After almost 15 years, state-owned Oil India Limited's (OIL) Khagorijan oil field in eastern Assam's Dibrugarh started operation on Saturday. Assam Chief Minister Himanta Biswa Sarma attended the ceremonial function of resumption of Khagorijan oil field of OIL at Rohmoria, operations of which were suspended since November 2007 due to administrative and environmental issues.