WATER-LEACHABLE CONSTITUENTS FROM HYDRAULIC FRACTURING PROPPANTS COLLECTED FROM ROADSIDE DUMPS IN SOUTHEASTERN NEW MEXICO

The production of oil and gas from unconventional sources has been spurred by hydraulic fracturing, where pressure-induced fractures are filled with proppant to increase reservoir permeability. To increase proppant penetration, retention, and porosity, many different types of proppants with varying sizes, shapes, densities, and strengths have been developed to optimize petroleum recovery under different formation conditions. Additionally, resin coated proppants (RCPs), where silica sand or ceramic proppants are coated with an organic polymer, have been developed to improve proppant performance (e.g., by reducing proppant return during initial flowback). Since millions of pounds of proppants are typically added to each hydraulicly fractured well, the extensive use of these materials poses a risk to both the environment and human health. Although much of the previous research has focused on silicosis from exposure during mining and hydraulic fracturing operations, little attention has been given to the potential effects from transportation and improper disposal of proppants.

In southeast New Mexico, various Federal and State agencies have reported illegal roadside dumping of proppants. These dumps include truckloads of excess proppant and residual proppant off-loaded during truck cleaning. In this study, we collected samples from five illegal dumps in the vicinity of the Delaware Basin. Each proppant sample was subjected to water leaching to determine what chemical constituents could be introduced to the environment during weathering. Leachates, made using a 3:1 liquid-to-solid ratio, had non-purgeable dissolved organic carbon concentrations up to 114 mg C/L and reactive phenol concentrations up to 54 mg phenol/L. Compounds identified through extraction of leachates and gas chromatography-mass spectrometry (GC-MS) analysis included various substituted phenols, isomers of bisphenol F, and methylene diphenol diisocyanate (MDI), indicating the presence of RCPs at dump locations. Trace metal concentrations in proppant leachates were generally low. Understanding the leachable chemicals from proppants is key to assessing the environmental effects of these illegal dumps and provides information on the source of compounds found in oil and gas produced waters.