State-owned Oil and Natural Gas Commission is to increase crude production by up to 4 million tonnes per annum by 2013-14. Talking to reporters during a recent visit to Hyderabad ONGC Chairman and Managing DirectorSudhir Vasudeva said the Public Sector Undertakings is spending Rs 26,000 crore in developing 10 clusters involving about 34 marginal fields in both western and eastern offshore. He said most of them will be completed by 2013-14.Marginal field is any oil field or well that is nearing end of its commercial life and the production rates of these fields will be low and economically not viable under regular conditions.