Abstract
Challenging formations offer most of the evident drilling problems including lost circulation and stuck pipe events that result in financial and timeline setbacks globally. By providing optimized drilling tactics to address issues with loss/gain and mechanical/chemical instability, unconventional technologies are available to address these difficulties. Owing to inherent lost circulation, influx and stuck pipe risks in Kirthar Belt in Sindh Pakistan, the operator had to spot various LCM pills along with facing various stuck-pipe incidents in most of the offset wells, resulting in the revision of the casing program.
This study assesses the use of multiphase-foam drilling to penetrate the fractured Kirthar and Laki limestone, offering lost circulation and the chemically and mechanically unstable Ghazij shale, offering wellbore stability and stuck-pipe risks. The study also shows the management of water influx from the Kirthar formation, reducing its impact on Ghazij shale which swells in the presence of an aquatic medium. To overcome these challenges, an efficient design of compressible, multiphase-foam system was designed along with the different base fluids utilized for the drilling. The presence of water influx always limits the effectiveness of the chemical inhibition properties of drilling fluid. This paper evaluates the optimal design of a foam system while utilizing spud mud as well as silicate mud while drilling across loss prone Kirthar and unstable Ghazij respectively. Multiphase-foam drilling offered ECD less than 2 ppg by utilizing the base fluid of mud weight equivalent to 8.7 ppg.
Foam drilling enabled the operator to drill throughout without spotting LCMs or cement plugs, resulting in saving 42% of the section allocated time. An analysis is provided with respect to management of 16 BPH of influx with foam system. A statistical comparison between ROPs while utilizing a conventional mud and foam system shows an increment of ROPs by 35% while utilizing the multiphase system. This paper focuses on engineered study of design of multiphase foam system along with the onsite execution for future prospect applications as well.