Earth’s Cryosphere, 2021, vol. XXV, No. 3, pp. 30–36
GASES AND GAS HYDRATES IN THE EARTH’S CRYOSPHERE
ZONE OF STABILITY OF METHANE HYDRATES IN THE AREA OF THE SREDNEVILYUISK GAS-CONDENSATE FIELD (VILYUI SYNECLISE)
A.D. Duchkov1, V.P. Semenov2, L.S. Sokolova1, A.I. Sivtsev3
1 Trofimuk Institute of Petroleum Geology and Geophysics, SB RAS, Akademika Koptyuga prsp. 3, Novosibirsk, 630090, Russia; duchkovad@ipgg.sbras.ru 2 Melnikov Permafrost Institute, SB RAS, Permafrost str. 36, Yakutsk, 677010, Russia; semenov.vp@rambler.ru 3 TAAS-Yuryakh Neftegazodobycha LLC, Ammosova str. 18, Yakutsk, 677018, Russia; sivtsevai@tyngd.rosneft.ru
The results of determining the lower boundary of the methane hydrate stability zone based on geothermal measurements in 22 wells of the Srednevilyuisk gas-condensate field have been presented. A graphical method has been applied, which consisted in comparing the thermograms with a phase diagram characterizing the equilibrium conditions of formation for the methane gas hydrates contained in the upper deposits of the field. At present, the upper gas deposits of the field (depths of 1035 and 1057 m) are located only 60–70 m below the stability zone. An approximate assessment of changes in the location of the lower boundary of the stability zone of methane hydrates in the Late Neopleistocene–Holocene has been made. It has been revealed that during the cold periods (~130 and 15 thousand years ago), the stability zone could fall below the upper gas deposits of the Srednevilyuisk field by 20–50 m.
Key words: Vilyui syneclise, Srednevilyuisk gas-condensate field, permafrost, methane natural gas hydrate stability zone, boundaries of the zone, Late Pleistocene–Holocene