California Code, Public Resources Code - PRC § 3157

(a) For purposes of this article, “well stimulation treatment” means any treatment of a well designed to enhance oil and gas production or recovery by increasing the permeability of the formation.  Well stimulation treatments include, but are not limited to, hydraulic fracturing treatments and acid well stimulation treatments.

(b) Well stimulation treatments do not include steam flooding, water flooding, or cyclic steaming and do not include routine well cleanout work, routine well maintenance, routine removal of formation damage due to drilling, bottom hole pressure surveys, or routine activities that do not affect the integrity of the well or the formation.