Effect of swab and surge pressure on the time-dependent wellbore natural fracture development

Abstract

Drilling engineers continue to grapple with the persistent challenge of maintaining wellbore stability. Throughout the drilling process, the wellbore pressure experiences fluctuations induced by various factors such as swab and surge pressure, leading to potential instability. This study employs a numerical approach, utilizing Abaqus software, to investigate the impact of swab and surge pressure on the natural fracture growth within the wellbore and the evolving pore pressure. A computational tool developed with MATLAB is then utilized to ascertain a safe operational mud window by assessing the time-dependent collapse and fracture pressures. The findings illustrated a notable increase in fracture width as a function of time in response to swab and surge pressure, with the most significant percentage increase reaching 69.92%. Notably, a 69.16% augmentation in fracture width is observed in the immediate vicinity of the wellbore following the application of swab and surge pressure. However, parameters such as fracture length, loss circulation rate, and pore fluid pressure exhibited marginal changes post-integration of swab and surge effects. The examination of the time-dependent wellbore stability after integration of swab and surge pressure indicated a narrowing of the initial mud window as a function of time, with a 14.33% increase in collapse pressure and a 13.80% decrease in fracture pressure. The numerical model verification against analytical solutions demonstrated good agreement, highlighting its potential utility in optimizing particle size for wellbore reinforcement and mitigating lost circulation through natural fracture sealing.