as deep as 14,000 feet to as shallow as 2,000 feet,” has initial GORs of 6,000 cf/bbl or higher, producing more gas, the agency said.