<p>Hydraulic fracturing represents a prevalently utilized and efficacious technique for augmenting the permeability of tight reservoirs, and it has been extensively employed in oil and gas field engineering scenarios to facilitate the efficient exploitation of tight oil and gas resources. The most critical issue in hydraulic fracturing is the initiation and propagation of fractures, which determine the effectiveness and extent of the fracturing process. There are abundant shale oil resources in the Chang 8 reservoir of the Ordos Basin; however, studies examining the influence of interlayer and multilayer system lithology on hydraulic fractures remain limited. In this paper, using the method of true triaxial fracturing physical test, the hydraulic fracture initiation and propagation of various tight reservoirs were conducted with the Ordos Basin Chang8 Reservoir, and the effects of injection rate, type of fracturing fluid, lithology, and interlayer thickness on the initiation and propagation of hydraulic fracturing fractures were investigated. Results show that increasing injection rate promotes faster and more complete initiation and propagation of fractures. CO₂ has a lower viscosity and stronger compressibility, which enables the fluid to enter the pore space and create a localized pressurisation effect, thereby assisting in the generation of more complex fracture patterns. The mudstone samples display uncertain fracture propagation directions owing to their plastic characteristics, while the fractures in sandstone samples exhibit more regular patterns due to their higher brittleness. The fractures in the sand-mud interbedded specimens tend to form in the more brittle sandstone, expanding in the direction of maximum stress and then turning as they encounter the more plastic mudstone, eventually forming an “I” shape. The thickness of the interlayer does not significantly impact fracture propagation, while the orientation of the interlayer significantly affects the fracture expansion path.</p>