SOUVENIR COMMITTEE - Birbal Sahni Institute of Palaeobotany

Training Programme on “PALYNOLOGY IN FOSSIL FUEL EXPLORATION”
[ September 10-17, 2012 ]
HIGHT IMPACT PALYNOLOGY IN HYDROCARBON EXPLORATION IN
COMMERCIALLY PRODUCING BASINS OF INDIA WITH RECENT ACHIEVEMENTS OF
BSIP
NARESH C. MEHROTRA
Birbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow – 226007, India
E-mail: mehrotrabsip@rediffmail.com
With the fast growing hydrocarbon exploration activities in India, a good amount of subsurface
palynofossil data is continuously being generated from the various prospective sedimentary basins. Most
of the exploration work was carried out by Oil & Natural Gas Corporation Ltd. (ONGC), India's National
Oil Company. However, with the opening of exploration activities to private operators in the last decade,
a lot of geoscientific information has been generated. Palynological studies related to hydrocarbon
exploration have been mainly published by Mehrotra and associates in the last decade from ONGC and
Birbal Sahni Institute of Palaeobotany (BSIP).
A comprehensive account of stratigraphic palynology in the commercially producing basins of
India – Cambay, Mumbai Offshore, Cauvery, Krishna-Godavari (K-G) and Assam- Arakan has been
given by Mehrotra et al. (2002). This has been quickly followed by publication of additional information
on palynological biostratigraphy, source rock evaluation, palaeoenvironment and sequence
biostratigraphy, particularly from the Western Offshore and K-G basins. It includes Atlas of
dinoflagellate cysts from Mesozoic (Mehrotra & Aswal, 2003) and Tertiary (Mehrotra & Singh, 2003) of
Krishna-Godavari Basin and significant palynological information from several exploratory wells in
Mumbai Offshore (Mehrotra et al., 2002b and Kapoor & Swamy, 2007). Another major publication
dealing mainly with stratigraphic ranges of significant palynofossils was published (Mehrotra et al.,
2005). Recently Mehrotra et al. (2008) reviewed the available information on high resolution
biochronostratigraphy of petroliferous basins based on dinoflagellate cysts and spore-pollen data.
This presentation gives an updated account of palynostratigraphic, source rock evaluation and
palaeoenvironmental information from several petroliferous basins, especially the Western Offshore and
Krishna-Godavari (K-G), the two most prospective hydrocarbon bearing basins with special reference
to application of Dinoflagellate Cysts in Hydrocarbon Exploration. Forty-three dinoflagellate
biohorizons have been identified in the subsurface Tertiary sediments of Mumbai Offshore, facilitating a
high resolution correlation of oil bearing horizons. Integrated palynostratigraphic data from the Mesozoic
and Cenozoic has been compiled in a tabular form. Eighty-two dinoflgellate biohorizons have been
identified and tied up with foraminiferal data. A very fine dinoflagellate based stratigraphic resolution has
been achieved at most levels making it effective in geological modeling for hydrocarbon exploration
research in both Western Offshore and Krishna-Godavari basins. In Cambay Basin, five dinoflagellate
horizons have been identified with in Ypersian. In Cauvery Basin, dinoflagellate cysts have been found
useful for precisely dating Cretaceous to Early Eocene sediments and are partly tied up with planktonic
foraminifera. In Assam basin, seven biochronohorizons have been distinguished between Thanetian top to
Priabonian.
A recent research from BSIP showing first record of Type I matured, Liptinite organic matter
facies from Late Neoproterozoic of Rajasthan is considered significant. This throws open an entirely new
basin for hydrocarbon exploration from Neoproterozoic sediments in Rajasthan and other similar
prospective basins in India. Another recent find of acritarchs and algae suggest a Cryogenian to Ediacaran
age for the pre-Tertiary Sequence of Ganga Basin; this represents an extension of Marwar Super Group
sediments. Organic matter maturation studies indicate possibility of hydrocarbons in Ganga Basin. This is
a collaborative work of BSIP with ONGC.
Limitations of present biostratigraphic studies and future areas of focus have been identified.
The major petroliferous systems identified in Indian basins - Cambay, Western Offshore, K-G,
Cauvery and Assam-Arakan have been briefly dealt with. Potential source rock facies have been
identified and their distribution mapped in several promising areas for furthering exploration.
Birbal Sahni Institute of Palaeobotany, Lucknow
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