The effects of hindered settling on submarine lobe architecture.

Abstract

Submarine lobes form the final stretches of deepmarine sedimentary systems and are important targets for hydrocarbon exploration and production. Therefore, reliable predictions of reservoir geometry are important. However, seismic data sets are typically limited in the amount of detail they can resolve. Furthermore, outcrops of submarine lobes, which could serve as reservoir analogues are often only partially exposed in outcrop. Model studies can potentially make predictions about parts of the subsurface where information is limited. However, predictive models of lobe deposits are scarce and still at an early stage. In this study, an advection-settling model is presented that accounts for hindered settling. The model allows to make predictions on lobe geometry based on vertical grain size stratification, flow velocity and current duration. With this tool, the influence of hindered settling on lobe geometry has been investigated. The new model has been tested by modelling flume scale turbidity currents. Results show that incorporation of hindered settling can contribute to more realistic predictions of lobe apex thickness. The lobe thickness maximum is located further basinward for high density currents (>3% vol.), due to the effects of hindered setting. Its effects were found to increase with initial sediment concentration of the parental turbidity current. Moreover, settling velocities of finer grain sizes in turbidity currents are more affected by hindered settling. To further improve the predictive value of the model, additional processes need to be accounted for. Further work is necessary on incorporation of turbulence production at the break of slope, erosion at the channel-lobe transition zone and flow non-uniformity in turbidity currents.