Strong gas-condensate flows have been measured during testing of Tingu-1 since the well was perforated across a 7m interval in the Elevala sandstone last week.
At the end of the clean-up flow period, Horizon said the average flow rate was 48 million cubic feet of gas per day with no water, indicating high deliverability from the reservoir.
Horizon encountered elevated gas readings as the well was drilled through the Toro formation reservoir, which supported the initial result from the Elevala sandstone announced late last month.
Data from logging showed the well had encountered a liquid-rich gas column in the upper part of the sandstone and a gas water contact in the reservoir.
Horizon said the production testing result was encouraging for future production operations.
"The Tingu accumulation is potentially similar in size to the Elevala gas-condensate field (2C contingent resource of approximately 400 billion cubic feet of gas and 22 million barrels of condensate)," the company said in a statement.
"Horizon Oil, as operator of PRL 21, is currently carrying out front-end engineering and design of the Elevala and Ketu field developments.
"The Tingu gas-condensate accumulation will be incorporated in the development scope."
Participants in the PRL 21 joint venture are operator Horizon Oil (Papua) (45%), Talisman Energy Niugini (32.5%), Kina Petroleum (15%) and Diamond Gas Niugini (7.5%).
"Kina is very happy with the result of Tingu-1," Kina Petroleum managing director Richard Schroder said.
"The well stepped out 9km from the nearest well and achieved its goals of extending the field to the west as well as defining a gas water contact in the west.
"The well highlights the potential for the growth of resources in the Toro sands, which are considerably thicker than the equivalent section encountered in Elevala 1.
"This has implications for the updip potential at Tingu and further upgrades PPL 437 where Kina sees Tingu/Elevala look-alike structures.
"KPL last week announced a farm-out deal of PPL 437 to Heritage Oil and we foresee seismic acquisition and drilling a well in 2014."