Private equity-backed oil and gas venture Siccar Point Energy announced its first North Sea investment on Tuesday and said it planned to do more deals over the next year as cash-rich firms step up activity after a two-year rout in the sector. Siccar Point, headed by Jonathan Roger, a former Centrica executive, and backed by private equity firm Blue Water Energy and Blackstone (BX.N), acquired a 8.9 percent stake in the UK North Sea Mariner field from JX Nippon (5020.T). Several private equity, or PE, funds such as Carlyle Group (CG.O) and CVC Partners have joined forces with veteran energy executives in recent years to form companies seeking to snap up assets around the world amid the sharp drop in oil prices.