On May 16, Carlyle Group announced an investment in Tunisia-focused oil and gas explorer Mazarine Energy, which will also receive $500 million to make bolt-on acquisitions in Europe and North Africa. The size of the investment in Mazarine was not disclosed.

The deal is the first investment in more than a year for Carlyle International Energy Partners (CIEP), the private-equity firm's overseas oil and gas investment fund, which has more than $2.5 billion at its disposal, Marcel van Poecke, head of CIEP, said.

Private-equity funds including Carlyle, Riverstone and CVC Partners have built up significant firepower in recent years to invest in the oil and gas sector, which has struggled following the collapse in oil prices since mid-2014.

"I think we will see more deals this year. Very slowly the M&A [mergers and acquisitions] space is starting to pick up," van Poecke told Reuters.

Mazarine will seek investments in "low cost, low-risk opportunities" in onshore E&P assets, chairman and founder Edward van Kersbergen told Reuters. The company will focus on onshore fields in Romania, where CIEP acquired assets in March 2015 from Sterling Resources, as well as North Africa. "We want resources that we can develop in a relatively short space of time at a low technical cost," van Kersbergen said.

In Tunisia, Mazarine expects to start production of 1,500 barrels per day (bbl/d) to 2 Mbbl/d next year, according to van Kersbergen.

CIEP has, in recent years, created two companies to invest in assets in the North Sea and the Indian Subcontinent.

Neptune, the North Sea investment vehicle set up by CIEP and CVC Partners a year ago, and which is headed by former Centrica executive Sam Laidlaw, was expected to make an investment over the next 12 months, van Poecke said.