Abstract: The low rate of penetration (ROP) through the mudstone cap rock over the high pressure reservoirs in the oilfields in western South China Sea has been a challenge that perplexes the field operation.This paper focuses on the mechanism that cause the low ROP and summarizes a set of drilling speed-up technique appropriate for the mudstone cap rock by comparing the effect of different drilling speed-up methods used in the field. The study shows that the application effect of hydraulic pulse tool is remarkable, as evidenced by the facts that the ROP is increased 2.86 times in the 311.2 mm section and 2.56 times in the 215.9 mm section, respectively. It provides a reference to the subsequent offshore operations with the similar geological condition.