Experimental investigation on identification of lithologies and layered rock interface based on drilling vibration response

Abstract

The rapid and accurate acquisition of lithologies and rock interfaces is an important prerequisite for guiding the development of oil gas and solid mineral resources as well as the construction of tunnel engineering. However, few studies have been conducted to identify the lithologies and rock interfaces using drilling information. The author used a drilling test platform and an integrated drilling information acquisition system to conduct drilling vibration tests on rock samples of limestone, sandstone, and coal with different lithologies and rock strengths. The test results indicated the following: 1) The drilling vibration response can characterize the properties of the lithology and rock strength and can be used as a key index to distinguish the lithologies and rock layer interface. 2) There were substantial differences in the drilling response (WOB and torque) and vibration response (vibration velocity, acceleration, and amplitude) of the single rock sample. The mean axial vibration velocities of coal, limestone, and sandstone were 5.6, 7.3, and 13.9 mm/s, respectively. The mean axial vibration accelerations were 9.2g, 32.3g, and 13.1g, respectively. The mean amplitudes of the rock surface were 402.6, 588.3, and 2003.8 μm, respectively. The mean weight on the bit was 1.3, 2.6, and 3.5 kN,1 respectively, and the mean torque was 12.3, 25.1, and 33.6 N m, respectively. 3) For the combined rock samples, the drilling and vibration responses of the layered rock interface showed an evident surge. 4) The rock strength affected the drilling and vibration responses. The stronger the rock, the higher was the drilling response (WOB and torque), higher the vibration acceleration, and lower the vibration speed and amplitude. The drilling vibration response displayed a high sensitivity to rock strength. It could effectively characterize the strength characteristics of the rock to accurately identify the lithologies and layered rock interface.