An Experimental Study on the Impacts of Using Multiple PDC Cutters on Rock Cutting Process

The ultimate goal in drilling in oil and gas applications is to improve the rate of penetration (ROP) and one important factor that affects the ROP enhancement is Drill Bit. Today, PDC bit plays a significant role in drilling all types of formations. Besides the material development, bit design or a way of cutters arrangements on a bit is a regular challenge for bit designers to improve the bit performance. This concept has been experimentally studied in this work. Different sets of cutters arrangements containing three PDC cutters on a flat bit profile have been used to conduct a variety of experiments under atmospheric pressure on different rock samples including shale, sandstone, and limestone. Different cutters arrangements including spiral and reverse spiral sets and different spacing between the cutters are selected to investigate these bit design parameters. The measured forces for those two specific sets (spiral and reverse spiral) show the equal normal force but different forces on the bit plane. It is found that radial force on a cutter besides the cutter engagement area is also affected by changes in the cutting shape or cutting area. The efficiency of one specific cutters layout can be recognized by MSE and lateral force, as a tool to indicate stability. A force model is proposed to predict the acting forces on one PDC cutter and then, to integrate it into a full PDC bit. The model can be used as a reliable tool to study the rock-cutter interactions during the cutting process to avoid cyclic loading and damage to the cutters and to enhance the bit life. The experimental results show that cutters arrangements on bit strongly affect the bit performance. In the scope of this work, lower MSE can be obtained by a reverse spiral set of cutters arrangement but regards to the lateral force and stability, arranging the cutters spirally can provide better results.