Experimental Study on Hydraulic Fracture Propagation in Multilayered Tight Sandstone Reservoirs of the Tarim Basin in China

The tight sandstone reservoirs of the Tarim Basin in China are characterized by vertically stacked multi-sweet spots. However, the strong vertical heterogeneity and discontinuity limit the effectiveness of hydraulic fracturing for multilayered co-production. To investigate the mechanisms governing the vertical cross-layer propagation of hydraulic fractures in the multilayered sandstone reservoir, outcrop rocks of fine sandstone and siltstone from the area were collected. Subsequently, these rocks were cemented to fabricate multilayered experimental samples with lithological transition zones. Hydraulic fracturing experiments were performed to systematically study fracture propagation behavior, with particular focus on the influence of interlayered lithology, vertical stress differences, fracturing fluid injection rate, and fluid viscosity on vertical fracture growth. Experimental results demonstrate that hydraulic fracturing in multilayered sandstone can form both passivated and cross-layer fracture networks while also activating lateral propagation along lithological transition zones. When hydraulic fractures extend from high-brittleness layers to low-brittleness layers, their vertical propagation is limited, promoting shear activation along lithological transition interfaces. As the vertical stress difference increases, the vertical propagation range of hydraulic fractures expands progressively, with fracture morphology evolving from a passivated type to a single-wing cross-layer pattern and further developing into a bi-wing cross-layer geometry. Increasing the injection rate and viscosity of the fracturing fluid enhances cross-layer fracture propagation while suppressing the activation of lithological transition zones. The insights derived from this study can provide a theoretical foundation and engineering guidance for the design and implementation of hydraulic fracturing in multilayered tight sandstone reservoirs in the Tarim Basin.