The Eagle Ford Shale (EFS) is located in South Texas and the formation produces from various depths between 4,000 and 14,000 feet. The EFS takes its name from the town of Eagle Ford Texas where the shale outcrops at the surface in clay form. (Often, the Eagle Ford is mistakenly spelled as Eagleford.) The Eagle Ford is a booming shale play, results indicate there will be development activity for a long time to come. The EFS also benefits from high liquids yields across much of the play. Higher oil prices have helped spur development as oil, condensate, and NGLs (ethane, propane, and butane) all command better prices than natural gas. The Eagle Ford is a geological formation directly beneath the Austin Chalk Shale. It is considered to be the "source rock", or the original source of hydrocarbons that are contained in the Austin Chalk above it. The formation was also penetrated many times as operators targeted the Edwards Limestone formation along the Edwards Reef Trend.

The formation is best known for producing variable amounts of dry gas, wet gas, NGLs, condensate and oil. The most active area lies above the Edwards Reef Trend where the formation yields a gas-condensate production stream.

Unlike many other shale plays, it does not exhibit natural fracturing within the formation. The Eagle Ford Shale Counties maps below provide a list and detail on the 30 counties where the EFS is actively targeted. The core counties include an area that stretches from north of Gonzales down to Webb County at the Texas-Mexican border.