Liberty Resources II signed on Monday an agreement with Emerald Oil to exchange a portion of its holdings in Williston Basin, North Dakota, for additional acreage in the area and $7.8m in cash. The oil and gas company, which is funded by London-listed Riverstone Energy, will acquire 4,175 net acres in Williams County, which will add about 30 operated drilling locations to Liberty's current portfolio.The transaction is expected to close in September 2014, when the purchase price will be adjusted.Chris Wright, chief executive of Liberty, said that the acquisition will "accelerate development activity and continue to grow our holding in this key area". JF