Abstract

The southwestern plain of Taiwan is located south of the buried pre-Miocene Peikang basement high. Seismic data and lithofacies analysis data reveal that the depositional environments of Neogene sediments in the study area were quite diverse, ranging from deep marine to fluvial settings. Three major unconformable surfaces between Pre-Miocene/Miocene, Miocene/Pliocene and Plicene/Pleistocene can be defined from well data and also from seismic data terminations or strong amplitude contrast. The seismic facies analysis between the above mentioned sequence boundaries inferred from geologic column, well log and seismic character are implemented to physically settle the geologic seismic relations for petroleum exploration.

The extensive normal faulting in this area may result from warps of Plio-Miocene basin and rapid Plio-Pleistocene sediment influx. Seismic data also indicate that several major canyons eroded the Pliocene deltaic system and transported the sediment southward into deeper parts of the basin. There are four prospective styles of gas entrapment elongated structural culmination along north- dipping tension faults, rollover structures along south-dipping growth fault, unconformity traps and submarine fans. The drifting results show that the gas-bearing or gas-showing zones in the southwestern plain are quite varied, and almost all the sandstones interbedded in the Neogene formations are involved. Integrated study of seismic, geologic data are discussed to pinpoint the anticipated hydrocarbon accumulation.