Optimization of Tripping Speed to Minimize Surge & Swab Pressure

Abstract

Abstract Pressure changes due to surge and swab has been a concern in the drilling industry for many years. The fast and sudden movement of the drill string while pulling out of hole causes the wellbore pressure to decrease. This is due to the frictional forces between the pipe moving upward and the drilling mud that is stationary, which is known as the swab pressure. The opposite is also true, moving quickly inside wellbore will cause the pressure to increase, and this is known as the surge pressure. If these pressure changes become very high, the formation might get fractured which introduces influx leading to a kick. In severe cases, this kick might lead to a blowout which endangers human lives and environment. This article focuses on the fundamental theory of surge and swab in addition to the maximum pipe running speed that avoids surging and swabbing the well. Further, calculations are carried out to optimizing the maximum pipe tripping speed by employing different parameters as input values. Both laminar and turbulent flows are considered in addition to closed ended pipes since it is the most critical one. The objective of this study is to optimize the drilling parameters that specify the maximum pipe tripping speed with different hole's sizes and pipe dimensions. Moreover, this research offers the optimized values to identify the factors that heavily affect surge and swab pressures. The results show that annular space and bottom-hole assembly (BHA) length have significant effects on surge and swab pressure values. Sensitivity analysis shows that pipe size and mud rheology impacts surge and swab values, but not significant. In fact, it is the annular velocity which is heavily affected by BHA length and size. When it comes to casing, the size was not an issue because the annular space is larger compared to smaller casing sizes. In addition, study shows that depth plays vital roles that can be seen with smaller casing sized. This study will enhance the understanding of drilling problems while drilling due to surge or swab pressures.