The state giant started drilling four horizontal wells in Yingxiongling in Qinghai oilfield, part of the Qaidam basin in western province of Qinghai where oil exploration began in the 1950s, Petrochina's parent company CNPC said on Tuesday.

He didn't take an academic course, but picked up the subject autodidactically.

After so many years in the same field, the job had lost its luster.

He was granted permission to attend the meeting.