No abstract

The Horn River shale gas play has been estimated at 500 TCF. Multiple large slickwater fracture stimulations are applied to horizontal wells to initiate gas production. A typical Nexen Dilly Creek shale gas well pad has 16 to 20 horizontal wells drilled parallel to the principal insitu stress. The horizontal legs are spaced approximately 300 m apart. A typical well receives 16 to 25 fracture stimulations spaced at 100 m intervals along the horizontal lateral. A slant drilled observation well (Dilly Creek c-F1-J) was drilled and completed and between two stimulated wells. The drilling of the well was concluded in early November, 2013. A string of 2-3/8″ tubing was installed and the well was suspended until July 2014 when wells on the pad were fracture stimulated. During the suspension period a gas head from the formation developed. First indication of a well problem occurred during attempts to land data recorders in the tubing in June 2014, seven months after the well was suspended. Tubing joints were recovered, the deposits were analyzed and a casing inspection log was conducted. Lab tests were then conducted on several recovered tubing joints. Drilling, completions and suspension procedures were reviewed and analyzed. It was concluded that the untreated oxygen in the suspension fluid in combination with the 10% CO2 formation gas caused the severe tubing corrosion.