Abstract: In the East China Sea, the gas reservoirs are buried deeply, and the rocks have high degree of diagenesis, strong abrasiveness and poor drillability. φ212.7mm interval was the main deep reservoir. Generally, this interval is highly deviated well section and horizontal section. The borehole extended longer, and trajectory is complex. The ROP (rate of penetration) of conventional BHA was low, resulting in the wear of casing and drilling tools. The directional instrument can't meet the requirements of wellbore trajectory controlling due to signal fail and centralizer wear. Then we have to change BHA. To solve these problems, we used Vortex BHA at φ212.7mm interval in East China Sea, and good effects were obtained. The rate of penetration improved 20%~100%, and ratio of instrument failure was controlled. The wellbore trajectory met the basic requirements of the development of geological reservoir, and good economic results were obtained. In this paper, through the first application of Vortex BHA at φ212.7mm interval in the East China Sea, we compared the advantages and disadvantages of conventional BHA with Vortex BHA, and obtained some new understandings. In addition, we knew the problems which should be improved. This can provide a reference for drilling operation.