Practice and recognition of nitrogen drilling in Mandong-2 well

In order to prove the petroliferous situation of the Silurian system in Mandong-3 structure belt, combined with the reservoir characteristics of Mandong-2 well in Tarim Oilfield, nitrogen drilling is performed in the hole section ranging from 5818.50 m to 6200.00 m. Before the nitrogen drilling, the problems existing in the well and the solutions are studied. Based on this, the casing program, the bottomhole assembly (BHA), and the measurement while drilling (MWD) are designed. Meanwhile, corresponding plans to deal with all kinds of problems may occur in operation are developed. The Mandong-2 well is the first to be drilled by gas in desert hinterland in China. It also hits the record that the hole depth is the highest in gas drilling in China. The footage of nitrogen drilling interval is 381.5 m, the average penetration speed is 5.44 m/h which is 5.4 times higher than the mud drilling penetrating speed of Mandong-1 well next to it although they lie in the same structure and the same zone. The highest penetrating speed of it reaches 149.2 mm borehole in the deep zone in Tarim Oilfield. Two drilling bits are used in nitrogen drilling, the drilling time of a single drilling bit is 45 ∶ 05, and the footage is 230.4 m. It breaks the record of the maximum footage of a single drilling bit being 149.2 mm borehole in the deep zone in the oilfield. The successful operation of the nitrogen drilling of Mandong2 well shortens the drilling period, accelerating the exploration of the Mandong-3 structure belt. Valuable experience has been accumulated for the deep slim hole nitrogen drilling in China. It can be a good reference to the nitrogen drilling in similar wells.