South Arkansas is no stranger to oil development. El Dorado was born out of the business, but it's been a long time since oil has brought real prosperity to the region.
Robert Reynolds, president of Shuler Drilling Co. of El Dorado, said the Brown Dense formation has been on oil companies' minds for decades.
"We had learned there were what we call 'shows,' that is, evidence of oil and gas, in the Lower Smackover Brown Dense," he said. "And the earliest tests to see if it was usable occurred in 1950 or 1952."
C.H. Murphy & Co., the predecessor to El Dorado's current Murphy Oil Corp., tested the formation and confirmed the existence of oil and gas in the formation.
"Then, in the early '80s, there were a couple of tests," Reynolds said. "One was in Lafayette County and a couple more in Columbia County. They produced small amounts of oil - not enough to make a commercial well and not enough to justify drilling or completing another well."
The carbonate mudstone in the lower Smackover was too dense for conventional drilling. It wasn't until Southwestern Energy developed the technology to "frack" the formation that the real play in the Brown Dense began. This technique involves pumping a water mixture into the formation to fracture the rock and loosen the resources.
Fracking has been used to harvest natural gas from shale formations, including north-central Arkansas' Fayetteville Shale Play.