SPG, Ahmedabad Chapter Organizes Lectures on
‘A feasibility study on Low Frequency Passive Seismic Survey at the Mansa and Jotana in Cambay Basin and Ashokenagar in MBA Basin’
‘Magnetotelluric study to characterize sediment thickness (including Mesozoic) and major faults in Kachchh (Gujarat)’
Society of Petroleum geophysicists, Ahmedabad Chapter,organized special lectures on ‘A feasibility study on Low Frequency Passive Seismic Survey at the Mansa and Jotana in Cambay Basin and Ashokenagar in MBA Basin’ by Dr. A. P. Singh, Scientist-Bfollowed by ‘Magnetotelluric study to characterize sediment thickness (including Mesozoic) and major faults in Kutch (Gujarat)’ by Dr. Kapil Mohan, Scientist-C, of Institute of Seismological Research Department of Science and Technology(ISR), on 22nd January, 2019 at Gandhinagar.Talk was graced by Dr. Sumer Chopra,Director/Scientist-Gand Dr. M. Ravi KumarDirector General, ISR.
In last several years there is an increasing interest in phenomenon of low frequency (0.5-10Hz) anomalies over hydrocarbon reservoirs. Passive Seismic Method is a geophysical method that utilizes a spectral frequency from seismic data to identify a subsurface fluid behaviour / direct hydrocarbon indicator. In thefirst talk the preliminary results of the Low Frequency Passive Seismic surveys (LFPS), which were performed in Ashokenagar#1, Jotana area and Jaguli#1 area were shown. Cityshark 24-bits recorder coupled with a Lennartz LE3d (5s) velocity sensor and Tromino 3G (10s) instruments were used for Jotana, Mansa and Ashokenagar#1,Jaguli#1 fields respectively. The results shows very distinctive V/H ratio >1.5 for Ashokenagar#1 (oil/Gas well) as compared to low value at Jaguli#1 (Dry well). Higher V/H ratios are also observed near proposed location. LFPS survey in 3D grid pattern around proposed locations may be planned for optimal positioning of location. The doublet response instead of single peak as observed in V/H ratio plots need to be critically analysed to ascertain their sources. It may lead to some additional potential zones.
In the second talkit was mentioned that Sediment thickness mapping (including Mesozoics), Delineation of Fault lines (hidden also), Deep Crustal studies and geothermal source zone mapping can be done using Magnetotellurics. Estimation of Mesozoic Sediment Thickness in Kachchh - The total area of the basin is about 71,000 sq km of which on-land area is 43,000 sq km and off shore area is 28,000 sq km up to 200m bathymetry. The basins filled up with 1550–2500m of Mesozoic sediments and 550m of Tertiary sediments in on land region and up-to 4500mof Tertiarysediments in offshore region.
Mesozoic rocks are exposed in six regions viz. Kutch Mainland, Wagad Highland, islands of Pachham, Khadir, and Bela, and in Chorar Hills.Surveyed petroleum source rock distribution in different geological time-scale suggested that more than 50% of source rocks as well as reservoir rock are found in Mesozoic sediments.
Seismological laboratory visit and live data demonstration of earthquake monitoring/ seismograms was also a new experience for all participants.
The session was very informative, interactive and suggestions were taken from the participants for more such talks to be arranged in future.The meeting concluded with vote of thanks and memento to Dr. A. P. Singh, Dr. Kapil Mohan, Dr. Sumer Chopra and Dr. M. Ravi Kumar.