The development of gas condensate fields under the conditions of elastic water drive is characterized by uneven movement of the gas-water. Factors of hydrocarbon recovery from producing reservoirs which are characterized by the active water pressure drive on the average make up 50-60%. To increase the efficiency of fields development, which are characterized by an elastic water drive, a study of the effect of different volumes of carbon dioxide injection at the gas-water contact on the activity of the water pressure system and the process of flooding producing wells was carried out. Using a three-dimensional model, the injection of carbon dioxide into wells located at the boundary of gas-water contact with flow rates from 20 to 500 thousand m3/day was investigated. Analyzing the simulation data, it was found that increasing the volume of carbon dioxide injection provides an increase in accumulated gas production and a significant reduction in water production. The main effect of the introduction of this technology is achieved by increasing the rate of carbon dioxide injection to 300 thousand m3/day. The set injection rates allowed us to increase gas production by 67% and reduce water production by 83.9% compared to the corresponding indicators without injection of carbon dioxide. Taking into account above- mentioned, the final decision on the introduction of carbon dioxide injection technology and optimal technological parameters of producing and injection wells operation should be made on the basis of a comprehensive technical and economic analysis using modern methods of the hydrodynamic modeling of reservoir systems.

The study of flooding gas condensate reservoirs at different stages of depletion (25, 50, 75% of the dew point pressure and at the maximum condensation pressure) with different potential hydrocarbon content of 100, 300 and 500 g/m3 and different voidage replacement by using injection (50, 100 and 150%). The results showed a positive effect of water injection on the increase of the condensate recovery factor, but a decrease in gas production compared to the basic options of development at depletion drive. Thus, for formation systems with medium and high potential yield of liquid hydrocarbons C5+, the largest incremental production is obtained in the case when water injection begins with minimum depletion of formation energy. While for a formation system with a low potential yield (100 g/m3) the maximum technological effect is obtained under the condition of maximum depletion. In the case of medium and high C5+ yield in the formation gas, with a slight decrease in the formation pressure by 25 or 50% of the dew point pressure, the maximum increase in the condensate recovery factor is achieved at high injection rates with 100 or 150% voidage replacement. The obtained results can be used for rapid screening of potential methods of impact on the gas condensate reservoir, and the final decision concerning the technological parameters of production and injection wells operation will be made due to the results of optimization of multivariate hydrodynamic calculations using geological and technological models.

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Purpose is to increase oil recovery of deep oil deposits of the Dnipro-Donetsk oil-and-gas Ukrainian province with the use of nitrogen.Methods. Experiments, intended to residual oil displacement with the use of different driving agents, involved laboratory modeling of the process when a seam was simulated as such being close maximally to a real seam and samples of formation fluids were applied. The experiments, which materialized equilibrium displacement (without mass transfer), used seam models developed from cores of V-19n seam (Perekopivske deposit). 43 core samples were analyzed with 3.3 -226.0•10 -3 µm 2 permeability.Findings. Characteristics and applicability of nitrogen and flue gas to increase oil recovery have been analyzed. Theoretic prerequisites of the mechanism, aimed at oil displacement using nitrogen and flue gases, have been formulated. Results of the laboratory experiments of oil displacement by means of nitrogen within a porous environment have helped determine that minimum pressure of mutual oil and nitrogen dissolution is 36.0 -38.0 MPa. In terms of mutual mixing of agents at 110 -112°С temperature, 36.4 МPа gas injection pressure, and nitrogen pumping velocity being 1 cm 3 per 40 minutes, oil displacement ratio achieved 0.76 -0.78. Originality.For the first time, parameters of mixable oil displacement using nitrogen for the conditions of deep oil deposits of the Dnipro-Donetsk petroleum province in Ukraine have been determined. Efficiency of mixable nitrogen displacement to compare with water displacement and nitrogen displacement under equilibrium conditions has been proved. Practical implications.The advanced technique of nitrogen use to improve oil recovery in the context of deep oil deposits has been proposed. The technique is applicable to extract residual oil from the depleted deposits.

The object of research is water-driven gas-condensate reservoirs. Using the main hydrodynamic modeling tools Eclipse and Petrel from Schlumberger (USA), the study was carried out to improve the existing technologies for the displacement of residual gas reserves by carbon dioxide from the water-driven gas-condensate reservoirs. The carbon dioxide injection technology was tested in the V-16 reservoir of the Hadiach oil and gas condensate field (Ukraine). According to the study results, it was found that due to the injection of non-hydrocarbon gas, the cumulative water production are reduced compared to the depletion. Based on the obtained modeling results, the calculation of the predicted hydrocarbon recovery factors at the moment of carbon dioxide breakthrough into the production well was carried out according to the cumulative formation water production. According to the calculations, it was found that the implementation of the enhanced gas recovery technology provides significantly higher ultimate hydrocarbon recovery compared to the depletion. The predicted gas recovery factor when injecting carbon dioxide into the V-16 reservoir increases by 2.95 % of the residual gas reserves, and the condensate recovery factor for these conditions by 1.24 %. Based on the study results, the technological efficiency of using carbon dioxide as an injection agent to increase the hydrocarbon recovery from water-driven reservoirs was established. According to the simulation results, the implementation of the technology of carbon dioxide injection into the V-16 reservoir of the Hadiach oil and gas condensate field can significantly increase the hydrocarbon recovery from the deposit, thereby increasing the production capacity of the field.