THREE-DIMENSIONAL GEOMODELING TO IDENTIFY SPATIAL RELATIONS BETWEEN LITHOSTRATIGRAPHY AND POROSITY IN THE KARST CARBONATE BISCAYNE AQUIFER, SOUTHEASTERN FLORIDA by Richard Westcott A Thesis Submitted to the Faculty of The Charles E. Schmidt College of Science in Partial Fulfillment of the Requirements of for the Degree of Master of Science Florida Atlantic University Boca Raton, Florida December 2014 ACKNOWLEDGEMENTS The author wishes to express his sincere thanks and love to his wife, children, and parents for their support, patience and encouragement throughout the writing of this manuscript. The author is grateful to the staff of the Department of the Geosciences of Florida Atlantic University and the United States Geological Survey for providing help, use of their facilities, computer resources and equipment while conducting the study. iv ABSTRACT Author: Richard L. Westcott Title: Three-dimensional geomodeling to identify spatial relations between lithostratigraphy and porosity in the karst carbonate Biscayne aquifer, Southeastern Florida Institution: Florida Atlantic University Thesis Advisor: Dr. Tara Root Degree: Master of Science Year: 2014 In southeastern Florida, the majority of drinking water comes from the Biscayne aquifer. This aquifer is comprised of heterogeneous limestones, sandstones, sand, shell and clayey sand with zones of very high permeability. Visualizing the spatial variations in lithology, porosity and permeability of heterogeneous aquifers, like the Biscayne, can be difficult using traditional methods of investigation. Using the Roxar IRAP RMS software multi-layered 3D conceptual geomodels of the lithology, cyclostratigraphy and porosity were created in a portion of the Biscayne aquifer. The models were built using published data from borehole geophysical measurements, core samples, and thin sections. Spatial relations between lithology, cyclostratigraphy, porosity, and preferential flow zones were compared and contrasted to better understand how these geologic features were inter-related. The models show local v areas of differing porosity within and cross-cutting different cycles and lithologies. Porosity in the Biscayne aquifer study area follows a hierarchy attributed to lithofacies with a pattern of increasing porosity for the high frequency cycles. This modeling improves understanding of the distribution and interconnectedness of preferential flow zones, and is thus an invaluable tool for future studies of groundwater flow and groundwater contamination in the Biscayne aquifer. vi THREE-DIMENSIONAL GEOMODELING TO IDENTIFY SPATIAL RELATIONS BETWEEN LITHOSTRATIGRAPHY AND POROSITY IN THE CARBONATE BISCAYNE AQUIFER, SOUTHEASTERN FLORIDA FIGURES ......................................................................................................................................... x 1. INTRODUCTION ....................................................................................................................... 1 PROBLEM STATEMENT ....................................................................................................... 1 BACKGROUND ...................................................................................................................... 5 BISCAYNE AQUIFER ...................................................................................................... 5 SCOPE OF STUDY ................................................................................................................ 10 OVERVIEW OF THESIS ....................................................................................................... 11 2. PREVIOUS STUDIES............................................................................................................... 12 BISCAYNE AQUIFER ........................................................................................................... 12 OVERVIEW OF GEOMODELING ....................................................................................... 18 GEOMODELING STRATIGRAPHY .............................................................................. 18 GEOMODELING FACIES .............................................................................................. 21 PORE TYPE GEOMODELING ....................................................................................... 22 GEOMODELING POROSITY ........................................................................................ 24 APPROPRIATE GEOMODELING FOR THE LAKE BELT STUDY AREA ............... 25 vii 3. METHODS ................................................................................................................................ 26 SOFTWARE .................................................................................................................... 26 INPUT DATA SOURCES ...................................................................................................... 29 GEOLOGIC DATA .......................................................................................................... 29 LITHOFACIES AND CYCLOSTRATIGRAPHY .......................................................... 29 POROSITY ....................................................................................................................... 31 LAND SURFACE DATA ................................................................................................ 33 BUILDING THE MODELS ................................................................................................... 33 CREATING THE LAND SURFACE .............................................................................. 33 CREATING THE CYCLE TOP SURFACES .................................................................. 35 STRUCTURE & ZONE MODELING ............................................................................. 37 CREATING THE GRIDDED MODELS ......................................................................... 38 RAYMER HUNT POROSITY MODELING .................................................................. 41 FACIES MODELING ...................................................................................................... 43 INTERPRETATION & ANALYSIS ...................................................................................... 44 4. RESULTS .................................................................................................................................. 45 RELATIONSHIP BETWEEN SPATIAL VARIATIONS IN CYCLE STRATIGRAPHY, LITHOFACIES AND POROSITY ............................................................ 45 QUALITATIVE SIDE BY SIDE COMPARISONS ........................................................ 45 QUANTITATIVE ANALYSIS OF POROSITY TRENDS ............................................. 48 REYMER HUNT POROSITY ......................................................................................... 57 viii 5. DISCUSSIONS OF APPLICATIONS OF THE MODELS ...................................................... 58 INFERENCES ABOUT GROUNDWATER FLOW.............................................................. 58 ASSISTING IN THE DEVELOPMENT OF GROUNDWATER FLOW MODELS ...... 60 6. CONCLUSION .......................................................................................................................... 62 BIBLIOGRAPHY .......................................................................................................................... 64 ix FIGURES Figure 1 – Lake Belt Study Area ..................................................................................................... 4 Figure 2 - Cross Section of Relation between geologic and hydrogeologic units ........................... 6 Figure 3 - Map of the Biscayne aquifer and study area ................................................................... 7 Figure 4 - Map of south Florida and the base of the Biscayne aquifer. ........................................... 8 Figure 5 - Facies geomodel created for the Lake Belt study area ................................................. 11 Figure 6 - Ophiomorpha from burrowing callianassid shrimp ....................................................... 13 Figure 7 - Porosity table indicates how major pore types are related to lithofacies and porosity .......................................................................................................................... 14 Figure 8 - Lithofacies and pore classes .......................................................................................... 15 Figure 9 - Correlation of ages, formations, stratigraphy, and hydrogeologic units ....................... 16 Figure 10 - Depositional environments, pore classes and lithofacies ............................................ 17 Figure 11 - Three-dimensional view of the facies association model ............................................ 20 Figure 12 – Facies geomodel of a carbonate shoal reservoir ......................................................... 22 Figure 13 - 3-D hydrogeologic model with pore classes .............................................................. 23 Figure 14 – Flow property modeling based on object-models ....................................................... 24 Figure 15 - Flow chart for Geomodeling of the Lake Belt area. .................................................... 28 Figure 16 – Scaled facies table ...................................................................................................... 30 Figure 17 – Sonic logs side by side comparisons of optical bore hole images and logs ................ 32 Figure 18 - Comparison