Methods of setting depth range with credibility of conductor for deepwater drilling based on probability statistics

• The setting depth of conductor directly affects the mechanical stability of subsea wellhead.
• The bearing capacity growth factor of subsea soil has a great influence on the setting depth of conductor.
• We can obtain the predictive value of target point's coefficient containing probability information.
• We can obtain the setting depth range with credibility of conductor, which is good for designing.
• Designers can calculate the setting depth of conductor with other uncertain factors and control the potential risks.

Becasuse of the deep water depth and long riser of deepwater drilling, the stability of subsea wellhead is threatened. Meanwhile, the setting depth of conductor directly affects the mechanical stability of subsea wellhead. Through analyzing the impact of different factors on the setting depth of conductor, we found that the bearing capacity growth factor of subsea soil has a great influence on the setting depth of conductor. However, the coefficient is a regional and empirical constant, which seriously affects the accuracy and reliability of the results. In this paper, probability statistics and geostatistics methods are employed to count the bearing capacity growth factor of target point's adjacent wells, as well as transplant and predict the target point through differential arithmetic, which can obtain the predictive value of target point's coefficient containing probability information. Finally, we can obtain the setting depth range with credibility of conductor. This is conducive to designers to calculate the setting depth of conductor with other uncertain factors taken into account, and reasonably control the potential risks.