Implementation of Circular Wave Measurements and Multiple Drilling Parameter Analysis in Rock Anisotropy Evaluation

A laboratory procedure has been developed to evaluate the anisotropy of Rock Like Material (RLM), granite, red shale, and green shale. This procedure involves detailed anisotropy evaluation steps through implementing circular ultrasonic wave velocity measurements, representing physical measurement and multiple drilling parameters (MDP), representing drilling performance. The physical tests involved circular pattern measurements of compressional and shear wave velocities, VP and VS, respectively. The drilling tests involved drilling samples of each rock in different a 25.4 mm Diamond Coring bit. The MDP included the study of the variations of Rate of Penetration (ROP), bit cutter Depth of Cut (DOC), Revolution Per Minute (RPM), and Torque (TRQ). The MPD were studied as function of orientations under atmospheric pressure. In addition to the physical and drilling evaluation, mechanical tests, such as Oriented Unconfined Compressive Strength (OUCS) were also used in rock anisotropy evaluation. Concrete with fine aggregate and Portland cement is used as RLM for much of the laboratory work. This material was cast into cylinders measuring 101.6 mm by 152.4 mm and 203.2 mm by 203.2 mm, from which NQ; 47.6mm core samples were taken. Coring was performed in three main orientations including 0°, 45°, and 90°. Characterization tests were performed on the RLM cores as they were conducted on the natural rock that included granite and red shale as isotropic and vertical transverse isotropic rocks, respectively. A fully instrumented lab-scale rotary drilling rig was used in conducting the drilling experiments. Details on the strategy for the tests on the anisotropy evaluation with results from laboratory work on natural rocks and RLM are reported. Result of the effect of shale anisotropy orientation on the drilling parameters that influence ROP as means of anisotropy evaluation are also, reported.