基于三级反馈调节的控压钻井回压自动调控方法

井口压力的自动调节与反馈控制是控制压力钻井技术(MPD)得以成功应用的根本。现有的井口回压控制方法较少考虑节流阀系统结构特征及流通特性，存在控制响应慢，控制效果差的问题。针对井口回压控制上述问题进行研究，基于节流阀的工作特性、电液比例控制原理、反馈控制方法，提出了一种井口压力三级反馈控制方法，实现了一级开度曲线双向反馈控制，二级井口回压快速粗调，三级井口回压精细反馈控制。制定了该三级反馈控制方法的详细实现流程，开发了井口回压控制模块，通过实验验证了控制方法的响应时间和精度，井口回压控制精度误差在±0.1 MPa以内，新的井口回压精细控制方法为井筒压力的精细控制奠定基础。

Automatic backpressure control techniques of MPD drilling based on three-layer feedback regulation method

The automatic regulation and feedback control of wellhead pressure is fundamental for the successful application of managed pressure drilling technique (MPD). Existing wellhead backpressure control method has less consideration on the structural and circulation characteristics of the throttle valve system, which results in the problems of slow control response and poor control effect. In order to solve these problems, this paper proposed a new three-layer feedback wellhead pressure control method based on the operating characteristics of throttle valve, the electro-hydraulic proportional control principle and the feedback control method. In this method, the first control layer is opening curve bidirectional feedback control, the second layer is fast rough regulation of wellhead backpressure and the third layer is the refined feedback control of wellhead backpressure. Then, the detailed implementation process of this three-layer feedback control method was formulated and the wellhead backpressure control module was developed. Finally, its response time and accuracy were experimentally verified. It is indicated that the wellhead backpressure control accuracy is within ±0.1 MPa. This new refined wellhead backpressure control method lays the foundation for the refined control of wellbore pressure.