Abstract: The passage analyzed the application of unconventional Ø241.3 mm hole in the Bohai Region. Through establishing the BHA control equation of the unconventional wellbore, the finite difference method is used to analyze the variation of BHA of Ø241.3 mm borehole with WOB and the position of the stabilizer, the passage concluded that the stabilizer combined with the single stabilizer should be placed above 18 m from the bit and WOB should be below 150 kN. When the stabilizer is placed at about 18 m from the bit, the well inclination can be controlled within a large range of WOB and the deviation prevention effect of double stabilizer combination is better than single stabilizer combination. Results also show that the ROP of Ø241.3 mm borehole is better than that of Ø311.2 mm borehole and the posiible complex situation of Ø241.3 mm borehole is less than that of Ø311.2 mm borehole as well, when analyses ROP and complex situation prediction of the two kinds borehole.