Is there a subvertical zones over oil and gas deposits? What physical parameters you found?
We have prepared a aquifer panel diameter based on the borehole data received from Groundwater department. We have plotted the borehole data and depth of sediment deposition in the Luni River Basin, Rajasthan. We did not carried out any Basin characterization or analysis for any oil or gas deposit. At places, depth of sediment plotted more than 300 m. in the basin. Soon after the publication of the research paper, one organization, reported huge oil/gas deposit in the Kutch area of Gujarat ie. at the tail end of the Luni River and at the ouftlow of the Luni river basin.
There are alteration zones documented above hydrocarbon accumulations that are thought to be generated via perculation processes and also via diffusion through the rock column (Veeken et al 2012 Petroleum Geoscience, Vol 18 p59-72). No top seal of a HC trap is 100% perfect and always some leakage occurs from the reservoir. The geoelectric method for hydrocarbon exploration is using this phenomenom and allows to detect Induced Polarisation anomalies in the overburden directly above the deeper seated HC reservoir. This is caused by growth of epigenetic pyrite crystals that have a very high electric polarisation characteristics.
Shallow geochemical alteration zones are also created by local increased organic activity (e.g.Schumacher, D. & Abrams, M. (eds). 1996. Hydrocarbon Migration and its Near Surface Expression. American Association of Petroleum Geologists, Memoir, 66).
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One has to be very careful here. In an undisturbed zone with a uniform hydrocarbon in place, gas is expected to rest on the oil in a reservoir bearing both fluids. Supposing we have tiny layer of a non-porous rock resting on a reservoir sand for instance, up before another sand body on top? Now if this sand body if filled with gas infiltration.....then that sub-vertical distinction will be labelled. Secondly if the region is disturbed (Fracking as the case maybe) the top sand can also be invaded by gas from a possible adjacent gas filled reservoir bucket, hence detailed analysis could also show the separation.
I will send you a drawing that shows the subvertical zone above the Muradkhanli oil field in Azerbaijan. And it shows generalized temperature data obtained from numerous wells, and data on the magnetic susceptibility of rocks taken from these wells, in the contour zone and beyond the contour part of the deposits. And the decrease in density in the contour part of the deposits is calculated using the formula obtained by me. I established a decrease in the magnetic susceptibility and density of rocks and an increase in temperature in the subvertical zone above the deposit (that is, in the contour part of the deposit).
Sincerely prof. V.G.Gadirov
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