Due to the lithology difference between layers and pronounced vertical heterogeneity

the main fractures are difficult to extend vertically in thin interbedding tight sandstone reservoirs. Increasing the fracture extension rate can effectively promote the fracture extension crossing the layer. A three-point bending fracture experiment was carried out using prefabricated cement-sandstone specimens to study the effect of extension rate on fracture path. The digital image correlation method monitored the fracture process zone (FPZ) development characteristics when the fracture extends to the bedding. A prediction model of fracture extension path considering rate effect is proposed based on fracture dynamics theory. The results indicate that at low fracture extension rates

the fracture geometry exhibits a tortuous pattern

accompanied by a short and wide FPZ. Conversely

at high extension rates

the fracture geometry becomes smooth

with a long and narrow FPZ. FPZ is discrete and has the characteristics of mutual attraction. The fracture expands from low-strength rock to high-strength rock. At low propagation speeds

a high-strain zone (FPZ) forms in advance at the bedding plane

facilitating the extension of fractures along the bedding

causing the cracks to propagate along the layers upon reaching these interfaces. In contrast

this phenomenon is not observed during high-speed crack propagation. A positive correlation exists between the tensile strength of the rock and the average tensile strength of fractures traversing the unit. Fractures with low extension rates preferentially propagate along micro-defects

leading to a reduction in the tensile strength of the rock. Conversely

fractures with high extension rates preferentially propagate along self-similar directions

causing an increase in the tensile strength of the rock due to the tearing of numerous high-strength components. As the angle between the fracture and bedding increases

the fracture's ability to traverse the layer improves. The effect of the angle is maximized when it reaches 30° between the fracture and bedding

gradually diminishing beyond this threshold. These research findings hold significant implications for optimizing hydraulic fracturing parameters

enhancing fracture height

and boosting oil and gas production in thin interbedded tight sandstone reservoirs.