Mitigation of Reinjection Returns in Palinpinon-II, Philippines

Abstract

Palinpinon-II production field has three sectors producing steam from separate modular power plants: 20MW in the Balasbalas sector, 20MW in the Nasuji sector, and 40MW in the Sogongon sector. For the Nasuji sector, the simultaneous discharge test in 2012 confirmed that the excess steam can support a 45MW power plant. Seven (7) production wells in the Nasuji Sector will soon supply steam to a new 45MW Nasulo Plant that will be commissioned in 2014. The production sustainability at this high extraction rate was tested for a total of 6 months with 6 out of 7 production wells simultaneously discharged in 2011-2012. The required injection capacity for the 45MW production is 187 kg/s. Since the preferred injection capacity is only 80 kg/s from NJ1RD and NJ2RD, full operation would require an additional injection well. Steam decline in the neighboring Balasbalas Sector was observed within two months after termination of the simultaneous discharge testing. This can be attributed to the overloading of the preferred load of injection wells in Nasuji that resulted to injection returns during the Nasuji simultaneous discharge testing to all of Palinpinon-II Sectors, i.e. injection returns were observed in 5 Nasuji wells and all of the wells in the Sogongon Sector. To accommodate additional brine from full load operation of the 45MW Nasulo power plant and to disperse injection fluids farther to the north of the present Nasuji injection sink, it was recommended to pursue drilling of a new reinjection well NJ3RD. Rehabilitation of the existing Nasuji-Sogongon cross country injection line interconnection is also recommended for operational flexibility in implementing injection strategy for sustainable steam production.