Houston-headquartered Swift Energy Company today said the Kauri-A4 well had reached its total depth of approximately 4636m (true vertical depth 4036m) and had intersected several of the primary targeted formations, including the Kauri sands, lower Tariki sands and Cretaceous sands.

However, electric logs showed the lower Tariki and Cretaceous sands to be non-commercial at the well bore and SENZ decided to plug back and to test the shallower Kauri sands.

Total gross thickness of the Kauri sandstone interval encountered was about 321m, from the 2395m mark. Core samples indicated the porosities were 15-22%, with permeability of 8-13 millidarcies. The most prospective section, of about 15-22m depth, was encountered near the top of the Kauri sands and that would be tested during the next few weeks.

Swift Energy said it appeared likely this interval contained gas or gas-condensate and was possibly fractured.

Industry commentators say Kauri-A4 has probably encountered some "reasonably tight" gas, which might need artificial stimulation before commercial flow rates can be obtained. Several years ago Fletcher Challenge Energy successfully fracced the more northern Mangahewa field to finally get an estimated 101bcf of recoverable gas from that tight field.

Swift Energy said Kauri-A4 had intersected the targeted seismic anomaly that had been identified just above the Kauri sand that was intersected by the Kauri-A1 well drilled last year.

Swift Energy Company president Terry Swift said the significant sand sequence warranted further evaluation. "But it is important to point out that we need to conduct production tests before we can determine the commercial viability of this horizon.

"While disappointed that the lower Tariki sand was wet at this location, the quality of the sand in this well exceeds our expectations, and this information can help us identify the more prospective areas for those Tariki sands."

The well intersected the lower Tariki at a vertical depth of about 3831m and this section had approximately 65m of gross thickness with excellent sand quality comparable to the more northern commercial Tariki and Ahuroa fields.

Industry commentators say Swift Energy should not be too disheartened at having only minor hydrocarbon shows while drilling through the Tariki sands, as similar things happened when FCE first drilled Tariki and Ahuroa during the mid-1980s. These and other wells later proved productive.

Swift spudded the Kauri-A4 exploratory well on June 22, with multiple objectives in the Kauri sands, Tariki sands and the Cretaceous.

The Parker Drilling 246 rig is now scheduled to be moved to the nearby, but more northerly, Rimu prospect to drill a development well aimed at providing additional throughput for the Rimu production station.