Calculation of Transient Fluctuation Pressure in Deep Water Dual Gradient Drilling

摘要

Transient fluctuation pressure is extremely harmful during the drilling process. Fluctuation pressure can cause problems such as kicks or blowouts and lost circulation. Mastering and calculating fluctuation pressure is of great significance for reducing drilling accidents, increasing drilling speed and reducing drilling costs. In this paper, a mathematical model of downhole transient fluctuation pressure is established for the deepwater dual gradient drilling process. The mathematical model is solved by the characteristic line method and the finite difference method. The effects of drilling fluid performance (density, consistency coefficient, fluidity index), drilling speed and drilling acceleration on transient fluctuation pressure were analyzed. The results show that the transient fluctuation pressure increases with the increase of drilling fluid density, and the greater the penetration speed, the more obvious the increase. The consistency coefficient K and the fluidity index n have the same effect on the transient fluctuation pressure. The performance is as follows: the maximum transient fluctuation pressure increases with the increase of K(n), and when the acceleration changes greatly, the amplitude of the fluctuation decreases with the increase of K(n) value. The greater the drilling speed or the drilling acceleration, the greater the transient fluctuation pressure. The calculation results have a certain reference function for better control of the drilling speed and drilling fluid performance at the drilling site.