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Imprints of Eocene Strata in Purnea Basin-a Potential Rock for Hydrocarbon Exploration

Jitendra Kumar and Mahipal Singh Negi
ONGC, KDMIPE, Dehradun, India

Successful exploration results from the application of new interpretations of old data, acquisition of new data and viewing of data in ways not attempted before. Frontier basins represent true frontiers in petroleum exploration and pose great challenge to the explorationists. The industry, of late , is increasingly looking towards them for new discoveries. Purnea basin is also one such basin where possibility of additional sequence of Eocene (Subathu equivalent) has been envisaged which augments the hydrocarbon prospectivity of the basin. This sedimentary sequence, yet to be encountered in any well in the basin, is discernible in some seismic sections in the north-western sector of the basin adjoining Nepal. The sequence is exposed in the foothills of the Himalayas and encountered in the Biratnagar-1 well immediately north of Indo-Nepal border. Pending further investigation, this sequence has been tentatively correlated to the Eocene package encountered by Shell in its well Biratnagar#1 in adjoining Nepal It is a seismic package whose seismic character is distinctly different from the overlying younger Tertiary sediments and underlying Gondwana sediments . Studies indicate that it is confined mainly to the eastern part of Monghyr-Saharsa ridge and partly on the northwestern corner of the basin. Purnea basin predominantly hosts thick sequence of prospective Gondwana sediments but presence of Eocene strata immensely enhances the prospectivity of the basin and solicits a change in the existing litho-stratigraphy of the basin.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery