DEFINITION of 'Acidizing'

A type of well stimulation treatment used to improve the permeability of reservoir rocks. Acidizing involves pumping acids into the well in order to dissolve the rock, which improves production by creating channels in the rock to allow oil and natural gas to reach the well. Acids can also be used to dissolve debris found in the well.


Acidizing is most often used in aging wells that are reaching the end of their productive lives. As a process it is designed to squeeze any additional oil deposits from the reservoir. Because acid can corrode metal used in the well, most acidizing chemicals are used alongside a mixture of water and other chemicals that can protect the well from the effects of powerful acids.

In oil and natural gas production, acidizing may be more appropriate than hydraulic fracturing (“fracking”) in some situations. Fracking creates channels in underground rock formations by blasting a mixture of water and chemicals at high pressures. Acidizing does not require the same high pressure, instead relying on the acid to dissolve permeable sediments. In shale deposits that are not uniformly arranged, such as those created in areas with substantial tectonic activity as in the state of California, acidizing may do a better job at unlocking deposits. In some situations both fracking and acidizing are used, a process called acid fracking.

The types and concentrations of acids used in acidizing are often not disclosed by production companies, though hydrochloric and hydrofluoric acids have been known to be used. Because of this ambiguity it may be more difficult to understand the safety of the process, especially as it relates to groundwater. Acidizing remains less regulated than many other oil and natural gas production techniques, though several states, including California, have proposed legislation and regulations that could impact investors in exploration companies.