Simulation of Gas/Oil Gravity Drainage in a Stack of Interacting Blocks: Pseudo Relations for a Limited Number of Gridblocks

Wit, Krijn; Clemens, Torsten; Rijkels, Lex

doi:10.2118/77722-ms

Cited by 9 publications

(3 citation statements)

References 6 publications

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“…Likewise, Rubin (2007) developed a hybrid of subdomain and dual permeability models to simulate gasoil gravity drainage in the presence of reinfiltration and partial capillary continuity between matrix blocks. Wit et al (2002) presented a procedure to calculate pseudo relative permeability curves for a stack of interacting blocks in gas-oil gravity drainage simulations. carried out miscible displacement experiments in a number of matrix-fracture configurations.…”

Section: Laboratory Experiments In Fractured Porous Mediamentioning

confidence: 99%

Development of an Efficient Embedded Discrete Fracture Model for 3D Compositional Reservoir Simulation in Fractured Reservoirs

et al. 2013

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Summary Many naturally fractured reservoirs around the world have depleted significantly, and improved-oil-recovery (IOR) processes are necessary for further development. Hence, the modeling of fractured reservoirs has received increased attention recently. Accurate modeling and simulation of naturally fractured reservoirs (NFRs) is still challenging because of permeability anisotropies and contrasts. Nonphysical abstractions inherent in conventional dual-porosity and dual-permeability models make them inadequate for solving different fluid-flow problems in fractured reservoirs. Also, recent technologies for discrete fracture modeling may suffer from large simulation run times, and the industry has not used such approaches widely, even though they give more-accurate representations of fractured reservoirs than dual-continuum models. We developed an embedded discrete fracture model (DFM) for an in-house compositional reservoir simulator that borrows the dual-medium concept from conventional dual-continuum models and also incorporates the effect of each fracture explicitly. The model is compatible with existing finite-difference reservoir simulators. In contrast to dual-continuum models, fractures have arbitrary orientations and can be oblique or vertical, honoring the complexity of a typical NFR. The accuracy of the embedded DFM is confirmed by comparing the results with the fine-grid, explicit-fracture simulations for a case study including orthogonal fractures and a case with a nonaligned fracture. We also perform a grid-sensitivity study to show the convergence of the method as the grid is refined. Our simulations indicate that to achieve accurate results, the embedded discrete fracture model may only require moderate mesh refinement around the fractures and hence offers a computationally efficient approach. Furthermore, examples of waterflooding, gas injection, and primary depletion are presented to demonstrate the performance and applicability of the developed method for simulating fluid flow in NFRs.

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Section: Laboratory Experiments In Fractured Porous Mediamentioning

confidence: 99%

Development of an Efficient Embedded Discrete Fracture Model for 3D Compositional Reservoir Simulation in Fractured Reservoirs

et al. 2013

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“…The matrix permeability has a strong impact on the gas/oil gravity drainage rate and time of gas breakthrough at the bottom of the matrix. The characteristic drainage time of a block T (assuming infinite gas mobility and no capillary pressure) is given by (Wit et al 2002): n Fig. 10 shows that the gas breakthrough without diffusion is related to the reciprocal of the matrix permeability as expected from equation (3).…”

Section: Matrix Permeabilitymentioning

confidence: 70%

The Role of Diffusion for Non-Miscible Gas Injection into a Fractured Reservoir

Yanze

Clemens

2011

SPE EUROPEC/EAGE Annual Conference and Exhibition

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To improve oil recovery from pervasively fractured reservoirs, gas injection can be considered. In such reservoirs, the fractures typically provide the flowpaths but contain a limited amount of the oil whereas the matrix often has orders of magnitude lower permeabilities but contains the oil.To improve oil recovery from such reservoirs, gas/oil gravity drainage can be applied. In this process, a gravity stable displacement can be achieved.If gas is injected which is not in equilibrium with the oil, the non-equilibrium gas components diffuse from the fracture system into the matrix and the components of the oil diffuse towards the fracture system. This results in a modification of the properties of the oil affected by diffusion and gravity drainage rates accordingly.The effects of non-equilibrium gas injection into a pervasively fractured reservoir were studied at the example of an Austrian reservoir. This type of gas injection results in a zone of decreased oil viscosity for gases such as CO 2 and CH 4 at the interface of the gas and the oil in the matrix. This zone of lower oil viscosity increases the gas/oil gravity drainage rates.The results show that the effect of diffusion can increase cumulative oil production up to 25 % compared with a case neglecting the effect of diffusion. The effect of diffusion could be determined for various parameters such as permeability, porosity, fracture spacing and matrix block height. While for some of the parameters, the effect of diffusion scales with the square root of time (e.g. permeability), for others an exponential relationship has been determined (fracture spacing).The results derived for the example reservoir can be used more generally to screen whether the effect of diffusion should be incorporated into reservoir studies concerning non-equilibrium gas injection and how large the error could be in case that diffusion is neglected.

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“…In Iran, the largest reservoirs are fractured carbonates which are mostly oil and mixed wet and contain more than 30 billion barrels of oil (Wit et al 2002). Producing oil from these reservoirs is difficult, since usual production mechanisms like water injection and countercurrent imbibition do not work.…”

Section: Introductionmentioning

confidence: 99%

Miscible GOGD Using CO2 in One of the Iranian Fractured Reservoirs - A Case Study

et al. 2011

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Advantages of CO 2 in enhanced oil recovery for Iranian oil reservoirs offers a unique opportunity to boost incremental oil recovery and reducing emissions of greenhouse gas through geological sequestration. Moreover, because of the dominant role of gravity force in gas injection process in fractured reservoirs, and also relatively low minimum miscibility pressure (MMP) of CO 2 , therefore, miscible CO 2 injection with Gas Oil Gravity Drainage (GOGD) mechanism can be considered as an efficient method in most carbonate reservoirs.In this paper, different production strategies such as vertical and horizontal immiscible and miscible gas injection were applied to find the optimum EOR method in one of the under-saturated Iranian fractured reservoirs.To aim this goal, a study with simulation approach was conducted while the effect of gravity drainage on recovery was investigated besides other mechanisms. A complete analysis of phase behavior, PVT properties of reservoir fluid and CO 2 mixture was done. These data were applied in designing of the slim tube and full field simulation model. A fully compositional reservoir simulator was employed to understand the reservoir characteristics, also, verifying the suitability of CO 2 injection.Material balance analysis indicated the original oil in place (OOIP) is about 910 million STB with a relatively strong water support. The maximum oil production of 60,000 STB/D was assumed in all simulation cases. Reservoir simulation results revealed that additional oil recovery could be obtained from this fractured reservoir by miscible gas injection, while gravity drainage was the main displacement mechanism. In case of vertical well production, the model predicted an increase in oil recovery about 24 and 28% OOIP for immiscible and miscible CO 2 injection respectively. Considering horizontal producers and gravity drainage as the dominant production mechanism, immiscible and miscible gas injection will enhance oil production more than 28 and 36% OOIP respectively.

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Simulation of Gas/Oil Gravity Drainage in a Stack of Interacting Blocks: Pseudo Relations for a Limited Number of Gridblocks

Cited by 9 publications

References 6 publications

Development of an Efficient Embedded Discrete Fracture Model for 3D Compositional Reservoir Simulation in Fractured Reservoirs

Development of an Efficient Embedded Discrete Fracture Model for 3D Compositional Reservoir Simulation in Fractured Reservoirs

The Role of Diffusion for Non-Miscible Gas Injection into a Fractured Reservoir

Miscible GOGD Using CO2 in One of the Iranian Fractured Reservoirs - A Case Study

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