Application of self-oscillating rotary percussion drilling tools in Shengli Oilfield

The self-oscillating rotary percussion drilling tools are set above the bit. The drilling fluid flows through the self-oscil-lator with high speed and hydraulic pulse is formed and is imposed on the percussion transmission rod, following with the generation of low amplitude but high frequency mechanical shock power, which can be passed to the bit and improve the rock breaking efficiency. The generated hydraulic pulse is transmitted down further and blown off through bit ports, which will form pulse jet flow and can improve the downhole flowing domain and the efficiency of downhole cleaning. Meanwhile, the instant negative pressure pulse generates local instant underbalance and changes the rock breaking stress status of downhole rock surface, which improves the rate of penetration sig-nificantly. The system is tested in Sha-3 and Sha-4 formations in Shengli Oilfield. The results show the rate of penetration is significantly increased no matter with cone bit or PDC bit, and the rate of penetration of all the tested formation sections increases more than 30%, so the technique could be a novel method of increasing the rate of penetration.