Analysis of the effects of process variations on delta morphology and stratigraphy in Delft3D computational models

Analysis of the effects of process variations on delta morphology and stratigraphy in Delft3D computational models

Chen, F.

Storms, J.E.A. (mentor)
Walstra, D.J.R. (mentor)

Civil Engineering and Geosciences

Geoscience & Engineering

Petroleum Engineering and Geosciences

2014-09-29

Deltaic reservoirs are of great significance in both exploration and production of oil & gas and they have aroused increasing interest during the recent years. Coastal engineering deals with sediment transport on a millisecond and micron scale, while geology deals with sequence stratigraphy on a millenary and 10-100 km scale. However, relatively less is known in between, and the effect of different processes cannot be separately analysed. The presented study is one way of understanding what effect would different processes, namely river discharge, tidal influence and sediment supply D50, have on the evolution, morphology and stratigraphy of a delta, on a decades and parasequence scale, by using Delft3D process-based modelling techniques. The approach adopted in the study is to setup a reference case with Delft3D based on literature study and Deltares/TU Delft expertise, to simulate the building out process of a delta. On top of that, 36 geologically and hydrodynamic realistic models were set up by systematically varying the tidal conditions, river discharge and sediment fractions in the supply. Upon their finishing, the area, rugosity, length to width ratio, dip magnitude, dip magnitude variance and dip azimuth angular dispersion, and sand fraction distribution have been measured for each of the numerical deltas. These results are then either plotted or visualized and compared with the reference case and also between each other. The study results suggest that (1) channel activity magnitude as indicated by the rugosity is positively related to mean river discharge and inversely proportional to the tidal influence; (2) the effect of tide and river discharge cannot be separated, since they interact with each other in a system. Higher combined strength of tidal and riverine forcing leads to larger mean foreset dip magnitudes, larger variance in dip magnitudes, and a lager dip azimuth angular dispersion. Sand body distribution is more continuous in low discharge and low tidal influenced situations; (3) The different dry bed densities of sediments supplied and their correspondent transport formula influences delta’s morphology in a significant way. With increasing D50, the deltas show: smaller area given the same mass of sediment, higher rugosity, more avulsions, lower length to width ratio, steeper foreset slopes, larger dip magnitude variance and less clean sand bodies.

finite element analysis
Delft3D process-based modelling
tidal influence
river discharge
sediment supply
rugosity
sand distribution

http://resolver.tudelft.nl/uuid:f5a7cd12-47e8-4343-be71-a6c995bc0074

2014-09-24

Student theses

master thesis

(c) 2014 Chen, F.