RESTORING WELLBORE INTEGRITY IN A COLD BRINE AND CONDENSATE INJECTOR, MAK-BAN GEOTHERMAL FIELD, PHILIPPINES

Abstract

Bul-25 has the second highest capacity of five cold brine and condensate injection wells located in the Mak-Ban Geothermal Field, Philippines. Cold brine and condensate are mixed together in a single injection system (CBCIS); the condensate component of the stream is found to cause corrosion along the surface piping and also in the wellbore casing. To protect the integrity of the cemented 9 ? in (244.5 mm) casing, a 7 in (178 mm) hangdown liner was installed in Bul-25 in 1987. As part of the wellbore integrity monitoring program of steam field operator, Philippine Geothermal Production Company, Inc., casing inspection caliper (CIC) surveys were regularly conducted on Bul-25. In 2011, the CIC indicated a casing hole on a shallow portion of the hangdown, along with signs of significant corrosion and pittings elsewhere along the hangdown. The well was placed in the 2017 workover program to replace its hangdown with a cemented secondary tieback casing.
During the workover, the hangdown liner was retrieved in separate sections due to its condition. Additionally, visual inspection of the liner during the pull-out confirmed the findings of the 2011 CIC survey, with sections of severe corrosion found throughout the string. A total of 2110 ft (643 m) of hangdown liner was successfully extracted and 55 joints of 7 in (178 mm) casing were run and cemented afterwards.
An injection capacity test performed after the cementing of the new tieback using 2 rig pumps and a cementing unit showed that the well accepted 24 bpm (3.84 m3/m) for a total testing time of 28 mins. Two weeks after the workover, Bul-25 was successfully re-commissioned as a cold brine and condensate injector with its wellbore integrity fully restored and no changes to its previous performance.