“Although further analysis is required, initial results indicate a small increase in proven reserves in this part of the field,” Oil Search said.

“However, the potential reserves in Greater Juha have been reduced to around 2Tcf of gas, confirmation of which will be subject to further appraisal drilling, with Juha-4 planned to follow Juha-5.”

Over the weekend, reservoir pressure information acquired in the well confirmed that the Toro Formation is water bearing. Reliable pressure points have defined a potential gas-water contact (GWC) in this part of the field and confirmed an extension of the minimum gas column of about 50m.

“The gas column, from the highest known gas in Juha 1 to the GWC defined by pressure readings in Juha 5, is now about 250m,” Oil Search said.

Juha is in a remote and difficult-to-reach part of the highlands and will need substantial reserves to justify the high development costs. Oil Search and ExxonMobil were hoping to prove up to 4Tcf of gas and 150 million barrels of condensate, and may have to reconsider their options if the Greater Juha area contains no more than 2Tcf.

Oil Search has said it sees Juha as the potential feed source for a proposed liquids cycling plant that has a preliminary capital cost estimate of about $850 million for production of around 45,000 barrels per day. It could later be linked into a liquefied natural gas project, the company has said.

The participants in Juha 5 are Oil Search with a 31.5% stake, ExxonMobil (56%) and Merlin Petroleum (12.5%). While ExxonMobil is operator of the PRL 2 permit, Oil Search is operating the Juha wells.

In other news, Netherland Sewell and Associates in Dallas has certified Oil Search’s 1P (proven) reserves at 61.4 million barrels of oil equivalent, and 2P reserves (proven and probable) at 81.7MMboe, Oil Search said on Friday.

Oil Search also had 941.5MMboe, comprising gas and associated liquids, in its resource inventory, taking the company’s total 2P oil and gas reserves plus gas and associated liquids resources to just over 1 billion barrels of oil equivalent.