Abstract
TCPL has recently carried out ‘reconnaissance or exploration’ 3-D surveys, in three different blocks, each designed to solve a different type of problem. In each case a considerable improvement in data quality and the resulting structural/stratigraphic interpretation was achieved.
The Kupe South structure is a wrench-induced feature cross-cut by numerous small-medium faults. Stratigraphic changes across the prospect produce a variable quality seismic event at the top reservoir level.
The Pataka Prospect comprises a narrow horst block trend within the Oakura fault zone, offshore New Plymouth. Accurate determination of potential reserves required a reliable interpretation of the fault configuration, and the amount of displacement of the reservoir horizon by the critical faults.
The Waitara Prospect is affected by a ‘no-data’ zone possibly associated with volcanics in the near surface. It was necessary to define the extent and nature of the no-data zone and to calculate the effect of the interpreted volcanics on the time structure map.
Prior to the surveys we modelled the effects of such critical parameters as sail-line separation, final interpolation spacing and the dimensions of the 3-D grids using existing 2-D data.
Good results were obtained with a wider line spacing than is strictly required for true 3-D. Whilst the Reconnaissance 3-D method has not removed all of the difficulties with interpretation, a considerable improvement was obtained in data quality and ease of interpretation.
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