###### Abstract  
This work delineates a comprehensive study of one of the main problems that contributes towards nonproductive time (NPT) in a drilling operation, which is lost circulation. The focus of this study was to investigate the performance of walnut, graphite, and marble, which are three widely used and industry-available granular lost circulation materials (LCMs). Additionally, the study aimed to establish a particle size selection guideline for better operational performance and plugging efficiency. Four water-based carrier fluid systems (water-bentonite mix, water-polymer mix, and two polymer-salt systems) were tested with the LCMs in this study. Dry and wet particle size degradation studies were conducted on all the LCMs with the different carrier fluid systems to study their compatibility and efficiency. The effect of the carrier fluid type was proven to be significant only on marble particles size degradation; walnut and graphite were not affected by the carrier fluids and showed consistent size degradation performance with all fluids. The results of this work led to newly developed particle size selection guidelines to enhance plugging efficiency--guidelines that are custom-made for each material by taking into consideration the rate of the degradation and type of material and by correlating the findings with fracture width. Applying this method of investigation to the current lost circulation management practice can help resolve many lost circulation incidents by effectively and efficiently selecting the appropriate LCM. l 31 August 2021 24 September 2021 28 September 2  
techniques, which include the \"ready-made\" pill designed by service companies, cement plugs, and non-formation-specific formulations, have reached the current limit of their effectiveness, especially when it comes to complicated conditions such as conductive fractures as well as weak and depleted formations. LCM manufacturers claim that these new materials will solve the issue, and yet, it is difficult to determine which new materials are appropriate for a given situation. Hence, lost circulation problems still exist. Oil and gas companies will often face fluid loss during drilling operations. Many drilling hazards could be the direct result of loss circulation, such as hole collapse, stuck pipe, and blowouts [5]. The main cause of fluid losses is drilling through zones with natural fractures, cavernous zones, or a high permeability matrix [6; 7; 8]. To cure mud losses, many operators' first approach is the addition of LCMs in the drilling fluid. The use of the LCM is mainly intended to cure existing losses, but using LCM as a preventive practice has been documented [9]. Research and development efforts on the lost circulation problems must be aligned with many factors, such as, drilling fluid selection, size degradation of the LCM upon shearing, and finally implementing ways to strengthen the fracture gradient of the formation. The particle size distribution of the LCM is the only widely used method for designing and planning the sealing or plugging mechanism to mitigate a lost circulation event. One of the criteria for selecting which material to use is the correlation between the particle size and the fracture width or pore size. This criterion assumes that both the anticipated fractures/pore sizes and the selected LCM particle size distribution (PSD) will be maintained when the material reaches the thief zone or fracture downhole. Size degradation is due to mechanical shearing or a dynamic force that acts on the particles of the LCM by the mud pumps, drill string, wellbore annulus, and bit nozzles [10]. Many authors in the literature have spent a lot of time and effort studying size degradation. [PERSON] et al. (2016) examined the size degradation of two LCMs (graphite and marble) using a flow loop [11]. The study revealed that the graphite showed a 16% PSD reduction in size, while ground marble recorded a PSD size reduction of 35%. [PERSON] et al.