SHORT-TERM VARIABILITY
OF THE MERCURY CONTENT IN HYDROCARBON GASES AS AN INDICATOR OF DYNAMIC PROCESSES
IN THE LITHOSPHERE (Abstract)
Ryzhov, V.V.1; Mashyanov, N.R.1; Pogarev, S.E.1;
Ozerova, N.A.2
1Earth’s Crust Res. Inst.,
St. Petersburg State Univ., Russia; 2Instit. of Geology of Ore Deposits, Petrology, Mineralogy and Geochemistry,
RAS, Russia)
The mercury content in
oil and gas fields depends on the regional geological location of these
deposits. The highest concentration of mercury is observed in hydrocarbon
deposits bound up with the crossing of deep-fault zones of different orientation
(Ozerova, 1986).
Research conducted over the years at
different gas deposits revealed a substantial variability of the average
mercury content in investigated gas pools, which ranges from 1.5 to 15 times
(Mashyanov et al., 1999).
Zeeman AAS technique RA-915 (by Lumex
Ltd.) has been used for direct continuous measurements of mercury in hydrocarbon
gases.
The short-term regular variations of
mercury content in hydrocarbon gases were discovered for the first time
in 1990 at the Oposhnya deposit (Ryzhov et al., 1998), and then were studied
at another mercury-bearing Mirnenskoye gas-condensate field.
The most stable harmonics oscillate
with periods of 0.3 to 2.5 hours. Relatively low-frequency oscillation with
a period of 25 hours is seemed to correspond to calculated lunar tidal cycle.
The oscillation magnitudes range from 10 to 80 % of the average content
of mercury in a gas. Medium frequencies are characteristic of individual
gas wells, even within the limits of one productive horizon. A remarkable
feature of these harmonics is the multiplicity and good agreement of their
periods with phases of the Earth's seismo-gravitational oscillations.
An oscillatory mechanism of the mercury
adsorption-desorption in a porous gas-bearing medium is assumed. A possible
application of the observed phenomena for the earthquake prediction is discussed.
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