A Thermal Simulator for Naturally Fractured Reservoirs

Chen, W.H.; Wasserman, M.L.; Fitzmorris, Robert

doi:10.2523/16008-ms

Cited by 12 publications

(7 citation statements)

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“…Saidi (1983) discretized the matrix blocks in the vertical and radial directions in a three-phase dual porosity simulator. Gilman (1986), Chen et al (1987), Lee and Tan (1987), and Beckner et al (1991) used similar approaches to improve the matrix representation in dual porosity simulations. Matrix block subdivision gave better resolution of pressure and saturation gradients, but significantly increased the computational cost of dual porosity simulations.…”

Section: Improvements In Dual Porosity Simulationmentioning

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: Improvements In Dual Porosity Simulationmentioning

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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“…Some investigators have proposed matrix-subgridding schemes such as the multiple interacting continua (MINC) model (Chen et al, 1987;Gilman and Kazemi, 1988;Wu and Pruess, 1988;Beckner et al, 1991) as an alternative to DP models to better represent any spatial variation in pressure and saturation in the matrix. However, idealized fracture-matrix geometries (e.g., concentric squares in 2D) are still assumed.…”

Section: Introductionmentioning

confidence: 99%

The Upscaling of Discrete Fracture Models for Faster, Coarse-Scale Simulations of IOR and EOR Processes for Fractured Reservoirs

Hui

Mallison

Fyrozjaee

et al. 2013

Day 2 Tue, October 01, 2013

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Improved and enhanced oil recovery (IOR/EOR) processes, such gas injection and waterflooding, are difficult to model accurately in fractured reservoirs due to complicated multiphase physics and the strong property contrast between permeable natural fractures and tight matrix rock. Traditionally, fractured reservoirs are modeled using coarse dual-porosity (DP) simulation models that idealize the fracture system. Consequently, important recovery physics can be missed, causing misleading flow predictions. We present an unstructured discrete-fracture-matrix (DFM) approach for three-phase, fully compositional simulations of IOR/EOR processes. We generate detailed DFM grids that represent several thousand realistic discrete fractures and different well configurations. These grids are then discretized for IOR/EOR flow simulations. We apply the flow-based multiple subregion (MSR) technique with two subregions to generate unstructured coarse-scale fracture models that are directly based on the DFM sector models. We next employ MSR upscaling to create corresponding structured DFM-based dual-porosity, dual-permeability (DPDK) models, computing parameters like shape factors and effective fracture permeabilities. We lastly generate conventional DPDK models by invoking simplifying assumptions and analytical equations. Using DFM results as reference solutions, we find the following order of decreasing accuracy: MSR, DFM-based DPDK, and conventional DPDK models. The DPDK models result in significant inaccuracies at individual wells when important fluid movement (e.g., gas breakthrough) is missed. The errors at sector scale are lower due to cancellation of errors at wells. The simulation results indicate that oil recovery and injected fluid breakthrough behavior are a complicated function of the reservoir heterogeneity, well configurations, and phase behavior. Large modeling errors can potentially lead to the selection of a sub-optimal injectant. One to two orders of computational speedup are achieved from the upscaling. These findings point to the need for systematic upscaling of realistic DFM representations to generate fast and accurate coarse fracture models for the assessment of field-development IOR/EOR schemes.

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“…The naturally fractured reservoirs are very common around the world, and are very important sources of oil and gas. There has been active research regarding the naturally fractured reservoirs for a long period of time [1][2][3][4][5][6][7][8] . Fluid and heat flow in naturally fractured reservoirs still provides researchers with an ample amount of extremely challenging problems.…”

Section: Introductionmentioning

confidence: 99%

A Parametric Study of the Effects of Reservoir and Operational Properties on the Performance of Steam Displacement of Heavy Oil in Naturally Fractured Reservoirs

Cicek¹

2005

All Days

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fax 01-972-952-9435. AbstractThis research effort discusses the effects of a comprehensive range of fluid, rock-fluid and operational properties on the efficiency of steam injection in naturally fractured reservoirs with heavy oil. For this purpose, a fully implicit dualporosity/dual-permeability simulator is developed, and the model is applied to an inverted nine-spot pattern in a naturally fractured reservoir with heavy oil. The effects of the reservoir and operational properties on the steam displacement of heavy oil are studied comparatively in naturally fractured reservoirs with and without interacting matrix blocks and in approximate single porosity realizations of these naturally fractured reservoirs.The field scale numerical model is three-dimensional and three phase accounting for capillary, gravitational and viscous forces. The model solves for (n HC +5) primary variables simultaneously, where n HC is the number of hydrocarbon components. The fully implicit model formulates all reservoir and operational parameters as functions of all the primary variables. The model is linearized using the Newton-Raphson method. A direct and an iterative solver is used in the solution of the system of linear equations.The simulations of steam injection in naturally fractured systems are carried out for long periods of time in order to test the features of the model under strained conditions. The model is verified against the Fourth and Sixth SPE Comparative Solution Projects.This study should help in screening naturally fractured reservoirs for steam injection, and in designing steam injection operations in these reservoirs.The comparative analysis of the effects of reservoir and the operational parameters in naturally fractured reservoirs should provide insight into the range of confidence of heavy oil recovery from naturally fractured reservoirs by steam injection.

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A Thermal Simulator for Naturally Fractured Reservoirs

Cited by 12 publications

References 0 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 Upscaling of Discrete Fracture Models for Faster, Coarse-Scale Simulations of IOR and EOR Processes for Fractured Reservoirs

A Parametric Study of the Effects of Reservoir and Operational Properties on the Performance of Steam Displacement of Heavy Oil in Naturally Fractured Reservoirs

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