The primary drill target could be massive sulphides 130m thick and covering an area of about 1.5km by 450m at 426m below surface.
Secondary drill targets are likely to represent shallower supergene mineralisation, according to Castillo.
The prospects were originally generated by BHP in the late 1990s, but not drilled according to Castillo "likely due to the prevailing downturn in base metal prices at the time induced by the 1998 Asian financial crises".
The exact timeframe for Castillo's drill testing has not been disclosed.
Mt Oxide, ground in Zambia, and ground in Broken Hill comprise the prospects Castillo hopes will transform it into a mid-tier copper group.
Castillo looks likely to be raising funds in the near future given it started the June quarter with A$1.3 million and was expecting to spend more than $400,000.
Shares in Castillo were up 15% to 3c in late trade, capitalising the company at $23 million.