Although abandoned channels are a ubiquitous and important sedimentary feature in fluvial deposition systems, nonetheless as a geomorphologic unit they have been seriously ignored in seismic investigations for reservoir characterization. As a geomorphologic unit, it is either regarded as part of the whole of the channel or it is directly ignored. The reason for this is that the principal part of traditional hydrocarbon reservoir architecture analysis focuses upon the sandy sedimentary unit, not the mudstone which is thought to dominate abandoned channels. In addition, the channel fill lithology as such can be acoustically close to the surrounding rock, which seriously hinders its identification. But abandoned channels result from a final stage of fluvial or channel segment evolution, and as such can be characterized by either siltstone or mudstone filling in a decreased flow energy environment. In this high-frequency sequence stratigraphic investigation of a Neogene Gulf of Thailand fluvial system, there are three distinct pattern-types recognized: meander cutoff, channel chute avulsion, and entire abandonment. The first two patterns are local abandonment of channel segments during fluvial lateral migration and the latter one is the result of entire channel abandonment at the end of a major fluvial forced-regression episode. This study demonstrates that the abandoned channels and their fill indeed can be recognized as recorded on seismic horizon slices within the channel sandstone belt where they represent a large degree of lithologic variability and consequently reservoir quality.

Presentation Date: Wednesday, October 14, 2020

Session Start Time: 9:20 AM

Presentation Time: 9:20 AM

Location: Poster Station 8

Presentation Type: Poster

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