"I'm just hoping that I have enough ballots," said Joan Hollekim, the county auditor in Mountrail County, North Dakota's biggest oil producer. She increased her ballot printing order by 25 percent, and already has more than 600 early votes, a record.Beth Innis, the auditor in neighboring Williams County, said she's already booked more than 2,500 absentee votes, which is double what she expected. "I thought it would be big," Innis said of the rising number of voters. "I didn't think it would be this big." In North Dakota, the only state that does not have voter registration, any citizen over 18 who has lived in the same place for at least 30 days can cast a ballot. That would include oilfield workers who may actually be living elsewhere and commute home to see their families. Democrat Heidi Heitkamp and Republican Rick Berg are both pitching hard for the votes of North Dakota's energy workers. In a final campaign swing this week, Berg visited an oilfield trucking service company, a natural gas processing plant and a coal mine in western North Dakota. Heitkamp talks up her advocacy for North Dakota's oil and coal industries when she served as state attorney general and tax commissioner. In one of her television ads, she speaks over the noise of a passing train of oil tanker cars while promising to support development of a new North Dakota refinery to process crude. The oil industry is making sure its work force knows how to participate. A recent newsletter from the North Dakota Petroleum Council instructed workers who live in recreational vehicles or "skid shacks"â¿¿ tiny huts, often no larger than a single-car garage, which can be hauled on flatbed trailers â¿¿ how to request mail ballots. The Brighter Future Alliance, a nonprofit group with ties to prominent North Dakota Republicans, has conducted voter information workshops in several of the temporary housing camps dotted throughout western North Dakota.