Ming Tang
Southwest Petroleum University, China
Title: Accuracy analysis of narrow-slot approximation technique for predicting surge and swab pressure
Biography
Biography: Ming Tang
Abstract
Surge and swab pressures have been known as main reasons to cause drilling problems, such as lost circulation, formation fracture, fluid influx, kicks, and even blowouts. Accurate prediction of surge and swab pressures is crucially important to avoid drilling problems caused by downhole pressure surge. Both of the yield power law and Casson models fit actual drilling mud very well. To date, however, no analytical solution for flow of yield power law fluids and Casson fluids in a concentric annulus has been published. Most of the available methods are developed based on narrow-slot approximation technique, which predict surge and swab pressure with high accuracy only at high diameter ratio. In order to evaluate the accuracy of the surge and swab pressure models based on narrow-slot approximation technique both for yield power law and Casson fluids, this paper presents exact numerical models in concentric annulus for yield power law and Casson fluids, respectively. Parameters study was conducted to analyze the sensitivity of surge and swab pressure to input parameters. The accuracy was evaluated with different drilling fluid rheological and annular geometry parameters, and then modified equations were introduced to improve the application range and precision for surge and swab pressure models based on narrow-slot approximation technique. The performance of the modified equations have been tested by use of experimental results. A satisfactory agreement has been obtained.