###### Abstract
(2012) conducted a size degradation lab experiment on three materials: walnut hulls, graphite, and ground marble. The shearing speed was 7000 revolutions per minute (RPM) for intervals of 5 and 15 min. Their results revealed that the large particles were more prone to degradation than the finer particles. Their results also demonstrated that walnut and graphite show a lower percentage of degradation and were able to sustain the high shear. Ground marble degraded the most and thus was not recommended for wellbore strengthening or lost circulation applications [12]. The study reported in this paper agrees with the conclusions of [PERSON] et al. but takes the study beyond the basic degradation study. Each material behaves differently under high shear because of the different physical and chemical properties of these materials [13]. To fully understand the underlying science requires an analysis of the type of fluid used and the impact of size degradation on LCM plugging efficiency. There is a need for further investigation of the effect of the material size degradation due to shearing with regard to the plugging efficiency. There is clearly a wide gap between understanding the impact of degradation and the ability of the LCM to adequately perform fracture sealing [14]. Many guidelines have been introduced in the literature for addressing the selection of the optimum bridging mechanism. These various guidelines are used in the industry to choose the particle size of bridging materials that can form an efficient external filter cake and minimize formation damage. Table 1 summarizes several of the current selection guidelines. These guidelines correlate fracture width with the size of LCM to achieve the paramount sealing of the fracture. The first criterion states that the median particle size (D\({}_{50}\)) must be approximately equal to or greater than one-third of the average pore throat size. A different criterion introduced by [PERSON] (1977) states that the volume of the LCM must be 5% or more of the total solids volume in the solution to attain the optimum bridging [15]. [PERSON] et al. developed a criterion that is based on a lab-scale and field application. In their criterion, the D\({}_{90}\) of material must be equal to the pore size to reduce the fluid invasion [16]. [PERSON] et al. produced different criteria for bridging the pore size and suggested that the five D-values must be considered in the selection criteria. D\({}_{10}\) has to be higher than the smallest pore in the formation, D\({}_{25}\) must be equal to one-seventh of the average pore size, D\({}_{50}\) must be equal to or larger than one-third of the formation pore throat size, D\({}_{75}\) must be less than two-thirds the pore throat size, and D\({}_{90}\) should be equal to the largest pore throat size [17]. Furthermore, [PERSON] presented a bridging guideline that considers the fracture width being equal to the D\({}_{50}\) of the PSD of the bridging materials [18]. The objective of all these guidelines is the same--to plug the fracture or pore throat that leads to managing and resolving the lost circulation problem. The essential factor in developing these guidelines was the dry particle size distribution of the material without considering the impact of the drilling fluid, any possible size degradation, and the type of the material. This study sheds light on the degradation rate of LCMs in different fluids and shows degradation effects on plugging different fracture width sizes. The traditional particle size selection guidelines are in need of an enhancement, and hence, by taking into consideration the rate of the degradation, type of material, and correlating those findings with the fracture width size, this study developed a new particle size selection guideline that is custom-made for each material. These guidelines demonstrate material performance based on the dry and wet particle size distribution (PSD) and examine the impact of material choice and fluid interaction when plugging a given fracture width size.