Evaluation of the Respirable Crystalline Silica Content in Common Oilfield Minerals

Abstract

Abstract The amount of the respirable fraction of crystalline silica is a concern within the oilfield and other industries using mineral products. Current measurement and reporting techniques typically identify total silica content, but do not test for, or report, the respirable fraction. In order to address this situation, special measurement techniques have been employed to more accurately report the respirable crystalline silica (RCS) values. Crystalline silica is a commonly occurring impurity in most mined minerals and its presence as fine respirable particles (smaller than 16 μm) in a material can necessitate specific hazardous warning labels due to the potential health effects. Mineral additives are added to drilling fluids in large quantities, creating a need for the industry to monitor associated RCS levels. This study establishes a useful technique to determine typical RCS values encountered for two ubiquitous oilfield commodities, barite and calcium carbonate, which are known to contain naturally occurring silica. Isolating the respirable fraction of these materials from the bulk is possible using a sedimentation technique with the fine particulate analyzed for its crystalline silica content by Fourier transform infrared (FTIR) spectroscopy. Barite and calcium carbonate from various worldwide sources were tested using this improved method. This paper will present the data to establish observed levels of RCS for the analyzed samples. Additionally, this paper will demonstrate the suitability of the methodology applied in this study to support the evaluation of RCS in other oilfield minerals.