BY SIMON HALL
KUALA LUMPUR—Exxon Mobil Corp. is starting work with Russia’s OAO Rosneft in assessing what could be massive reserves of shale oil in Western Siberia, the U.S. oil giant’s chief executive, Rex Tillerson, said Tuesday.
“There is huge shale potential in shale rocks in West Siberia…we just don’t know what the quality is,” Mr. Tillerson said in an interview.
The exploration work will take years to establish if the reserves are commercially viable and are part of a strategic agreement Exxon reached earlier this year with state-controlled Rosneft, Russia’s largest oil producer.
“Rosneft wished to participate in some resource development opportunities …