Alternative asset manager Blackstone Group is blazing through fundraising for its second energy-focused private equity fund and is expected to hold a final close by the end of the year above its $4 billion target, said people familiar with the effort.

The New York-based firm plans to hold a first closing on a "substantial" amount for Blackstone Energy Partners II in a matter of weeks, said two of these people. The initial closing would enable Blackstone to begin writing equity checks for deals using the new fund.