"Australia is our cornerstone and it is a very important area for us," he said in a rare interview in Perth.
"We have a range of discussions with the Australian government and we are very happy with their support, and because Australia has a very stable political setting and legal framework and financial regime that is very stable."
Inpex is in the final stages of ramping up production at Ichthys LNG to its full capacity of 8.9 million tonnes a year of LNG, plus LPG and condensates. After shipping its first LNG cargo in June, Mr Okawa said Ichthys reached its 100th LNG cargo milestone on November 15 after ramping up production more smoothly than expected.
Inpex's Ichthys LNG plant near Darwin has now shipped 105 LNG cargoes. Shaana McNaught
The venture, which is owned 26 per cent by French oil major Total and also involves several Japanese LNG buyers and Taiwan's CPC Corporation, represents Japan's largest single foreign investment in any sector.
It has now delivered 178 cargoes in all, including 105 shipments of LNG, 25 of LPG, 18 of condensates from the onshore operation in Darwin, and 30 exported directly from the offshore site, 220 kilometres off the Kimberley coast.
The huge project was originally budgeted at $US34 billion when it was given the green light for construction in January 2012 but suffered cost blowouts and delays.
Mr Okawa said Inpex's primary focus is on reaching and then maintaining full production at Ichthys to generate the cash flows required for expansion. That will involve looking at replacement gas opportunities as fields mature.
But Inpex has has room to expand Ichthys, with space at its onshore LNG site outside Darwin for four additional LNG trains.
Gas for that could come from a range of sources, Mr Okawa said, pointing to Inpex's own undeveloped fields in the Browse Basin and offshore gas from other companies, as well as potentially onshore shale gas in the NT.
"There is a combination of onshore and offshore because ... we have so many opportunities, and first of all we need to see all options and what will be the most appropriate for our further expansion."
Inpex is still in the early stages of gearing up for drilling at its own onshore acreage in the NT, with Mr Okawa signalling a lengthy process still in train to secure consents and approvals.
Meanwhile, Mr Okawa flagged a potential further reshuffle of interests at Darwin LNG as a result of Santos' $2.2 billion buyout of ConocoPhillips from the project and the expected shift towards using gas from Santos' Barossa field as flows reduce from the Bayu-Undan field.
That shift is expected to result in a shake-up of Darwin LNG as the various partners decide whether to also buy into Barossa, or potentially withdraw.
Mr Okawa said Inpex is "very happy" with its current 11.38 per cent stake in Darwin LNG and suggested it may consider buying into Barossa.
"If we decided to retain in Darwin LNG that will be the option. But at the moment we are very happy with our current shareholding. I want to see what will happen in the new structure, then after we think about that."
Inpex, which has a stake in Shell's giant floating LNG project at Prelude, also in the Browse Basin, is also on the hunt for additional reserves, taking up 100 per cent of a new exploration block in July in the federal government's latest licensing round.
The 3460 square kilometre block that lies west of Bayu-Undan and north-east of Ichthys and Prelude is understood to be prospective for oil.
Meanwhile, Inpex is reported to be seeking to sell out of its more mature oil production assets in Western Australia, but Mr Okawa describes the reports as speculation.
Bernstein Research has also suggested that Inpex could consider an initial public offer of its Australian business, although the company has denied that any such move is on its radar.