Abstract

The Rub' Al-Khali desert with its extensive and massive sand dunes presents difficult technical and logistic problems for reflection prospecting. The steep angle of repose of the sand dune faces and the low velocity of the air-filled sand cause significant delays to the reflected waves. In the dunes, in order to maintain the fidelity of both the downgoing and upcoming waves, small dynamite source and receiver arrays are each contoured to a single elevation. In the flat sabkhas, larger arrays are maintained.After application of dune statics (which are derived initially from an average velocity for the sand and then refined with residual refraction statics), the small arrays are summed so as to simulate the larger arrays used on the flat sabkhas. When the terrain is dominated by dunes, increased use of small arrays reduces the maximum spread length to the detriment of the deeper reflections. Where this occurs, a second set of dynamite patterns is fired so as to increase the effective receiver arrays from 120 to 240. In this manner the simulated spread length is maintained at a minimum of 12,000 ft.The traces resulting from the array simulation on the dunes are then gathered, along with the sabkha traces, into mixed fold common-depth point (CDP) gathers and processed conventionally. This technique results in the recording of high-quality, broadband reflection profiles with improved continuity beneath the dunes.

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