L2 formation of X Oilfield in western South China Sea is of characteristic of low porosity, low permeability and well controlled reserves, and long well interval, drainage area and controlled reserves can be significantly increased by adopting ultra-short radial radius drilling technology. Flexible drill pipe and drill bit was used in Well WZ-X1 to perform kick-off operation with only 2.4 m footage to increase inclination from 37 °to 87 °, and hold its inclination by drilling 60-62 m alongside reservoir with trajectory control margin of ±2°. This paper highlights the trajectory control technology with research of BHA, build-up and hold drill bit, and accurate calculation. During the field operation, drilling parameters were adjusted on the basis of formation variation and outstanding trajectory effect was accomplished and ultra-short radial radius trajectory control technology was achieved. This technology can solve the problem of trajectory control and extend horizontal section of reservoir. It can increase wellbore drainage area and well control reserves, providing technical reference for future operation.

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