The new estimate comprises 40.9 million tonnes of indicated resources at 1.08% nickel and 0.05% cobalt and an inferred resource of 29Mt at 0.96% nickel and 0.06% cobalt, using a 0.8% nickel cut-off grade.
Contained nickel is up 36% to 720,000 tonnes.
The company said nearly all of the inferred material from the 2008 estimate had been converted to indicated, while a further 20Mt had been delineated.
The new estimate used data from 117 diamond drillholes completed since the last estimate.
A BFS for Acoje will be completed midyear, based on an atmospheric tank leaching operation that could be developed in stages.
Pilot testwork indicated cash costs of $US4.33 per pound of payable nickel.
Meanwhile, ENK just completed a 2174 diamond infill drill program on its neighbouring Zambales Chromite Mining Corporation project.
A 23.5Mt resource was announced for the project in 2007, based solely on test pit data.
The company will release an updated resource in the June quarter.
ENK shares closed half a cent higher to A17.5c.