New Delhi: Oil Marketing Companies (OMCs) witnessed a bad start on the stock market today as S&P Oil and Gas Index plunged 0.52 percent to settle at 13,721.43. Shares of most state-owned companies and also private ones did not fare well on the index. While Gas Authority of India Limited (GAIL) went down 1.19 percent, Hindustan Petroleum Corporation Ltd (HPCL) saw a 0.95 percent decline and Bharat Petroleum Corporation Ltd (BPCL) plunged 0.65 percent.