Oil production in Missouri has more than doubled since 2008 but the state's geology and other factors continue to hinder the industry.

The Kansas City Star reports the state produced 201,000 barrels of oil in 2013. Most of the increase in oil production comes from Cass, Jackson, St. Louis, Vernon and Atchison counties.

Shari Dunn-Norman, a geosciences and petroleum engineering professor, says Missouri's oil is typically at shallow depths, so it doesn't have enough natural pressure to be easily recovered. And most of the oil is heavy and flows slowly.

Industry workers use large oilers of water heated with natural gas and inject it into the oil, which makes drilling and recovery more expensive.

Dunn-Norman says cheaper methods will be needed for Missouri's oil industry to grow.