During recent years the active development of Achimov deposits in the Urengoy oil and gas-condensate field has begun. The development of these deposits will not only reduce the gas production decline rate from traditional Cenomanian and Valanginian deposits, but will also allow to increase the production of liquid hydrocarbons. The cumulative extraction of gas from these deposits in 2017 exceeded 20 BCM, while production of the hydrocarbon condensate (including unstable and deethanized) amounted to approximately 9 million tons. It is planned to reach the production level of Achimov gas in Urengoy field of 40 BCM/year [1 - 3]. Achimov deposits were discovered in other fields as well, for example in the Yamburg field. The activity of Wintershall Holding GmbH for development of the Achimov deposit is represented by two Joint Ventures with PAO Gazprom – AO Achimgaz with the operating Gas Treatment Plant UKPG-31  and OOO Achim Development with the future UKPG-41 and UKPG-51. These plants are designed for gas treatment in accordance with STO Gazprom 089-2010 and extraction of unstable gas-condensate with the properties according to STO Gazprom 5.11-2008 as well as Technical Specifications TU 05751745-02-88 "Unstable gas-condensate in mixture with the associated oil". The composition of unstable condensate (UC) includes not only hydrocarbons C5+, butanes and propane, but ethane and even methane as well. The target components for further processing are the hydrocarbons C5+ and propane-butane fraction. Field gas treatment at the gas-condensate fields of the Extreme North is mainly performed using the low-temperature separation technology (LTS). The natural gases of Achimov deposits are characterized by the following properties, which allow the identify them as a separate research object .