<p>Given the differences in rock mechanical properties and the unclear influence of fracturing parameters on hydraulic fracture propagation in heterogeneous marine-continental transitional shale reservoirs, a three-dimensional hydraulic fracturing model was established using Abaqus finite element software to analyze how lithological variation and fracturing parameters affect hydraulic fracture propagation. The results show that: (1) During the expansion of three-dimensional hydraulic fractures in marine-continental transitional facies, a “necking” phenomenon occurs. This effect becomes more severe and frequent with increasing rock facies heterogeneity. (2) The vertical lithological heterogeneity of transitional facies is influenced by interlayer lithology. Limestone and sandstone interlayers promote hydraulic fracture propagation, while mudstone interlayers typically inhibit it. However, at an injection rate of 20 m³/min, the fracture propagation morphology in mudstone interlayers becomes more complex, facilitating propagation. (3) The “necking” morphologies of hydraulic fractures, influenced by the dual heterogeneity of the marine-continental transitional facies, mainly include fingering, tadpole, landslide, drum mound, and landslide-drum mound types. (4) In reservoirs with the dual heterogeneity of marine-continental transitional facies, the maximum fracture width depends on the perforation location and interlayer lithology. A “clayey-siliceous-clayey” sequence yields the greatest width when perforated in clayey shale, while a “siliceous-clayey-siliceous” sequence does so when perforated in siliceous shale.</p>