Seismic refraction study, single well test and physical core analysis of anthropogenic degraded Peat at the Badas Peat Dome, Brunei Darussalam

Abstract

The Badas peat dome located in the Belait district is one of the biggest peat domes in Brunei. Over the years, this area has seen a noticeable loss of peatland due to fires and infrastructure development. In this paper, the anthropogenic effects on the Badas peat dome were studied for three survey areas using seismic refraction surveys, core analysis and single well tests. Satellite images were used to confirm the extent of past peat fires in the area. Using these methods, this study has identified multiple peat, sand and clay layers demonstrating the stratigraphic heterogeneity that can be present in tropical peatlands. In particular, a sand horizon underlying the peat deposits was identified which has the potential to be a significant hydrogeological flow unit. Groundwater level interpretations from 2D velocity data were correlated to groundwater levels from coring. In order to determine the degradation impact on peat through lowering of groundwater levels using these methods we produced a subsurface reconstruction at two locations with different levels of peat degradation. Single well tests conducted in this study showed that disturbed peat had lower hydraulic conductivities with an average of 1.73 × 10−5 m/s compared to undisturbed peat with an average of 6.66 × 10−5 m/s. A combination of these methods (seismic refraction, single well test and coring) are suitable for identifying different levels of peat degradation. In addition, these methods can be suitable for profiling in tropical peatlands, for identifying groundwater levels as wells as identifying significant hydrogeological flow units.