Publications

In well correlation, biostratigraphy typically underpins the chronostratigraphic framework. Unfortunately, biostratigraphy has some shortcomings. These issues arise because biostratigraphic analysis is commonly performed using cuttings data which is prone to caving, mixing during transport and improper sampling. These issues can lead to erroneous age interpretation which can make well correlation sometimes inaccurate. In order to improve the chronostratigraphic correlation in the West Natuna Basin, an integrated approach using log characters, the biostratigraphic data and the seismic has been utilized. The first step of this method was to characterize the key seismic markers (i.e. reflectors) which are continuous and consistent across the study area. These markers potentially represent flooding surfaces, regionally extensive coal layers or other major events. These markers were then tied to each well and used as age-equivalent horizons. The seismic markers were then compared and combined when possible to the biostratigraphic age to form an integrated interpretation. Finally, incised valleys identified on seismic were incorporated with the environment signal from the biostratigraphic analysis to interpret sequence stratigraphic surfaces. After combining this data, it was observed that the seismic markers rarely matched the biostratigraphic age. Based on the relative quality of the data, the seismic markers were interpreted to be more reliable and therefore were used as the primary source for the chronostratigraphic framework. For major events such as sequence boundaries (SB) and maximum flooding surfaces (MFS), a combination of seismic and biostratigraphy were used. Using these methods, five seismic markers, seven possible sequence boundaries (SB) and two maximum flooding surfaces (MFS) were identified. In conclusion, this study illustrates that biostratigraphy alone may not be sufficient to identify and correlate key events. An integrated approach using both seismic and biostratigraphy is the best method to determine chronostratigraphic correlation. For the West Natuna Basin, this methodology has provided new insights in correlation of the Miocene Arang Formation across the basin. Keywords: Chronostratigraphy, Biostratigraphy, Seismic Marker, West Natuna Basin, Arang Formation