Marginal field refers to a field which due to various factors (geologic, geographic, technological or economic) may not produce enough net income to make it worth developing at a given time. However; should technical or economic conditions change, such a field may become commercially viable. It is usually associated with small pockets of hydrocarbons that have a plateau of a few years.

Currently, ONGC has more than 165 such small and marginal fields totaling reserves of more 297 MMT. Most of these are far away from existing infrastructures, located at great water depths or contain insufficient reserves distributed in multiple pays to consider development on a stand-alone basis. Concerted efforts involving complex combination and integration of human resources, advanced technologies improving scale of economies by integrated cluster development and changed economic scenario, many of these fields could be made economically feasible. This led to monetization of 53 fields till date and 69 fields are under various stages of monetization.

The paper illustrates through case histories the approach followed for the integrated development of these marginal fields in offshore, with special emphasis on: - grouping of marginal fields with economic fields, cluster development, modularization and standardization of process facilities/wells for optimizing cost, revamping existing jack-ups as mobile processing, CAPEX reduction through hired FPSO and use of advanced techniques like multilaterals, dual completions, zones transfers etc.

Due to these initiatives, oil production for ONGC’s offshore marginal fields is expected to peak at about 1,25,000 bopd and gas production will peak at about 17 MMm3/d in 2014-15.

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