Collapsed Casing

Collapsed casing in drilling is the failure of the steel pipe (casing) that is inserted into an oil or gas wellbore to provide structural integrity.  The casing can collapse due to excessive external pressure, deformation, or mechanical failure.  When this happens, the casing no longer maintains its intended shape, leading to a reduction or complete loss of the well's structural integrity.  This can cause significant issues, including difficulty in further drilling operations, compromised well safety, and potential environmental hazards.  Preventing casing collapse involves proper design, material selection, and installation procedures, along with regular monitoring and maintenance.

Causes of Casing Collapse

Excessive External Pressure  -  If the external pressure exerted by the surrounding rock or fluid exceeds the casing's designed strength, it can cause the casing to buckle or collapse.
Improper Installation  -  Incorrect installation procedures, such as not centralizing the casing properly or not cementing it correctly, can lead to uneven pressure distribution, increasing the risk of collapse.
Corrosion  -  Over time, the casing can corrode due to exposure to harsh environments, weakening its structural integrity and making it more susceptible to collapse.
Mechanical Damage  -  During drilling or other operations, the casing might be damaged by tools or equipment, leading to a weakened state and eventual collapse.
Thermal Stresses  -  Changes in temperature, especially in deep wells, can cause expansion and contraction of the casing, potentially leading to collapse if the material is not able to withstand these stresses.

Consequences of Casing Collapse

Lost Circulation  -  Drilling fluids might escape into the surrounding formation, leading to a loss of well control.
Difficulty in Running Tools  -  The collapse can create obstructions, making it difficult to run drilling tools or production equipment through the well.
Well Integrity Compromise  -  A collapsed casing can lead to communication between different formations, causing potential contamination or loss of hydrocarbons.
Increased Costs  -  Repairing or sidetracking a well with a collapsed casing is often expensive and time-consuming.