Carbonated reservoirs with high percentage of CO2 have been discovered and produced in the Brazilian pre-salt cluster. Recovery techniques, such as CO2-WAG, have hence been evaluated and applied, as in the Lula field. Although studies demonstrate the advantages of this technique, it is still difficult to estimate an increase in oil recovery. Thus, this work presents a methodology to evaluate the impacts of the main phenomena that occur and how CO2 recycling can benefit the management of these fields. The results showed an increase in recovery with the modeling of the main phenomena such as relative permeability hysteresis and aqueous solubility of CO2, accompanied by a significant increase in CO2 injection. However, the recycling of the CO2 produced was shown to be fundamental in the reduction in this injection and to increase the NPV. The results showed a 4% increase in oil production and 9% in NPV, considering a producer–injector pair.
The present study aims to deepen the investigations of a previous study, in order to rank which variables are more critical to CO2-WAG process Enhanced Oil Recovery and which injection schemes and parameters are more effective when capillary pressure and relative permeability are adapted to Brazilian pre-salt scenario. The methods compared were Water Alternating Gas (WAG) and Hybrid Water Alternating Gas, considering saturation dependent hysteresis modeled through Larsen-Skauge model. A detailed and reliable Equation of State for oil with high pressure, and unusual natural carbon dioxide content (8.4%) was developed based in published data to match rheology and swelling measurements. The model was a small scale water-wet carbonate/stromatolite reservoir model with the same set of relative permeability and capillary pressure with hysteresis and entrapment data were modeled as basis for pre-salt Brazilian reservoir data. The optimization were analized including hysteresis and entrapment data from the literature. The reservoir model well constraints for each strategy were meant to be as realistic as possible, the recovery was optimized using an optimization tool, and the cases were analyzed comparatively. The most important effects were ranked and the best injection scheme and parameters were determined for the studied case in order to clear conclusions about the importance of fluid and petrophysical mechanisms for miscible final oil recovery. Among a series of petrophysical phenomena needing further investigations on their influence on oil recovery, relative permeability is of critical importance. Nonetheless, its representation in reservoir simulation is quite a complicated task. It may incorporate hysteresis effects (at least three different models that can be used), and it may present three-phase behavior (extrapolated from two phase relative permeability experimental data). Just like relative permeability hysteresis, there are at least four different models available to represent three phase relative permeability. In the present work, only Larsen and Skauge model was addressed. As a consequence of all complexities involved, for some subtle changes in the injection scheme, such as the injector operating restraints, make recoveries sensitive to hysteresis and passive of improvement. Simulations indicated that an incremental oil recovery of about 11%, in both WAG and HWAG schemes when hysteresis was considered compared to no-hysteresis case. Optimization of well operating conditions and constraints (bottom-hole pressure of producers and injectors, gas and water rate limits) has a significant effect on oil recovery and production rates.
The water-alternating-gas process (WAG) was originally proposed to improve sweep efficiency during gas injection and it combines the advantages of gas and water flooding, better microscopic displacement efficiency and improved macroscopic sweep, respectively. Carbon dioxide is an attractive gas to be used in the Enhanced Oil Recovery (EOR) process, mainly, when the oil in place contains some dissolved CO2 which is produced in the gas phase. The WAG-CO2 can be an attractive recovery method in reservoirs with oil containing CO2. Also, it is a manner to store CO2, representing a viable solution to the greenhouse gas problem. In WAG process simulation, it is necessary to shut-in and shut-off the injector wells alternately in order to change the injection fluid. This procedure results in an elevated simulation time compared to the EOR process with injection of a unique fluid. A numerical approach is investigated to physically represent the WAG process with reduced computational time. In this approach, denominated as Pseudo WAG process, water and CO2 are simultaneously injected into the simulation model, maintaining the same amount of injected fluid. The possibility of the Pseudo WAG process to adequately represent the WAG-CO2 is analyzed using a compositional simulator. To execute the simulations, it is necessary to have equations of state (EOS) that properly represent the oil phase behavior. EOS tuning is based on PVT experimental data of oil available in literature. The EOS is validated before being used in a simulation model. Results indicate that WAGCO2 is an effective method to recover oil containing CO2. The Pseudo WAG process is capable of adequately representing the WAG-CO2 process in terms of production parameters, such as cumulative oil and water productions. The numerical approach of the Pseudo WAG process significantly reduces the simulation time compared to the WAG process. This approach can be useful to simulate WAG-CO2 processes in heterogeneous reservoirs in order to reduce the CO2 emissions into the atmosphere.
Purpose: This study aims to analyze how transformative learning (TL) theory has contributed to sustainability practices in management and Education for Sustainable Development (ESD) and what kind of strategies can direct future practices in the field. Method/design/approach: An exploratory and inductive study to synthetize primary qualitative case studies was conducted. After screening 241 articles extracted from the Web of Science database, we identified 13 empirical papers highlighting TL theory and sustainability. Then, a meta-synthesis of these qualitative case studies was conducted based on the key characteristics of TL. Results and conclusion: Six theoretical propositions were elaborated, showing that the TL theory has contributed to sustainability through some influential factors on process, conditions, and results. In addition, based on these dimensions, the study provides some strategies for future practices. Research implications: The findings of this study have both theoretical and practical contributions, which can direct organizational and educational politics and practices. Originality/value: Sustainability and ESD are current topics in the academy in favor of the Sustainable Development Goals (SDGs). However, there is a lack of studies on the development of theoretical strategies towards sustainability practices in management and ESD from a transformative learning TL approach. Thus, this study shed more light on the topic.
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