Multiple fault diagnosis of down-holeconditions of sucker-rod pumping wellsbased on Freeman chain code and DCA

It is important to achieve continuous, stable and efficient pumping well operation in actualoilfield operation. Down-hole pumping well working conditions can be monitored in real-time and areasonable production scheme can be designed when computer diagnosis is used. However, it is difficultto make a comprehensive analysis to supply efficient technical guidance for operation of the pumpingwell with multiple faults of down-hole conditions, which cannot be effectively dealt with by the commonmethods. To solve this problem, a method based on designated component analysis (DCA) is used inthis paper. Freeman chain code is used to represent the down-hole dynamometer card whose importantcharacteristics are extracted to construct a designated mode set. A control chart is used as a basis forfault detection. The upper and lower control lines on the control chart are determined from standardsamples in normal working conditions. In an incompletely orthogonal mode, the designated mode setcould be divided into some subsets in which the modes are completely orthogonal. The observed data isprojected into each designated mode to realize fault detection according to the upper and lower controllines. The examples show that the proposed method can effectively diagnose multiple faults of down-holeconditions.