Abstract: The exploration focus of Bohai Oilfield is gradually moving towards the middle and deep strata, which are characterized by high compressive strength, poor drillability and difficult deviation control.When the high-dip packed hole assembly which is used in conventional vertical wells is used for the drilling of middle and deep strata, the important factors restricting the improvement of rate of penetration (ROP) are difficult deviation control and small adjustable range of weight on bit (WOB).The field application in BZ19-6 Block shows that the contradiction between borehole inclination and WOB is solved well by introducing the vertical-guide bottom hole assembly (BHA).And a result, the ROP is improved, the borehole inclination is well controlled, the wellbore quality is guaranteed effectively, and the operation cycle is shortened significantly.In conclusion, the vertical-guide BHA is worthy to be popularized and applied in the subsequent exploration drilling.