Prostar Capital aims to acquire what it regards as undervalued companies and assets in the area and has recruited Trap Oil to help it find suitable targets.
The move provides another vote of confidence in the North Sea on the part of international investors.
It follows a series of deals in which oil and gas firms from around the world have bought into the UK North Sea or increased their exposure to the area.
Deals such as Korea National Oil Corporation's £1.9bn takeover of Aberdeen-based Dana Petroleum in 2010 reflected the buyers' belief that assets were worth more than the maket appeared to recognise.
A number of private equity firms have invested in the UK North Sea in recent months.These include London-based Petroleum Equity and Norway's HitecVision.
Aim-listed Trap Oil said: "Prostar's management believes that there is considerable value in the North Sea, and has established a substantial fund targeted at acquiring undervalued assets and companies in the region."
A spokeswoman for the firm said the fund was worth more than $100m.
The agreement provides a boost for Trap Oil following a challenging period for the firm, which bought Banchory-based Reach Oil & Gas for £30m in 201.
Last month Trap Oil said it had cut directors' pay for this year by 20 per cent and "trimmed" staff levels after losing £10.3m before tax in 2013
Trap Oil, which has a stake in the producing Athena oil field, said it had returned some promising assets to the authorities as it was unable to progress them with parners.
In the results announcement chief executive Mark Groves Gidney said it was hard to get risk capital to invest in the North Sea.
Yesterday he said the Prostar agreement could generate significant value and growth in the company's portfolio in coming years.
Mayfair-based Trap Oil will get a 2.5% interest in qualifying acquisitions made by Prostar.
It will get a 2.5% cash payment when they are sold, depending on conditions.
The company can opt to acquire up to a 5% interest in any asset covered by the agreement with Prostar.
Separately, Trap Oil has agreed a deal with Suncor under which it will acquire an additional 50.6% interest in the Romeo discovery West of Shetland in return for carrying a bigger share of the cost of qualifying work on the Niobe licence.
Mr Groves Gidney said the transaction could also generate significant value.
He added: "With other projects and potential new business streams currently at an advanced stage of negotiation, we look forward to an exciting next phase in the group's development."
The deal with Suncor will leave Trap Oil with a 73% interest in Romeo and a 28% stake in Niobe.
Prostar Capital has offices in New York and Australaia and specialises in investing in energy and infrastructure assets.