¹Geoscientific Department, PNOC Energy Development Corporation, Ft. Bonifacio, Taguig City, Philippines
²Energy Research Laboratory, Department of Energy, Ft. Bonifacio, Taguig City, Philippines


 

Fuga-1 is the first wildcat well drilled in Fuga island, Babuyan Channel, Philippines to test the gas potential of the Middle Miocene Sicalao Limestone. It encountered Early Miocene to Plio-Pleistocene neritic to bathyal sequences within the entire drilled depth of 5892’. Early Pliocene (N19), Late Miocene (N17-Tf3) and Middle Miocene (NN6-NN7) clastics from surface to 4500’ are dominated by thinly-bedded siltstones, claystones, and fine-grained sandstones with coarse-grained sandstones and conglomerates as occasional interbeds. Intermittent shifts to a carbonate facies at the N17-Tf3 boundary at 1970’ and within the Middle Miocene sequence at 3290’-4500’ are evident with an increase in the bioclastic framework hosted by a micritic matrix or occasional microsparite cement. The Early Miocene (NN1-NN4) clastics from 4500’ to 5892’ consist of basaltic hyaloclastite and volcanic conglomerate in the upper part and fine-grained clastics in the lower section. The older conglomerates are altered to a low-temperature hydrothermal suite of opal, tridymite, cristobalite, chlorite-vermiculite and zeolites such as laumontite. Abundant and varied species of planktonic and benthonic foraminifera characterize the Late Miocene to Early Pliocene deposits, in contrast to the underlying sediments where the faunal content is rare.p>

Top Late Miocene to Early Pliocene sedimentation is influenced by episodic andesitic volcanism based on abundant admixture of juvenile volcanic detrita. Early Miocene deposition is likewise associated with submarine basaltic volcanism. Proximity to volcanic centers together with deep depositional settings likely hampered the development of potential reservoirs.