Well blockage mechanism and blockage removal technology in Keshen 2 Gas Field

76% of the gas wells in Keshen 2 Gas Field in Kuqa foreland of Tarim Oilfield suffer well blockage, which leads to the decrease of tubing pressure and gas production rate and even shut down and off production. The on-site sandwash sampling by coiled tubing shows that well blockage mainly occurs in local hole sections. The “microscopic+macroscopic” analysis reveals that the stemming is mainly composed of calcium carbonate scale and there is complex blockage of “circumferential reservoir+well”. The developed blockage removal fluid system of “9% hydrochloric acid+1% hydrofluoric acid” has the scale dissolving capacity of 94.42% and the sand dissolving capacity of 34.17% and meets the requirement on the corrosion rate of 13 Cr tubing. Four sets of blockage removal technologies with “connection of tubing and casing?” and “existence of liquid injection pathway?” as the main considerations are prepared based on the cognitions on the blockage laws. In addition, the “well blockage removal” is upgraded to “well-circumferential reservoir” blockage removal. By the end of 2019, blockage removal operation of gas well had been performed 14 well times in Keshen 2 Gas Field, and its efficiency is 86%. After the operation, average single-well tubing pressure is increased from 29.7 MPa to 44.1 MPa, average single-well absolute open flow is increased from 26.8×10⁴ m³ to 123.3×10⁴ m³ and production rate is increased by 3.6 times. In this way, failed wells and abnormal wells are recovered efficiently. The research results provide the reference for the blockage treatment in other domestic and foreign oilfields with the same geological and well conditions as the high pressure gas field in Kuqa foreland.