Well drilling device and method for controlling bottom hole pressure by monitoring flow

The invention discloses a well drilling device and method for controlling bottom hole pressure by monitoring flow. The well drilling device comprises a slime pump inlet flow measuring system, a return pressure pump inlet flow measuring system, a drilling liquid reversing-out flow measuring system, an automatic throttling pipe converging system, a rotation control head, a liquid-gas separator and a vibration screen. The inlet of the slime pump inlet flow measuring system is connected to a slime tank through a pipeline. The outlet of the slime pump inlet flow measuring system is connected to a drilling rod through a pipeline, reaches the rotation control head from a drill and a borehole by passing the bottom of the drilling rod in an annular space mode, and is communicated with an inlet pipeline of the automatic throttling pipe converging system and an outlet pipeline of the return pressure pump inlet flow measuring system. The return pressure inlet flow measuring system is connected to the slime tank through a pipeline. The outlet of the automatic throttling pipe converging system is connected with the inlet of the drilling liquid reversing-out flow measuring system. The outlet of the drilling liquid reversing-out flow measuring system is connected with the inlet of the liquid-gas separator through a pipeline. The liquid-gas separator is provided with two branches, wherein one branch is connected to the vibration screen and connected to the slime tank through the vibration screen and the other branch is connected to a combustion opening. The well drilling device and method for controlling the bottom hole pressure by monitoring the flow can effectively control or eliminate adverse affection on well drilling, wherein the adverse affection is caused by shaft bottom leakage and losses or overflowing which can cause.