Analysis of Longitudinal Cracks of Casing in Heavy Oil Thermal Recovery Well

Abstract

This paper investigates cracking failure of the casing tube. There were longitudinal cracks in the heavy oil thermal recovery well occurred in an oil field. The fracture cause of casing was analyzed by macrographic observation, chemical composition analysis, mechanical property test, metallographic analysis, scanning electron microscope (SEM) and residual stress calculation. The results showed that the crack of the failed casing originates from the external surface of the pipe and has the characteristic of intergranular propagation. The fracture characteristics are brittle fracture. The conclusion showed that stress corrosion cracking(SCC) is the main cause of longitudinal crack of casing in the heavy oil thermal recovery well. Under the combined action of external corrosive media and internal stress, SCC cracks are generated on the surface of casing, and the cracks propagate along grain boundaries and finally lead to cracking and failure of casing. Some recommendations were proposed to avoid similar failures.