Study of Oil Recovery Mechanisms in Complex Natural Fracture Systems using Embedded Discrete Fracture Models

Vo, Hai X.; Mallison, Brad; Kamath, Jairam; Hui, Robin; Dufour, G.

doi:10.2118/201463-ms

Cited by 4 publications

References 32 publications

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An Integrated EDFM+DPDK Hybrid Workflow for Hierarchical Treatment of Fractures in Practical Field Studies

Hui

Mallison

Thomas

et al. 2022

SPE Western Regional Meeting

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Natural fracture systems comprise numerous small features and relatively few large ones. At field scale, it is impractical to treat all fractures explicitly. We represent the largest fractures via Embedded Discrete Fracture Modeling (EDFM) and account for smaller ones using a dual-porosity, dual-permeability (DPDK) idealized representation of the fracture network. The hierarchical EDFM+DPDK approach uses consistent discretization schemes and efficiently simulates realistic field cases. Further speed-up can be obtained using aggregation-based upscaling. Capabilities to visualize and post-process simulation results facilitate understanding for effective management of fractured reservoirs. The proposed approach embeds large discrete fractures as EDFM within a DPDK grid (which contains both matrix and idealized fracture continua for smaller fractures), and captures all connections among the triple media. In contrast with existing EDFM formulations, we account for discrete fracture spacing within each matrix cell via a new matrix-fracture transfer term and employ consistent assumptions for classical EDFM and DPDK calculations. In addition, the workflow enables coarse EDFM representations using flow-based cell-aggregation upscaling for computational efficiency, as well as finite-volume tracer-based flux post-processing to analyze production allocation and sweep. Using a synthetic case, we show that the proposed EDFM+DPDK approach provides a close match of simulation results from a reference model that represents all fractures explicitly, while providing runtime speedup. It is also more accurate than previous standard EDFM and DPDK models. We demonstrate that the matrix-fracture transfer function agrees with flow-based upscaling of high-resolution fracture models. Next, the automated workflow is applied to a waterflooding study for a giant carbonate reservoir, with an ensemble of stochastic fracture realizations. The overall workflow provides the computational efficiency needed for performance forecasts in practical field studies, and the 3D visualization allows for the derivation of insights into recovery mechanisms. Finally, we apply a flux post-processing scheme on simulation results to understand expected waterflood performance.

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An Integrated EDFM+DPDK Hybrid Workflow for Hierarchical Treatment of Fractures in Practical Field Studies

Hui

Mallison

Thomas

et al. 2022

SPE Western Regional Meeting

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A Hybrid Embedded Discrete Fracture Model and Dual-Porosity, Dual-Permeability Workflow for Hierarchical Treatment of Fractures in Practical Field Studies

Hui

Mallison

Thomas

et al. 2023

SPE Reservoir Evaluation &Amp; Engineering

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Summary Natural fracture systems comprise numerous small features and relatively few large ones. At field scale, it is impractical to treat all fractures explicitly. We represent the largest fractures using an embedded discrete fracture model (EDFM) and account for smaller ones using a dual-porosity, dual-permeability (DPDK) idealized representation of the fracture network. The hybrid EDFM + DPDK approach uses consistent discretization schemes and efficiently simulates realistic field cases. Further speedup can be obtained using aggregation-based upscaling. Capabilities to visualize and post-process simulation results facilitate understanding for effective management of fractured reservoirs. The proposed approach embeds large discrete fractures as EDFM within a DPDK grid (which contains both matrix and idealized fracture continua for smaller fractures) and captures all connections among the triple media. In contrast with existing EDFM formulations, we account for discrete fracture spacing within each matrix cell via a new matrix-fracture transfer term and use consistent assumptions for classical EDFM and DPDK calculations. In addition, the workflow enables coarse EDFM representations using flow-based cell-aggregation upscaling for computational efficiency. Using a synthetic case, we show that the proposed EDFM + DPDK approach provides a close match of simulation results from a reference model that represents all fractures explicitly, while providing runtime speedup. It is also more accurate than previous standard EDFM and DPDK models. We demonstrate that the matrix-fracture transfer function agrees with flow-based upscaling of high-resolution fracture models. Next, the automated workflow is applied to a waterflooding study for a giant carbonate reservoir, with an ensemble of stochastic fracture realizations. The overall workflow provides the computational efficiency needed for performance forecasts in practical field studies, and the 3D visualization allows for the derivation of insights into recovery mechanisms. Finally, we apply a finite-volume tracer-based flux post-processing scheme on simulation results to analyze production allocation and sweep for understanding expected waterflood performance.

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Insights on Gas and Water Coning/Channeling Processes in a Fractured Carbonate Reservoir from Embedded Discrete Fracture Modeling

Vo,

Flodin,

Hui

et al. 2023

SPE Western Regional Meeting

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Coning is the mechanism describing movement of water from an aquifer and/or gas from gas-cap into the perforations of a producing well. The interface between the fluid phases deforms into a cone shape if the reservoirs are relatively homogeneous. In fractured reservoirs, water/gas incursions can take the form of discrete channels through fractures that connect the water/gas zone to the wellbore. Coning/channeling tends to increase the cost of production operations and influences the overall recovery efficiency of oil reservoirs. The coning/channeling processes constitute one of the most complex problems pertaining to oil production. This study investigates coning/channeling in an Atlantic margin pre-salt fractured carbonate reservoir using Embedded Discrete Fracture Modeling (EDFM) to gain a better understanding of the processes in fractured reservoirs. This study focused on a sector Discrete Fracture Network (DFN) that was used to create a full-field Dual Porosity-Dual Permeability (DPDK) model. The DFN was used to generate end member models that capture the range of connectivity, geometry, and heterogeneity of fracture systems thought to exist in the field based on well log and core analysis. The sector area of interest also included existing producers and injectors and future infill wells. The coning/channeling phenomena were modeled using the EDFM method. The models were flow simulated using representative initialization, field management logic, and well producing rules, based on the history-matched full-field DPDK model. Mitigation methods to reduce coning impacts were also investigated. EDFM, which represents the fracture network explicitly, provides insight on gas and water coning/channeling processes in a fractured carbonate reservoir. We find that fractures can lead to local channeling and coning. The degree of channeling and coning is a function of flow rates, fracture properties, and matrix-fracture exchange which in turn depends on rock property contrast between matrix and fractures. If matrix permeability is sufficiently high, matrix-fracture exchange is significant and fractures can act like leaky pipes. The effect of local gas coning/channeling is stronger in cases of isolated fractures surrounded by lower permeability rock. Water and gas coning can occur at the same time and interact with each other. Mitigation methods such as reducing well rates and use of selective completions can be applied to manage the gas and water coning/channeling.

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Study of Oil Recovery Mechanisms in Complex Natural Fracture Systems using Embedded Discrete Fracture Models

Cited by 4 publications

References 32 publications

An Integrated EDFM+DPDK Hybrid Workflow for Hierarchical Treatment of Fractures in Practical Field Studies

An Integrated EDFM+DPDK Hybrid Workflow for Hierarchical Treatment of Fractures in Practical Field Studies

A Hybrid Embedded Discrete Fracture Model and Dual-Porosity, Dual-Permeability Workflow for Hierarchical Treatment of Fractures in Practical Field Studies

Insights on Gas and Water Coning/Channeling Processes in a Fractured Carbonate Reservoir from Embedded Discrete Fracture Modeling

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