Benchmarking Drilling Performance of PDC and Hybrid Bits in an OffshoreInterbedded Environment,Based on Bit Design and Features

摘要

Interbedded formations are challenging to drill due to its potential to trigger torsional instability issues whiledrilling at low depth-of-cut(DOC),which could damage the bit due to impact and result in low penetrationrate or an undesired trip.Wells drilled in the Guyana-Suriname Basin face a similar challenge as the wellspenetrate interbedded shale and carbonates,causing conventional polycrystalline diamond compact(PDC)bits to lose their cutting efficiency due to impact damage while drilling the hard,interbedded formation.Using a detailed bench-marking methodology,offset drilling data was analyzed and the results wereutilized to optimize bit design to meet these challenges.Mechanical specific energy(MSE),which quantifiesdrilling efficiency,indicates formation changes and signals the advanced dull condition or damage.Whencoupled with dull bit forensics,MSE provides insight for iterative bit design optimization to mitigate drillingchallenges.The outcome of a detailed benchmarking process led to the selection and deployment of a 12 1/4-in.hybridbit to drill directionally through interbedded formation,which significantly improved drilling performanceand bit durability.The hybrid bit combined PDC and tungsten carbide insert(TCI)rolling cutting elementsand delivered balanced aggressiveness to improve torisonal stability.Post-well analysis showed rolling DOCcontrol offered by the hybrid bit delivered higher penetration rate.The comparison of the drilling mechanicsof the hybrid versus PDC highlighted limited drilling efficiency of PDC bits in interbedded formation.Thehybrid bit drilled 54% more carbonates than the best PDC offset run.Drilling dynamics data also highlightedlower levels of vibrations with the hybrid bit.In addition,the hybrid dull condition was better than the PDCbits,suggesting improved durability compared to the previously-used PDC bits.This paper demonstrates time and depth based surface and downhole drilling data,when supplementedwith rock strength analysis using a suitable benchmarking process,can provide insight about drillingmechanics.When matched with an application specific bit,it leads to sustained drilling performanceimprovement.