## 1 Introduction  
Understanding the flow and fluid transport potential of shale hydrocarbon reserves necessitates describing their textural qualities, such as porosity and permeability. The amount of pore space and reservoir permeability influences the amount of hydrocarbons stored in the rocks. Despite its tight sandstone and siltstone compositions interbedded with shale, the Lower Triassic Montney Formation of British Columbia (100-300 m thick) features fine-grained elastic deposits classified as gas shale plays. Prior to recent breakthroughs in horizontal drilling and hydraulic fracture stimulation, the unconventional source rock layers of the Montney Formation were not economically viable [1]. Unconventional hydrocarbon shale reservoirs have received less attention than conventional sandstone reservoirs in core examinations utilizing traditional analytical techniques such as X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The standard industry practice for unconventional reservoirs is to conduct a mineralogical investigation of chosen samples to calibrate the petrophysical data provided by downhole logging devices. As a result, quantitative (or semi-quantitative) mineralogical analyses are carried out over the entire drilled stratigraphic sequence. These findings are crucial because the relative concentrations of the (mineral) constituents can make or break a potential resource play [2]. The presence of illite in petroleum reservoirs may play a crucial role in influencing management and production activities within the petroleum sector, as its exact value might have major implications. The precipitation of substances within reservoir pores has been observed to have negative effects on both porosity and permeability, leading to the obstruction of fluid flow. This phenomenon is particularly prominent in reservoirs with low porosity and permeability, such as tight reservoirs [2; 3]. Nevertheless, illite is predominantly favored for the purpose of hydraulic fracturing due to its tendency to signify rocks that are brittle and non-reactive to water [2; 4]. The principal elements of illite in shale strata are detrital mica, its weathering products, and diagenetic illite production during burial [4]. Illite, a potassium aluminum phyllosilicate clay mineral, is widely found in shale and other sedimentary rock formations. This mineral group includes clay minerals with a 1 nm X-ray powder diffraction repeat [5; 6; 7; 8; 9]. Within this classification, mixed-layer illite/smectite (I/S) is a distinct form of illite in which the unit cell layers are shuffled like playing cards [10]. I/S is common in shales; a significant amount of illite may also be I/S. In most sedimentary basins and geologic periods, the percentage of illite in I/S increases with depth and temperature [11]. Smectite can gradually transform into illite in a solid state or layer-by-layer, with the illite ultimately inheriting the fundamental structure of smectite [12]. [PERSON] [13] has recently proposed elemental particles and interparticle diffraction to explain mixed-layer clays. Although other minerals, such as smectite and feldspar, disintegrate in shales, illite crystals tend to form in them. While the subject of I/S remains disputed, an increase in the illite content in I/S with increasing burial depth indicates the formation of progressively thicker illite crystals [14]. The precise value of illite may play a significant role in the administration and production procedures of petroleum reservoirs. The weight percentage of illite obtained here is the product of rigorous, experimental analysis of core samples. Although beneficial, these methods have limitations due to their reliance on core samples, which can sometimes be unavailable or lost, and the substantial effort and cost involved in drilling even a small number of wells. In addition, most logging instrument operations currently available cannot directly measure the illite, only the total clay.