Wpływ rezydualnego nasycenia gazem poniżej stwierdzonego kontaktu woda–gaz na proces eksploatacji złoża

Natural gas fields over millions of years are exposed to various geological factors that affect their final state and shape. It happens that after some time of production, the reservoir has additional energy and greater gas resources than originally expected. The reason for this may be residual gas saturation below the specified gas–water contact, which has not been included in previous analyzes. Disregarding the residual hydrocarbon zone may lead to erroneous conclusions about resources, recovery factors and water breakthrough time. In this paper the residual gas zone impact on the production process from a real gas-condensate reservoir has been analyzed. The calculations were conducted using a dynamic reservoir model created in Eclipse numerical simulator. For the purpose of the analysis, 6 dynamic models were made. On their basis, an analysis of the impact on cumulative gas and water production was carried out for parameters such as: critical gas saturation in the residual zone and volume of aquifer. Based on the presented example, the overall gas initial in place after taking into account the residual zone has increased about 19%. However, the impact of the residual gas zone on cumulative gas production is not clearcut and its presence can have a positive as well as negative impact on the cumulative gas production. The size and type of the impact resulting from presence of the residual gas zone is directly related to the geological and reservoir conditions in the given reservoir and the way of production operation. The obtained results indicate also that the residual gas zone may affect the water breakthrough time in production wells as well as total volume of produced water.