Application of Multi-Phased Drilling Fluid Technique to Cope up with the Drilling Challenges in the Unorthodox, Elevated Wells in the Frontier Region, Baluchistan, Pakistan

Abstract This study discusses the use of multi-phased drilling fluids along with the innovative equipment specific to unconventional drilling to deliver optimized drilling operations in the unorthodox drilling environment along with their application to deal with future drilling challenges in surface hole sections in such settings. Frontier Region is located in the Suleiman Fold Thrust Belt that lies in the Baluchistan province of Pakistan, on the northwest edge of the Indian tectonic plate. The belt is about 200,000 square kilometers in size, However, the unconsolidated nature of formations at tall cliffs much above mean sea level makes the conventional drilling operations of surface hole sections impossible due to complete loss scenario, hole cleaning issues and low ROPs. The challenging formations encountered in surface hole sections are rubbly limestone and nodular shales with most evident drilling problems of lost circulation, stuck pipe events and poor hole cleaning resulting in financial and timeline setbacks. Moreover, further complexities related to loss/gain make operators revise their casing plans and wellbore trajectories along with revised engineering studies. By providing optimized drilling tactics to address the issues with loss/gain and mechanical/chemical instability, unconventional technologies are available to address these difficulties and meet deadlines. Owing to these drilling challenges in Suleiman Fold Belt Region in Baluchistan Pakistan, the operator had to spot various loss circulation material (LCM) pills via conventional drilling mud but failed to manage bottom hole ECDs. The simultaneous presence of loss prone limestones and unstable shale at elevated cliffs of about 420m (1100m above MSL) made the surface sections more challenging to drill due complete losses and poor ROPs. To cope up with the challenges, the gas medium was injected into the drilling fluid homogenously to make the drilling fluid lighter that allowed the operator to drill the surface sections with sub-hydrostatic bottom hole circulating pressures as low as 0.19 SG leading to stable returns, excellent hole cleaning and much improved ROP due to the reduced chip hold down effect. This not only made the previously undrillable wells drillable but also improved economics and timelines via improving ROP almost 10 folds. By Opting this multi-phased drilling technique along with the innovative equipment specific to unconventional drilling, the drilling industry can successfully cope up with the future drilling challenges faced in surface sections in the unorthodox drilling environments.