The well had encountered elevated gas readings over an 800m interval from 760m to the 1560m target depth. However, listed Perth-headquartered Tap said on Friday afternoon that the results of the logging program, including the taking of pressure readings, showed the well had intersected thinly bedded siltstones and shales. No effective reservoir beds were present.

Tap chief executive Paul Underwood said the elevated gas readings and log data demonstrated the existence of hydrocarbon charge in the basin. While a valid trap was present, the lack of a reservoir precluded a commercial accumulation.

Tap had identified a number of other prospects in the permit where reservoir quality might improve and these would be evaluated in the near-term. Data from Tawatawa-1 would be a valuable resource for Tap's ongoing exploration program, Underwood added.

However, leading explorationist Steve O’Connor said it would have been strange if some gas had not been encountered. If that gas was methane then explorers needed to remember that in shales methane behaved differently from other heavier gases, moving via diffusion.

“The popular geological model is wrong as it does not account for the deposition of turbidites which are not deposited in highs but in lows,” said the New Plymouth-based Diligenz managing director.

Tawatawa-1 was only the second well to be drilled in the area. The 1994 Titihaoa-1 well, 35km to the southwest of Tawatawa-1, had intersected interpreted reservoir quality gas sands which were not tested due to the lack of a gas market at the time of drilling in 1994.