Damaged Wellhead Rehabilitation Well OK-5, Palinpinon-II Production Field Negros Oriental, Philippines

Abstract

In the Philippines, most geothermal fields are located in mountainous, rugged terrain and coupled with the regular visits of typhoons bringing with it heavy precipitation that create favorable conditions for landslides to occur.
A major landslide with an estimated volume of 50,000 cubic meters occurred on October 23, 1998 that hit Wells OK 5 and BL 2D in Palinpinon II production field. The debris devastated the wells and its pipelines. The wellhead tee flange above the master valve of Well OK 5 was sheared-off at its neck and the well discharged at fullbore to the atmosphere ("wild well").
The task of the wellhead rehabilitation faced a number of physical obstacles like unfavorable weather condition, noise due to the discharge, mud, and steam venting from the cracked casings. A major challenge was on "taming" the " wild well" to access the wellhead cellar and replacement could be done on the sheared-off tee, cracked anchor casing and production casings, and master valve. Teamwork and the years of experience contributed to the success of the well rehabilitation. The rehabilitation took 6 ? months and Php 30 million charged to business interruption insurance.