f Integrating Biostratigraphy with Seismic for Sequence Stratigraphic Interpretation in The Malay Basin

Biostratigraphy is routinely run on most wells in the Malay Basin, but it’s value in interpreting sequence stratigraphic succession has not been fully assessed. For the first time, biostratigraphy has been fully integrated with seismic to construct a regional sequence stratigraphic succession of the Oligocene to Pliocene sediments of the basin. A comprehensive biostratigraphic database from over 40 wells has been reviewed within a regional seismic grid. The data shows that most of the biostratigraphic assemblages are driven by sequence stratigraphic processes that are largely attributed to sea level and climatic changes. The lowstand systems tract can be differentiated from the transgressive and highstand systems tracts by the low proportion of mangrove-derived pollen (especially Rhizophora type), the high represenation of dry-cool palynomorph elements, and in many instances pollen the presence of acmes of pollen from an unusual type of peat swamp, termed ‘Kerapah’ swamp. The transgressive surface is often marked by an increase in foraminiferal abundance, and coincides at the onset of increasing mangrove-derived pollen. The transgressive systems tract is generally characterized by the increased abundance of mangrove-derived pollen coinciding with the main period of sea level rise. The maximum flooding surface is often differentiated by an acme of foraminifera and nannofossils. In outer shelf and upper bathyal environments, the maximum flooding surface is often indicated by an acme of deep and/or cold water of foraminifera. Within the highstand systems tract, pollen suggesting a warm and wet climate tends to dominate, and benthic milioliid foraminifera may be common. Through properly assessing the above biostratigraphic parameters, major sequence stratigraphic stratal surfaces and their associated system tracts can be recognized on Biostratigraphic data alone. These surfaces are positioned into a seismic framework by determining their fit with stratal termination patterns of onlap and downlap. By holding a workshop session in a workstation environment, horizons with anomalies between seismic and biostratigraphy can be adjusted iteratively. Typically, both disciplines contribute more or less equally to positioning stratal surfaces and constructing the sequence stratigraphic model. Currently 21 sequences (third and fourth order) are recognised in the Malay Basin based on the strengths of both seismic and biostratigraphy. This review demonstrates that the sequence biostratigraphigraphic approach, integrated with seismic sequence stratigraphy provides a more robust sequence stratigraphy than that obtained when using either discipline on its own. It is strongly recommended that future Malay Basin sequence interpretation should be conducted as a joint process with respect to the interpretation of sequence stratigraphic surfaces; with the integration of biostratigraphic and seismic data taking place in a workstation environment. Both disciplines can add value to the other if used together.