Effect Evaluation of Drainage Gas Recovery by Velocity String in Sulige Gas Field

The universal features of the gas wells in Sulige gas field are low pressure, low production rate, and the liquid-carrying capabilities of the wells that are poor. Accompanied with the gas well entering the process of middle and late life span, the pressure of the well bottom gets low and the liquid-carrying capability of the well becomes poorer. Liquid-carrying capability of gas well could be effectively improved by using velocity string. However, the former effect evaluations of drainage gas recovery by velocity string are confined to individual well. On the basis of all the gas wells which use the technology of velocity string in Sulige gas field, classification evaluations are made in this paper according to the pretest gas production rate. The technological principle of drainage gas recovery by velocity string is analyzed, and the model of critical liquid-carrying which fits for Sulige gas field is derived. Then, coiled tubing of φ38.1 mm is optimally selected which serves as velocity string according to this model. Finally, the scope of applications of drainage gas recovery by velocity string in Sulige gas field is obtained and the new application fields of this technology are proposed.