The potential to confidently apply water-based drilling fluids in unconventional shale formations has been studied using engineered nanoparticles to minimize shale permeability through physically plugging the nanometer-sized pores. This paper discusses the development of nanoparticle technology and testing protocols developed using Marcellus and Mancos as shale candidates. In addition, new methods to better understand the plugging mechanism are currently under evaluation.
Nanoparticles in this study are specifically designed to physically plug the nanometer-sized shale pores, thereby reducing pressure transmission in the shale. Silica nanoparticles are commericially available and can be engineered to meet all specifications needed for the purpose. The particle size can vary between 5 and 100 nanometers (nm) and. The right sizes of nanoaprticles can be selected and in combination with a correct fluid loss package can minimize the fluid rock interaction. Surface treatment on the nanosilcia particle has been discovered to have a major influence on the final performance. It was revealed that appropariately sized nanoparticles with surface treatments compatible with ions present in drilling and formation fluids is required for effective plugging.
Marcellus and Mancos shales were used in the development phase due to their wide industry interest and geological similarity. The authors examined an in-house method, still under development, using the Shale Membrane Test that is intended to provide quantitative plugging and filter cake measurements using various shale samples.