A Bloomberg report seems to indicate that:

Iranian forces yesterday entered Iraqi territory at dawn, and occupied well number 4 in the East Maysan field in al-Fakah region, 450 kilometers (280 miles) south of Baghdad, Border Guard General Zafer Nazmi said. The Iranian forces positioned tanks around the well.

“They positioned tanks around it and dug trenches,” Nazmi said by phone from Basra. “They are still there, they raised the flag.”

East Maysan in southern Iraq is an old oil field that is no longer in production, according to Nazmi. Iraq is the third largest oil producer in the Middle East after Saudi Arabia and Iran.