Fractures are extremely important in the delivery of hydrocarbons in carbonates. Generally, fracture porosity is not related to original rock fabric. Earlyformed fractures tend not to be as effective as latestage fractures for fluid flow. Early-formed fractures in carbonates may be distinguished by their highly variable length. They are filled with sediment and early cement, and are formed by volume change of sediment or by gravity.
Meteoric fractures fill with cement or residual soils, cave filling, or caliche.
In addition, they are uncemented, oil stained, and oriented relative to tectonic stresses.