ABSTRACT: New Seismic Data Enhances Oil Prospects in New Zealand's East Coast Basin

FRANCIS, DAVE, Consultant, Lower Hutt, New Zealand, and HARRY MCQUILLAN, Consultant, Nelson, New Zealand

New seismic data of excellent quality has recently been acquired in the Gisborne Plains area, East Coast, New Zealand. The area is well known for its several oil and gas seepages most of which have long been active.

Good sandstone reservoir potential has recently been documented in the region in the upper, lower, and middle Miocene, within a very thick clastic sequence. These reservoir sandstones include stacked lowstand lobes and wedges, which can also be recognized in the newly acquired seismic sections.

The regional extent and maturity of both oils and gases indicate widespread source rock distribution. There are several likely source rock formations, which include Early and Late Cretaceous and Paleocene marine carbonaceous shales, and possibly younger formations.

The surface geology of the Gisborne region demonstrates a compressive wrench regime highly favorable to the development of closed fold structures. Rapid burial by thick sedimentary sequences occurred during the Late Miocene and Pliocene, providing late maturity conditions.

Older seismic coverage in the region has been of poor resolution. Asia Pacific Oil has recently acquired 80 km of seismic lines with excellent results. Key reflectors have been identified throughout the section, including probable Miocene sandstone intervals which can be correlated with documented reservoir sequences.

Structures indicated by this newly acquired seismic data are broad and gentle, with potential for both good structural prospects and stratigraphic traps. Deeper and relatively simple structures are discernible down to 3.6 s two-way traveltime (probably Lower Cretaceous on basement).

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)