But the company added that, “Wireline logs have not been definitive in determining the presence of hydrocarbons in these formations and attempts to obtain formation pressures and samples were unsuccessful.”

Cooper said it believed that hydrocarbon saturations could not be accurately determined due to the effects of drilling mud filtrate and lost circulation material (LCM).

“The well experienced mud losses whilst drilling and LCM was required to control those mud losses,” the company said.

“The invasion of mud filtrate into formations tends to flush hydrocarbons away from the near wellbore thereby making log identification of those hydrocarbons difficult.”

The forward plan is to drill ahead to the casing point at 2500m, log the lower interval from 2141-2500 metres, set 13-3/8” casing then drill ahead to the Kujung oil primary objective, which is prognosed to be at about 3020m.

Cased-hole production tests may be run after the well reaches total depth, depending on the drilling results in the Kujung formation.

Currently the well is at a depth of 2141m, where Cooper has decided to change the drill bit.

Kurnia-1 is in the South Madura production-sharing contract on the Indonesian island of Madura.