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Chemostratigraphy and Its Impact from Exploration and Development of Tertiary Oil Fields in Rajasthan, North West India

Tim Pearce1, J. H. Martin2, and P. M. Compton3
1Chemostrat Ltd, Welshpool, United Kingdom
2Chemostrat Ltd, United Kingdom
3Cairn India Ltd., Vipul Plaza, Sun City, Gurgaon 122002, Haryana, India

Important oil reservoirs lie in Tertiary continental sequences in the Barmer Basin of North West Rajasthan. The Barmer Basin is an extensional strike-slip and dip-slip influenced rift basin that developed in the Paleocene to Eocene. The best reservoirs so far encountered, occur in the early syn-rift succession of the basin in the Fatehgarh Formation. The interval consists of predominantly fluvial / lacustrine deposits with rare marginal marine influences in the subsurface.

Members within the Fatehgarh Formation are difficult to correlate, with repetitive e-log signatures and a paucity of age-diagnostic flora/fauna. An alternative method of correlation was required in order to develop regional play fairway maps, and intra-field to sub-regional correlation schemes. Chemostratigraphy has been applied to over 1400 core and cuttings samples from 14 wells from the Mangala and Aishwariya Fields. This study has resulted in the establishment of a robust independent hierarchical high-resolution chemostratigraphic scheme, based on stratigraphic variations in sandstone and silty claystone geochemistry, which can be related to systematic changes in sediment provenance and palaeoenvironment.

The chemostratigraphic correlation framework forms one component of a multidisciplinary stratigraphic approach that has been used to develop regional play fairway maps, to improve subregional correlation and enhance reservoir modelling within each field development.

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