The maps above show the active drilling rigs in the Eagle Ford Shale area of Texas, from Baker-Hughes interactive maps.
Here's some background information on Eagle Ford:
"The Eagle Ford has gone from obscurity in 2008 to now being the #3
play in all the United States (based on number of rigs drilling), after
the Permian Basin in southwest Texas and the Bakken in North Dakota.
Pioneer Natural Resources (PXD-NYSE) says they get a 70% pre-tax rate
of return at Eagle Ford. EOG Resources (EOG-NYSE) says it’s 80% for
them. Marathon Oil (MRO-NYSE) says it’s over 100% for them on some condensate wells (condensate is a Natural Gas Liquid that’s really more like a very light oil and often gets a better price than oil).
The formation is 400 miles long and 50 miles wide with an average
thickness of 250 feet—thicker than the North Dakota Bakken. It is
estimated that the Eagle Ford formation has a total recoverable resource
of roughly 3 billion barrels of liquids (that’s oil and some NGLs) with
a potential output of 420,000 barrels a day (bopd)."