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Acidizing Oil Wells, a Sister-Technology to Hydraulic Fracturing: Risks, Chemicals, and Regulations


The United States has seen resurgence in petroleum production, mainly driven by technology improvements in unconventional oil and gas stimulation from shale formations. Hydraulic fracturing, one of the unconventional oil and gas stimulation technologies, has caught a lot of public attention that has led to more research on it and its impacts as well increased debate over more regulatory oversight. Other unconventional oil stimulation techniques have more or less been left out of the discussion. One of these less frequently discussed techniques is acidizing. Acidizing is a term used for all types of acid use that increase or keep up well productivity or injectivity. The use of these unconventional stimulation techniques has greatly increased over the past decade. The expansion of tight oil and shale gas extraction using unconventional oil stimulation has raised concerns about its potential environmental and health impacts. These concerns include potential direct impacts to groundwater and surface water quality, water supplies, and air quality. Much attention has been on the impacts of hydraulic fracturing with little to no attention on acidizing. This research looks at the acidizing process and for the first time defines what the chemicals of acidization are, in what amount they are used, and what their toxicity is.

The analysis of the present data shows there have been over 600 instances of acidizing in urbanized Southern and Central California from April 2013 to August 2015. Although most of the chemicals of acidizing are similar to hydraulic fracturing, those used most frequently are different. There are close to 200 specific chemicals used in acidization, with at least 28 of them being F-graded hazardous chemicals, which are known carcinogens, mutagens, reproductive toxins, developmental toxins, endocrine disruptors, or high acute toxicity chemicals. Some are used frequently in the range of 100 - 1000 kg per treatment, such as hydrofluoric acid, xylene, diethylene glycol and ethyl benzene. Unlike hydraulic fracturing the chemical concentrations in acidizing are high, ranging from 6-18%, and the waste returns can be highly acidic, in the range of pH 0-3.

In addition to analyzing the chemicals and their potential impacts this research looks at the legal framework for regulating acidizing activities. Provisions of several federal environmental laws can apply to acidizing activities. The federal role in regulating O&G extraction activities has been the subject of considerable debate and legislative proposals for several years. The Administration has pursued a number of regulatory initiatives related to unconventional O&G development, primarily hydraulic fracturing, under existing statutory authorities. Acidizing, however, has been almost entirely been left out of new proposals. This research sheds light on this topic and suggests areas where acidizing can be better regulated.

In addition to looking at the federal laws and state bills in place for regulating acidization, this research specifically looks at a better regulating scheme for stormwater runoff from oil and gas facilities. Contaminated stormwater runoff from oil and gas operations can pose a significant threat to surface waters. The research examines the extent of this threat and recommends more specific permitting requirements and best management practices to protect surface waters.

With increasing use of unconventional oil stimulation techniques like acidizing, it is important to understand the technology, the threats caused by them, and how to best protect the public and environment from any potential harm. This dissertation research attempts to shed light on these issues related to acidizing.

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