Laser beam backscattering as a new tool to study the effect of inhibitors on shale particles-water interactions: A real-time analysis

Abstract The interaction between clay-rich shales formations and water is one of the most relevant factors for well instability in drilling operations, representing a significant challenge for the oil and gas industry. To minimize the problems related to water sensitivity, chemical additives or inhibitors are incorporated into water-based drilling fluids, acting over the water-shale interactions and maintaining the integrity of the sedimentary rock. In this work a novel approach is proposed to gain new information about the dynamics of the inhibitory process and to evaluate the shale inhibition efficiency of different chemical additives using a laser beam backscattering technique. This technique is based on the analysis of laser backscattering profiles promoted by dispersed particles in a suspension, which results in a particle chord length distribution (CLD). The technique was adequate for monitoring the consequences of the interactions between water and shales, differentiating its reactivities by monitoring the effect of different inhibitors on each system's CLD over time. Two cationic inhibitors (KCl and PDADMAC, a cationic polymer) were tested, and the obtained results showed that the inhibition phenomenon is more than the inhibitor itself, and it depends on the shale structure and the capability of the inhibitor to interact with its clay stacks. A methodology was also developed to calculate an inhibition efficiency score (IES), in which the technique's real-time factor enables it to estimate how much better an inhibitor is when compared to others over time. Among the evaluated systems, the inhibitor that achieved the biggest efficiency for shale was KCl, resulting in 69%.