The flaring occurred on Saturday.
Discovered nearly half a century ago, Pasca A is a carbonate pinnacle reef that lay dormant as it lacked a commercially viable development solution.
It is located in permit PPL328 in 93m of water, 256km west of Port Moresby.
Twinza managing director Huw Evans said the flaring was the result of a lot of hard work since first signing the licence in 2011.
"A very rich gas condensate came from the field which will underpin what we hope to be the first offshore development in the Gulf of Papua," Evans said.
"With the help of the Minister and the department and other stakeholders, we will see project development granted at the end of March next year, which then could lead to first production at the end of 2020."
Evans said Twinza had already invested almost K155 million (US$48 million) into the project and would invest a further K811 million (US$250 million) when a development licence was granted.
An agreement was signed in August with Baker Hughes to provide drilling services, wellheads and pressure control equipment at Pasca A.
The service company will also provide an integrated gas processing solution from the wells through to point of export once a final investment decision has been reached.
Minister for Petroleum Fabian Pok congratulated the company on its milestone, thanking Twinza for having the confidence to invest in the area.
"We will continue to work closely to ensure that it comes to fruition and we will receive the benefit for both the country and the company," he said.
Twinza estimates Pasca A contains 19 million barrels of condensate and 20MMbbl of LPG.