Developing calibrated models of bit-rock interactions
Varel UK Ltd manufactures and services application specific roller cone and fixed cutter drill bits. The company has a track record of innovation and also of collaboration with Scottish Universities in the design and manufacture of small drill bits.
High Rates of Penetration (ROPs) with a good borehole stability in hard rock or heterogeneity formation (eg: Chert, Conglomerates, Granite) remains one of the major challenges in downhole drilling. Existing methods in these rock types using fixed cutter bits usually lead to uncontrolled energy distribution resulting in multiple and slow bit runs, or risks of roller cone bit bearing failures and lost time fishing cones. Varel identified a need to develop a more effective way of drilling offshore frontier fields that contain sections with chert or fractured granite/ conglomerates.
This development would be a significant advance in drill bit design, offering cost benefits by reducing drilling time and maximizing bit life in exploration and development drilling.
Having engaged with OGIC, Varel embarked on a research collaboration with the University of Aberdeen. The project aimed to gain better understanding of the mechanics of force generation and its relationship with the drilling parameters. The research involved an extensive experimental study to collect data allow to develop calibrated mathematical models.
The project was carried out in the state of the art drilling rigs available at the Centre for Applied Dynamics Research (CADR) of the School of Engineering, the University of Aberdeen.
These rigs allow investigation of the cutting mechanics of a single insert and drilling through various rock formations at different rotary speeds and Weight on Bit (WOB).
The University performed a comprehensive experimental assessment of the performance single cutters and micro drillbits to determine the influence of its design on the efficiency of drilling through hard formations.
“This has been highly rewarding experience for the University to work with the Varel team on such a fundamental and practically important project. The findings should facilitate development of a new mathematical model for interactions between drill-bits and drilled formations and ultimately lead to designs of highly competitive new generation drill-bits”.
Marian Wiercigroch, Professor of Engineering, University of Aberdeen
“Aberdeen University Engineering have been excellent partners in this project which, in its approach, has broken new ground and led to several paths of research worthy of further investigation”.
Jason Marchant, North Sea Manager, Varel UK Ltd