Borehole structure optimization based on pre-drill risk assessment

Borehole structure design based on pre-drill risk assessment and considering risks related to drilling operation is the precondition for safe and smooth drilling operation. Major risks related to drilling operation include lost circulation, blowout, sidewall collapsing, sticking and failure of drilling tools etc. In the study, data from neighboring wells was used to calculate the profile of formation pressure with credibility in the target well, then the borehole structure design for the target well was assessed by using the drilling risk assessment to predict engineering risks before the start of drilling, finally, the prediction results were used to optimize borehole structure design to prevent such drilling risks. The newly-developed technique provides a scientific basis for lowering probability and frequency of drilling engineering risks, and shortening time required to drill a well, which is of great significance for safe and high-efficient drilling.