--> ABSTRACT: Prediction of the Geometry and Property of Turbidite Sands Using a Two-Dimensional Process-Response Computer Model, by Jianjun Zeng, Donald R. Lowe; #91020 (1995).

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Prediction of the Geometry and Property of Turbidite Sands Using a Two-Dimensional Process-Response Computer Model

Jianjun Zeng, Donald R. Lowe

We used a turbidity-current sedimentation model to predict the geometry and grain-size make-ups of turbidite sands formed by individual turbidity currents in response to 1. changing submarine channel gradients, and/or channel depths, 2. varying suspended sediment concentration of flows, and 3. different sediment grain-size composition at sources. Our results include:

1) Turbidites formed by model turbidity currents on steeper slopes have greater down-dip extensions, with greater bed thicknesses and coarser sands than turbidites formed by similar turbidity currents on gentler slopes, when sampled at the same down-dip locations. Repeating runs can predict fining- and thinning-upward turbidite sequences formed by turbidity flows originated from retrogressive slope failures, and coarsening- and thickening-upward sequences formed by flows originated from progressive failures. 2) Turbidite sands formed by model high-density flows are characterized by coarser grain size with poorer-sorting than turbidites formed by more dilute flows when sampled at the same down-dip locations, because of the higher flow competence and resulting fine-sediment bypassing. T is is in agreement with published laboratory observations on the texture of high-density turbidity current deposits. 3) Turbidites formed by flows fed by silt-dominated sources (termed sometimes high-efficiency flows) have more tabular-elongate geometries, with lower surface relief than those formed by otherwise similar flows fed by sand-dominated sources. This is consistent with observed sediment-source controls on the modern fan morphology.

With ongoing improvement efforts, this process-response model can be used together with 3D seismic image analysis tools to predict more precisely the geometry and down-dip and vertical heterogeneity of turbidite sands, and therefore to provide a more realistic geological data base for reservoir simulation with limited well-control.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995