Research on the Mechanism and Identification Method of Borehole Ballooning in Deepwater Strata

Abstract

Deepwater oil and gas resources are abundant and prone to induce Borehole Ballooning due to narrow safe density window, fractured formation and wellbore pressure fluctuation. A wellbore-formation coupling model was established by considering the flow moiré calculation, fluid compressibility and flow path expansion of different fluids in different situations, combined with a wellbore fracture deformation model considering fracture opening and equivalent damage radius, and then combined with the field data to determine the initial and boundary conditions, and numerically solved the continuity equations and the equations of motion by applying the method of eigenlines. Combined with the actual data of Borehole Ballooning in Mexican wells, the programmed calculations were carried out, and the results show that the influence of starting and stopping the pump on Borehole Ballooning should not be neglected, and the change of Borehole Ballooning under different flow rates was simulated respectively. Compared with the change of Borehole Ballooning without Borehole Ballooning, Borehole Ballooning corresponding to Borehole Ballooning changes slower, and it takes a longer time for Borehole Ballooning to reach a stable pressure, and the bigger the change of pumping speed is, the more obvious is Borehole Ballooning. The larger the pumping speed change, the more obvious the respiratory effect, the more respiratory leakage and return, and the respiratory return is slightly smaller than the respiratory leakage.