In a statement, the group said that out of the purchase price of US$212.5mil, the net amount paid at completion was US$123.65mil after taking into account various adjustments including the deposit of US$15mil.
It added that all conditions were fulfilled as at Jan 20, 2022.
Fortuna's asset portfolio comprises interest and operatorship in five production sharing contracts in Malaysia and Vietnam.
Following the acquisition, Hibiscus said it expects its average daily oil and gas production to increase nearly threefold.
"Almost 50% of the production comprises gas.
"The addition of gas production is expected to present a better balance to our Group’s asset portfolio in terms of price stability, markets and operations.
"Such diversification represents a key aspect of our energy transition strategy as natural gas has been regarded as an important bridging fuel as the world transits to a lower carbon energy mix," said Hibiscus managing director Kenneth Gerard Pereira.
In light of the announcement, trading in Hibiscus's shares has been halted from 9am to 10am on Tuesday.
The share last traded at 88 sen apiece on Monday.