Horizontal well reversed drilling tool combination designing method

The invention discloses a horizontal well reversed drilling tool combination designing method. The horizontal well reversed drilling tool combination designing method comprises the following steps of giving all design parameters; calculating a drill column axial force at a starting point of a horizontal section; calculating a drill column spiral buckling factor at the starting point of the horizontal section; judging whether a drill column of the horizontal section buckles spirally or not; calculating a drill column spiral buckling factor corresponding to a common drill pipe of a deflecting section; judging whether the common drill pipe of the deflecting section buckles spirally or not; calculating a hole drift angle corresponding to a depth of setting of a heavy weight drill pipe; calculating a drill column axial force at the position of the depth of setting of the heavy weight drill pipe; calculating a drill column spiral buckling factor of a well section of the heavy weight drill pipe; judging whether the heavy weight drill pipe buckles spirally or not; calculating a drill column axial force at a deflecting point; and calculating the using length of the heavy weight drill pipe. According to a drilling tool combination designed by the method, spiral buckling of the drill column on the lower portion can be avoided, friction resistance is reduced, and bit pressure transmission efficiency and horizontal extension capability are improved.