The Application of Wellbore Embedded Discrete Fracture Model (EDFM) in Fracture Diagnosis Through DTS and Well Interference Analysis PDF Download
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Author: Zihao Zhao
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The advancement of hydraulic fracturing techniques has boosted the economic development of the unconventional reservoir. The created complex fracture networks provide a high-conductivity flow channel for the production and increase the ultimate recovery. However, they also posed great challenges to efficiently model the flow inside. The newly developed Embedded Discrete Fracture Model (EDFM) enables efficient fracture modeling without sacrificing accuracy. It has been widely applied in many challenging research topics associated with complex fracture networks including Enhanced Geothermal System, gas huff-n-puff, well interference analysis, and automatic history matching. But the mechanism of EDFM makes it hard to incorporate a discrete wellbore module into the commercialized simulator, which limits its application in some topics that require detailed wellbore modeling. The objective of this study is to establish a new workflow that can integrate EDFM with a fully-coupled wellbore-reservoir model to simulate the flow behavior. The idea is to generate the pseudo parameters for the simulator input to force the simulator to get the correct wellbore perforation and trajectory information with EDFM. The developed wellbore EDFM module is integrated with thermal EDFM to simulate the temperature distribution in the wellbore and reservoir with complex fracture networks, which is applied as the forward model for fracture diagnosis through Disributed Temperature Sensing (DTS). A field case is conducted, which verifies the potential application of our workflow in fracture diagnosis. By matching the temperature distribution along the wellbore, we can estimate the fracture geometry and properties, which provide valuable information for future operation optimization. Subsequently, we applied our wellbore EDFM module to simulate the well interference through fracture hits. It verifies the great capacity of our wellbore EDFM module to handle complex flow regimes inside the wellbore even when counter flow exists. It is also the first time for the simulator to handle the wellbore flow at closed wells. Our newly developed wellbore EDFM should have great potential in other research topics in the future
Author: Zihao Zhao
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The advancement of hydraulic fracturing techniques has boosted the economic development of the unconventional reservoir. The created complex fracture networks provide a high-conductivity flow channel for the production and increase the ultimate recovery. However, they also posed great challenges to efficiently model the flow inside. The newly developed Embedded Discrete Fracture Model (EDFM) enables efficient fracture modeling without sacrificing accuracy. It has been widely applied in many challenging research topics associated with complex fracture networks including Enhanced Geothermal System, gas huff-n-puff, well interference analysis, and automatic history matching. But the mechanism of EDFM makes it hard to incorporate a discrete wellbore module into the commercialized simulator, which limits its application in some topics that require detailed wellbore modeling. The objective of this study is to establish a new workflow that can integrate EDFM with a fully-coupled wellbore-reservoir model to simulate the flow behavior. The idea is to generate the pseudo parameters for the simulator input to force the simulator to get the correct wellbore perforation and trajectory information with EDFM. The developed wellbore EDFM module is integrated with thermal EDFM to simulate the temperature distribution in the wellbore and reservoir with complex fracture networks, which is applied as the forward model for fracture diagnosis through Disributed Temperature Sensing (DTS). A field case is conducted, which verifies the potential application of our workflow in fracture diagnosis. By matching the temperature distribution along the wellbore, we can estimate the fracture geometry and properties, which provide valuable information for future operation optimization. Subsequently, we applied our wellbore EDFM module to simulate the well interference through fracture hits. It verifies the great capacity of our wellbore EDFM module to handle complex flow regimes inside the wellbore even when counter flow exists. It is also the first time for the simulator to handle the wellbore flow at closed wells. Our newly developed wellbore EDFM should have great potential in other research topics in the future
Author: He Sun (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Distributed temperature sensing (DTS) is an enabling technology for fracture diagnosis and multiphase flow measurement in unconventional areas. Fracture characterization and flow profiling are crucial to evaluate the performance of hydraulic fractures. Enhanced Geothermal Systems (EGS) have gained great attention since they promise to deliver geographically disperse, carbon-free energy with minimal environmental impact. The objective of our DTS data analysis workflow is to provide a high-resolution quantitative diagnosis of hydraulic and natural fractures, which will benefit the fracturing operation design and decision-making process in the unconventional reservoir. Natural fracture networks have a major impact on EGS heat extraction. The objective of our model is to evaluate the impact of natural fracture networks on EGS producing temperature profiles. In this work, we developed a comprehensive numerical forward model for DTS data analysis and EGS economic evaluation. Our model includes reservoir and wellbore models. Also, the flow and thermal models are fully coupled. A thermal embedded discrete fracture model (Thermal EDFM) is developed to handle the thermal modeling of complex fracture networks. Subsequently, we implemented an ensemble smoother with multiple data assimilation (ESMDA) as the inverse model to match DTS data and characterize fractures. The DTS analysis with our model provides a high-resolution solution since the fracture diagnosis and flow profiling are performed for each fracture. The hydraulic and natural fracture properties and geometry such as fracture half-length, height, and fracture conductivity are evaluated. Our EGS model provides a comprehensive economic evaluation since we consider the flow and temperature behavior in each fracture without any upscaling. Although numerous simulators are developed for DTS data analysis and EGS economic evaluation, relatively few existing models can handle the full-physics such as complex fracture geometry and multiphase flow. Our models are more rigorous than the prior models to simulate and match the field DTS and EGS data
Author: Mauricio Xavier Fiallos Torres
Publisher:
ISBN:
Category :
Languages : en
Pages : 278
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Book Description
Shale field operators have vested a tremendous interest in optimal spacing of infill wells and further fracture optimization, which ideally should have as little interference with the existing wells as possible. Although proper modeling has been employed to show the existence of well interference, few models have forecasted the impact of multiple inter-well fractures on child wells production and also implemented Huff-n-Puff and injection containment methods. These prognoses of the reservoir simulations abet to optimize further hydraulic fracture designs and improve the efficiency of Enhanced Oil Recovery (EOR) in unconventional reservoirs. This thesis presented a rigorous workflow for estimating the impacts of spatial variations in fracture conductivity and complexity on fracture geometries of inter-well interference when modeling EOR Huff-n-Puff. Furthermore, we applied a non-intrusive embedded discrete fracture modeling (EDFM) method in conjunction with a commercial reservoir simulator to investigate the impact of well interference through connecting fractures by multi-well history matching, to propose profitable opportunities for Huff-n-Puff application. In this sense, the value of our workflow relies on a robust understanding of fracture properties, real production data validation, and the add-on feature of multi-pad wellbore image logging interpretation in the process. First, according to updated production data from Eagle Ford, the model was constructed to perform four (parent) wells history matching including five inner (child) wells. Later, fracture diagnostic results from well image logging were employed to perform sensitivity analysis on properties of long interwell connecting fractures such as number, conductivity, geometry, and explore their impacts on history matching. However, the estimation of these inter-well connecting fractures which were employed for enhanced history matching varied significantly from unmeasured fracture sensitivities. Finally, optimal cluster spacing was recommended considering interwell interference. The obtained results lead our study to the implementation of Huff-n-Puff models that capture inter-well interference seen in the field and their affordable impact sensitivities focused on variable injection rates/locations and multi-point water injection to mimic pressure barriers. The simulation results strengthen the understanding of modeling complex fracture geometries with robust history matching and support the need to incorporate containment strategies when EOR Huff-n-Puff is implemented. Moreover, the simulation outcomes show that well interference is present and reduces effectiveness of the fracture hits when connecting natural fractures. As a result of the inter-well long fractures, the bottom hole pressure behavior of the parent wells tends to equalize, and the pressure does not recover fast enough. Furthermore, the EDFM application is strongly supported by complex fracture propagation interpretation from image logs through the child wells in the reservoir. Through this study, multiple containment scenarios were proposed to contain the pressure in the area of interest, considering more than 2000 hydraulic fractures. The model became a valuable stencil to inform the impacts on well location and spacing, the completion staging, initial huff-n-puff decisions, and subsequent containment strategies (e.g. to improve cycle timing and efficiency), so that it can be expanded to other areas of the field. The simulation results and understandings afforded have been applied to the field satisfactorily to support significant reductions in offset fracture interference by up to 50% and reduce completion costs up to 23% while improving new well capital efficiency. Consequently, these outcomes support pressure containment benefits that lead to increased pressure build, reduced gas communication, reduced offset shut-in volumes, and ultimately, improvements in net utilization and capital efficiency
Author: Joseph Alexander Leines Artieda
Publisher:
ISBN:
Category :
Languages : en
Pages : 280
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Book Description
Recent advances in fracture network characterization have identified high degrees of heterogeneity and permeability anisotropy in conventional reservoirs and complex fracture network generation after well stimulation in unconventional reservoirs. Traditional methods to model such complex systems may not capture the key role of fracture network geometry, spatial distribution, and connectivity on well performance. Because of the ubiquitous presence of natural fractures in conventional and unconventional reservoirs, it is key to provide efficient tools to model them accurately. We extend the application of the embedded discrete fracture model (EDFM) to study the influence of natural fractures represented by discrete fracture network (DFN) models on well performance. Current state-of-the-art modeling technologies have been able to describe natural fracture systems as a whole, without providing flexibility to extract, vary, and group fracture network properties. Our developed implementations analyze fracture network topology and provide advanced mechanisms to model and understand fracture network properties. The first application features a numerical model in combination with EDFM to study water intrusion in a naturally fractured carbonate reservoir. We developed a workflow that overcomes conventional methods limitations by modeling the fracture network as a graph. This representation allowed to identify the shortest paths that connect the nearby water zone with the well perforations, providing the mechanisms to obtain a satisfactory history match of the reservoir. Additionally, we modeled a critically-stressed carbonate field by modeling faults interactions with natural fractures. Our workflow allowed to discretize the hydraulic backbone of the field and assess its influence on the entire field gas production. Our next application applies a connectivity analysis using an efficient and robust collision detection algorithm capable of identifying groups of connected or isolated natural fractures in an unconventional reservoir. This study uses numerical models in combination with EDFM to analyze the effect of fracture network connectivity on well production using fractal DFN models. We concluded that fracture network connectivity plays a key role on the behavior of fractured reservoirs with negligible effect of non-connected fractures. Finally, we performed assisted history matching (AHM) using fractal methods to characterize in a probabilistic manner the reservoir properties and to offer key insights regarding spatial distribution, number, and geometry of both hydraulic and natural fractures in unconventional reservoirs. In this work, we provided computational tools that constitute the foundations to conduct advanced modeling using DFN models in conjunction with EDFM in several reservoir engineering areas such as well-interference, water intrusion, water breakthrough, enhanced oil recovery (EOR) efficiency characterization, and fracture network connectivity assessments. The benefits of our work extend to conventional, unconventional, and geothermal reservoirs
Author: Kamy Sepehrnoori
Publisher: Elsevier
ISBN: 0128196882
Category : Business & Economics
Languages : en
Pages : 306
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Book Description
The development of naturally fractured reservoirs, especially shale gas and tight oil reservoirs, exploded in recent years due to advanced drilling and fracturing techniques. However, complex fracture geometries such as irregular fracture networks and non-planar fractures are often generated, especially in the presence of natural fractures. Accurate modelling of production from reservoirs with such geometries is challenging. Therefore, Embedded Discrete Fracture Modeling and Application in Reservoir Simulation demonstrates how production from reservoirs with complex fracture geometries can be modelled efficiently and effectively. This volume presents a conventional numerical model to handle simple and complex fractures using local grid refinement (LGR) and unstructured gridding. Moreover, it introduces an Embedded Discrete Fracture Model (EDFM) to efficiently deal with complex fractures by dividing the fractures into segments using matrix cell boundaries and creating non-neighboring connections (NNCs). A basic EDFM approach using Cartesian grids and advanced EDFM approach using Corner point and unstructured grids will be covered. Embedded Discrete Fracture Modeling and Application in Reservoir Simulation is an essential reference for anyone interested in performing reservoir simulation of conventional and unconventional fractured reservoirs. Highlights the current state-of-the-art in reservoir simulation of unconventional reservoirs Offers understanding of the impacts of key reservoir properties and complex fractures on well performance Provides case studies to show how to use the EDFM method for different needs
Author: Yifei Xu
Publisher:
ISBN:
Category :
Languages : en
Pages : 246
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Book Description
Fractured reservoirs have gained continuous attention from oil and gas industry. A huge amount of hydrocarbon are trapped in naturally fractured carbonate reservoirs. Besides, the advanced technology of multi-stage hydraulic fracturing have gained a great success in economic development of unconventional oil and gas reservoirs. Fractures add complexity into reservoir flow and significantly impact the ultimate recovery. Therefore, it is important yet challenging to accurately and effectively predict the recovery from fractured reservoirs. Conventional dual-continuum approaches, although effective in the simulation of naturally fractured reservoirs, may fail in some cases due to the highly idealized reservoir model. The unstructured-grid discrete fracture models, although flexible in representing complex fracture geometries, are restricted by the high complexity in gridding and high computational cost. An Embedded Discrete Fracture Model (EDFM) was recently developed to honor the accuracy of discrete fracture models while keeping the efficiency offered by structured gridding. By dividing the fractures into segments using matrix cell boundaries and creating non-neighboring connections (NNCs), the flow influence of fractures can be efficiently modeled through transport indices. In this work, the EDFM was implemented in UTCHEM, a chemical flooding in-house reservoir simulator developed at The University of Texas, to study complex recovery processes in fractured reservoirs. In addition, the model was applied in commercial simulators by making use of the non-intrusive property of the EDFM and the NNC functionality offered by the simulators. The accuracy of the EDFM in the modeling of orthogonal, non-orthogonal, and inclined fractures was verified against fine-grid explicit fracture simulations. Furthermore, case studies were performed to investigate the influence of hydraulic fracture orientations on primary depletion and the impact of large-scale natural fractures on water flooding processes. The influence of matrix grid size and fracture relative permeability was also studied. Finally, with modifications in NNC transmissibility calculation, the EDFM was applied to the modeling of a multi-lateral well stimulation technology. The accuracy of the modified formulations was verified through comparison with a multi-branch well method. The simulations carried out in this work confirmed the flexibility, applicability, and extensiveness of the EDFM.
Author: Qiwei Li (M.S. in Engineering)
Publisher:
ISBN:
Category :
Languages : en
Pages : 134
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Book Description
An appropriate well spacing plan is critical for the development of shale reservoirs. The biggest challenge for well spacing optimization is interpreting the subsurface uncertainties associated with hydraulic and natural fractures. However, most studies have calibrated the uncertainties by single history matching, which does not take the non-uniqueness of history matching into account. Therefore, the objective of this study is to develop an integrated assisted history matching (AHM) and embedded discrete fracture model (EDFM) workflow for well spacing optimization by considering multiple uncertainty realizations and economic analysis. We applied this workflow for an actual shale gas reservoir without natural fractures and another shale gas reservoir with complex natural fractures. Firstly, we captured the distribution of uncertainty parameters of matrix and fractures using AHM based on the production data. Uncertain parameters of matrix include matrix permeability, matrix porosity, and three relative permeability parameters, while hydraulic fractures uncertainties consist of fracture height, half-length, width, conductivity, and water saturation. And the uncertain parameters of natural fractures are the number of natural fractures, conductivity, and length. The input cases can be prepared by combining AHM solutions with different well placement scenarios. Then we performed reservoir simulation to all cases and forecasted the gas and water production in the long-term. Gas estimated ultimate recovery (EUR) per well can be analyzed to predict the influence of well interference and the critical well spacing. Finally, we estimated the net present value (NPV) for all cases and predicted it by k-nearest neighbors (KNN) proxy model to better understand the relationship between well spacing and NPV. The optimum well spacing can be obtained from the maximum NPV. Our integrated workflow is straightforward and practical, with great accuracy, and efficiency. We can predict the optimum well spacing for most shale gas reservoirs by capturing the multiple realizations of uncertainties
Author: Mahmood Shakiba
Publisher:
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Category :
Languages : en
Pages : 0
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Book Description
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.
Author: Yifei Xu (Research engineer)
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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The simulation of fractured reservoirs is a challenging topic in reservoir simulation owing to the complexity of fracture geometry and recovery processes related to fractured reservoirs. Reliable and efficient numerical models are required for the representation of hydraulic and natural fractures in conventional and unconventional reservoirs. The objective of this work is to develop a numerical approach for simulating complex fractures and complex recovery processes in fractured reservoirs using various types of computational grids. This research is an extension of the Embedded Discrete Fracture Model (EDFM). In this work, methodologies were developed to model various types of 2D and 3D complex fracture geometries. The EDFM was also extended to handle several types of computational grids, including corner-point grids, locally-refined grids, and unstructured grids with mixed elements. Geometrical algorithms were developed and implemented in a general-purpose preprocessing code for the calculation of EDFM connection factors in such grids. The use of the EDFM with matrix grids using various numerical approximation schemes, such as finite-volume method and element-based finite-volume method, was also studied. Furthermore, the model was improved regarding modeling fracture transient flow and dynamic fracture behaviors. For the simulation of hydraulically fractured unconventional reservoirs, various important flow mechanisms were implemented in a compositional simulator. The simulator was used to investigate the relative importance of these mechanisms. The developed methodology was applied to a series of synthetic and realistic case studies. The accuracy of the model was confirmed through comparison with other models for simulating various types of fracture geometries in different hydrocarbon recovery processes. A high computational performance was also achieved using the model. Furthermore, based on the results of this research, for long-term production forecasting, the accuracy of the EDFM is not sensitive to the type of grid, the detailed gridding around fractures, or the numerical approximation scheme, if a similar gridblock size is used in the simulations. For the simulation of short-term flow, the combination of the EDFM with nested grid refinement greatly improves the simulation accuracy for various flow regimes. The modeling of dynamic fracture behaviors and unconventional reservoir flow mechanisms demonstrates the flexibility of the proposed approach in incorporating different physics
Author: Ali Moinfar
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Naturally fractured reservoirs (NFRs) hold a significant amount of the world's hydrocarbon reserves. Compared to conventional reservoirs, NFRs exhibit a higher degree of heterogeneity and complexity created by fractures. The importance of fractures in production of oil and gas is not limited to naturally fractured reservoirs. The economic exploitation of unconventional reservoirs, which is increasingly a major source of short- and long-term energy in the United States, hinges in part on effective stimulation of low-permeability rock through multi-stage hydraulic fracturing of horizontal wells. Accurate modeling and simulation of fractured media is still challenging owing to permeability anisotropies and contrasts. Non-physical abstractions inherent in conventional dual porosity and dual permeability models make these methods inadequate for solving different fluid-flow problems in fractured reservoirs. Also, recent approaches for discrete fracture modeling may require large computational times and hence the oil industry has not widely used such approaches, even though they give more accurate representations of fractured reservoirs than dual continuum models. We developed an embedded discrete fracture model (EDFM) for an in-house fully-implicit compositional reservoir simulator. EDFM borrows the dual-medium concept from conventional dual continuum models and also incorporates the effect of each fracture explicitly. In contrast to dual continuum models, fractures have arbitrary orientations and can be oblique or vertical, honoring the complexity and heterogeneity of a typical fractured reservoir. EDFM employs a structured grid to remediate challenges associated with unstructured gridding required for other discrete fracture models. Also, the EDFM approach can be easily incorporated in existing finite difference reservoir simulators. The accuracy of the EDFM approach was confirmed by comparing the results with analytical solutions and fine-grid, explicit-fracture simulations. Comparison of our results using the EDFM approach with fine-grid simulations showed that accurate results can be achieved using moderate grid refinements. This was further verified in a mesh sensitivity study that the EDFM approach with moderate grid refinement can obtain a converged solution. Hence, EDFM offers a computationally-efficient approach for simulating fluid flow in NFRs. Furthermore, several case studies presented in this study demonstrate the applicability, robustness, and efficiency of the EDFM approach for modeling fluid flow in fractured porous media. Another advantage of EDFM is its extensibility for various applications by incorporating different physics in the model. In order to examine the effect of pressure-dependent fracture properties on production, we incorporated the dynamic behavior of fractures into EDFM by employing empirical fracture deformation models. Our simulations showed that fracture deformation, caused by effective stress changes, substantially affects pressure depletion and hydrocarbon recovery. Based on the examples presented in this study, implementation of fracture geomechanical effects in EDFM did not degrade the computational performance of EDFM. Many unconventional reservoirs comprise well-developed natural fracture networks with multiple orientations and complex hydraulic fracture patterns suggested by microseismic data. We developed a coupled dual continuum and discrete fracture model to efficiently simulate production from these reservoirs. Large-scale hydraulic fractures were modeled explicitly using the EDFM approach and numerous small-scale natural fractures were modeled using a dual continuum approach. The transport parameters for dual continuum modeling of numerous natural fractures were derived by upscaling the EDFM equations. Comparison of the results using the coupled model with that of using the EDFM approach to represent all natural and hydraulic fractures explicitly showed that reasonably accurate results can be obtained at much lower computational cost by using the coupled approach with moderate grid refinements.
