Viability Of Brown Dense Oil Field a Mystery

by Luke Jones  on Monday, Jun. 4, 2012 12:00 am  

The analysis, Ratchford said, can take months before true production is seen. He estimated the results wouldn't be known until the end of the year.

A History of Oil
It's not the first time south Arkansas has seen oil interest, of course.

"The Brown Dense is the lower part of the Jurassic Smackover formation," Ratchford said. "The upper Jurassic Smackover formation is part of a zone up there called Reynolds oolite. Historically, there's been a lot of production at the upper Smackover."

The whole formation lies north and south of the Arkansas-Louisiana border.

In the early 20th century and beyond, oil barons drilled conventional wells in the more accessible upper Smackover, and because of the rock's natural porosity and permeability - or its internal empty space and the interconnectedness of that empty space - the oil flowed readily. El Dorado, among other towns, blossomed around that production.

But deeper down in the lower Smackover is carbonate mudstone.

"Its permeability and porosity is about like a slab of concrete," Ratchford said. "It can have a lot of oil still in place, but because the rock is so tight, it doesn't give up that oil easily."

The first test of the Brown Dense was a vertical well drilled in 2008 by Border Exploration LLC of Lafayette, La. That well is now plugged and abandoned, and Ratchford noted that the Geological Survey was studying some of the core extracted from the well. When complete, that study will reveal information about the Brown Dense reservoir and assess its resources.

"We also have some proposals to work with the industry that have not been approved yet," he said.

Since then, technological innovation has given energy companies the ability to hydraulically stimulate the stone, inducing millions of tiny fractures that increase its porosity and permeability. The fracturing technique, commonly known as "fracking," is similar to the technique used by Southwestern and other exploration companies to harvest natural gas from the Fayetteville Shale Play in north-central Arkansas.

Geologists have understood for decades that valuable minerals were trapped in shale and mudstone, Ratchford said. But until the advent of fracking, the cost of extracting it exceeded the value of the oil or gas.

Ratchford said the Brown Dense was the only area in Arkansas where companies were fracking for oil.



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