Efficacy of Oil and Gas Produced Water as a Road Dust Suppressant PDF Download

Author: Audrey Stallworth
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Languages : en
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Book Description
Particulate matter (PM), specifically particles with diameters less than 10 m (PM10) and 2.5 m (PM2.5) make up one of the six Criteria Air Pollutants regulated by the United States Environmental Protection Agency (US EPA). The monitoring of these pollutants has shown that a significant portion (around 35%) of PM10 in the United States is generated from vehicle traffic on unpaved roads. PM10 can travel great distances once generated, creating a myriad of environmental, health, and practical issues. A variety of dust suppressants have been developed over the years to prevent the generation of PM from unpaved roads. One of the most common dust suppressants is brine; ions such as magnesium and calcium are successful at hindering dust generation, and thus have been incorporated into commercially available dust suppressants. Unfortunately, commercial dust suppressants can be cost prohibitive in the rural areas which they are most needed. As a result, industrial byproducts are seen as a favorable form of dust suppression. The example focused on in this thesis is the use of oil and gas produced water. Oil and gas produced water, or OGPW, is generated in high volumes annually during the oil and gas extraction process, and can contain high concentrations of calcium and magnesium, as well as sodium. Several states across the United States have developed regulations regarding the use of OGPW for road maintenance tasks such as deicing and dust suppression, and the practice has been going on for decades. However, few studies have been conducted to confirm the efficacy of OGPW as a dust suppressant. Oil and gas produced water can vary in composition across the United States, and can contain several potential pollutants, such as lead and radium. Recent research has pointed away from recommending the use of OGPW and has raised questions about the environmental effects of the practice. The work presented in this study aims to provide an additional tool for determining the appropriateness of using not only OGPW as a dust suppressant, but other byproducts as well. A method was developed to model dust generation on an unpaved roadbed by creating a laboratory-scale model for the treated roadbed surface and measuring the dust generated by subjecting the treated roadbed to mechanical agitation in a small rotating drum. The method was calibrated by using synthetic brines that modeled the three mechanistic controls of brine dust suppression: 1) moisture, 2) sodium content, with the sodium adsorption ratio (SAR), and 3) total dissolved solids (TDS). The results from the synthetic brines were then compared to oil and gas produced waters. This method showed that while OGPW was effective at preventing dust generation, it did not perform as well as its commercial counterparts, with differences in efficacy varying between produced waters. Therefore, the variation of oil and gas produced water chemistry across the United States was analyzed using the United States Geological Surveys Produced Waters Database. Based on average SAR and TDS OGPW values, the oil and gas produced water from some states was more likely than others to be suitable for use as a dust suppressant; produced water from states in the NE/Midwest (MI, OH, PA, NY, WV), as well as FL, AR and GA would likely perform well as a dust suppressant. States which do not have ideal OGPW for dust suppression (WA, OR, NV, CA, MT, WY, CO, SD, IA and MO), due to low TDS values, may still be useful in other beneficial use situations, such as irrigation. It is recommended that efficacy testing be conducted using OGPW samples from any state before they are approved for use, especially using local road materials. Next, two OGPW samples tested in this study were treated to remove radium via co-precipitation with barium and strontium sulfate, and then applied to road discs and tested using the developed method. Based on the results of this test, treating oil and gas produced water to remove radium before application reduces efficacy slightly. Finally, a small set of alternative fluids were tested in order to see how other dust suppressants performed in comparison to common commercial brines and OGPW. The method developed in this work demonstrated that OGPW dust suppression is not ineffective, but given the known concerns with the composition of these fluids, treatment before application would be beneficial. On a larger scale, the method developed in this work should provide an accessible way to evaluate dust suppressants.