Physical-mechanical and Drillability Characteristics of Ziliujing Conglomerate Formation in Western Sichuan Basin of China
Tianshou MA1#+, Yun ZHANG1, Qiang SU2, Nian PENG1, Gongsheng ZHU1
1Southwest Petroleum University, China, 2PetroChina Southwest Oil & Gas Field Company, China

The conglomerate rock is usually featured by strong heterogeneity, high abrasiveness, and poor drillability due to its complex composition and texture, which brought a huge challenge for drilling efficiency. In order to guide the drill bit selection and high-efficiency drilling, the physical, mechanical, and drillability characteristics were investigated for conglomerate rock that collected from the lower Jurassic Ziliujing formation in the Western Sichuan Basin of China. The mineral composition, SEM micro-structure, P- and S-wave velocities, uniaxial and triaxial compressive testing, drillability, abrasiveness were systematically tested and analyzed. The mechanical properties and anti-drilling ability of Ziliujing formation were proposed for a typical deep well of S-07, and the distribution characteristics were analyzed. The results indicated that the Ziliujing rock is rich-in quartz and clay minerals, due to the co-existing of strong quartz gravel and weak argillaceous cement, the Ziliujing rock shows strong heterogeneity. The relationships are roughly linear among UCS, drillability, and grinding weight loss with P-wave velocity. The Young’s modulus, UCS, internal friction angle, drillability, and abrasiveness meet the Weibull distribution pattern, while only the Poisson’s ratio meets the Kernel Smooth distribution pattern. The Ziliujing formation has the Young’s modulus of 38.61±17.08GPa, the Poisson’s ratio of 0.327±0.006, the UCS of 93.02±40.89MPa, the internal friction angle of 49.21±11.00°, the drillability of 8.04±1.54, and the abrasiveness grade of 4.32±1.94. The mechanical properties and anti-drilling ability of logging interpretation are in good agreement with the experimental data. Thus, the Ziliujing formation is a kind of hard rock with strong heterogeneity, high strength, poor drillability, and medium abrasiveness. The physical-mechanical and drillability results can be utilized to guide the drill bit selection and high-efficiency drilling.