Nighthawk Energy, the US-focused oil development and production company, has reported the presence of hydrocarbons at the Mississippi Spergen formation.In a drilling and development update on the Arikaree Creek oilfield at its 100% controlled and operated Smoky Hill project in the Denver-Julesburg Basin, Colorado, the company reported that logging and testing of the Silverton 16-10 well had confirmed an oil column in the formation.The company said that the pay zone was consistent in characteristics to the three existing producing wells in the field and confirmed the southward extension of Arikaree Creek into a larger fault-bounded structure.Completion work on the Silverton 16-10 well was underway with first production expected in early July 2013, the company said.The Snowbird 9-15 well, meanwhile, had been drilled and logged with initial analysis indicating potential pay in the Mississippian Spergen formation, the company added.Stephen Gutteridge, Chairman of Nighthawk, commented: "The confirmation of an oil column in the Silverton 16-10 well is hugely significant for the potential upside in the Arikaree Creek oilfield."He added: "The three previous discoveries are all located on a relatively narrow fault-bounded structure. The Silverton well has now confirmed the southward extension of the oil column into a larger structure, covering potentially six times the acreage of the smaller fault-bounded block. If the Snowbird 9-15 appraisal well confirms that the oil column extends significantly further to the south, then the implications for production and reserves are very positive."Nighthawk Energy's share price was up 5.57% to 5.50p at 10:34 on Thursday.MF