Centrifugation as a method of analyzing effectiveness of clay stabilizers for water-based fracturing fluids

This paper provides a basic reference for clay description, clay/fluid interaction, clay stabilization, and clay/fines migration.The three types of clay stabilization including ion exchange, coating of clay particles, and modification of surface affinity toward water are described in detail.The evolution of the "7% KCl rule" is discussed, and the effect of pH on clays is investigated.The damaging potential of destabilized or migrating clays is illustrated by considering the volumetric and surface areas contacted by typical stimulation treatments.Traditional methods to test for clays using X-ray diffraction (XRD), scanning electron microscope (SEM), and coreflooding are discussed.The challenges faced when using this testing in unconventional reservoirs and the impacts of using drill cuttings are described.The drill cuttings testing method is illustrated along with the recommended testing frequency throughout a play.Ranges of clay type and amounts are given for various shale and tight-sand formations in Oklahoma.An example of clay content is presented that illustrates the variability and distribution of clay material in a single formation.It is concluded that most formations in Oklahoma have a significant amount of clay material, which can vary dramatically within a formation.The potential for clay damage is significant even in low-clay-content formations; however, clay damage can be mitigated through new testing methods, proper clay characterization, and the use of clay-control additives.This paper attempts to determine how much clay is "too much" and what type of clay stabilization is appropriate based on drill cuttings clay-control testing.