Offshore Trinidad sediment are the result of clastics sediments from the Orinoco River in Venezuela. The high rate of sediment influx results in thick clastic sequences with a mixture of sands and shales. Because of the large amount of sand, the influence of anisotropy in the region is less evident than in data from the western African region (Alkhalifah, 1997a). Nevertheless, taking anisotropy into account yields better images, as well as better understanding of the subsurface lithology.
The first line of seismic data shown in this paper was acquired as a 2-D line in 1984 in the regional dip direction (confirmed from 3-D data). The line is approximately 30 km long with a source-to-receiver spacing ratio of 2. As a result, the maximum fold in the data is 60 and the maximum offset acquired, 3200 m, is lower than what is typically acquired nowadays. Such offsets are, nevertheless, sufficient for applying the dip-moveout inversion of Alkhalifah (1997a) since this method does not require long offsets. However, the non-hyperbolic inversion of Alkhalifah (1997b) is not appropriate for this data since this inversion relies on the availability of large offsets. The peak frequency in the data is around 30 Hz.
The second line of data from the Trinidad region is newer data (acquired in 1989), with offsets that extend to 6 km. This 2-D line was also acquired in the regional subsurface dip direction. The source-to-receiver spacing ratio here is 3, and the maximum fold in the data is 90. Due to the large offsets acquired, the more flexible non-hyperbolic inversion is used on this data. The peak frequency for this data is closer to 40 Hz.