Abstract
Coring natural rocks (granite) and synthetic rocks (rock like material, RLM) using diamond impregnated coring bit was performed by A rigid coring system. RLM and granite were previously tested to be isotropic rocks by the author [1, 2, 3, 4] A baseline procedure was developed for isotropic rock characterization [2] and this work is to contribute to the developed baseline procedure by considering downhole dynamic weight on bit (DDWOB). The drilling parameters involved in the analysis included rate of penetration (ROP) depth of cut (DOC), rpm, and torque. All parameters were studied as a function of DDWOB at 300 and 600 input rpm. A fully instrumented laboratory scale rotary drilling rig was used with 5 liter/minute water flow rate. Samples were first cored in 47.6 mm diameter in the desired orientations. Samples of granite were cored in two perpendicular directions (vertical and horizontal) and samples of RLM were cored in three directions including vertical, oblique, and horizontal. The coring experiments were performed using 25.4 mm diamond impregnated coring bit. At each input rpm and at each applied static weight, multiple coring runs were repeated and then averaged; therefore, each point of the displayed data was averaged of at least three repeated experiments at the same inputs. DDWOB was recorded by a load cell fixed beneath the sample holder and connected to a Data Acquisition System that records at 1000 HZ sampling rate. Several sensors were used to record the required data, including operational rotary speed, advancement of drill bit for ROP calculation, and motor current for torque measurement. Results showed similar trends in different orientations at the same inputs demonstrating RLM and granite isotropy. The results also showed the influence of DDWOB on ROP, DOC, rpm, and torque (TRQ) expanding the baseline procedure through considering DDWOB for isotropic rock characterization.
An experimental investigation into the borehole drilling and strata characteristics
