Stage Difference Analysis of Well Shutdown Failures in Coalbed Methane Horizontal Wells

To identify the main controlling factors of well shutdowns in different production stages of coalbed methane (CBM) horizontal wells, this study investigated the production parameters and pump inspection records of 25 horizontal wells in Huabei Oilfield. This paper first summarizes the types, causes, and impact degrees of well shutdown faults. Then, it conducts an analysis focusing on the four core production stages—water drainage, production increase, stable production, and production reduction—and clarifies that the key fault difference across stages lies in the variation in main fault types. The following results show that: (1) a total of 15 types of shutdown faults occurred during production, which are classified into four categories: coal–sand mixture-related faults, gas intrusion-related faults, supporting equipment faults, and other faults. Coal–sand mixture are the core inducement (accounting for 52%), followed by gas intrusion (accounting for 22%). (2) The impact of faults varies significantly: wellbore blockage, pump sticking, and flexible shaft breakage caused by coal–sand mixture and high current due to gas intrusion have a significant impact on production; environmental protection issues only occur in the water drainage stage and do not affect production; supporting equipment faults have a short handling cycle and minimal impact. (3) Shutdown faults exhibit obvious stage characteristics: In the water drainage stage, faults are mainly caused by environmental protection, power outage, and other factors, while high current due to pump sticking is the core downhole fault; in the production increase and stable production stages, pump sticking and flexible shaft breakage induced by coal–sand mixture are dominant; in the production decline stage, gas intrusion problems intensify, and the proportion of coal–sand mixture -related faults decreases but remains the main inducement.