Analysis of the Combination Mud and Gas Flow Rates for Hole Cleaning in Reservoir Zone of SAJ-16 Geothermal Well

Abstract

Geothermal drilling operations face unique challenges in maintaining wellbore stability and effective cuttings transportation due to high temperature formations and fracture zones. This study aims to analyze the combination of mud and gas flow rates in the reservoir zone of geothermal well SAJ-16 to determine the op-timal parameters for slightly underbalanced drilling. Hydraulic simulations were performed using Beggs & Brill correlation and WellPlan software to evaluate bottom hole pressure (BHP), equivalent circulating density (ECD), and cuttings transport ratio (CTR). The results show that increasing gas flow rates reduce BHP and ECD, thus allowing unbalanced conditions but with the risk of for-mation collapse if the bottom hole pressure below the collapse pressure limit. Conversely, higher mud flow rates increase fluid velocity and CTR, improving cuttings transport efficiency while reducing the potential for cutting bed. Rec-ommendation mud flow rate for 12-1/4” hole section is 600-910 gpm and gas flow rate are 500-1000 scfm. While, mud flow rate for 9-7/8” hole section is 500-787 gpm and gas flow rate are 500-3000 scfm, due to maintaining BHP be-tween reservoir pressure and collapse pressure also achieving CTR value > 0,70. The findings provide a reference for optimizing drilling parameters in geother-mal wells to minimize non-productive time and operational risks.