Theoretical and Experimental Studies of Internal Cuttings Removal Bit

Abstract

Abstract The oil and gas exploration without rig (also known as badger exploration) is a novel exploration technology that removes the need for fixed rig drilling, bringing with it the promise of huge savings in terms of time and money and its low impact on the environment. The implementation of this technology is an autonomous exploration tool, which can drill into rock using an electrically powered bit to loosen and crush the formation ahead of it, and crushed cuttings is moved through the device and deposited in the space behind it. Because there is no drilling fluid in badger drilling, a new way of transporting cuttings is urgently needed. In this paper, a new kind of bit named internal cuttings removal (ICR) bit is developed for badger exploration, and it can not only drill rock but also collect and transport cuttings to the bit behind through the inner cavity of the bit. Compared with the common polycrystalline diamond compact (PDC) bit, the junk slots are removed, but the helical blades and screw conveyor are added on the ICR bit. Theoretically, the two effects of rotating helical blades on cuttings moving are studied, based on the conditions of low and high rotating speed, respectively. Moreover, the rate of cuttings removal of the ICR bit is given in formulas, and in order to ensure the cuttings is removed from bottomhole timely, and the maximum permissible rate of penetration (ROP) of the ICR bit is proposed. Finally, two samples of the ICR bit with different structural parameters were built and tested in dry and wet rock drilling experiments, and experimental results show that the ICR bit can achieve the expected goal of ICR, but wet cuttings has a significant influence on the performance of the ICR bit. By comparing the drilling results of two bits, it can be found that the concave blade surface, a small number of blades, and small inner cone angle have the positive effects on the cuttings removal of the ICR bit. The above work is helpful for the development and implementation of badger exploration technology.