Imaging the giant Azeri and Chirag fields and the Deep Water Portion of the Gunashli field (ACG) in the Caspian Sea is a complex challenge. While the basic structure is a simple, large anticline, seismic imaging is hindered by a combination of mud volcanoes, shallow gas, complex overburden, high attenuation and multiples. Towed Streamer (TS) data successfully images some of the field, but significant uplift is seen on Ocean Bottom (OB) data.

In this paper the results of 2D field trials are analysed to understand how cleaner and higher resolution images may be obtained. Several passes of a 2D line were acquired in the field trials, with varying acquisition configurations and, unusually, recording simultaneously into TS and OB receivers. The limiting factors in existing data are examined, the potential benefits of deeper receiver towing and denser OB acquisition assessed, and recommendations made for future 3D acquisition.

Some well-established benefits of deep tow data are verified, such as the reduction in swell noise and decreased impact of the 0Hz ghost notch1. However, it is also shown that after careful denoise and deghosting, the shallow tow data is of similar quality. For OB data it is demonstrated that slow, aliased noise limits both data quality and useable bandwidth and that denser acquisition can successfully sample and remove this noise.

Particularly, it is shown that survey design must not only provide sampling of primary signal, up to a desired frequency, but also provide at least one processing domain in which the slowest and most complex noise modes are un-aliased to the same frequency. This usually occurs naturally in towed streamer surveys which have densely sampled shot gathers, but is not always the case for OB surveys.

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