Oil and gas production handbook An introduction to oil and gas production

Well workover is the process of performing major maintenance on an oil or 
gas well. This might include replacement of the tubing, a cleanup or new 
completions, new perforations and various other maintenance works such as 
the installation of gas lift mandrels, new packing, etc.  
 
Through-tubing workover operation is work performed with special tools that 
do not require the time-consuming full workover procedure involving 
replacement or removal of tubing. Well maintenance without killing the well 
and performing full workover is time-saving and often called well