Development of technology of gas condensate extraction from the formation in the conditions of retrograde condensation

Abstract

The object of research is gas condensate fields at a late stage of their development under conditions of a decrease in reservoir pressure below the pressure of condensate separation from a gaseous state. Reservoir losses of condensate during the development of deposits in depletion mode can reach 78 %, which entails the need to use various methods of stimulating the reservoir system to remove it. The most acceptable method is the use of a cycling process by re-injection (recirculation) of the produced and separated gas into the formation. A significant disadvantage of the cycling process is the long-term conservation of gas reserves as a result of its re-injection into the reservoir and significant capital and operating costs for dry gas injection. From a technological point of view, the use of the cycling process is constrained by the low value of the sweep efficiency. Dry gas that is injected has a lower viscosity in terms of the gas-condensate mixture is withdrawn from the reservoir, and under the conditions of the heterogeneous structure of the reservoir, its rapid breakthrough from injection to production wells takes place and, as a result, a decrease in the efficiency of condensate recovery. As an alternative to the cycling process for extracting retrograde condensate from the reservoir, it has been proposed to squeeze it out with water.

The paper proposes a unified waterflooding system, actually displacing condensate with water or a gas-water mixture. This is achieved by controlled operation of injection and production wells. First, gas is taken from the wells, and with the appearance of water in the product, methods of intensifying the transfer to the surface are used. If necessary, the wells are switched to forced production mode. The results of laboratory studies carried out on real samples of core material from the Andriyashivske gas condensate field (Ukraine) are presented. The directions of the implementation of gas-water repression in gas condensate fields with the parallel use of restrained reservoir gas available in the reservoir are substantiated. The technology allows to extract up to 50 % of the condensate dropped out in the reservoir.