STUDY ON FEATURES OF FIXED THROTTLE VALVE

In order to balance formation pressure during drilling, throttle valve is required to provide back pressure towards hole bottom. And it is impossible to provide sufficient back pressure to balance the formation pressure by only one throttle valve when drilling through high pressure formation. During the actual field work one fixed throttle valve and one adjustable throttle valve are often combined together to exert enough back pressure. The fixed throttle valve adopts an elongated bore to realize pressure reduction, which can reduce the pressure of the incoming liquid down to below 50 MPa so as to adjust the back pressure exerted on the hole bottom safely and reliably to kill the well successfully. Therefore the fluid dynamics theories and the advanced flow analysis software ANSYS are used to conduct numerical calculation and analysis regards the effects of bore diameter and length of the fixed throttle on pressure reduction. The study results show the numerical calculation results are similar to the theoretical values, which has provided theoretic basis for proper selection of fixed throttle at the well site.