Philip W. Choquette

Bio: Philip W. Choquette is an academic researcher from Marathon Oil. The author has contributed to research in topics: Diagenesis & Dolomite. The author has an hindex of 10, co-authored 13 publications receiving 2375 citations.

Geologic Nomenclature and Classification of Porosity in Sedimentary Carbonates

Abstract: Pore systems in sedimentary carbonates are generally complex in their geometry and genesis, and commonly differ markedly from those of sandstones. Current nomenclature and classifications appear inadequate for concise description or for interpretation of porosity in sedimentary carbonates. In this article we review current nomenclature, propose several new terms, and present a classification of porosity which stresses interrelations between porosity and other geologic features. The time and place in which porosity is created or modified are important elements of a genetically oriented classification. Three major geologic events in the history of a sedimentary carbonate form a practical basis for dating origin and modification of porosity, independent of the stage of lithification. These events are (1) creation of the sedimentary framework by clastic accumulation or accretionary precipitation (final deposition), (2) passage of a deposit below the zone of major influence by processes related to and operating from the deposition surface, and (3) passage of the sedimentary rock into the zone of influence by processes operating from an erosion surface (unconformity). The first event, final deposition, permits recognition of predepositional, depositional, and post epositional stages of porosity evolution. Cessation of final deposition is the most practical basis for distinguishing primary and secondary (postdepositional) porosity. Many of the key postdepositional changes in sedimentary carbonates and their pore systems occur near the surface, either very early in burial history or at a penultimate stage associated with uplift and erosion. Porosity created or modified at these times commonly can be differentiated. On the basis of the three major events heretofore distinguished, we propose to term the early burial stage "eogenetic," the late stage "telogenetic," and the normally very long intermediate stage "mesogenetic." These new terms are also applicable to process, zones of burial, or porosity formed in these times or zones (e.g., eogenetic ceme tation, mesogenetic zone, telogenetic porosity). The proposed classification is designed to aid in geologic description and interpretation of pore systems End_Page 207------------------------------ and their carbonate host rocks. It is a descriptive and genetic system in which 15 basic porosity types are recognized: seven abundant types (interparticle, intraparticle, intercrystal, moldic, fenestral, fracture, and vug), and eight more specialized types. Modifying terms are used to characterize genesis, size and shape, and abundance of porosity. The genetic modifiers involve (1) process of modification (solution, cementation, and internal sedimentation), (2) direction or stage of modification (enlarged, reduced, or filled), and (3) time of porosity formation (primary, secondary, predepositional, depositional, eogenetic, mesogenetic, and telogenetic). Used with the basic porosity type, these genetic modifiers permit explicit designation of porosity origin and evolution. Pore shapes are classed as irregular or regular, and the latter are subdivided into equant, tubular, and platy shapes. A grade scale for size of regular-shaped pores, utilizing the average diameter of equant or tubular pores and the width of platy pores, has three main classes: micropores (< 1/16 mm), mesopores (1/16-4 mm), and megapores (4-256 mm). Megapores and mesopores are divided further into small and large subclasses. Abundance is noted by percent volume and/or by ratios of porosity types. Most porosity in sedimentary carbonates can be related specifically to sedimentary or diagenetic components that constitute the texture or fabric (fabric-selective porosity). Some porosity cannot be related to these features. Fabric selectivity commonly distinguishes pore systems of primary and early postdepositional (eogenetic) origin from those of later (telogenetic) origin that normally form after extensive diagenesis has transformed the very porous assemblage of stable and unstable carbonate minerals into a much less porous aggregate of ordered dolomite and/or calcite. Porosity in most carbonate facies, including most carbonate petroleum reservoir rocks, is largely fabric selective.

Karst Hydrogeology and Geomorphology

Abstract: CHAPTER 1. INTRODUCTION TO KARST. 1.1 Definitions. 1.2 The Relationship Between Karst And General Geomorphology And Hydrogeology. 1.3 The Global Distribution Of Karst. 1.4 The Growth Of Ideas. 1.5 Aims Of The Book. 1.6 Karst Terminology. CHAPTER 2. THE KARST ROCKS. 2.1 Carbonate Rocks And Minerals. 2.2 Limestone Compositions And Depositional Facies. 2.3 Limestone Diagenesis And The Formation Of Dolomite. 2.4 The Evaporite Rocks. 2.5. Quartzites And Siliceous Sandstones. 2.6 Effects Of Lithologic Properties Upon Karst Development. 2.7 Interbedded Clastic Rocks. 2.8 Bedding Planes, Joints, Faults And Fracture Traces. 2.9 Fold Topography. 2.10 Paleokarst Unconformities. CHAPTER 3. DISSOLUTION: CHEMICAL AND KINETIC BEHAVIOUR OF THE KARST ROCKS. 3.1 Introduction. 3.2 Aqueous Solutions And Chemical Equilibria. 3.3 The Dissolution Of Anhydrite, Gypsum And Salt. 3.4 The Dissolution Of Silica. 3.5 Bicarbonate Equilibria And The Dissolution Of Carbonate Rocks In Normal Meteoric Waters. 3.6 The S-O-H System And The Dissolution Of Carbonate Rocks. 3.7 Chemical Complications In Carbonate Dissolution. 3.8 Biokarst Processes. 3.9 Measurements In The Field And Lab Computer Programs. 3.10 Dissolution And Precipitation Kinetics Of Karst Rocks. CHAPTER 4. DISTRIBUTION AND RATE OF KARST DENUDATION. 4.1 Global Variations In The Solutional Denudation Of Carbonate Terrains. 4.2 Measurement And Calculation Of Solutional Denudation Rates. 4.3 Solution Rates In Gypsum, Salt And Other Non-Carbonate Rocks. 4.4 Interpretation Of Measurements. CHAPTER 5. KARST HYDROLOGY. 5.1 Basic Hydrological Concepts, Terms And Definitions. 5.2 Controls On The Development Of Karst Hydrologic Systems. 5.3 Energy Supply And Flow Network Development. 5.4 Development Of The Water Table And Phreatic Zones. 5.5 Development Of The Vadose Zone. 5.6 Classification And Characteristics Of Karst Aquifers. 5.7 Applicability Of Darcy's Law To Karst. 5.8 The Fresh Water/Salt Water Interface. CHAPTER 6. ANALYSIS OF KARST DRAINAGE SYSTEMS. 6.1 The 'Grey Box' Nature Of Karst. 6.2 Surface Exploration And Survey Techniques. 6.3 Investigating Recharge And Percolation In The Vadose Zone. 6.4 Borehole Analysis. 6.5 Spring Hydrograph Analysis. 6.6 Polje Hydrograph Analysis. 6.7 Spring Chemograph Interpretation. 6.8 Storage Volumes And Flow Routing Under Different States Of The Hydrograph. 6.9 Interpreting The Organisation Of A Karst Aquifer. 6.10 Water Tracing Techniques. 6.11 Computer Modelling Of Karst Aquifers. CHAPTER 7. SPELEOGENESIS: THE DEVELOPMENT OF CAVE SYSTEMS. 7.1 Classifying Cave Systems. 7.2 Building The Plan Patterns Of Unconfined Caves. 7.3 Unconfined Cave Development In Length And Depth. 7.4 System Modifications Occurring Within A Single Phase. 7.5 Multi-Phase Cave Systems. 7.6 Meteoric Water Caves Developed Where There Is Confined Circulation Or Basal Injection Of Water. 7.7 Hypogene Caves: (A) Hydrothermal Caves Associated Chiefly With Co2. 7.8 Hypogene Caves: (B) Caves Formed By Waters Containing H2s. 7.9 Sea Coast Eogenetic Caves. 7.10 Passage Cross-Sections And Smaller Features Of Erosional Morphology. 7.11 Condensation, Condensation Corrosion, And Weathering In Caves. 7.12 Breakdown In Caves. CHAPTER 8. CAVE INTERIOR DEPOSITS. 8.1 Introduction. 8.2 Clastic Sediments. 8.3 Calcite, Aragonite And Other Carbonate Precipitates. 8.4 Other Cave Minerals. 8.5 Ice In Caves. 8.6 Dating Of Calcite Speleothems And Other Cave Deposits. 8.7 Paleo-Environmental Analysis Of Calcite Speleothems. 8.8 Mass Flux Through A Cave System: The Example Of Friar's Hole, W.Va. CHAPTER 9. KARST LANDFORM DEVELOPMENT IN HUMID REGIONS. 9.1 Coupled Hydrological And Geochemical Systems. 9.2 Small Scale Solution Sculpture - Microkarren And Karren. 9.3 Dolines - The 'Diagnostic' Karst Landform? 9.4 The Origin And Development Of Solution Dolines. 9.5 The Origin Of Collapse And Subsidence Depressions. 9.6 Polygonal Karst. 9.7 Morphometric Analysis Of Solution Dolines. 9.8 Landforms Associated With Allogenic Inputs. 9.9 Karst Poljes. 9.10 Corrosional Plains And Shifts In Baselevel. 9.11 Residual Hills On Karst Plains. 9.12 Depositional And Constructional Karst Features. 9.13 Special Features Of Evaporite Terrains. 9.14 Karstic Features Of Quartzose And Other Rocks. 9.15 Sequences Of Carbonate Karst Evolution In Humid Terrains. CHAPTER 10.THE INFLUENCE OF CLIMATE, CLIMATIC CHANGE AND OTHER ENVIRONMENTAL FACTORS ON KARST DEVELOPMENT. 10.1 The Precepts Of Climatic Geomorphology. 10.2 The Hot Arid Extreme. 10.3 The Cold Extreme: 1 Karst Development In Glaciated Terrains. 10.4 The Cold Extreme: 2 Karst Development In Permafrozen Terrains. 10.5 Sea Level Changes, Tectonic Movement And Implications For Coastal Karst Development. 10.6 Polycyclic, Polygenetic And Exhumed Karsts. CHAPTER 11. KARST WATER RESOURCES MANAGEMENT. 11.1 Water Resources And Sustainable Yields. 11.2 Determination Of Available Water Resources. 11.3 Karst Hydrogeological Mapping. 11.4 Human Impacts On Karst Water. 11.5 Groundwater Vulnerability, Protection, And Risk Mapping. 11.6 Dam Building, Leakages, Failures And Impacts. CHAPTER 12. HUMAN IMPACTS AND ENVIRONMENTAL REHABILITATION. 12.1 The Inherent Vulnerability Of Karst Systems. 12.2 Deforestation, Agricultural Impacts And Rocky Desertification. 12.3 Sinkholes Induced By De-Watering, Surcharging, Solution Mining And Other Practices On Karst. 12.4 Problems Of Construction On And In The Karst Rocks - Expect The Unexpected! 12.5 Industrial Exploitation Of Karst Rocks And Minerals. 12.6 Restoration Of Karstlands And Rehabilitation Of Limestone Quarries. 12.7 Sustainable Management Of Karst. 12.8 Scientific, Cultural And Recreational Values Of Karstlands.

Spectrum of pore types and networks in mudrocks and a descriptive classification for matrix-related mudrock pores

Abstract: Matrix-related pore networks in mudrocks are composed of nanometer- to micrometer-size pores. In shale-gas systems, these pores, along with natural fractures, form the flow-path (permeability) network that allows flow of gas from the mudrock to induced fractures during production. A pore classification consisting of three major matrix-related pore types is presented that can be used to quantify matrix-related pores and relate them to pore networks. Two pore types are associated with the mineral matrix; the third pore type is associated with organic matter (OM). Fracture pores are not controlled by individual matrix particles and are not part of this classification. Pores associated with mineral particles can be subdivided into interparticle (interP) pores that are found between particles and crystals and intraparticle (intraP) pores that are located within particles. Organic-matter pores are intraP pores located within OM. Interparticle mineral pores have a higher probability of being part of an effective pore network than intraP mineral pores because they are more likely to be interconnected. Although they are intraP, OM pores are also likely to be part of an interconnected network because of the interconnectivity of OM particles. In unlithifed near-surface muds, pores consist of interP and intraP pores, and as the muds are buried, they compact and lithify. During the compaction process, a large number of interP and intraP pores are destroyed, especially in ductile grain-rich muds. Compaction can decrease the pore volume up to 88% by several kilometers of burial. At the onset of hydrocarbon thermal maturation, OM pores are created in kerogen. At depth, dissolution of chemically unstable particles can create additional moldic intraP pores.

Geologic Nomenclature and Classification of Porosity in Sedimentary Carbonates

Abstract: Pore systems in sedimentary carbonates are generally complex in their geometry and genesis, and commonly differ markedly from those of sandstones. Current nomenclature and classifications appear inadequate for concise description or for interpretation of porosity in sedimentary carbonates. In this article we review current nomenclature, propose several new terms, and present a classification of porosity which stresses interrelations between porosity and other geologic features. The time and place in which porosity is created or modified are important elements of a genetically oriented classification. Three major geologic events in the history of a sedimentary carbonate form a practical basis for dating origin and modification of porosity, independent of the stage of lithification. These events are (1) creation of the sedimentary framework by clastic accumulation or accretionary precipitation (final deposition), (2) passage of a deposit below the zone of major influence by processes related to and operating from the deposition surface, and (3) passage of the sedimentary rock into the zone of influence by processes operating from an erosion surface (unconformity). The first event, final deposition, permits recognition of predepositional, depositional, and post epositional stages of porosity evolution. Cessation of final deposition is the most practical basis for distinguishing primary and secondary (postdepositional) porosity. Many of the key postdepositional changes in sedimentary carbonates and their pore systems occur near the surface, either very early in burial history or at a penultimate stage associated with uplift and erosion. Porosity created or modified at these times commonly can be differentiated. On the basis of the three major events heretofore distinguished, we propose to term the early burial stage "eogenetic," the late stage "telogenetic," and the normally very long intermediate stage "mesogenetic." These new terms are also applicable to process, zones of burial, or porosity formed in these times or zones (e.g., eogenetic ceme tation, mesogenetic zone, telogenetic porosity). The proposed classification is designed to aid in geologic description and interpretation of pore systems End_Page 207------------------------------ and their carbonate host rocks. It is a descriptive and genetic system in which 15 basic porosity types are recognized: seven abundant types (interparticle, intraparticle, intercrystal, moldic, fenestral, fracture, and vug), and eight more specialized types. Modifying terms are used to characterize genesis, size and shape, and abundance of porosity. The genetic modifiers involve (1) process of modification (solution, cementation, and internal sedimentation), (2) direction or stage of modification (enlarged, reduced, or filled), and (3) time of porosity formation (primary, secondary, predepositional, depositional, eogenetic, mesogenetic, and telogenetic). Used with the basic porosity type, these genetic modifiers permit explicit designation of porosity origin and evolution. Pore shapes are classed as irregular or regular, and the latter are subdivided into equant, tubular, and platy shapes. A grade scale for size of regular-shaped pores, utilizing the average diameter of equant or tubular pores and the width of platy pores, has three main classes: micropores (< 1/16 mm), mesopores (1/16-4 mm), and megapores (4-256 mm). Megapores and mesopores are divided further into small and large subclasses. Abundance is noted by percent volume and/or by ratios of porosity types. Most porosity in sedimentary carbonates can be related specifically to sedimentary or diagenetic components that constitute the texture or fabric (fabric-selective porosity). Some porosity cannot be related to these features. Fabric selectivity commonly distinguishes pore systems of primary and early postdepositional (eogenetic) origin from those of later (telogenetic) origin that normally form after extensive diagenesis has transformed the very porous assemblage of stable and unstable carbonate minerals into a much less porous aggregate of ordered dolomite and/or calcite. Porosity in most carbonate facies, including most carbonate petroleum reservoir rocks, is largely fabric selective.