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Scarborough gas field

Structure: Scarborough Gas Field
Location: Carnarvon Basin
Top of HRDZ: 0-100 ms
Amplitude Anomalies: Large
Intensity: High

Figure 21a shows an image of the seafloor over the Scarborough gas field generated using 2D seismic data. The seismic data consists mainly of 1,250 m-spaced, WNW–ESE oriented, dip lines. The image has had colour drape applied to reveal the broad, seafloor structure and sun illumination enhancement to highlight the detailed features. The features present are interpreted to be pockmarks, which extend over a region of exceeding 50 km². An area of strong seismic amplitude anomalies near the sea floor (Fig. 21b) corresponds to the location of the pockmarks.

The effects seen on Figures 21a and b may be similar to those noted by Hovland et al (1987). These workers described gas-related pockmarks in the North Sea which had increased seismic reflectivity, caused by near-surface, carbonate-cemented sands. Similar prominent seafloor amplitude anomalies, which relate to localised seafloor induration around hydrocarbon seeps, have been described on the Yampi Shelf in the north-eastern Browse Basin by O’Brien et al (1998b, 2000).

Figure 21. a) Seafloor pockmarks above the Scarborough gas field (5 km graticule). b) Near-surface seismic amplitude anomalies above the Scarborough gas field.