Geophysical exploration of the Kotuku oil prospect, Westland.

Gravity measurements were made over the entire lengths of 6 lines and seismic measurements over the central portions of lines 1, 2 and 4. The principal objective of the work was to locate and define the fault whose existence had been inferred from earlier gravity and seismic work and from the logs of wells Aratika 2 and 3. The gravity work suggests a throw of about 1650m. Depths to basement throughout the area surveyed are shown with a dome clearly outlined west of the fault. A point of difference with the earlier gravity model of basement relief is that in the vicinity of Aratika 3 the basement dip is interpreted as 18 degrees to the NE in good agreement with the dip of the sediments near the bottom of the hole. A study by Fisk was also made to determine the saline water leaks in the streams near the Kotuku Oil leaks.