ENGINEERING GEOIOGY PROBLOMS OF DEEP DRILLING AND ITS STRATEGY IN SICHUAN NATURAL GAS WELL

Geologic setting is complicate in Sichuan basin. Due to unforeseeable engineering geology problems that make the discrepancy of real drilling and design, and results in drilling complication and trouble. It not only endangers safety drilling and realization of geologic target, but also restricts seriously the improvement of drilling speed and increases drilling cost. The paper analyses the main engineering geology problems of deep drilling and their features in Sichuan natural gas well, such as abnormal formation pressure,sidewall unstability, and reservoir damage etc., and proposes preventive measures.At the same time, the paper also proposes that treatment the relation of four pressures well (formation pressure, caving pressure, leakage pressure and drilling fluid pressure) and analysis drilling engineering geology problems during drilling design and operation are very important. It is key of improvement design quality and realization safety drilling. Drilling engineering is special geologic engineering. The establishment of Drilling Engineering Geology has important significance for the development of drilling technology and improvement of drilling benefit.