Sedimentology and stratigraphy of late synrift to early postrift, humid-tropical fluvio-lacustrine deposits: Late Oligocene to Early Miocene K Group, Malay Basin
File(s)
Author(s)
Binti Lokman, Irdawati
Type
Thesis
Abstract
A sedimentary facies analysis of fluvio-lacustrine strata deposited in the early postrift phase from the Late Oligocene to Early Miocene (ca. 25.2-21 Mya) K Group in the southern and southeastern Malay Basin is presented. The study is based on c. 600 m of core (from 11 wells), well logs, biostratigraphic data and c. 7410 km2 post-stacked depth migrated 3D seismic reflection dataset.
The study investigates the stratigraphy, sandstone bodies quality and stratigraphic architectural distribution of the K Group, which consists of large-scale, freshwater-dominated megasequence (up to 650 m thick; typically 100-250 m). The sequence stratigraphic synthesis concludes that the K Group represents a regressive- to transgressive-dominated succession, which accumulated in the largely landlocked Malay Basin during its early postrift phase and under a humid-tropical climate setting.
The K Group facies analysis identifies five facies associations (FA): (1) multi-storey braided channels (FA1), (2) single-storey fluvio-distributary channels (FA2), (3) floodplain to lacustrine deposits (FA3), (4) mouth bars (FA4), (5) transgressive and abandonment deposits (FA5). Thick (30-70 m) FA1 deposits form c. 13 km-wide braidplains interpreted as major trunk rivers concentrated in the NE part of the study area. Three key interpreted seismic surfaces (Horizons 1-3) are identified. Three types of seismic facies (SF) are defined using reflector terminations and calibrated to core where available: (1) SF1 (shallow lacustrine facies) interpreted as FA3 and K Shale equivalent, (2) SF2 (fluvio-distributary channels to shallow lacustrine) is FA2-FA5 equivalent, and (3) SF3 (multi-storey braided channels) corresponds to FA1. Seismic attributes mapping calibrated with well data defines various fluvial styles e.g. braidplain, dendritic- and sinuous- channels at- and away from well control.
Laterally equivalent and more heterogeneous facies successions comprise alternations of single-storey channels (FA2), often preserved at the top of coarsening upward facies successions (FA4), interpreted as distributary channel and fluvial-dominated lacustrine deltas, respectively.
The study investigates the stratigraphy, sandstone bodies quality and stratigraphic architectural distribution of the K Group, which consists of large-scale, freshwater-dominated megasequence (up to 650 m thick; typically 100-250 m). The sequence stratigraphic synthesis concludes that the K Group represents a regressive- to transgressive-dominated succession, which accumulated in the largely landlocked Malay Basin during its early postrift phase and under a humid-tropical climate setting.
The K Group facies analysis identifies five facies associations (FA): (1) multi-storey braided channels (FA1), (2) single-storey fluvio-distributary channels (FA2), (3) floodplain to lacustrine deposits (FA3), (4) mouth bars (FA4), (5) transgressive and abandonment deposits (FA5). Thick (30-70 m) FA1 deposits form c. 13 km-wide braidplains interpreted as major trunk rivers concentrated in the NE part of the study area. Three key interpreted seismic surfaces (Horizons 1-3) are identified. Three types of seismic facies (SF) are defined using reflector terminations and calibrated to core where available: (1) SF1 (shallow lacustrine facies) interpreted as FA3 and K Shale equivalent, (2) SF2 (fluvio-distributary channels to shallow lacustrine) is FA2-FA5 equivalent, and (3) SF3 (multi-storey braided channels) corresponds to FA1. Seismic attributes mapping calibrated with well data defines various fluvial styles e.g. braidplain, dendritic- and sinuous- channels at- and away from well control.
Laterally equivalent and more heterogeneous facies successions comprise alternations of single-storey channels (FA2), often preserved at the top of coarsening upward facies successions (FA4), interpreted as distributary channel and fluvial-dominated lacustrine deltas, respectively.
Version
Open Access
Date Issued
2022-02
Date Awarded
2023-09
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Johnson, Howard
Jackson, Christopher
Sponsor
Petronas
Publisher Department
Earth Science & Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)