Drilling speed improving techniques in Fudong area of Zhunggar Basin

The geological condition in Fudong area of Junggar basin is complex. The upper formations are well developed with mudstone, so the wellbore stability is weak. Abnormal high pressure exists in the lower formations, and the homogeneity of rock is poor with multiple interbeds. All of them lead to the difficulty of bit type selection and wellbore structure optimization, high frequency of downhole accident, low rate of penetration and long drilling duration. Matched technologies to improve drilling speed are researched, such as formation pressure analysis and rock characteristic parameters assessment, wellbore structure optimization, PDC bit type selection, and drilling mud selection. And great achievements have been obtained. Compared with the previous scenario, the average rate of penetration is increased by 30.4%, downhloe accident ratio is reduced to 0.35% and drilling duration is reduced by 10.5 d. The no technical casing program has been realized on many wells, and the drilling cost is greatly decreased. Application of the technology has succeeded in the area, and it plays a very important role in accelerating the process of oil and gas exploration in Fudong area.