Evaluation on the Production Effect of Coiled Tubing in Fuling Shale Gas Field

Coiled tubing (CT) is widely used in the Fuling Shale Gas Field as a gas production string, and its specifications are mainly ϕ50.8 mm×4.45 mm and ϕ38.1 mm×3.68 mm. The production effect of CT in different shale gas wells are different. For the goal involved analyzing the reasons for the differences and improving the application effect of CT in shale gas wells, based on the field applications, the production effect of CT was evaluated from the perspectives of shale gas well liquid carrying effect, wellbore pressure loss and stable production capacity of gas wells. Further, the influences of CT diameter, setting depth and setting timing on CT production effect were analyzed. The results showed that the critical liquid carrying capacity could be reduced by 38% using ϕ50.8 mm×4.45 mm CT rather than the ϕ60.3 mm×4.83 mm conventional tubing. The water gas ratio had a significant influence on the production effect of coiled tubing. The larger water gas ratio, the CT diameter and setting depth could more significantly influence the wellbore pressure loss and gas well stable production time. For shale gas wells with a water gas ratio of 0–1.5 m³/10⁴m³ the earlier the ϕ50.8 mm×4.45 mm CT was set, the longer the stable flow production period, and the higher the cumulative gas production in the flow production period. The research demonstrated that the application of CT could achieve the continuous and stable production of shale gas wells with low water gas ratio, and the result could play a guiding role in improving the application effect of CT in Fuling Shale Gas Field.