MPD wellbore pressure control method based on linear throttle valve

To address the key problems influencing the pressure control accuracy in the process of MPD, this paper carried out original researches from bottom-level control hardware to top-level calculation model and control method. Firstly, in view that existing throttle valves can hardly realize fine back pressure control, a new concept of linear pressure drop control of axial dynamic optimization of open area was put forward, and the throttle valve whose pressure drop varies linearly with the opening in the opening range of 25%-85% was designed. Then, in view that wellbore pressure can be hardly calculated accurately and the control model is complicated, a kind of real-time model coefficient prediction method was established to realize the real-time accurate calculation of bottom hole pressure. Finally, wellbore pressure serials control was realized by means of fast back pressure control, so as to solve the difficulty in the fine wellbore pressure control. Wellbore pressure control module was developed, and the control method was verified by virtue of experiment and application, which showed that the control accuracy of bottom hole pressure is up to 0.2 MPa. The research results provide theoretical and technical support for the fine wellbore pressure control.