The Application of Bioevent for Refine Stratigraphic Correlation: An Example for Baram Field, West Baram Delta, Sarawak, Malaysia

Abstract

In oil & gas development, the subsurface geological geometry is important in constructing reservoir model of the area. Hence, the understanding of reservoir lateral extension is very crucial as an input to the model. At present, the stratigraphic and reservoir correlation established in the fields were developed using lithological characteristics. Although it works in some part of the field, however, significant problems have been realized particularly with regard to discrepancies in the static and dynamic models. The objective of this study is to establish a new time based correlation using bio-sequence stratigraphic approach. As lithological based correlation is likely to be facies dependent, the time based correlation would allow correlation to be achieved across different depositional/lithological facies. Through this approach a more workable correlation framework could be developed, and thus providing a more appropriate stratigraphic correlation across the studied field. Thus, an integration of 3D seismic, well logs and biostratigraphic data and application of bioevent as markers for better reservoir correlation. West Baram delta was selected for study area. It is structurally complex region. A huge amount of sediments were loaded onto the delta forms a massive thickness of regressive delta. The syn-depositional structures such as growth faults, contributed to major challenges for sequence correlations. Therefore, a resolution to stratigraphic correlation needed especially during field development. This study focused on the application of high resolution biostratigraphy using microfossils occurrences which called ‘bioevent’. Bioevents are not limited to age zonations only, but represents the changes of microfossils assemblages, abundance, diversity and also acme. All these changes were translated into boundaries and used as correlation datums. The biostratigraphic data sets were reinterpreted and grouped into several sets i.e. main groups, biofacies and morphogroups. Through integration with logs, substantial bioevents that can be seen in all/most of the wells, were picked and described. As a results, nine (9) time based correlation markers have been established and six (6) significant bio-events have been observed. All these bioevents were than integrate with logs and post to seismic for correlations purposes.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018