SIMULATING METAL RELEASE FROM DRILL CUTTINGS ASSOCIATED WITH NATURAL GAS EXTRACTION FROM THE MARCELLUS SHALE

The purpose of this research was to determine the extent to which metals from Marcellus Shale drill cuttings and surrounding units will be affected by drilling operations and the subsequent waste disposal method. This was determined by characterizing metal release using one day, thirty day, and four month cold acid leaches, microwave digestion, XRF, and XRD. First the drill cuttings were leached under anaerobic conditions using 1% HCl to determine the quantity and kinetics of metal release under conditions that simulate drilling operations. Then samples were microwave digested in a 1% HCl and 10% HNO₃ acid solution to determine the total acid extractable metal concentrations. The samples were also analyzed using XRF to determine the total metal concentrations. Lastly, the cuttings were analyzed using XRD to determine how mineralogy affects metal concentration and subsequent release. The combination of these analytical techniques were used to determine the relation between metal release and rock type during drilling operations and the subsequent disposal of the drill cuttings. Initial results indicate that the Marcellus Shale contains as well as releases larger amounts of As, Cd, Cu, Mo, Ni, and Zn than the surrounding rock units. The quantity of some of the metals that are released could have negative impacts from a toxicology perspective if monitoring methods do not account for short and long term differences in mineral dissolution rates and mechanisms.