The objective of the speculative surveys by DGH is to add our knowledge on unexplored and poorly explored areas of Indian Basins. DGH has carried out several surveys to upgrade information covering a total area of 2 million sqkms of which, 84% is in offshore and 16% in onland.
Surveys Undertaken By DGH:.
Out of total, satellite gravity surveys over the eastern and western offshore areas and Andaman account for 1.642 million sq. kms. (82%). Joint venture offshore speculative geophysical surveys within the same area in eastern offshore and Andaman cover about 0.246 million sq. kms. (12%). These latter surveys have given valuable clues to structure, tectonics, sedimentary thickness and play recognition in the deep waters, and have provided inputs for modeling studies and for the preparation of a hydrocarbon prospect map of the area.
A 2D seismic coverage of 0.053 million sq. km. was achieved in 1997-98 in the onland areas of U.P., Bihar and M.P. 2D seismic survey was repeated in Bihar in 2002-03 over 0.05 million sq. km. These surveys were carried out to bring out favourable traps / structures of Vindhyan and Ganga basins. A new lower Vindhyanpaleo-embayment comprising of a number of high and low basement features has been mapped for the first time. These studies have led to the demarcation of certain prospective areas and 1 block each in Vindhyan basin and Ganga basin with new data were awarded under second round of NELP. One more block was awarded in NELP-IV round. In 2003-04, 805.0 GLK 2D seismic data have been acquired from Chambal Valley area to assess the prospectivity of the western part of the Vindhyan basin. One block has been awarded in the Vindhyan basin under NELP-V.
In the deep waters of the Andamans, and of the east and west coasts of India including the southern tip, 2D seismic surveys were carried out between 1999 and 2007, acquiring a total of about 41,174 LKM of data.
Geochemical surveys were carried out in the Chambal Valley of the Vindhyan basin over 0.035 million sq. km. and over 0.043 million sq. km. of Kutch onland. Out of this 0.043 million sq.km. area, 0.033 million sq.km. falls within the Kutch reconnaissance (aero-magnetic) survey area of 0.038 million sq.km., and hence not included for purposes of totaling. The samples collected in these areas show maturity of sediments and have revealed the presence of C2+ gases. During 2003-04, 350 soil samples were collected to carry out geochemical studies in Chattisgarh basin, covering an area of 0.035 million sq.km. During 2004-05 geochemical surveys have been carried out in Cuddapah and Bhima-Kaladgi basins and an additional 0.118 million sq.km have been covered in these basins. During 2005-06, regional surface geochemical surveys were carried out in Mizoram area of Assam-Arakan basin. 300 soil samples covering an area of about 10,000 sq.km. were collected along existing roads and analysed for light hydrocarbon gases.
Shallow offshore geochemical surveys were initiated by DGH through NGRI for the first time. Collection of core samples were attempted in the relinquished block KK-OSN-2000/1 in the offshore Gulf of Mannar. The research vessel CRV SagarPurvi owned by the National Institute of Ocean Technology (NIOT) was used for the purpose. However, dur to poor core sample recovery, the campaign had to be suspended. It is now proposed to carry out survey in the offshore Pondicherry area in the relinquished part of the block CY-OS/2.
DGH has initiated studies for estimation of oil shale resources in Assam and neighboring area of Arunachal Pradesh. The first phase of the investigations is likely to commence towards end of 2006.
Integrated geophysical surveys, carried out jointly by DGH and NGRI in the northwestern part of the Deccan Syneclise, revealed sub-trappean Mesozoic-Gondwana sediments with a maximum thickness of 3 Kms.
Aero-magnetic surveys amounting to 24,723 LKM were carried out in Himalayan Foreland area during the year 2003-04, 2004-05 and 2005-06.