Numerical modeling CO2 injection in a fractured chalk experiment

Alavian, Sayyed Ahmad; Whitson, Curtis Hays

doi:10.1016/j.petrol.2011.02.014

Cited by 10 publications

(3 citation statements)

References 3 publications

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“…Alavian and Whitson also attempted to model this experiment with the Eclipse 300 simulator but chose to increase the surface (separator) temperature from 15 to 30 °C and decrease the fracture permeability to a low 80 md, which increases the simulated oil recovery through viscous forces to compensate for the limitations in the diffusion modeling. Alavian and Whitson also simulated a similar experiment and again found that the results with and without Fickian diffusion are similar using both the SENSOR and Eclipse 300 simulators and that the measured recovery could only be reproduced through viscous forces by lowering the fracture permeability to 26 md. Recent versions of the Eclipse simulator do have an option to compute diffusion from chemical potential gradients, but they still suffer from the limitations of the dual-porosity fracture model and the mass balance violations caused by allowing only matrix-diagonal diffusion coefficients, as discussed above.…”

Section: Numerical Examplesmentioning

confidence: 78%

Fickian Diffusion in Discrete-Fractured Media from Chemical Potential Gradients and Comparison to Experiment

Moortgat

Firoozabadi

2013

Energy Fuels

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Fickian diffusion can be an important oil recovery mechanism from fractured reservoirs by gas injection, especially when gravitational drainage is inefficient. Without diffusion, injected gas will flow predominantly through the fractures, resulting in early breakthrough and low oil recovery, but compositional gradients between the fractures and the matrix can drive considerable cross-flow. Additionally, this species exchange can lead to favorable phase behavior, such as swelling and viscosity reduction of oil in the matrix. The modeling of Fickian diffusion in fractured reservoirs has been hampered by two deficiencies in existing simulators. The first is the use of the generalized classical Fick's law for multicomponent mixtures, which violates molar balance. The second is the computation of diffusive fluxes across grid edges aligned with phase boundaries. Traditionally, diffusive fluxes are derived from gradients in compositions, computed by finite differencing of compositions in neighboring grid cells. This approach fails when one grid cell contains only gas and the neighboring cell only oil, because the compositional gradients are only defined within a single phase. This problem often occurs in fractured domains when the fractures fill with injected gas while the matrix blocks remain in single-phase oil. We implement an alternative approach, in which gradients in chemical potential are the driving force for Fickian diffusion. Unlike phase compositions, chemical potentials do not require phase identification and the gradient can be computed self-consistently across phase boundaries. Away from phase boundaries the two approaches are equivalent. We demonstrate the strengths of our implementation by simulating experiments in which CO 2 is injected in a tall vertical core surrounded by fractures. After injecting CO 2 for 22 days, 65% of the oil in place is recovered. However, modeling with a commercial simulator results in only 12% recovery, despite adjusting parameters. We present additional examples at larger scales that further confirm the promising prospects of CO 2 injection for enhanced oil recovery in fractured reservoirs and show the equivalence of the composition-and chemical-potential-based formulations in the absence of sharp phase boundaries.

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Section: Numerical Examplesmentioning

confidence: 78%

Fickian Diffusion in Discrete-Fractured Media from Chemical Potential Gradients and Comparison to Experiment

Moortgat

Firoozabadi

2013

Energy Fuels

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“…Miscible displacement processes have been developed as a successful method to improve oil recovery from naturally fractured reservoirs (NFRs). − The success of a miscible displacement process in NFRs largely depends on the degree of mass exchange between the solvent in the fracture and the oil in the matrix. − , When the injected fluid is fully miscible with the oil in the matrix, there is no capillary-driven cross-flow between matrix and fracture. Moreover, because of the existence of highly conductive and interconnected fracture networks, viscous forces are usually negligible compared to gravity forces. ,− Consequently, gravity drive and diffusion–dispersion drive are considered to be the dominant mechanisms responsible for the miscible recovery from NFRs. , The relative contribution of each of these controlling mechanisms (i.e., diffusion and gravity) can be examined using characteristic times.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Interactions between Matrix and Fracture during Miscible Gravity Drainage in Naturally Fractured Reservoirs

Ameri

Farajzadeh

Suiçmez

et al. 2015

Ind. Eng. Chem. Res.

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Miscible gas or solvent injection has received increasing attention in recent years as an efficient method for improving oil recovery from naturally fractured reservoirs. Because of the large permeability difference between fracture and matrix, the success of this method depends to a large extent on the degree of enhancement of the mass-exchange rate between the solvent flowing through the fracture and the oil residing in the matrix. In this study, a series of experiments were conducted to investigate the mass-transfer rate between the fracture and the matrix when a solvent is injected through the fracture system. The effects of injection rate, fracture aperture, water saturation, matrix wettability, and fluid properties on the recovery behavior were examined. The interaction between the matrix and fracture was visualized for solvent injection by means of computed tomography (CT) scanning, which can be used to validate theories of enhanced transfer in fractured media. The results obtained with a simulation model, which takes diffusive, gravitational, and convective forces into account, showed good agreement with the experimental results within an acceptable range of accuracy.

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“…Several authors have studied immiscible gas and MCM gas injection processes in fractured reservoirs by numerical modeling. ,,− Uleberg and Høier, based on compositional reservoir modeling, showed that the developed miscibility level in a fractured reservoir is significantly higher than for a conventional one-dimensional, single-porosity system. In the numerical simulations of Suicmez et al the best results, regarding the ultimate recovery and drainage rate, were obtained for the case where miscibility develops through repeated contacts between the injected gas and the oil in the matrix (i.e., developed miscibility conditions).…”

Section: Introductionmentioning

confidence: 99%

Effect of Non-equilibrium Gas Injection on the Performance of (Immiscible and Miscible) Gas–Oil Gravity Drainage in Naturally Fractured Reservoirs

et al. 2013

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In naturally fractured reservoirs, improving the matrix−fracture interactions is critical to the success of the applied improved oil recovery method. Therefore, a study of the mechanisms that control the mass exchanges between fracture and matrix can help to optimize recovery. This paper concerns an experimental and simulation study to investigate the performance of the gas−oil gravity drainage process in naturally fractured reservoirs. In this study, five gas injection experiments were conducted at different miscibility (i.e., immiscible and fully miscible) conditions using CO 2 , N 2 , and a synthetic flue gas composed of 20% (v/v) CO 2 and 80% (v/v) N 2 . The impact of switching from an immiscible (i.e., nitrogen or flue gas) gas to a non-equilibrium and fully miscible CO 2 injection is investigated. The effect of miscibility on the block−block interaction is also examined using a stacked core with an impermeable barrier. The results reveal that injection of non-equilibrium gas with higher solubility in the oil phase results in a zone of decreased oil viscosity, which leads to an improved gravity mediated recovery. The results also show that the ultimate oil recovery increases considerably once miscibility is achieved. A numerical model is implemented to perform compositional simulations of multiphase, multicomponent gas injections at different miscibility conditions. Agreement of the developed model with the experimental results indicates that gravity drainage, capillary holdup, and mixing are the main controlling mechanisms.

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Numerical modeling CO2 injection in a fractured chalk experiment

Cited by 10 publications

References 3 publications

Fickian Diffusion in Discrete-Fractured Media from Chemical Potential Gradients and Comparison to Experiment

Fickian Diffusion in Discrete-Fractured Media from Chemical Potential Gradients and Comparison to Experiment

Dynamic Interactions between Matrix and Fracture during Miscible Gravity Drainage in Naturally Fractured Reservoirs

Effect of Non-equilibrium Gas Injection on the Performance of (Immiscible and Miscible) Gas–Oil Gravity Drainage in Naturally Fractured Reservoirs

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