Browsing by Subject "EDFM"
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Item Mobility control of gas injection in highly heterogeneous and naturally fractured reservoirs(2016-05) Cavalcante Filho, Jose Sergio de Araujo; Sepehrnoori, Kamy, 1951-; Delshad, Mojdeh; Mohanty, Kishore; Chin, Lee; Moinfar, AliSince a significant portion of the world's oil reserves resides in naturally fractured reservoirs (NFR), it is important to maximize oil production from these reservoirs. Mobility control EOR techniques, such as water alternating gas (WAG) and foam injection, may be used in NFRs to improve oil recovery. Foam injection may be modeled by empirical or mechanistic models, the latter being capable of representing foam generation and coalescence effects. Numerical models are needed to evaluate EOR techniques in NFR. The Embedded Discrete Fracture Model (EDFM) is capable of representing conductive faults or fractures and describing NFR and unconventional reservoirs as a triple porosity medium (hydraulic fractures, natural fractures, and matrix). This work aims at developing a general EDFM framework to allow the evaluation of different mobility control EOR methods in NFR. The mobility control EOR methods evaluated were the WAG and continuous foam injection. The formulation used to evaluate mobility control by foam injection in NFR was the population balance assuming local equilibrium and the Pc* models. Nanoparticle transport models (Two Site and Two Rate models) were implemented and validated to allow simulation of nanoparticle stabilized foam injection. An EDFM preprocessor was further developed and validated against the in-house fully implicit simulator, unstructured grid models from the literature and fine-grid models using a commercial simulator. Simulation run time was reduced by applying a porosity cut-off in the fracture cells assuming constant fracture conductivity. Validation case studies included multi-fractured wells producing through depletion and a 2D quarter five-spot production scheme (water and miscible gas injection) in NFR. We obtained a good agreement between EDFM, unstructured grid, and fine-grid models. Application case studies included 3D models under water, miscible gas and WAG injection, which confirmed the efficiency of the EDFM in modeling complex fracture networks. We used the EDFM to simulate multilateral well stimulation and we performed an automated history matching of the production data of a field test. The foam model and the nanoparticle transport models were validated against experimental data from the literature. It is concluded that the effect of fractures on hydrocarbon production depends on fracture network connectivity, which may be modeled using the EDFM preprocessor. Simulation results using mobility control EOR methods show considerable improvements in oil recovery due to a postponement in gas breakthrough.Item Modeling and simulation of fluid flow in naturally and hydraulically fractured reservoirs using embedded discrete fracture model (EDFM)(2014-12) Shakiba, Mahmood; Sepehrnoori, Kamy, 1951-Modeling and simulation of fluid flow in subsurface fractured systems has been steadily a popular topic in petroleum industry. The huge potential hydrocarbon reserve in naturally and hydraulically fractured reservoirs has been a major stimulant for developments in this field. Although several models have found limited applications in studying fractured reservoirs, still more comprehensive models are required to be applied for practical purposes. A recently developed Embedded Discrete Fracture Model (EDFM) incorporates the advantages of two of the well-known approaches, the dual continuum and the discrete fracture models, to investigate more complex fracture geometries. In EDFM, each fracture is embedded inside the matrix grid and is discretized by the cell boundaries. This approach introduces a robust methodology to represent the fracture planes explicitly in the computational domain. As part of this research, the EDFM was implemented in two of The University of Texas in-house reservoir simulators, UTCOMP and UTGEL. The modified reservoir simulators are capable of modeling and simulation of a broad range of reservoir engineering applications in naturally and hydraulically fractured reservoirs. To validate this work, comparisons were made against a fine-grid simulation and a semi-analytical solution. Also, the results were compared for more complicated fracture geometries with the results obtained from EDFM implementation in the GPAS reservoir simulator. In all the examples, good agreements were observed. To further illustrate the application and capabilities of UTCOMP- and UTGEL-EDFM, a few case studies were presented. First, a synthetic reservoir model with a network of fractures was considered to study the impact of well placement. It was shown that considering the configuration of background fracture networks can significantly improve the well placement design and also maximize the oil recovery. Then, the capillary imbibition effect was investigated for the same reservoir models to display its effect on incremental oil recovery. Furthermore, UTCOMP-EDFM was applied for hydraulic fracturing design where the performances of a simple and a complex fracture networks were evaluated in reservoirs with different rock matrix permeabilities. Accordingly, it was shown that a complex network is an ideal design for a very low permeability reservoir, while a simple network results in higher recovery when the reservoir permeability is moderate. Finally, UTGEL-EDFM was employed to optimize a conformance control process. Different injection timings and different gel concentrations were selected for water-flooding processes and their impact on oil recovery was evaluated henceforth.Item Performance evaluation of CO2 EOR in tight oil formation with complex fracture geometries(2016-05) Zuloaga Molero, Pável; Sepehrnoori, Kamy, 1951-; Yu, WeiThe recent development of tight oil reservoirs has led to an increase in oil production in the past several years due to the progress in horizontal drilling and hydraulic fracturing. However, the oil recovery factor expected is still very low even after the wells have been fractured and therefore, tight formations are considered good candidates for enhanced oil recovery (EOR). One of the most suitable solutions to improve the oil recovery is the carbon dioxide (CO2)-based EOR. Although the injection of CO2 is not new for conventional oil reservoirs, its practice in tight oil formations is still a relatively novel idea. Two injection-production strategies are often employed: continuous CO2 injection or flooding and CO2 Huff-n-Puff. However, it is not clear which scenario is the best strategy to achieve an optimal recovery, which highly depends on many uncertain reservoir and fracture parameters and it is not clearly understood until recently. Another challenge of the estimation of the incremental recovery of these injection approaches is to properly model the hydraulic fractures and CO2 transport mechanism. The actual hydraulic fracturing process often creates complex fracture networks, especially when the fracture propagates in a formation with a large amount of pre-existing natural fractures. In this study, the CO2-EOR effectiveness is simulated and analyzed by comparing the Huff-n-Puff and the continuous injection scenarios. The effect of matrix permeability on the comparison of well performance of these two scenarios was investigated. Subsequently, Design of Experiment and Response Surface Methodology is used to perform sensitivity studies with four uncertain parameters including matrix permeability, number of wells, well pattern, and fracture half-length to determine the best injection approach. In addition, an efficient methodology of embedded discrete fracture model (EDFM) is introduced to explicitly model complex fracture geometries. The effects of complex fracture geometries on well performance of CO2 Huff-n-Puff and CO2 continuous injection were also investigated as well as the effect of natural fractures. The analysis of the CO2-EOR effectiveness confirms that the appropriate modelling of the complex fractures geometry plays a critical role in estimation of the incremental oil recovery. This study provides new insights into a better understanding of the impacts of reservoir permeability, complex hydraulic fractures and natural fractures on well performance during CO2-EOR process in tight oil reservoirs and in the determination and design of the optimal injection-production scheme to maximize the oil recovery factor for multi-fractured horizontal wells.