10:45 AM - 11:00 AM
[MGI31-01] Experimental investigation of the applicability of rate of penetration model considering the degradation of PDC bit owing to bit wear
Keywords:Drilling, Rate of penetration model, PDC bit, Wear
Rock drilling is often required at the beginning of geological industrial activities such as georesource exploitation. A rate of penetration (ROP) model describes how fast a bit drills, and its accuracy is of importance in optimizing the drilling plan and thus promoting geological industries. Bingham (1964) analyzed the data of laboratory drilling experiments using a roller-cone bit and proposed a model in which ROP is proportional to the power of the weight on bit (WOB). In the model, the pre-exponential coefficient, a, and the exponent, b, are rock-dependent constants. However, ROP decreases as the bit gets worn with drilling, even for the same values of WOB and rock strength. Miyazaki et al. (2022) conducted laboratory drilling experiments using polycrystalline diamond compact (PDC) bits with different degrees of wear and proposed an ROP model in which the pre-exponential coefficient, a, depends on the wear degree while the exponent, b, is constant regardless of the wear degree of bit. Miyazaki’s model is based on the laboratory experimental data obtained by drilling the rock specimens with uniaxial compressive strengths of 80-120 MPa using the PDC bits before and after use at actual drilling sites. Its applicability beyond the conditions of Miyazaki et al. (2022) should be investigated by performing laboratory drilling experiments under different conditions, e.g., wear degree of bit and rock strength.
In the present study, we analyzed the experimental data obtained by drilling the rock specimens with the comparable or higher strength than those used in Miyazaki et al. (2022), using a smaller PDC bit than that used in Miyazaki et al. (2022), with four different degrees of wear. The analyzed data include those reported by Imaizumi et al. (2017). The data for the highest degree of bit wear are currently being analyzed. The exponent, b, of the bit at the very early stage of the drilling operations was significantly higher than that of Miyazaki et al. (2022), whereas the results for the other two degrees of bit wear appeared to be almost consistent with Miyazaki et al. (2022). The exponent, b, was independent of rock strength, when the degree of bit wear was the same. These results suggest that the Miyazaki’s model is broadly applicable to the cases where the wear degree of bit and rock strength are in the typically expected range of actual drilling, with the exception of the very early stage of drilling. The experimental data analyzed in the present study were partly obtained in a research and development project of Japan Organization for Metals and Energy Security.
In the present study, we analyzed the experimental data obtained by drilling the rock specimens with the comparable or higher strength than those used in Miyazaki et al. (2022), using a smaller PDC bit than that used in Miyazaki et al. (2022), with four different degrees of wear. The analyzed data include those reported by Imaizumi et al. (2017). The data for the highest degree of bit wear are currently being analyzed. The exponent, b, of the bit at the very early stage of the drilling operations was significantly higher than that of Miyazaki et al. (2022), whereas the results for the other two degrees of bit wear appeared to be almost consistent with Miyazaki et al. (2022). The exponent, b, was independent of rock strength, when the degree of bit wear was the same. These results suggest that the Miyazaki’s model is broadly applicable to the cases where the wear degree of bit and rock strength are in the typically expected range of actual drilling, with the exception of the very early stage of drilling. The experimental data analyzed in the present study were partly obtained in a research and development project of Japan Organization for Metals and Energy Security.