A Fresh Look at Deepwater West Balabac

R. B. Savella, J. B. Barajas, G. P. Revilla

PNOC Exploration Corporation

The West Balabac area is located in the southernmost tip of Palawan forming the northern extension of the North Borneo Basin. It is considered the northern extension of the NW Sabah basin and is mostly in deepwater. The area is relatively underexplored – there is sparse 2D seismic data (almost all in the shallow shelf area) and 10 wells have been drilled (last way back in 1981). There are no discoveries in the West Balabac area but on the Malaysian border, several oil and gas fields are found. Malaysia’s first deepwater discovery, estimated to contain 400-700 MMBO, is found southwest of the area. The only well in the West Balabac area with significant hydrocarbon show is the Abo-abo 1 well, which flowed gas albeit non-commercial.

The most prominent geologic feature of the area is the NE-trending Palawan Trough, which has been interpreted as an extinct subduction zone where the older proto-South China Sea, which is the leading edge of the rifted Asia margin, subducted beneath a younger sedimentary sequence with an Eocene oceanic basement. Outcrops in onshore southern Palawan show Eocene ophiolites thrusted over older ophiolites Cretaceous in age. In the West Balabac area, two geologic terranes are therefore present – a depocenter that is floored by the attenuated Asian continental fragment and a depocenter floored by oceanic material.

Although quite different in origin, both these terranes are attractive sites for petroleum exploration. The section associated with the Asian continental margin has already been proven with an active petroleum system. Carbonate build-ups, turbidite fan lobes and folded sedimentary sequences have been identified. While the sedimentary section associated with the Eocene, an active petroleum system also exists. Several wells drilled were able to flow gas. The most common play in this terrane are folded sequences, probably part of the accretionary prism associated with the subduction zone.

With increasing crude oil prices, the recent deepwater discoveries in offshore Malaysia and advances in deepwater drilling coupled with a fresher understanding of the area, the area is an attractive area for exploration, which certainly deserves another look.