A Large-Scale Well Stimulation Campaign at Mahanagdong Geothermal Field (Tongonan), Philipines

Abstract

The Mahanagdong B production sector of the Greater Tongonan Geothermal Field was faced with a serious steam supply problem in the first half of 1997, with only 14 MWe available at the wellhead of seven production wells for a 60 MWe power plant. Significant thermal degradation of the resource brought about by extensive drilling prevented the discharge of most wells even with the aid of air compression and nitrogen gas lifting. Detailed analysis of reservoir and drilling data also revealed that all the wells had been muddamaged. The problem was compounded by the contractual obligation of PNOC-EDC to produce the 60 MWe equivalent of steam to the power plant by the middle of the year. A comprehensive well stimulation campaign was executed through which the situation was returned to a manageable level by June 1997. The strategy involved the simultaneous use of two coiled tubing units, one rig and two acidizing equipment spreads, all on one pad, to stimulate, discharge and commission the seven production wells in less than three months.