The company said it did not expect the outcome of its review to affect its ability to maintain the current level of dividends, or its long-term contractual rights to all gas associated with Kupe, which feeds its gas-fired units at Huntly.
Chief executive Marc England said the sale of its interest in Kupe was "not a fait accompli".
The asset comprises the oil and gas field off the south Taranaki coast and an onshore production station near Hāwera. It is the third highest producing oil and gas asset in New Zealand.
England said Kupe had a strong production history, with three significant reserve upgrades over the past 10 years.
England said the field, which is exempt from the Government's ban on new offshore exploration, courtesy of its existing permits - had strong potential.
The field itself is a core fuel supplier for the New Zealand market, with 15 years of remaining production, he said.
Chief financial officer Chris Jewell said the venture is part-way through an onshore project to install equipment allowing the plant to operate at its design output. The project is due for completion in mid-2021.
"The joint venture has started to consider the second phase of development which may consist of further drilling for both production and potentially exploration," he said in a conference call.
Further development would require capital, which would make Genesis a different proposition than the one taken on when the company undertook its IPO and listing in 2014.
Jewell said a decision on Kupe, one way or the other, would not affect the company's ability to pay dividends at the current level.
He added that the exploration ban would make already permitted areas more valuable at a time when gas production is declining.
England said Genesis had been "a good owner and a happy owner" of the asset.
"We are at a key moment where we need to make a choice, so a review is all about understanding the different options for us."
The field's other owners are the operator, ASX-listed Beach Energy and NZOG.
The carrying value of the company's oil and gas assets has been put at $307m in its annual report but Jarden's director of research, Grant Swanepoel, estimated the stake to be worth anything between $300m and $500m.
He said the rush to "green" assets among investors was happening more quickly than many had thought.
"Generally, having gas and oil operating assets is not good for a lot of investors," he said.
"For them the risk is exacerbated by what goes on in the press and by investors pushing back on companies like Genesis."
The move made sense in context of the company's plan to become less reliant on fossil fuels through Future-Gen. "I see it as a positive move, and I think the market will give them credit for pursuing it," said Swanepoel.
"Kupe has been a good asset for them but it's just another thing for business to have to manage, so they can simplify.
"And the simpler Genesis becomes, the easier it is to invest in."
Genesis expects to release a decision on Kupe by the middle of next year.
