This paper presents the results of the evaluation of the petroleum pot
ential of the deep-water acreage of Philodrill, GSEC 66, or what the a
uthors call the ''Northwest Malampaya Block''. All the elements necess
ary for a major hydrocarbon accumulation are believed to be present in
the block. Probable source rocks are the deep-water Nido Limestone, t
he pre-Nido Early Tertiary syn-rift section, and pre-Tertiary sediment
s. Potential reservoirs include the Nido reefal buildups, Nido and pre
-Nido detrital and/or fractured carbonates, Early Miocene Galoc elasti
c equivalent turbidites and pre-Nido sediments. The principal play-typ
es recognized in the area are the Late Oligocene to Early Miocene reef
s and the erosional/karsted carbonate highs. After evaluation of avail
able pre-1982 seismic data, an acquisition program of 1625 km was unde
rtaken. Eleven leads/prospects were delineated in the area after the i
nterpretation of this new seismic data. Two prospects were upgraded to
drillable status (the Santa Monica Prospect and the Ipil Prospect). T
he Santa Monica Prospect is a well-defined four way dip closure on the
Nido Limestone with a vertical closure of over 1500 feet and an areal
closure of over 20,500 acres. The Ipil Prospect is a gently closed fe
ature developed at the Nido Limestone platform level with an areal clo
sure of over 11,600 acres and a vertical relief of 400 feet. The techn
ical merits of the delineated huge prospects, combined with the very f
avorable deep-water exploration terms of the Philippines and their pro
ximity to the soon-to-be-developed Malampaya-Camago Field, make this b
lock a very promising area for further exploration work. (C) 1997 Publ
ished by Elsevier Science Ltd.