ABSTRACT: Mindoro Island, a Rifted Microcontinent in Collision with the Philippines Volcanic Arc: Basin Evolution and Hydrocarbon Potential

BIRD, P. R., N. A. QUINTON, M. N. BEESON, and C. BRISTOW, Kirkland Resources, Harpendon, Hertfordshire, United Kingdom

Mindoro Island is the easternmost part of the Palawan-Mindoro microcontinent that rifted away from the south China margin during the early Oligocene. Sea floor spreading carried Mindoro southward until the late Miocene, when collision with the Philippines Arc in the east, and other terranes to the south began. This paper considers the collision tectonics, which operated at the eastern end of the microcontinent, that resulted in the inversion and thrusting of the rifted margin of Mindoro. These processes are documented by seismic data and field outcrop. The syn- and post-rift sedimentary sequences contain prospective source and reservoir intervals. Subsequent burial and deformation have resulted in the generation and entrapment of hydrocarbons, as proved by recent discoveries near Nort Palawan and by the existence of several oil seeps on Mindoro Island.

The structural history of the area is divided into four phases: (1) syn-rift, early Eocene-middle Oligocene; (2) drift, late Oligocene-middle Miocene; collision, middle to late Miocene; transpression, latest Miocene-present.

The erosional events that separate these stratigraphic sequences can be identified on seismic data. The sequences show characteristic differences in stratigraphy and structure, which control their prospectivity.

Syn-Rift Sequence--consists of nonmarine arkosic sandstones at the base, becoming marine toward the top and including platform and reefal limestones.

Drift Sequence--this records an overall regression, beginning with the deposition of marine shales sandstones and detrital limestones and passes upward into deltaic sands, shales, and coals. This sequence contains reservoir quality sandstones and several potential source horizons.

Collision/Transpression Sequence--on Mindoro Island this interval is dominated by coarse clastics derived from the uplifted collision zone. In offshore areas to south and west, away from the collision zone with the arc, a more uniform blanket of parallel bedded shale and calceous siltstones were deposited. These form a regional seal to structural traps, which may contain significant volumes of hydrocarbons.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)