Salt and Sediment Dynamics

About this book

Salt and Sediment Dynamics presents a thorough treatment of salt and sediment interactions and the implications of such interactions for sub-salt exploration. The book emphasizes and utilizes recent discoveries on many aspects of salt and sediment interactions, provides the theoretical framework for interpreting the increasing amount of available data on salt and sediments, and develops a self-consistent dynamical evolution model of salt structures and their interaction with surrounding sediments. The model developed in the text consists of an evolving salt structure that influences sediment motion with self-consistent evolution of sediments and salt shape. The resulting stress and strain in the sediments and the thermal focusing effects of the salt are evaluated. The salt and sediments in the model are consistent with observed geometries, a result of having freely adjustable, observation-controlled model parameters. In addition, the book describes case histories in a variety of geological settings, thus explaining aspects of the genesis and development of salt structures, of their impact on sedimentary structural evolution, and of the impact of sediments on salt masses. The techniques developed by the authors expand the current state-of-knowledge regarding the evolution and dynamics of salt structures and increase the potential for effective sub-salt hydrocarbon exploration.

Contents

Introduction SECTION A: FACETS OF SALT AND SEDIMENT INTERACTIONS Salt Velocity from Temperature and Thermal Indicator Anomalies: Lulu-1, Danish North Sea Introduction Theory The Lulu-1 Diapir, Danish North Sea Discussion: Sensitivity Analysis. Dynamics. Conclusion Appendix A: Equations for Determining Relative Salt Speed Appendix B: Quasi-Equilibrium Model of Diapirism Salt Insertions in Sedimentary Sequences: Impacts on Temperature and Thermal Maturation One-Dimensional Representations: Introduction. Description of the Model. Temperature Distribution. Influence on Thermal Maturation of Hydrocarbons. Sensitivity Tests of Two Salt Cases. Discussion and Conclusion. Two-Dimensional Representations: Heat Flow Model. Temperature Distribution Around Salt Sills. Hydrocarbon Maturation. Semi-Infinite Salt Sheets. Finite Horizontal Salt Sill. Semi-Infinite Inclined Salt Sills. Conclusions. Multiple Salt Bodies: Two Synthetic Tests. Salt in the Northern Gulf of Mexico. Temperature Anomalies in the Northern Gulf of Mexico. Discussion. Temperature Dependence of Salt Thermal Conductivity: Introduction. Basic Equations and Solution. Numerical Illustrations. Discussion and Conclusions. Salt Insertions in Sedimentary Sequences: Impacts on Sediment Distortion and Sediment Fracturing Modeling Sediment Fracturing Around Rapidly Moving Lateral Salt Sheets: Introduction. Methods. Model Results. Discussion. Summary. Erosion Estimate from Salt/Sediment Shapes: Barents Sea, Norway: Review of Methods. The Method Applied to a Mushroom Salt Diapir. A Synthetic Test. A Case History in Barents Sea, Norway. Discussion. Hydrocarbon Migration Speed Estimates: Green Canyon Block, Gulf of Mexico: Introduction. Stratigraphic Evidence. Synthetic Tests. Model Resolution to d13Cmixed Measurements. Application. Duscussion and Implications. Conclusions. Appendix: Mixing. HC Steady Flow/Microbial Degradation. Least Squares. Simple Estimates of Dynamical, Thermal, and Hydrocarbon Maturity Factors Formulae for Making Estimates: Dynamical Aspects. Thermal Maturity Aspects. Applications to a Gulf of Mexico Salt Structure: Background Information. Dynamical Considerations. Miocene Uplift. Thermal Maturity Considerations. Hydrocarbon Migration. Conclusions. Overpressure Build-Up in Formations Underlying Salt Sheets in the Gulf of Mexico: Physical Conditions in Formations Underlying Salt Sheets. Dynamical Models of Physical Properties of Sub-Salt Formations. Discussion and Conclusion. Integrated Model Requirements Rim Syncline Diapiric Stem Mushroom Cap Overhang Salt Volume Geometrical Anisotropy of Diapirs Sedimentary Bed Distortions Basinal Evolution Thermal Anomalies and Thermal Maturation Faulting and Fracturing Consistency Arguments SECTION B: SELF-CONSISTENT SALT AND SEDIMENT DYNAMICS Modeling Present-Day Salt Shapes Introduction. Experimental Model Studies. Mathematical Models. Logic Structure of the Model Procedure. Present-Day Salt Shapes Sensitivity Analysis Examples of Present-Day Salt Shapes - North Louisiana Salt Basin Summary Appendix: Construction of a 2-D Salt Shape. Determination of the Best Parameter Values Deposition and Deformation of Sedimentary Beds Around an Evolving Salt Shape Introduction Grid Construction: Primary Grid. Secondary Grid. Evolving Salt Shapes, Deposition, and Motion of Sediments: Input Sediment Thicknesses in the Grid. Smoothing Bed Positions. Summary Appendix 1: Track Construction. Equal Spacing and Spline Interpolation. Appendix 2: A Time-Evolving Salt Shape. Inverse Methods for Time-Dependent Parameters. Appendix 3: Smoothing Procedure. Modeling Stress-Strain Development Through Time Introduction Modeling Strain: Correction of the Grid. Calculation of Strain Through Time. Modeling Evolution of Stress: Calculation of Stress Through Time. Approximations of Rock Properties With Depth. Examples: Overhang Structure. Plug-Shaped Structure. Summary Thermal Focusing of Heat Introduction Calculation of Temperature Anomalies Examples: Temperature Anomalies Around Different Shapes. Effects of Varying Temperature-Controlling Parameters. Thermal Histories Around a Moving Salt Sheet. Conclusions Summary SECTION C: APPLICATIONS AND CASE HISTORIES North Louisiana Salt Basin - Test Case 1 Introduction Present-Day Shape Combined Evolution of Salt and Sediments: Models 1-3. Sensitivity Analysis. Structural History - Summary. Deformation History Temperature Histories: Models 1 and 3. Summary Norwegian-Danish Basin - Test Case 2 Introduction Present-Day Shape Combined Evolution of Salt and Sediments: Models 1 and 2. Structural History - Summary. Temperature Histories Summary Pseudo-3D Modeling of the Combined Evolution of Salt and Sediments: A Danish North Sea Example Introduction Present-Day Shapes Combined Evolution of Salt and Sediments Thermal History Stress and Strain Development Discussion General Summary References

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