Investigation of gas-oil gravity drainage (GOGD) in fractured reservoirs using CO2

In this research, gas-oil gravity drainage (GOGD) mechanism for naturally fractured reservoir is investigated using analytical and numerical approaches. For numerical approach, CMG-GEM commercial software and it newly implemented GOGD functionalities is used. The models of fractured reservoirs, without barrier, with one barrier and two barriers, are created in BUILDER and simulated in GEM (compositional model). It is found that the results of simulations are consistent with the analytical results for immiscible gas injection. The effect of gas type on the oil recovery was investigated by injecting methane and carbon dioxide. Although, immiscible conditions are considered, because of solubility of CO¬2 in oil, injection of CO2 leads to more oil recovery (5% in our example) and gas breakthrough occurs later. In addition, foam assisted GOGD (FGOGD) mechanism is investigated in research, and the process (FGOGD) is simulated. We found that mobility control of gas remarkably improves oil recovery (6% in our example). We also investigated the efficiency of GOGD and FGOGD mechanisms from thermodynamic point of view using exergy concept. As well, for defining more sustainable production system, different scenarios are considered, and exergy analysis is done for each scenario. The scenarios are related to CO2 capture methods and used energy source, namely, renewable (solar) and natural gas energy, in production process. We consider that CO2 is obtained from air via direct air capture (DAC) technology and from gas power plants. In the research, invested exergy and CO2 intensity of each scenario are also calculated. We found that when CO2 is captured from gas power plants, production system is more sustainable from exergy point of view, because DAC technology requires more invested exergy, however, from environmental point of view considerable amount of CO2 could be captured from atmosphere via DAC technology. As well, in foam case, because of additional processes in production process, invested exergy is high in comparison without foam case. In addition, using of renewable energy in production process significantly decreases the emitted carbon dioxide. Thus, if we consider global warming crisis, these aspects are also important.