Integrated Modeling of Reservoir Fluid Properties and Multiphase Flow in Offshore Production Systems (Petroleum Engineering)

The book is intended for practicing engineers in the oil industry, researchers, and graduate students interested in designing and simulating offshore hydrocarbon production systems. It approaches offshore oil production systems from an integrated perspective that combines the modeling of thermophysical properties of reservoir fluids and their flow as a multiphase mixture in wellbores, flow lines, and risers. The first part of the book presents an internally consistent method to compute the critical parameters and acentric factor of Single Carbon Number (SCN) fractions of petroleum mixtures using state-of-the-art multivariate fitting techniques. The procedure is illustrated and validated using flash and differential liberation data from actual field samples. In the second part of the book, mechanistic multiphase flow models are discussed in light of their ability to predict the pressure, temperature, and phase holdup of production fluids in wellbores, flow lines, and risers. Multivariate fitting procedures are again applied to evaluate the sensitivity of the results with respect to closure relationship parameters, such as slug body gas holdup, wall shear stress, and wall roughness in pipelines and production tubing. Finally, the modeling framework is validated using actual field data from offshore production wells. Preface Contents Symbols and Abbreviations Roman Greek Subscripts and Superscripts Abbreviations 1 Introduction 1.1 Motivation 1.2 Oil Constituents 1.3 Classification of Reservoirs 1.4 Volumetric and Phase Behavior 1.5 The Flow of Oil Mixtures 1.6 Well Flow Rate Determination 1.7 Scope and Objectives of the Book References 2 Thermodynamics of Petroleum Mixtures 2.1 Introduction 2.2 Equations of State 2.2.1 Van der Waals Equation 2.2.2 Modern Equations of State 2.2.3 Further Improvements 2.2.4 Solution of Cubic Equations of State 2.2.5 Mixing Rules 2.3 Vapor-Liquid Equilibrium 2.3.1 Types of Problems and Formulation 2.3.2 Chemical Potential and Fugacity of a Component 2.3.3 Calculation of Equilibrium Constants 2.3.4 Solving the Vapor-Liquid Equilibrium Problem 2.3.5 Stability Analysis in Flash Calculations 2.4 Obtaining the Thermodynamic Properties of the Mixture 2.5 Characterization of Oil Reservoir Fluids 2.5.1 Critical Properties, Acentric Factor and Specific Heat of SCN Fractions 2.5.2 Splitting the Heavy Fraction 2.5.3 Lumping Components 2.5.4 Model Fitting 2.6 Preliminary Results References 3 Developing a Fluid Model 3.1 Introduction 3.2 Initial Assumptions 3.3 New Expressions for the Angular Coefficient of the alpha(T) Function 3.3.1 Consistency Test and Extrapolation of Current Expressions 3.3.2 Fitting of New Functions 3.4 New Correlations for the Characterization of SCN Fractions 3.4.1 Consistency Test and Extrapolation of Current Correlations 3.4.2 New Fitting of Exponential Functions 3.4.3 Results and Comparisons 3.5 Methodology for Fitting the Proposed Fluid Model 3.5.1 Introduction of Fitting Coefficients 3.5.2 Definition of the Minimum Set of Variables 3.5.3 Composition of the Objective Function 3.5.4 Objective Function Optimization Using the Response Surface Methodology 3.5.5 Definition of Weights, Results and Comparison 3.6 Empirical Correlations for the Calculation of Other Properties 3.6.1 Thermodynamic Properties of Formation Water 3.6.2 Transport Properties 3.7 Results and Validation References 4 Fluid Flow in Oil Production Systems 4.1 Introduction 4.2 Stratified Flow 4.2.1 Interface Shape 4.2.2 Shear Stresses 4.3 Annular Flow 4.3.1 Shear Stresses 4.3.2 Liquid Entrained Fraction 4.4 Bubbly and Dispersed Bubble Flows 4.4.1 Slip Law Parameters 4.4.2 Wall Shear Stress 4.5 Slug and Elongated Bubble Flow 4.5.1 Slip Law Parameters 4.5.2 Gas Volume Fraction in the Liquid Slug 4.5.3 Wall Shear Stress 4.6 Flow Pattern Determination 4.6.1 Liquid Film Stability 4.6.2 Gas Bubbles Stability 4.6.3 Liquid Slug and Dumitrescu-Taylor Bubble Stability 4.7 Solution of Two-Phase Flows Using the Mechanistic Approach 4.7.1 North Sea Model 4.7.2 Gulf of Mexico Model 4.8 Preliminary Results References 5 Simulation of Offshore Production Systems 5.1 Introduction 5.2 Conservation Equations 5.2.1 Mass Conservation 5.2.2 Momentum Conservation 5.2.3 Energy Conservation 5.3 Heat Transfer in Offshore Production Wells 5.4 Application of the Marching Algorithm 5.5 Data Collection and Model Construction 5.6 Preliminary Results 5.6.1 Qualitative Analysis of the Profiles Obtained 5.6.2 Calculation of Pressure Drop in Offshore Production Wells References 6 Improving the Fluid Flow Model 6.1 Introduction 6.2 Identification of the Most Relevant Parameters 6.2.1 Introduction of Fitting Coefficients 6.2.2 Effect of Fitting Coefficients on Pressure Drop Estimates 6.3 Survey of Alternatives to Current Calculation Methods 6.3.1 Wall Shear Stress in Bubbly Flow 6.3.2 Volume Fraction of Gas in the Liquid Slug for the Slug Pattern 6.4 Review of Wall Roughness in Production Tubing and Pipelines 6.5 Accuracy Test and Definition of the Best Set 6.6 Results and Validation 6.6.1 Flow Pattern, Volumetric Fraction and Pressure Gradient Maps 6.6.2 Calculation of Pressure Drop in Offshore Production Wells 6.6.3 Simulations with a Simplified Reservoir Model References 7 Concluding Remarks 7.1 Modeling the Properties of Oil Reservoir Fluids in the Pre-salt Cluster 7.2 Two-Phase Flow Modeling in Pre-salt Offshore Production Wells 7.3 Integration Between the Two Disciplines References Appendix A Obtaining the Roots of Cubic Equations of State Appendix B Calculation of Departure Functions B.1 Redlich-Kwong Equation of State B.2 Peng-Robinson Equation of State Appendix C Weighting of Liquid Phase Properties Provides an integrated approach involving reservoir fluid modeling and multiphase production simulation.Contains extensive validation and recommendations based on actual field data.Introduces multivariate fitting procedures to model fluid properties and flow phenomena.