Browsing by Subject "Oil reservoir engineering--Simulation methods"
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Item Development and implementation of a narually fractured reservoir model into a fully implicit, equation-of-state compositional, parallel simulator(2005) Naimi-Tajdar, Reza; Sepehrnoori, Kamy, 1951-; Miller, Mark A.Naturally fractured reservoirs contain a significant amount of the world oil reserves. A number of these fields contain several billion barrels of oil. In naturally fractured reservoirs, fluids exist in two interconnected systems: the rock matrix, which usually provides the bulk of the reservoir volume, and the highly permeable rock fractures. Accurate and efficient reservoir simulation of naturally fractured reservoirs is one of the most important, challenging, and computationally intensive problems in reservoir engineering. Parallel reservoir simulators developed for naturally fractured reservoirs can effectively address the computational problem. A new accurate parallel numerical simulator for large-scale naturally fractured reservoirs, capable of modeling fluid flow in both rock matrix and fractures, has been developed. The simulator is a parallel, 3D, fully implicit, equation-of-state compositional model that uses numerical tools for solving very large, sparse linear systems arising from discretization of the governing partial differential equations. A generalized dual porosity model, the multiple-interacting-continua (MINC), has been implemented in this simulator. The matrix blocks are discretized into subgrids in both horizontal and vertical directions to offer a more accurate transient flow description in matrix blocks. We believe this implementation has led to a unique and powerful reservoir simulator that can be used by small and large oil producers to help them in design and prediction of complex gas and waterflooding processes on their desktops or a cluster of computers. Some features of this simulator, such as modeling both gas and water processes with the ability of two dimensional matrix subgridding for naturally fractured reservoirs, to the best of our knowledge are not available in any commercial simulator. For coupling of the fracture and matrix continua, no analytical approximations are made. Instead, numerical methods are used to treat the transient flow of fluid between matrix and fractures. The development was performed on a cluster of processors, which has proven to be a very efficient and convenient resource for developing parallel programs. The results were successfully verified against analytical solutions and commercial simulators (ECLIPSE, IMEX, and GEM). Excellent agreement was achieved for a variety of reservoir case studies. Applications of this model for several enhanced oil-recovery processes (including gas and water injection) are demonstrated. The effects of matrix subgridding on the accuracy of the results of the simulation runs are investigated. The study showed that in some circumstances the results of simulators without matrix subgridding generated more than 50% error in oil-recovery calculations. Simulation results using the simulator on a cluster of processors are also presented. Excellent speedups were obtained using the simulator in conjunction with solving a variety of problems.Item Implementation of full permeability tensor representation in a dual porosity reservoir simulator(2001-08) Li, Bowei; Miller, Mark A.; Sepehrnoori, Kamy, 1951-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 vii 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 viii 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.Item IRSS: integrated reservoir simulation system(2005) Zhang, Jiang; Sepehrnoori, Kamy, 1951-Increasing hydrocarbon production via advanced technologies commonly involves the use of numerical simulation of the associated processes to minimize the risk involved in development decisions. The oil industry today requires much more detailed analysis with a greater demand for reservoir simulations with geological, physical, and chemical models than in the past. Without detailed simulations it is very unlikely that cost effective recovery processes can be developed and applied economically. Although reservoir simulation software is currently available, there are still many obstacles to its widespread and effective use in the upstream oil and gas industry. These include: z Data preparation and output analysis are often extremely time-consuming because of the amount and complexity of the required data. z Large uncertainties associated with the petrophysical properties and methods for incorporating these uncertainties into performance predictions are not currently time- or cost-effective. z Performance optimization using reservoir simulation is tedious and inefficient because of the time and effort required for generating, processing, and analyzing a large number of scenarios. The goal of this dissertation is to design and implement a user-friendly framework to overcome some of the abovementioned obstacles to promote the routine application of reservoir simulation in the processes of design and optimization. The framework includes several modules to identify the variables that have the most impact on hydrocarbon recovery using the concept of experimental design and response surface method. Several oil reservoir simulators such as VIP 1 , ECLIPSE 2 , and UTCHEM are integrated to perform the flow simulations associated with different hydrocarbon recovery processes. The framework implements an economic model that automatically imports the simulation production data to evaluate the profitability of a particular design. A large number of reservoir simulations can be run efficiently using a cluster of computers. This is the first time that a computing platform is developed with all these capabilities. Several field-scale applications are studied using our approach: - Well placement optimization taking into account reservoir and fluid uncertainties, - Surfactant/polymer flooding design and optimization with uncertainties in reservoir characterization, residual oil saturation, surfactant adsorption, price of crude oil and chemical, and discount rate, and - A surfactant remediation process with uncertainties in aquifer properties. According to our experience, the approach proposed in this dissertation can significantly save time for process optimization by a large factor compared to traditional method. This time savings includes for input preparation, postprocessing the simulation results, and the simulation execution time. A case study presented in this work shows that the clock time savings can be of the order of 40 for processing 158 surfactant/polymer simulations using UTCHEM.Item Large-scale conditional simulation : domain and matrix decomposition and the moving template model(1995-05) Lima, Luiz Cavalcante de; Not available