Practice and understanding on nitrogen drilling of tight sandstone reservoir in Kuqa Depression Well X

Through theoretical research and inhouse test on under-balanced (UBD) drilling technology, a set of complete nitrogen drilling programs applicable to high pressure and high production tight sandstone reservoir has been formulated, which includes reasonable gas injection equipment supporting program, bottom hole assembly, well configuration design as well as the whole technological process. Take X-Well in the east of Kuqa Depression as an example, compared with the conventional drilling fluid drilling technology used in drilling of tight sandstone reservoirs in a number of adjacent wells, the penetration rate of X Well was improved by 24.3 times as a maximum, and the drilling cycle was shortened by 62 d to the most extent, and the single well production was 4.2 times that of offset well. The success of nitrogen drilling in tight sandstone reservoir in X Well shows again that the use of nitrogen drilling technology in tight sandstone reservoir can increase the ROP, shorten the drilling cycle and increase the single well productions. It also verifies the safe practicability of nitrogen drilling technology and equipment, laying out a foundation for promoting this nitrogen drilling technology in tight sandstone reservoir of high pressure and high production in Kuqa region and even nationawide.