Abstract:

The traditional automatic control of CBM is easy to overshoot and lag, making the automatic control technology of CBM recovery just stay in the level of data acquisition and simple remote control. Therefore, the problems existing in the traditional PID control algorithm in the automatic control of CBM drainage is discussed, and the causes of over harmonic and lagging phenomenon are analyzed, so as to put forward the loose coupled automatic control technology of CBM wellbore flow rule model combined with PID control algorithm. The upper computer adopts digital analog multi parameters coupling to reduce the difficulty of automatic control, after that, initializes user instructions. In the loosens coupling algorithm, the digital analog parameters are used as the error range value to improve the efficiency of PID control and effectively make up for the shortcomings of traditional one. Loose coupling automatic control can also avoid the destructive development of single parameter control, which is suitable for many unique production modes of CBM, such as slow flow pressure reduction by constant casing pressure and constant production, and slow casing pressure reduction by steady flow pressure. It has a high popularization value in the automatic drainage of CBM.

Key words: coalbed methane（CBM）, wellbore flow, loosely coupled, PID control, auto-control