Analysis on the workover reasons for complex CBM well and test on rod checking technology

Workover is carried out frequently when complex coalbed methane (CBM) directional wells of over 1 100 m deep are in operation. However, the conventional workover technologies by pump inspection can not deal with this purpose effectively. Under this background, the reasons for the workover of 50 CBM wells in Block C were analyzed and compared. It is shown that tubing leakage,pump failure and sucker rod dropout are the main reasons for frequent workover, and mechanical wear and serious corrosion are the dominant influential factors of workover. Then, a new operation mode which is about rod testing workover, was proposed. The rod testing operation is a suite of technical measures, including downhole equipment service state prediction, supporting techniques and construction and operation. It is characterized by simple process, short construction period and high input/output ratio. Field applications have demonstrated that the rod testing is an economical and effective workover technology suitable for complex CBM wells.