Cause Analysis on Casing Pressure Increasing and Tubing Connections Galling in Well DN2-6

The cause of casing pressure increasing in well DN2-6 was investigated and tubings taken out from this well were inspected one by one. It was found that there were one tubing pierced and many tubings connections galled, and the galling reason was also analyzed. The results show that the tubing perforation resulted in the casing pressure increasing, and tubing connection gallings were caused due to abnormal operation. Galling would reduce the tubing connection seal capability, but the galling tubing connections did not leak because the internal pressure borne by the tubing string was smaller than that of its seal capability after tubing perforation leaking.