Gradient Discretization of Hybrid Dimensional Darcy Flows in Fractured Porous Media

International audienceThis article deals with the discretization of hybrid dimensional model of Darcy flow in fractured porous media. These models couple the flow in the fractures represented as the surfaces of codimension one with the flow in the surrounding matrix. The convergence analysis is carried out in the framework of Gradient schemes which accounts for a large family of conforming and nonconforming dis-cretizations. The Vertex Approximate Gradient (VAG) scheme and the Hybrid Finite Volume (HFV) scheme are applied to such models and are shown to verify the Gradient scheme framework. Our theoretical results are confirmed by a few numerical experiments performed both on tetrahedral and hexahedral meshes in heterogeneous isotropic and anisotropic media

Modélisation et discrétisation des écoulements diphasiques en milieux poreux avec réseaux de fractures discrètes

This thesis presents the work on modelling and discretisation of two-phase flows in the fractured porous media. These models couple the flow in the fractures represented as the surfaces of codimension one with the flow in the surrounding matrix. The discretisation is made in the framework of Gradient schemes which accounts for a large family of conforming and nonconforming discretizations. The test cases are motivated by the target application of the thesis concerning the gas recovery under the hydraulic fracturing process in low-permeability reservoirsLes travaux de cette thèse portent sur la modélisation et la discrétisation des écoulements diphasiques dans les milieux poreux fracturés. On se place dans le cadre des modèles dits dimensionnels hybrides couplant l'écoulement dans la matrice 3D à l'écoulement dans un réseau de fractures modélisées comme des surfaces 2D. La discrétisation s'appuie sur le cadre abstrait des schémas gradients. Dans cette étude nous présentons deux classes de schémas de types Gradient Schemes sur ces modèles en monophasique et en diphasique. Les objectifs sont motivés par l'application cible de la thèse qui concerne les procédés de récupération assistée de gaz par fracturation hydraulique dans les réservoirs de très faibles perméabilité

Modelization and discretization of two-phase flows in porous media with discrete fracture networks

Les travaux de cette thèse portent sur la modélisation et la discrétisation des écoulements diphasiques dans les milieux poreux fracturés. On se place dans le cadre des modèles dits dimensionnels hybrides couplant l'écoulement dans la matrice 3D à l'écoulement dans un réseau de fractures modélisées comme des surfaces 2D. La discrétisation s'appuie sur le cadre abstrait des schémas gradients. Dans cette étude nous présentons deux classes de schémas de types Gradient Schemes sur ces modèles en monophasique et en diphasique. Les objectifs sont motivés par l'application cible de la thèse qui concerne les procédés de récupération assistée de gaz par fracturation hydraulique dans les réservoirs de très faibles perméabilitésThis thesis presents the work on modelling and discretisation of two-phase flows in the fractured porous media. These models couple the flow in the fractures represented as the surfaces of codimension one with the flow in the surrounding matrix. The discretisation is made in the framework of Gradient schemes which accounts for a large family of conforming and nonconforming discretizations. The test cases are motivated by the target application of the thesis concerning the gas recovery under the hydraulic fracturing process in low-permeability reservoir

Immiscible two-phase Darcy flow model accounting for vanishing and discontinuous capillary pressures: application to the flow in fractured porous media

International audienceFully implicit time-space discretizations applied to the two-phase Darcy flow problem lead to the systems of nonlinear equations, which are traditionally solved by some variant of Newton's method. The efficiency of the resulting algorithms heavily depends on the choice of the primary unknowns since Newton's method is not invariant with respect to a nonlinear change of variable. In this regard the role of capillary pressure/saturation relation is paramount because the choice of primary unknowns is restricted by its shape. We propose an elegant mathematical framework for two-phase flow in heterogeneous porous media resulting in a family of formulations, which apply to general monotone capillary pressure/saturation relations and handle the saturation jumps at rocktype interfaces. The presented approach is applied to the hybrid dimensional model of two phase water-gas Darcy flow in fractured porous media for which the fractures are modeled as interfaces of co-dimension one. The problem is discretized using an extension of Vertex Approximate Gradient scheme. As for the phase pressure formulation, the discrete model requires only two unknowns by degree of freedom

The Enlightenment of China Enterprises' Crises to Taiwan Enterprises in China

現代企業組織，包括是大陸企業或是大陸臺資企業，在面對危機時，首先必須考慮的是企業組織所處的環境結構。由於此種環境結構不同於過去，故其所形塑而成的危機問題也將不同於以往。本研究認為21世紀的環境結構的不同，企業危機管理至少需考慮以下三種結構要素。 第一、全球化下的多元衝突：全球化在「互賴程度的增加」、「遠距離的活動」與「時間和空間的壓縮」迫使下，形成一種開放、動態而非線性的全球體系系統。當全球體系愈開放之際，將造成衝突或危機發生多元形式與風險程度的改變，迫使企業組織必須正面應對而無發逃避。第二、民主化下的反商情結：民主化的推波助燃下，國內社會的兩極分化、貧富差距、政治分裂等深刻的社會問題已暴露無遺，改變了原本的政、商關係，進而產生了反商（企業）情結。故民主化的結構影響，已快速擴溢於大陸企業與臺資企業。第三、資訊化下的經營困境：對於企業經營者而言，必須同時兼顧知識管理中強調的正向情報分享與競爭情報中強調的反向情報拒止，才能克服企業經營的困境。透過軍事上所稱，「情報是戰爭之眼」是一種不變的定理，則包括大陸臺資企業的經營都必須嚴肅面對新一波資訊革命結構的影響。 本文的分析途徑包括危機處置分析與危機預防分析二個部份，研究架構從2012至2014年大陸企業主要危機案例展開，在危機處置的部份，提出企業危機根源和危機類型的因素；而在危機預防的部份，提出競爭情報循環、企業個案獲利與企業投入危機預防成本等因素，綜合此二部份以評估企業危機管理的成效。 建構一種綜合危機處置作為分析、競爭情報循環分析和危機預防發生機率計算的危機管理模式，為本文的第一個研究貢獻。第二，不將「危機處置」與「危機預防」二部份嚴格區分，而是將「危機處置」視為「危機預防」的一部份，重新定義企業危機預防的概念。第三，從大陸企業2012-2014年主要危機案例分析結果，理解大陸企業處理危機的方式，並提供臺資企業危機管理的運用和參考，為本文最主要的研究貢獻之一。Modern enterprises, including China enterprise and Taiwan enterprise, which they should consider what environments they will meet as they face crises. These crises are more complicated than before because the environments the enterprises meet are different than before too. In the 21 century, enterprises would consider the following at least three structural factors when they confront crises. 1. Multi-conflict in globaliazation: because of interdependence, remote activities, and time-space compression, globalization becomes an open, dynamic, and non-liner global system. The more open globalizqtion, the more sophisticated crises or conflicts, so enterprises must face and confront them. 2. Anti-business protest in democratization: democratization help facilitate social polarization problems of inequality and political disunity which change relation between politics and commerce and promote anti-enterprise protest. 3. Enterprise dilemma in informatization: in order to overcome enterprise operation dilemma, an entrepreneur would combine sharing knowledge and defending competitive intelligence. Through an military axiom, intelligence being an eye of war, all enterprise should confront operation dilmma in new waves structure of information revolution. The approaches of this study include two parts to evaluate the result of enterprise crises management. The first part is a crisis intervention which classified crises types and crises causes analysis from China enterprise crises between 2012 and 2014. The second part is a crisis prevention which involves competitive intelligence, enterprise profit, and crises prevention costs analysis. The contributions and findings of this thesis would be at least the following three. 1. Constructing an enterprise crisis management model that includes crisis intervention, competitive intelligence, and crisis occurring chance. 2. Redefining the concept of crisis prevention. Crisis intervention is one part of crisis prevention and they don't distinguish from each other. 3. Understanding the analysis results of China enterprise main crises in 2012 to 2014 and providing applications for Taiwan enyerprise crisis management.第一章 緒 論----------------------------------------------------1 第一節 研究動機-----------------------------------------------------1 第二節 研究目的-----------------------------------------------------4 第三節 研究問題-----------------------------------------------------6 第四節 研究範圍-----------------------------------------------------7 第五節 章節安排-----------------------------------------------------8 第二章 文獻探討----------------------------------------------------11 第一節 危機、衝突與風險---------------------------------------------11 第二節 衝突和危機的分類--------------------------------------------13 第三節 競爭情報與危機預防------------------------------------------16 第四節 大陸臺資企業特徵與危機來源----------------------------------18 第五節 大陸企業的危機類型（2009—2010年）----------------------------20 第三章 研究方法與架構----------------------------------------------23 第一節 研究方法----------------------------------------------------23 第二節 研究架構----------------------------------------------------26 第四章 案例分析-----------------------------------------------29 第一節 大陸企業主要危機事件背景------------------------------------29 第二節 大陸企業主要危機根源與分類----------------------------------38 第三節 危機案例之預防性分析----------------------------------------43 第四節 危機案例之發生機率分析--------------------------------------47 第五節 對臺資企業的啟示--------------------------------------------50 第五章 結 論-------------------------------------------------------54 第一節 研究發現與貢獻----------------------------------------------54 第二節 未來研究方向------------------------------------------------56 參考書目--------------------------------------------------------------5