Abstract
Improving the drilling Rate Of Penetration (ROP) is a target for oil and gas drilling companies. However, efficient drilling performance is not only measured by the improvement of ROP, but it is also measured by minimizing the mechanical specific energy, minimizing the bit wear rate, minimizing the NonProductive Time (NDP) impacted by the pre-mature bit wear and failure, as well as by reducing the overall drilling cost. Another approach of improving drilling performance is sought through optimal applications of drilling parameters including sufficient fluid flow rate for efficient hole cleaning and bit ball prevention, applying adequate Weight On Bit (WOB) that induces effective Depth Of Cut (DOC) without negatively inducing the bit wear rate to increase, and at optimal rotary speed. This research focuses on applying various techniques through multi stage drilling and coring in high strength formation using PDC bits and natural diamond impregnated coring bits to investigate potential micro cracks generation. The analysis of drilling and coring data includes evaluation of input drilling parameters such as WOB and rotational speed as well as the output data of ROP, DOC, torque, etc. The drilling experiments were laboratory based using a large lab scale of a fully instrumented drilling simulator. A high strength rocks were drilled, and water flow rate was used. Different applied WOB and rotational speeds were applied. The results of the analyzed data indicated variation in ROP (increasing and decreasing) when drilling different stages at the same conditions of the applied parameters. ROP was increased parallel to the predrilled section, where the ROP was found decreases when drilling the un-predrilled section. Corresponding data of torque also supported the ROP increase vs. which was influenced by possible rock weakened due to possible micro cracks generation in the predrilled section. Data analysis, results, and conclusions are reported.
