On May 6, Marathon Oil Corp. (NYSE: MRO) detailed its first-quarter 2014 financial results. The quarter ended March 31, the company said.

Its adjusted net income was $613 million, up from first-quarter 2013’s $361 million, the company said.

Total income from North American exploration and production (E&P) was $214 million, and this increase over first-quarter 2013’s $59 million loss was due to lower exploration expenses and higher net sales volumes from U.S. plays, the company said.

Sales volumes from its overall North American operations, excluding Alaska, had increased from first-quarter 2013, Marathon said, noting that the current amount was $213 million, compared to $193 million.

Marathon’s onshore domestic areas all had increased production. The Eagle Ford averaged 96,000 net barrels of oil equivalent per day (boe/d) in first-quarter 2014, the Bakken averaged 43,000 boe/d and the Oklahoma basins averaged 15,000 boe/d, the company said. These were each increases, over first-quarter 2013, of 7%, the company added.

Regarding a second-quarter outlook, overall North American E&P activity and volume should increase, the company said.

Houston-based Marathon Oil Corp. explores and produces oil and natural gas worldwide.