Abstract: Based on the generation mechanism of structural fractures，the development regularities of structural fractures in
sand-mud interbed of A Gas Field，Kuqa Depression are discussed in the paper，and the influencing factors are analyzed，and
the development model of structural fractures in sand-mud interbed is established. The analysis reveals that，influenced by the
fragility of sandstone and plasticity of mudstone，structural fractures in sand-mud interbed generate in sandstone layers first
and expand into mudstone layers to gradually form the fracture network. Fragile stones are easier to produce a great quantity of
fractures than plastic ones，thus the density of fractures in sandstone layers of sand-mud interbed is greater than that in mudstone
layers. Due to the difference of internal friction angle between sandstone and mudstone，the average dip angle of fractures in
sandstone layers is greater than that in mudstone layers. The smaller the thickness of single sandstone layer or mudstone layer is.
The better the development of fractures is the Strata with strong anisotropy always produce more fractures than homogeneous
ones. However，as the result of the anisotropy，one group of conjugated shear fractures would be restrained and another group
would be taken as the principal. The research result also demonstrates that，in the sand-mud interbed of A Gas Field，Kuqa
Depression，the thickness of each mudstone layer is less than 4.0 m，the limit value for fractures to penetrate mudstone layers.
Therefore，the fractures could penetrate mudstone layers and connect the upper and lower sandstone to form massive continued
hydrocarbon pore volume. Finally，the development model of fractures in sand-mud interbed is established according to the
above theoretical analysis.

Key words: and-mud interbed, structural fractures, development regularities, influencing factors, development model, KuqaDepression