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Author: Farhad Tarahhom
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
A large percentage of oil and gas reservoirs in the most productive regions such as the Middle East, South America, and Southeast Asia are naturally fractured reservoirs (NFR). The major difference between conventional reservoirs and naturally fractured reservoirs is the discontinuity in media in fractured reservoir due to tectonic activities. These discontinuities cause remarkable difficulties in describing the petrophysical structures and the flow of fluids in the fractured reservoirs. Predicting fluid flow behavior in naturally fractured reservoirs is a challenging area in petroleum engineering. Two classes of models used to describe flow and transport phenomena in fracture reservoirs are discrete and continuum (i.e. dual porosity) models. The discrete model is appealing from a modeling point of view, but the huge computational demand and burden of porting the fractures into the computational grid are its shortcomings. The affect of natural fractures on the permeability anisotropy can be determined by considering distribution and orientation of fractures. Representative fracture permeability, which is a crucial step in the reservoir simulation study, must be calculated based on fracture characteristics. The diagonal representation of permeability, which is customarily used in a dual porosity model, is valid only for the cases where fractures are parallel to one of the principal axes. This assumption cannot adequately describe flow characteristics where there is variation in fracture spacing, length, and orientation. To overcome this shortcoming, the principle of the full permeability tensor in the discrete fracture network can be incorporated into the dual porosity model. Hence, the dual porosity model can retain the real fracture system characteristics. This study was designed to develop a novel approach to integrate dual porosity model and full permeability tensor representation in fractures. A fully implicit, parallel, compositional chemical dual porosity simulator for modeling naturally fractured reservoirs has been developed. The model is capable of simulating large-scale chemical flooding processes. Accurate representation of the fluid exchange between the matrix and fracture and precise representation of the fracture system as an equivalent porous media are the key parameters in utilizing of dual porosity models. The matrix blocks are discretized into both rectangular rings and vertical layers to offer a better resolution of transient flow. The developed model was successfully verified against a chemical flooding simulator called UTCHEM. Results show excellent agreements for a variety of flooding processes. The developed dual porosity model has further been improved by implementing a full permeability tensor representation of fractures. The full permeability feature in the fracture system of a dual porosity model adequately captures the system directionality and heterogeneity. At the same time, the powerful dual porosity concept is inherited. The implementation has been verified by studying water and chemical flooding in cylindrical and spherical reservoirs. It has also been verified against ECLIPSE and FracMan commercial simulators. This study leads to a conclusion that the full permeability tensor representation is essential to accurately simulate fluid flow in heterogeneous and anisotropic fracture systems.
Author: Farhad Tarahhom
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
A large percentage of oil and gas reservoirs in the most productive regions such as the Middle East, South America, and Southeast Asia are naturally fractured reservoirs (NFR). The major difference between conventional reservoirs and naturally fractured reservoirs is the discontinuity in media in fractured reservoir due to tectonic activities. These discontinuities cause remarkable difficulties in describing the petrophysical structures and the flow of fluids in the fractured reservoirs. Predicting fluid flow behavior in naturally fractured reservoirs is a challenging area in petroleum engineering. Two classes of models used to describe flow and transport phenomena in fracture reservoirs are discrete and continuum (i.e. dual porosity) models. The discrete model is appealing from a modeling point of view, but the huge computational demand and burden of porting the fractures into the computational grid are its shortcomings. The affect of natural fractures on the permeability anisotropy can be determined by considering distribution and orientation of fractures. Representative fracture permeability, which is a crucial step in the reservoir simulation study, must be calculated based on fracture characteristics. The diagonal representation of permeability, which is customarily used in a dual porosity model, is valid only for the cases where fractures are parallel to one of the principal axes. This assumption cannot adequately describe flow characteristics where there is variation in fracture spacing, length, and orientation. To overcome this shortcoming, the principle of the full permeability tensor in the discrete fracture network can be incorporated into the dual porosity model. Hence, the dual porosity model can retain the real fracture system characteristics. This study was designed to develop a novel approach to integrate dual porosity model and full permeability tensor representation in fractures. A fully implicit, parallel, compositional chemical dual porosity simulator for modeling naturally fractured reservoirs has been developed. The model is capable of simulating large-scale chemical flooding processes. Accurate representation of the fluid exchange between the matrix and fracture and precise representation of the fracture system as an equivalent porous media are the key parameters in utilizing of dual porosity models. The matrix blocks are discretized into both rectangular rings and vertical layers to offer a better resolution of transient flow. The developed model was successfully verified against a chemical flooding simulator called UTCHEM. Results show excellent agreements for a variety of flooding processes. The developed dual porosity model has further been improved by implementing a full permeability tensor representation of fractures. The full permeability feature in the fracture system of a dual porosity model adequately captures the system directionality and heterogeneity. At the same time, the powerful dual porosity concept is inherited. The implementation has been verified by studying water and chemical flooding in cylindrical and spherical reservoirs. It has also been verified against ECLIPSE and FracMan commercial simulators. This study leads to a conclusion that the full permeability tensor representation is essential to accurately simulate fluid flow in heterogeneous and anisotropic fracture systems.
Author: Jia'en Lin
Publisher: Springer Nature
ISBN: 9811921490
Category : Science
Languages : en
Pages : 5829
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Book Description
This book focuses on reservoir surveillance and management, reservoir evaluation and dynamic description, reservoir production stimulation and EOR, ultra-tight reservoir, unconventional oil and gas resources technology, oil and gas well production testing, and geomechanics. This book is a compilation of selected papers from the 11th International Field Exploration and Development Conference (IFEDC 2021). The conference not only provides a platform to exchanges experience, but also promotes the development of scientific research in oil & gas exploration and production. The main audience for the work includes reservoir engineer, geological engineer, enterprise managers, senior engineers as well as professional students.
Author: Bowei Li
Publisher:
ISBN:
Category : Multiphase flow
Languages : en
Pages : 0
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Book Description
Transport and flow phenomena in porous media and fractured rock arise in many fields of science and engineering, including petroleum and groundwater engineering. Over the past few decades, there are two classes of models that have been developed for describing flow and transport phenomena in porous media and fractured rock. They are the continuum and discrete models. Continuum models include single porosity and dual porosity models. The latter is popularly applied in simulating flow in naturally fractured systems. Discrete feature models explicitly recognize the fracture system's geometrical properties, such as orientation and intensity. But shortcomings have been experienced for such discrete models in that large computational efforts are required for a realistic treatment of a heavily fractured system. Such a large fractured system may contain millions of fracture features. The huge demand of computational resources may seriously undermine the application of discrete models for such systems. Moreover, the discrete feature model is more difficult to use for multiphase flow and complex recovery mechanisms for oil recovery process. The dual porosity model, a subclass of the continuum model, is a favorable approach to study flow in naturally fractured systems. In the dual porosity approach, it is assumed that the fissured porous media can be represented by two colocated continua called the matrix and the fracture system. High conductivity but low storativity typically characterizes the fracture system, whereas the matrix is usually characterized as low conductivity but high storativity. The matrix generally acts as a source that transfers its mass to the surrounding fractures; then fluid is transported to production wells. There are two main reasons for the acceptance of dual porosity model. The first reason is its ability to handle the length scale inconsistency between matrix and fractures. It is impractical to simulate a fractured system by a single porosity approach if a matrix block is gridded to the fracture's length scale. But the dual porosity approach may divide the physical problem into two interactive problems. Therefore the dual porosity model captures the length scales of the physical problem, and is much easier to handle computationally. The second advantage of the dual porosity model is its capacity to address complex local phenomena at the matrix boundary surrounded by fractures. Conventional dual porosity models generally use a diagonal permeability tensor to formulate and discretize the flow equations for the fracture system. However, such practice does not always adequately reflect the characteristics of natural fractures characterized by heterogeneity and anisotropy ascribed to the fracture's varied orientation, apertures, and intensity. Therefore, conventional dual porosity models may overlook the naturally fractured system's directionality and heterogeneity. This study is designed to develop a novel approach to model fluid flow in natural fractured systems with a dual porosity approach. In the study, a full permeability tensor representation of fracture flow is implemented in the UTCHEM dual porosity chemical flood simulator. The full permeability tensor feature in the fracture system adequately captures the system's characteristics, i.e., directionality and heterogeneity. At the same time, the powerful dual porosity concept is inherited. The capability of modeling the local complex physical phenomena is maintained in the simulator. The implementation has been verified through studying waterflooding in a cylindrical reservoir, and waterflooding in a spherical reservoir. As an application of the implementation, a study on a naturally fractured system was conducted. Simulation results were compared with that generated by the Fracman simulator (Golder Associates, 2000) a discrete feature model. Another application is waterflooding through a fractured system using dual porosity approach. A conclusion can be drawn from all these studies that for a heterogeneous and anisotropic system, full permeability tensor representation of flow is necessary to accurately simulate flow in such system.
Author: Kamy Sepehrnoori
Publisher: Elsevier
ISBN: 0128196882
Category : Technology & Engineering
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: Yousef Kh. S. Hashem
Publisher:
ISBN:
Category : Gas fields
Languages : en
Pages : 304
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Book Description
Author: Bruno Ramon Batista Fernandes
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Reservoir simulators are important tools used in the oil industry for evaluating field opportunity, reservoir management, and reserve estimation. Such tools are based on complex physics and mathematics that require fast solution in order to provide better production scenarios and history matching. In this work, algorithms for solving the partial differential equations arising in modeling compositional miscible gas flooding and chemical EOR processes are presented. Herein, the algorithms presented are based on time discretization schemes known as IMPEC (Implicit Pressure explicit compositions), fully implicit and a combination of these two approaches known as adaptive implicit (AIM). The main goal of this work is to improve the performance of the simulations. For compositional miscible gas flooding, the following approaches are implemented: Natural variables, extensive global variables, and a novel intensive global variable fully implicit approach, an AIM from the literature, and a new AIM. The implementation considers Cartesian grids and fractured reservoirs using the embedded discrete fracture method. Additionally, all implementation considers up to four phases, which is novel for the adaptive implicit methods. For the chemical EOR the following formulations are developed: FI approaches (global variable, natural variable, and mixed variable) and a global variable adaptive implicit. All important features for polymer and surfactant flooding are considered. New models proposed in this work and in the literature to relative permeability, capillary desaturation curves, and critical micelle concentration are implemented to demonstrate the importance of handling the phase transition in order for the FI/AIM be successful in simulating real applications. In order to help the development of the aforementioned formulation an automatic differentiation tool was developed to reduce the timeframe for implementation. All the above formulations are implemented to Cartesian grids, but the global variables for chemical EOR is also implemented for corner point grids that can handle hanging nodes. We also develop a framework that can easily include any type of grid (Cartesian, corner point, unstructured) that is still under development. All the aforementioned formulations are included in two in-house simulators from The University of Texas at Austin named UTCOMPRS and UTCHEMRS. The results for both simulators are compared to the original IMPEC approaches of these simulators and to results of several commercial simulators. From the results, we can clearly observe that the new formulations proposed in this work not only are robust and improve the computational performance of the aforementioned simulators, but also have computational performance similar to the commercial simulators largely used in the oil industry
Author: Feng Pan (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 652
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Book Description
For a stress-sensitive or stress-dependent reservoir, the interactions between its seepage field and in situ stress field are complex and affect hydrocarbon recovery. A coupled geomechanics and fluid-flow model can capture these relations between the fluid and solid, thereby presenting more precise history matchings and predictions for better well planning and reservoir management decisions. A traditional reservoir simulator cannot adequately or fully represent the ongoing coupled fluid-solid interactions during the production because of using the simplified update-formulation for porosity and the static absolute permeability during simulations. Many researchers have studied multiphase fluid-flow models coupled with geomechanics models during the past fifteen years. The purpose of this research is to develop a coupled geomechanics and compositional model and apply it to problems in the oil recovery processes. An equation of state compositional simulator called the General Purpose Adaptive Simulator (GPAS) is developed at The University of Texas at Austin and uses finite difference / finite control volume methods for the solution of its governing partial differential equations (PDEs). GPAS was coupled with a geomechanics model developed in this research, which uses a finite element method for discretization of the associated PDEs. Both the iteratively coupled solution procedure and the fully coupled solution procedure were implemented to couple the geomechanics and reservoir simulation modules in this work. Parallelization, testing, and verification for the coupled model were performed on parallel clusters of high-performance workstations. MPI was used for the data exchange in the iteratively coupled procedure. Different constitutive models were coded into GPAS to describe complicated behaviors of linear or nonlinear deformation in the geomechanics model. In addition, the geomechanics module was coupled with the dual porosity model in GPAS to simulate naturally fractured reservoirs. The developed coupled reservoir and geomechanics simulator was verified using analytical solutions. Various reservoir simulation case studies were carried out using the coupled geomechanics and GPAS modules.
Author: Feng Pan
Publisher:
ISBN:
Category :
Languages : en
Pages : 652
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Book Description
For a stress-sensitive or stress-dependent reservoir, the interactions between its seepage field and in situ stress field are complex and affect hydrocarbon recovery. A coupled geomechanics and fluid-flow model can capture these relations between the fluid and solid, thereby presenting more precise history matchings and predictions for better well planning and reservoir management decisions. A traditional reservoir simulator cannot adequately or fully represent the ongoing coupled fluid-solid interactions during the production because of using the simplified update-formulation for porosity and the static absolute permeability during simulations. Many researchers have studied multiphase fluid-flow models coupled with geomechanics models during the past fifteen years. The purpose of this research is to develop a coupled geomechanics and compositional model and apply it to problems in the oil recovery processes. An equation of state compositional simulator called the General Purpose Adaptive Simulator (GPAS) is developed at The University of Texas at Austin and uses finite difference / finite control volume methods for the solution of its governing partial differential equations (PDEs). GPAS was coupled with a geomechanics model developed in this research, which uses a finite element method for discretization of the associated PDEs. Both the iteratively coupled solution procedure and the fully coupled solution procedure were implemented to couple the geomechanics and reservoir simulation modules in this work. Parallelization, testing, and verification for the coupled model were performed on parallel clusters of high-performance workstations. MPI was used for the data exchange in the iteratively coupled procedure. Different constitutive models were coded into GPAS to describe complicated behaviors of linear or nonlinear deformation in the geomechanics model. In addition, the geomechanics module was coupled with the dual porosity model in GPAS to simulate naturally fractured reservoirs. The developed coupled reservoir and geomechanics simulator was verified using analytical solutions. Various reservoir simulation case studies were carried out using the coupled geomechanics and GPAS modules.
Author: Nithiwat Siripatrachai
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Most existing compositional reservoir simulators often model fractures using local grid refinement, unstructured-grid, or fine-grid models. Modeling different scales of fractures requires a large number of grid blocks to capture the heterogeneity of the formation. Using a large number of grid blocks presents computational challenges, even with todays powerful processors. An enhanced matrix permeability on the grid block that hosts short-scale fractures is commonly used to eliminate natural fractures and simplify the model. Additionally, several existing multi-porosity models may not be able to capture heterogeneity and flow behavior in different porosity domains. Sequential flow assumption is frequently made in their models. Flows between different porosity types are not fully coupled, and in some model, a simplified inter-porosity transmissibility function is used for any porosity pairs. The oil and gas reserves and flow of reservoir fluids are strongly dependent on phase behavior. Large capillary pressure values are encountered in tight formations such as tight-rocks and shales. The tiny pore throats in these formations result in large capillary pressure. The effect of capillary pressure in tight formations can significantly impact the fluid phase behaviors in the reservoir during production and enhanced oil recovery (EOR) processes. Not incorporating this effect into the simulation can result in an inaccurate estimation of ultimate recovery as well as inefficient design and implementation of EOR techniques. In spite of this, the effect of capillary pressure on phase behavior in tight reservoirs has not been well studied using compositional simulation, especially for hydraulically fractured reservoirs.In this research, a fully implicit, multi-mechanistic, fully coupled, triple-porosity, triple-permeability compositional model has been developed for unconventional reservoirs. The hydraulically fractured tight rock and shale reservoir is treated as a triple-porosity system consisting of matrix blocks, natural fractures (micro fractures), and hydraulic fractures (macro fractures). Small-scale fractures are handled by a dual-continuum model. An embedded discrete fracture model is used to effectively and efficiently capture the flow dynamics of hydraulic fractures at any orientations, honoring the complexity and heterogeneity of the fracture networks. The triple-porosity model enables us to assign reservoir properties corresponding to the porosity type. The flows in three porosity types are fully coupled without making the assumption of sequential flow. The inter-porosity fluid transfer honors the geometry of the intersecting porosity pair. The development of the proposed numerical model incorporates the effect of capillary pressure on phase behavior. The transport of hydrocarbon follows a multi-mechanistic flow mechanism that is driven by pressure and concentration fields. The simulator has been validated with analytical solutions and a commercial reservoir simulator for a single-porosity model and a dual-porosity, dual-permeability model, both with and without grid refinement. With the proposed model, we can accurately capture major physics of transport phenomena that have been done to date and have the most realistic modeling of fluid flow in hydraulically fractured tight rock and shale reservoirs. The simulator is used in parametric studies to investigate the production performance from hydraulically fractured reservoirs under different modeling techniques and the effect of capillary pressure on phase behavior on reserves and ultimate recovery. The simulator is used to study the impact of inter-porosity transport on the recovery and fluid transport and phase behavior in hydraulically fractured tight rocks and shale formations under high capillary pressure. The outcomes of this project are an improved understanding of phase behavior and fluid flow in hydraulically fractured shale and tight rocks and an increased accuracy of the production prediction and ultimate recovery.
Author: J.L. Auriault
Publisher: CRC Press
ISBN: 1000108090
Category : Technology & Engineering
Languages : en
Pages : 972
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Book Description
These proceedings deal with the fundamentals and applications of poromechanics to geomechanics, material sciences, geophysics, acoustics and biomechanics. They discuss the state of the art in such topics as constitutive modelling and upscaling methods.
