Dynamic Friction Inversion and Segmented Control Technologies for Completion Strings in Ultra-Long Open-Hole Wells

To address the challenges of significant friction prediction errors and high buckling risks during the running of completion strings in ultra-long open-hole wells, a study on dynamic friction inversion and segmented control technologies was conducted. First, based on artificial intelligence clustering algorithms, the open-hole section was divided into three characteristic zones with low, medium, and high friction. By combining the simulated annealing algorithm to dynamically correct the friction coefficient, a three-dimensional nonlinear mechanical model of the string and wellbore was established. Then, by researching the coupling effect between the float collar depth and the drilling fluid density, a segmented regulation method based on friction zoning characteristics was proposed. This technology was applied in Well J108-2H. The optimal placement of the float collar was determined to be 2 600 m from the bottom, and drilling fluids with densities of 1.42, 1.46 and 1.51 kg/L were used for segmented regulation in the low, medium, and high friction intervals, respectively. This scheme controlled the equivalent circulating density within 1.90 kg/L, significantly reduced the degree of buckling, and ensured that the ϕ139.7 mm casing reached the designed well depth. The dynamic friction inversion and segmented control method overcomes the engineering limits caused by the nonlinear friction characteristics of complex trajectory wellbores and provides a technical means for the safe running of completion strings in ultra-long open-hole wells.