Neal L. Adair

Acoustic imaging of small water‐lain sand deposits

Reduced‐scale physical modeling of depositional systems, like submarine fans, river deltas, and point bars, provides insight into the formation and internal structure of the full‐scale systems which may become economic hydrocarbon reservoirs. Turbid water with controlled sediment concentration and flow velocity is discharged into a 3 m×5 m tank of still water to create deposits up to typically 10 cm thick. These deposits are imaged by a pencil‐beam high‐frequency (7 MHz) acoustic system to capture the evolution of deposit topography and by a broad‐beam lower‐frequency system (150 kHz) to image an internal structure. An x–y positioning system moves the transducer to create detailed 3D images. At 7 MHz, the deposit surface is ‘‘rough,’’ so significant backscattered energy is detected even for non‐normal incidence. This, together with the narrow beamwidth, allows the deposit elevation directly below the sensor to be measured independent of the local slope. The deposit surface is ‘‘smooth’’ to the 150 kHz sys...