Why Oil Wells Leak: Cement Behavior and Long-Term Consequences

Oil and gas wells can develop gas leaks along the casing years after production has stopped and the well has been plugged and abandoned. Explanations include channeling, poor cake removal, shrinkage, and high cement permeability. The reason is probably cement shrinkage that leads to circumferential fractures that are propagated upward by the slow accumulation of gas under pressure behind the casing.