T7, formerly known as Tanjung Offshore, acquired 16.48 million shares in Triangle from Tamarind, which has deep links with Triangle, and helps the junior operate the only field in the offshore Perth Basin.
T7 said the purchase gave it access to upstream assets, primarily Triangle's 78.75% interest in the 1300 barrels of oil per day Cliff Head field, which includes the underutilised onshore Arrowsmith stabilisation plant and pipeline, assets that could become more valuable if the Xanadu-1 well comes in later this year.
Triangle also owns the Reids Dome conventional gas project in Queensland's Bowen Basin.
"The investment enables the company to explore opportunities in the emerging Perth Basin oil and gas area located at the north of Perth, Western Australia," T7 said.
Cliff Head has a number of near-field opportunities to increase production that Triangle is investigating.
In the surrounding area, AWE has taken an option with Key Petroleum to potentially resume exploration for oil and gas in the surrounding area, which is operated by Pilot Energy.
T7 said it would fund the acquisition from its treasury.
Triangle managing director Rob Towner said that discussions with T7 had been ongoing for some time, but it was only in the last week that Tamarind had converted a note it held in Triangle into shares for sale to T7.
"They're looking to expand, and Tamarind has been selling them on this whole Perth Basin concept, and they like what they can see and what we are doing," he said.
"I don't believe they have any immediate plans to open up an office in Australia, but certainly the idea is that whenever we undertake major operations on Cliff Head they would like to be involved."
Tamarind retains a major Triangle shareholder at 10%.
Towner is aiming to travel to Singapore next month, prior to the spud of the Xanadu-1 well, in the hopes of deepening Triangle's ties with the investment community in Asia.
"It's a difficult market, and while we have a lot of things we want to do we need capital," Towner said.
"Just sitting there with Cliff Head producing oil isn't exciting enough, and it won't grow us.
"We're starting to sell our Perth Basin dream now, but there is still a lot of work to do."
The move into Triangle comes just weeks after T7 completed a deal with Honeywell International to boost revenue from its gas generators unit.
The company was appointed as Malaysian distributor by Honeywell, with growth expected in the double digits.
Gas generators already contribute 40% of the diversified T7's total turnover.