Analytic approach for the influence of waiting time on deepwater conductor stability

In deepwater jet drilling, the design of waiting time after surface conductors installation is crucial for safe and efficient well construction. Addressing the problems that current design methods are mostly developed by regional experience without comprehensive consideration of the vertical and lateral stability of conductors, it is necessary to develop a waiting time design approach with wider applicability and higher accuracy. Based on the pipe-soil interaction theory, this study analyzes the variation patterns of the vertical and lateral bearing capacities of surface conductors with waiting time from completion of jetting placement to the release of running tools. Through laboratory simulation experiments, the variation rules of soil recovery coefficient of cohesive soil and sandy soil with waiting time are studied. On this basis, an optimal waiting time design method comprehensively considering vertical and lateral stability is proposed. Laboratory experimental results show that under the same conditions, the recovery coefficient of cohesive soil is higher than that of sandy soil. Field application indicates that by using this method, the minimum waiting time required for the first spud-in phase of the target well to meet the requirements of vertical and lateral stability is 2.9 hours, which saves 10.6 hours compared to the traditional operation method of determining waiting time based on experience in adjacent wells. By quantifying the influence of soil properties and coupling vertical and lateral stability, this method establishes a more comprehensive theoretical design model and provides a scientific basis for the safe and efficient installation of conductors in deepwater drilling.