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Organo-Geochemical Characteristics of Kutch Lignites and Carbonaceous Shales and Its Application from Source Rock Evaluation

Mathews, Runcie P.1; Dutta, Suryendu 1; Banerjee, Santanu 1
1 Department of Earthsciences, IIT Bombay, Mumbai, India.

The Mesozoic and Cenozoic sequences are well exposed in the western Kutch. The Palaeogene lignites and carbonaceous shales around Panandhro and Matanomadh encompass one of the largest lignite deposits in the country. Earlier studies provided an insight into the petrological characteristics of these lignites. The present study involves organo-geochemical characteristics of the lignites and carbonaceous shales to reveal their hydrocarbon source rock potential. Elemental analysis, Infrared spectroscopy, Rock-eval pyrolysis and PY-GCMS were carried out in 51 samples collected from the mine sections. The high hydrogen (> 10 wt %) and moderate carbon content (> 60 wt %) and a high H/C ratio reveals the more aliphatic nature of resinites. The sulpher (>5wt %) and nitrogen content (<1%) suggest formation of lignite in a marine influenced environment, kerogen being terrestrial origin. The broad aromatic C=C stretching peak between 1650-1560 cm-1 and the I1/I2 ratio reveals the high aromaticity of lignites. The A factor (representing the changes in the relative intensities of aliphatic groups) and C factor (represents the changes in C=O groups) plots reveals the kerogen is of type II and III. The TOC content varies from 9.17 to 57.90 wt %. Rock eval Tmax value ranging from 405 to 429 degree Celcius indicates the lignites are thermally immature. Hydrogen index (HI) values range from 79 to 330 mg HC/g TOC. The source potential (S1+S2) yields range from 13.01 to 204.73 mg HC/g rock suggests the potential of Panandhro rocks to generate mix gas and oil. The solid bitumen which is dark colour with bright luster and found as fracture/fissure filling is similar to that of Neyveli and is of pre-oil generation type

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009