Abstract
Formation gravity displacement refers to the phenomenon of "overflow and leakage" in the same crack due to the difference in density between the drilling fluid and the formation fluid. In order to restrain the leakage accident caused by gravity displacement, this paper studies the formation gravity displacement window, studies the conditions of gravity displacement, and puts forward the corresponding solutions. In summary, this paper develops the wellbore-formation gravity displacement experimental device, carries out gas-liquid gravity displacement critical point experiments, summarizes and analyzes the formation gravity displacement window, and fits the critical point pressure curve of the gravity displacement window based on the results of constant pressure experiments. The existence of formation gravity displacement window was verified through computer simulation. The error between the fitting formula and the measured value is less than 10%, it can reflect the relationship between the gravity displacement window and the density difference, which is of guiding significance for on-site gravity displacement suppression and pressure-controlled drilling.
