Moscow. September 21. INTERFAX.RU – Scientists have found that at Yamburg oil and gas condensate field of Gazprom on the surface near the wells gassing, which can occur not only from the zone of permafrost, but also of the productive, including the Cenomanian horizons. Problem behind-the manifestations in the field is described in his article in the scientific journal “Gas industry” N. Avetov of LLC “Gazprom dobycha Yamburg”, E. Krasnov from the Institute of Geochemistry and analytical chemistry named after Vernadsky and Professor RGU named after Gubkin Vladimir Yakushev (in the article only the initials of the authors).
“In the process of operation of gas and gas condensate wells Yamburg oil and gas condensate field in almost all areas were found behind-the-casing gas shows of varying intensity”, – stated in the article. The authors do not generalize, how widespread this phenomenon in other fields of “Gazprom”. However, in the system of public procurement contracts the study or the elimination of behind-phenomena placed “Gazprom dobycha Noyabrsk, Gazprom dobycha Krasnodar”, “Gazflot” (offshore Kirinskoye gas and condensate field).
On the Yamburg field study stated: “Almost the entire territory of ANGCM common grigorovka in estuarine parts of the gas and gas condensate wells. Gas shows visually recorded in the estuarine funnel of thawing, filled by meltwater. Usually there is a release of gas to the surface in the form of wildness. Gas shows visually recorded directly around the borehole column and at the distance of 2-3 m from the mouth”.
In the area of ANGCM gas shows from the permafrost interval was recorded even during the initial drilling and testing wells. Then set a primarily local, biochemical Genesis of gases in permafrost zone. “To date, many of the wells are operated for 20-25 years and have formed a fairly extensive halo of thawing of frozen rocks around their trunks. Thawing was to change the strength and filtration-capacitive parameters of rocks and could lead to seepage through the permafrost interval deeper catagenetic gas from the upper productive horizons,” write Avetov, red and Yakushev.
To prove the hypothesis that the deeper the origin of the facing surface of the gas, the researchers analyzed the isotopic composition of carbon in methane and the component ratio of the gas, since each horizon has its own signature according to these parameters. In June of 2016 have taken samples of gas from four wells Kharvutinskaya area of ANGCM.
In samples from two wells were vnutrimatocny biochemical gas, “as it was observed in the first studies of the manifestations of vnutriorgannogo gas in the first studies of the manifestations of vnutriorgannogo gas AGCM”. “However, the isotopic composition of carbon in two other wells of the Cenomanian corresponds to the horizon, which tells about the deeper percolation of gas through the circuit in thawed permafrost around a working production wells”, the researchers said. The authors notice that the sources of deep gas can be not only deposits of Cenomanian, but the overlying rocks of the lower Paleogene, where the gas is identical in composition Cenomanian.
Scientists remind us that estuarine gas shows in the vicinity of the array thawing permafrost are fairly well-known phenomenon. In origin it may be local, vnutrimatocny biochemical gas or more in depth, introduced in the interval of the permafrost zone catagenesis, coal, or shale gas. The allocation of this gas are different from weak propulsive through surface water to strong gas emissions, especially in the first years of operation neteploizolirovannaya wells or while drilling the interval of the permafrost zone.