Analysis and precaution of drilling tools failure in shallow section of Dayi structure

Sandstone and mudstone stagger in shallow formation of Dayi structure with gravel layers locally, so the drillability is poor. In recent years, 13 deep wells were deployed in the area, while a total of 42 time drilling failures happened in shallow section, causing significant economic loss. In order to avoid frequent drilling failure in Dayi shallow strata, the early failures were collected, and indoor micro and corrosion tests were conducted. The main reason of the failure is that soft and hard staggered formation easily leads to drilling tools fatigue, with no nondestructive testing in time, and drilling rotation speed is too high, causing the probability of occurrence of fatigue failure increases. The measures to prevent drilling failure are proposed, which are properly adjusting drilling parameters and timely nondestructive testing. Good results have been achieved at the scene through the use of these measures.