Creation and presence of the hydraulic fracture can cause casing failure both during and after the fracturing operations. Although such failures are known to occur and have been a concern to many operators, the petroleum industry literature contains very little information on the subject.

During the fracturing operations, casing can fail under tension across the fractured interval either by de-threading of the collars or by tensile failure at perforations. The three main factors contributing to this failure are thermal shrinkage of the casing, off-balance fracture growth, and pseudo-openhole environment. Other contributing factors are borehole inclination with respect to the fracture plane, and the quality of the cement bond.

Factors contributing to casing failure during well production include changes in in-situ stresses due to reduction in reservoir pressure, off-balance fracture growth, formation layering and its inclination with respect to the wellbore, and shear strength of the interfaces. In particular, off-balance growth may create fractures that are not symmetrical with respect to the wellbore, and have different lengths in different layers. The resulting differential reservoir compaction induces shear stresses along the interfaces which can cause casing failure along the weakest interface.

The low formation shear strength along the propped fracture plane increases the probability of shear movement along it. Presence of the fracture will direct this movement towards the casing and can cause its shear failure. Rapid production pressure declines increase the shear stresses acting on the fracture plane and can cause movement along the fracture plane and casing failure.

You can access this article if you purchase or spend a download.