Technical Paper: Pointing Towards Improved PDC Bit Performance: Innovative Conical Shaped Polycrystalline Diamond Element Achieves Higher ROP and Total Footage

Society: AADE
Paper Number: AADE-13-FTCE-06
Presentation Date: 2013


Vibration induced impact damage/cutter chipping caused by inefficient shearing action at the center of a PDC bit can significantly reduce ROP and overall drilling efficiency in a wide range of formations. To solve the problem, a R&D initiative was launched to investigate new cutter designs and experiment with their count/placement to improve drilling efficiency and mitigate vibration. The research yielded an innovative conical shaped polycrystalline diamond element (CDE) with an ultra-thick synthetic diamond layer.

The conical element has undergone extensive laboratory testing to evaluate its potential to improve PDC bit performance. Using a single cutter test apparatus, engineers measured the element’s ability to fracture rock at varying depths-of-cut. They determined the CDE exhibits up to a 70% increase in cutting efficiency compared to standard PDC cutters.

Next, an existing PDC bit was modified to include the new conical diamond element at bit center. The CDE was positioned at bit center with the conical tip pointing vertically down towards the rock. The location of the conical element combined with the optimized placement of the conventional PDC cutters allows an unconfined rock column to develop. The stress relieved column is then continuously crushed by the centrally positioned conical element. This solves the fundamental center cutting structure issues enabling the bit to deliver faster penetration rates and reduce the potential for vibration.

A base Mi616 type bit was fitted with a CDE and run in North Dakota and Utah through a highly mixed sequence of formations where the primary objective was to increase ROP and to reach kick-off point (KOP) in one run. The CDE equipped PDC bit improved ROP over a longer interval drilled compared to benchmark PDCs used in offsets. Subsequent field testing has substantiated the CDE’s potential and how it can be used to deliver improved PDC bit performance.

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