CHARACTERIZATION OF OIL AND GAS DRILL CUTTINGS FOR CRITICAL MINERAL RECOVERY AND REUSE POTENTIAL AS SOIL SUPPLEMENTS

Expansion of unconventional oil and natural gas production over the past decade in the United States has resulted in record production of natural gas and oil in 2024. With the increase in production there is also an increase in associated oil and gas waste production such as drill cuttings. Millions of tons of drill cuttings generated from shale gas development are currently disposed of in landfills. Converting these cuttings into value product(s) such as critical minerals (CMs) and soil supplements, has the potential of reducing environmental impact of fossil fuel exploration as well as lower cost of waste management for the industry.

In this study, we evaluate whether portions of these cuttings could be converted into soil supplements and used as a domestic CMs source. We characterize the CMs distribution and extractability from 16 collected drill cuttings and core samples from major U.S. shale formations (Marcellus, Bakken, and Wolfcamp). A four-step sequential extraction, consisting of a sonicated soap step, sonicated ethylenediaminetetraacetic acid (EDTA) step, a mildly reducing agent, and an oxidizing agent, was developed to simultaneously extract CMs and convert the drill cuttings into soil supplements. Viability of converted drill cuttings as a soil supplement was determined with a seedling growth experiment.

Results show high concentrations of vanadium (V) (up to 1,575 ppm), barite (up to 5 wt.%), and rare earth elements (REE) concentrations (up to 253 ppm). Shales with high pyrite and total organic carbon (TOC) content also have the highest concentration of V, REE, and other CMs. High extractability of selected CMs such as REE (19-50%), Cu (31-54%), Zn (50-99%), and Ba (10-58%) show promising results. Other CMs such as V (0-5%) have low extractability and still require additional extraction method development. Converted drill cuttings are improved and safer soil supplements through a reduction in residual oil content (91%), Na (90%), and toxic heavy metals such as Pb and As (92%). Preliminary results show seedling growth in a mixture of converted drill cuttings with soil. These results show the potential for recovery of CMs from drill cuttings as an alternative domestic source considering the high volume of cuttings produced each year and the reduction of the environmental impact of fossil fuel production through the use of converted drill cuttings as a soil supplement.