Failure and integrity analysis of casings used for oil well drilling

Fatigue cracks were found in other pipes that, although did not lead to fast fracture, would have caused leaking during subsequent well completion and production. The most relevant conclusion is that future integrity of casings used for drilling could not be assured. Reducing cyclic drilling stresses below the actual fatigue strength of pipes and connections is not easy task; the industry tendency is to go to slim-hole DwC, with ever increasing operating loads. Therefore, the economic feasibility of using heat treated casing and more sophisticated DwC designs are highlighted. Large grained tube steels and premium connections are found to be the most cost-effective alternatives to ensure the casing would survive the cyclic torque and compression stresses without serious damage.