Figure 3

Fracture characteristics of different rock compositions. (a) Intershell fractures can be seen along the shells in shell limestone at 2,619.70 m for well J34; (b) A large number of connected shell fractures are visible in the clastic limestone at 2,931.06 m for well T1; (c) Intergranular fractures developed along the calcite grains, and corrosion traces can be seen in these fractures at 1,991.87 m for well X29; (d) Dolomite content is 70%, and no fractures were found at 1,452.0 m for well MX9; (e) Corrosion fractures are along the surface of clay minerals, mainly in thin interbed layers in Da13 at 1985.7 m for well X28; (e) Intergranular pore was found between quartz grains, but there were no fractures at 2711.42 m for well J61. (a,b) are shell-controlled fractures, (c) shows matrix-controlled fractures, (e) are non-fabric controlled fractures, and (d,f) have no fractures.