Acid Fracking

Collier Resources Company owns the mineral rights to some 800,000 acres of Southwest Florida.  They and their tenant oil companies claim it is not necessary to hydraulically fracture Florida’s bedrock limestone.  Nevertheless, Collier Resources has repeatedly and publicly refused to ban hydraulic fracturing from these lands. 

All oil comes from shale.  If there were no shale beneath the Colliers’ lands, there would be no oil. In shale saturated with a mix water and oil, over millions of years the oil (and/or gas) rises–it’s lighter than water.  In South Florida it rose into less-shaly overlying limestone. Conventional South Florida wells would drill down vertically, hoping to find a limestone pocket (or “sponge”) where such risen oil had been trapped  by a layer of overlying “anhydrite” rock. [Anhydrite = an (without) + hydrous (water-containing) ].

Modern “enhanced oil recovery” techniques, including horizontal drilling, now gives South Florida oil explorers two options: (1) they can drill horizontally in the overlying limestone for as much as two miles, hoping to find one or several such limestone pockets, or (2) they can drill horizontally for as much as two miles in the underlying shale, hoping to find “tight oil” in the shale that hasn’t yet risen into the limestone.

In the second case, the “enhanced oil recovery technique” of choice is “hydraulic fracturing”  or “fracking”. Whether the object is oil or gas, the idea is to detonate an explosive (or otherwise generate high pressure) in a fluid-filled wellbore, fracturing the rock.  The fracking fluid must contain a “propant” (like sand) to prop open any small fractures to allow the gas or oil to flow.  Lubricants and other additives are used to increase the dispersal of the propant and the degree of fracturing.

In the first case, however, the oil companies can still use a technique called “acid well stimulation” or “acid fracking”. In this process, large volumes of hydrochloric or hydrofluoric acid are pumped downhole into a well.  The acid does not fracture the rock (so, technically, it is not “hydraulic fracturing”)–it dissolves the rock, effectively making the bore hole bigger and allowing more crude oil to seep into the wellbore.

The fact that this process does not technically fracture the bedrock does not make it environmentally benign.  There is much justified environmental concern over the potential toxicity of fracking fluids, but even without fracking fluids, the “produced water” from oil and gas wells can be a much greater environmental threat. 

Further Reading

PetroWiki on Acid Fracturing

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