The Experts below are selected from a list of 42693 Experts worldwide ranked by ideXlab platform
Agus P Sasmito - One of the best experts on this subject based on the ideXlab platform.
-
a fractal network model for Fractured porous media
Fractals, 2016Co-Authors: Shuxia Qiu, Agus P SasmitoAbstract:The transport properties and mechanisms of Fractured porous media are very important for oil and gas reservoir engineering, hydraulics, environmental science, chemical engineering, etc. In this paper, a fractal dual-porosity model is developed to estimate the equivalent hydraulic properties of Fractured porous media, where a fractal tree-like network model is used to characterize the Fracture system according to its fractal scaling laws and topological structures. The analytical expressions for the effective permeability of Fracture system and Fractured porous media, tortuosity, Fracture density and fraction are derived. The proposed fractal model has been validated by comparisons with available experimental data and numerical simulation. It has been shown that fractal dimensions for Fracture Length and aperture have significant effect on the equivalent hydraulic properties of Fractured porous media. The effective permeability of Fracture system can be increased with the increase of fractal dimensions for Fracture Length and aperture, while it can be remarkably lowered by introducing tortuosity at large branching angle. Also, a scaling law between the Fracture density and fractal dimension for Fracture Length has been found, where the scaling exponent depends on the Fracture number. The present fractal dual-porosity model may shed light on the transport physics of Fractured porous media and provide theoretical basis for oil and gas exploitation, underground water, nuclear waste disposal and geothermal energy extraction as well as chemical engineering, etc.
Yimei Chen - One of the best experts on this subject based on the ideXlab platform.
-
Evaluation of geothermal energy extraction in Enhanced Geothermal System (EGS) with multiple fracturing horizontal wells (MFHW)
Renewable Energy, 2020Co-Authors: Facheng Gong, Tiankui Guo, Wei Sun, Bin Yang, Yimei ChenAbstract:Abstract The deep geothermal energy produced from Enhanced Geothermal System (EGS) has a great development prospect because of enormous potential and environmental friendliness. EGS process involves a complex thermal-hydraulic process, and Fractures in EGS are main channels for fluid flow and heat transfer, the understanding of which is crucial to the sustainable utilization of geothermal reservoirs. In this paper, a 3D thermal-hydraulic coupled numerical model is proposed to describe the interaction of fluid flow and heat transfer. Besides, the EGS with multiple fracturing horizontal wells (MFHW) is adopted to evaluate the effect of multiple hydraulic Fractures on geothermal energy extraction performance. The MFHW with multiple stimulated Fractures could increase fluid flow path and heat exchange area significantly, thereby enhance the heat recovery ability. Firstly, we analyzed the evolution of temperature and flow fields in EGS and compared the MFHW EGS with conventional vertical EGS. Secondly, the effects of fracturing parameters, including the Fracture number, Fracture Length, and Fracture conductivity, on heat extraction performance were investigated. Finally, the cost for drilling and hydraulic fracturing in MFHW EGS was calculated. The results indicate that MFHW EGS has a higher cumulative thermal production and a better heat extraction performance than that of conventional vertical EGS. For the optimization of hydraulic Fracture parameters, the cumulative thermal production firstly increases and then decreases as the Fracture number increases, the cumulative thermal production curve exists an inflection point of Fracture number. Longer Fracture Length and higher Fracture conductivity could enhance the cumulative thermal production, but the output growth slows down gradually. Considering economic cost, the best Fracture parameters for MFHW EGS in this paper are the Fracture number of 7, the Fracture Length of 300 m, and the Fracture conductivity of 350 μm2•cm, respectively. The research provides a better study for multiple fracturing horizontal wells (MFHW) EGS and helps to optimize Fracture parameters and geothermal reservoir management, which is conductive to improve the geothermal energy efficiency.
Reza Barati - One of the best experts on this subject based on the ideXlab platform.
-
simulating yield stress variation along hydraulic Fracture face enhances polymer cleanup modeling in tight gas reservoirs
Journal of Natural Gas Science and Engineering, 2019Co-Authors: Regina Tayong A, Mustafa M Alhubail, Belladonna Maulianda, Reza BaratiAbstract:Abstract Several measures have been taken to enhance the supply of fossil fuel energy in the United States during the last decades, some of which include the development and exploitation of very low permeability and low porosity reservoirs in challenging environments. These reservoirs usually require enhanced stimulation techniques such as multi-stage hydraulic fracturing and horizontal drilling to increase the contact between the wellbore and the producing formation for a profitable recovery. During the fracturing process, fluids are pumped into the reservoir under high pressure, to create Fractures through which gas flows back to the earth's surface during production. However, a layer of concentrated polymer forms on the Fracture faces limiting the loss of fluid to the formation during injection while impairing Fracture conductivity during production. The inadequacy of the Fracture conductivity after a Fracture treatment using cross-linked fluids is typically due to poor degradability of our polymers, proppant crushing, clay swelling in the case of incompatible fluids and formation damage. The objective of this work is to develop a Fracture cleanup model that simulates the rheological variations of filter cake and degraded fluids inside the Fracture by including the effect of breaker and polymer concentration on the yield stress of the fracturing fluid that result in variations in capillary pressure, Fracture conductivity, Fracture Length and formation damage during the cleanup process in unconventional tight gas formations. A dynamic 2-D, three-phase IMPES simulator, incorporating a yield-power-law-rheology (Herschel-Buckley fluids), has been developed in MATLAB to simulate variations in rheological properties of degrading fracturing fluids versus time and investigate the influence of several major parameters on the Fracture cleanup process. These parameters include variations in polymer concentration along the Fracture Length, breaker concentration variations, Fracture conductivity, Fracture Length, capillary pressure and formation damage with a novel correlation between yield stress and breaker concentration, which enhances post – Fracture well performance prediction in tight gas reservoirs. The three phases simulated here include water, gas and the gel phases. Simulation of the injection of fracturing fluids and fluid imbibition during the shut-in time indicated that for tight gas formations, fluid recovery increases with increasing shut-in time, increasing Fracture conductivity and Fracture Length irrespective of the yield stress of the fracturing fluid. Simulation of the production phase highlighted that increasing the capillary pressure to a maximum of 350.10 psi resulted in a 10.4% decrease in cumulative gas production. The rate of increase in the yield stress of the fracturing fluid along the Fracture face is proportional to the square of the volume of fluid loss to the formation. Production will be enhanced significantly with increasing breaker concentration indicating that simulation of the yield stress variation along the Fracture face presents a more realistic scenario of the Fracture cleanup process rather than assuming a constant value since the fluid loss to the formation and the polymer concentration distribution decrease with Fracture Length.
Shuxia Qiu - One of the best experts on this subject based on the ideXlab platform.
-
a fractal network model for Fractured porous media
Fractals, 2016Co-Authors: Shuxia Qiu, Agus P SasmitoAbstract:The transport properties and mechanisms of Fractured porous media are very important for oil and gas reservoir engineering, hydraulics, environmental science, chemical engineering, etc. In this paper, a fractal dual-porosity model is developed to estimate the equivalent hydraulic properties of Fractured porous media, where a fractal tree-like network model is used to characterize the Fracture system according to its fractal scaling laws and topological structures. The analytical expressions for the effective permeability of Fracture system and Fractured porous media, tortuosity, Fracture density and fraction are derived. The proposed fractal model has been validated by comparisons with available experimental data and numerical simulation. It has been shown that fractal dimensions for Fracture Length and aperture have significant effect on the equivalent hydraulic properties of Fractured porous media. The effective permeability of Fracture system can be increased with the increase of fractal dimensions for Fracture Length and aperture, while it can be remarkably lowered by introducing tortuosity at large branching angle. Also, a scaling law between the Fracture density and fractal dimension for Fracture Length has been found, where the scaling exponent depends on the Fracture number. The present fractal dual-porosity model may shed light on the transport physics of Fractured porous media and provide theoretical basis for oil and gas exploitation, underground water, nuclear waste disposal and geothermal energy extraction as well as chemical engineering, etc.
Olivier Bour - One of the best experts on this subject based on the ideXlab platform.
-
influence of spatial correlation of Fracture centers on the permeability of two dimensional Fracture networks following a power law Length distribution
Water Resources Research, 2004Co-Authors: Jeanraynald De Dreuzy, Philippe Davy, Caroline Darcel, Olivier BourAbstract:[1] Observations of outcrops of Fractured media show that Fractures are correlated at all scales of the medium and that there are also Fractures of sizes ranging from the microscale to the macroscale. Recent studies have shown that the correlation pattern is often a fractal characterized by its dimension Dc and that the Fracture Length distribution is a power law of characteristic exponent −a. We study the influence of these long-range heterogeneities on the equivalent medium permeability. Fracture correlation and Fracture Length are present at all scales of the medium and may thus influence the hydraulic properties and their scaling at all scales. We have numerically investigated the effect of the fractal correlation pattern and of the power law Length distribution on the equivalent permeability of Fracture networks. The correlation and the Length distribution have opposite effects on connectivity and permeability. Increasing correlation lets connectivity and permeability decrease and conversely for the Length distribution. In most cases, one of the characteristics (i.e., Length or correlation) supersedes the other. There is only a small area defined by a > 2 and a ≤ Dc + 1 where both characteristics have a simultaneous influence on permeability. In this area the influence of the correlation remains low, more precisely a scale increase of at least 5 orders of magnitude is required to produce a permeability increase of 1 order of magnitude. Although the correlation pattern does not have much influence on the equivalent permeability, its influence on the flow pattern increases from negligible for networks at threshold to important for dense networks.
-
hydraulic properties of two dimensional random Fracture networks following power law distributions of Length and aperture
Water Resources Research, 2002Co-Authors: Jeanraynald De Dreuzy, Philippe Davy, Olivier BourAbstract:[1] Field observations have revealed that the diffusion properties of Fractured materials are strongly influenced by the presence of Fractures. Using power law Fracture Length and Fracture permeability distributions currently observed on natural Fractured networks, we model the equivalent permeability of two-dimensional (2D) discrete Fracture networks by using numerical simulations and theoretical arguments. We first give the dependence of the network equivalent permeability, obtained at the scale of the network, on the characteristic power law exponents of the Fracture Length and Fracture permeability distributions. We especially show that the equivalent permeability depends simply on the geometrical mean of the local Fracture permeability distribution. Such networks are characterized by an increase of permeability with scale without limitations, provided that the Fracture Length and Fracture permeability distributions are broad enough. Although a correlation Length cannot be systematically defined, the flow structure is still characterized by simple properties. The flow is either extremely channeled in one dominant path or distributed in several separated structures. We show finally that the observed scale effects and flow structure are very different from the one obtained in the lognormal Fracture permeability distribution case.
-
hydraulic properties of two dimensional random Fracture networks following a power law Length distribution 1 effective connectivity
Water Resources Research, 2001Co-Authors: Jeanraynald De Dreuzy, Philippe Davy, Olivier BourAbstract:Natural Fracture networks involve a very broad range of Fractures of variable Lengths and apertures, modeled, in general, by a power law Length distribution and a lognormal aperture distribution. The objective of this two-part paper is to characterize the permeability variations as well as the relevant flow structure of two-dimensional isotropic models of Fracture networks as determined by the Fracture Length and aperture distributions and by the other parameters of the model (such as density and scale). In this paper we study the sole influence of the Fracture Length distribution on permeability by assigning the same aperture to all Fractures. In the following paper [de Dreuzy et al., this issue] we study the more general case of networks in which Fractures have both Length and aperture distributions. Theoretical and numerical studies show that the hydraulic properties of power law Length Fracture networks can be classified into three types of simplified model. If a power law Length distribution n (l) ∼ l−a is used in the network design, the classical percolation model based on a population of small Fractures is applicable for a power law exponent a higher than 3. For a lower than 2, on the contrary, the applicable model is the one made up of the largest Fractures of the network. Between these two limits, i.e., for a in the range 2–3, neither of the previous simplified models can be applied so that a simplified two-scale structure is proposed. For this latter model the crossover scale is the classical correlation Length, defined in the percolation theory, above which networks can be homogenized and below which networks have a multipath, multisegment structure. Moreover, the determination of the effective Fracture Length range, within which Fractures significantly contribute to flow, corroborates the relevance of the previous models and clarifies their geometrical characteristics. Finally, whatever the exponent a, the sole significant scale effect is a decrease of the equivalent permeability for networks below or at percolation threshold.
