Diagenesis Iv

The present volume continues the philosophy of gathering contributions on diagenesis on behalf of those requiring such periodic literary surveys, namely, academics and practitioners (teachers, researchers, and oil and ore explorationists).

Reservoirs generally consist of sandstones or carbonates exhibiting heterogeneities caused by a wide range of factors. Some of these formed depositionally (e.g. as channels, palaeosols, clay seams or salts), others may be diagenetic in origin (e.g. carbonate or silica cemented zones, authigenic clays, karstic surfaces). The severity with which diagenesis affects rock systems results from the interplay between the diagenetic process itself and the timescale over which it operated. The book provides a wide-ranging overview of diagenetic processes and responses in calcareous, argillaceous, arenaceous and carbon-rich (microbial and organic) sedimentary systems. It introduces diagenetic concepts, reviews existing knowledge, and shows how existing qualitative approaches might be developed in more quantitative ways. Several chapters consider mass balance calculations and the temporal and spatial aspects of diagenetic processes. It is unique, as a textbook, in providing such a breadth of diagenetic subject range and such depth of coverage in each topic. It provides a source reference for advanced students and professionals active in reservoir and aquifer studies.

Diagenesis is a highly developed, interdisciplinary field of study. It is reciprocal in that it borrows from numerous scientific or technological specialities and then, in turn, repays them with useful results. Too often, however, the information gained and concepts developed remain unintegrated instead of being utilized quickly by several related earth-science fraternities. This volume, the second of a multi-volume work, attempts to bring together such information, thereby assisting the individual and the research group in keeping up with the data explosion. There is no end in sight to diagenetic research because of its wide practical and intellectual appeals. Consequently, periodic reviews, such as presented in this volume, are greatly needed.

Sequence stratigraphy is a powerful tool for the prediction of depositional porosity and permeability, but does not account for the impact of diagenesis on these reservoir parameters. Therefore, integrating diagenesis and sequence stratigraphy can provide a better way of predicting reservoir quality. This special publication consists of 19 papers (reviews and case studies) exploring different aspects of the integration of diagenesis and sequence stratigraphy in carbonate, siliciclastic, and mixed carbonate-siliciclastic successions from various geological settings. This book will be of interest to sedimentary petrologists aiming to understand the distribution of diagenesis in siliciclastic and carbonate successions, to sequence stratigraphers who can use diagenetic features to recognize and verify interpreted key stratigraphic surfaces, and to petroleum geologists who wish to develop more realistic conceptual models for the spatial and temporal distribution of reservoir quality. This book is part of the International Association of Sedimentologists (IAS) Special Publications. The Special Publications from the IAS are a set of thematic volumes edited by specialists on subjects of central interest to sedimentologists. Papers are reviewed and printed to the same high standards as those published in the journal Sedimentology and several of these volumes have become standard works of reference.

Diagenesis of carbonates and clastic sediments encompasses the biochemical, mechanical, and chemical changes that occur in sediments subsequent to deposition and prior to low-grade metamorphism. These parameters which, to a large extent, control diagenesis in carbonates and clastic sediments include primary composition of the sediments, depositional facies, pore water chemistry, burial–thermal and tectonic evolution of the basin, and paleo-climatic conditions. Diagenetic processes involve widespread chemical, mineralogical, and isotopic modifications affected by the original mineralogy of carbonate and clastic sediments. These diagenetic alterations will impose a major control on porosity and permeability and hence on hydrocarbon reservoirs, water aquifers, and the presence of other important economic minerals. In this Special Issue, we have submissions focusing on understanding the interplay between the mineralogical and chemical changes in carbonates and clastic sediments and the diagenetic processes, fluid flow, tectonics, and mineral reactions at variable scales and environments from a verity of sedimentary basins. Quantitative analyses of diagenetic reactions in these sediments using a variety of techniques are essential for understanding the pathways of these reactions in different diagenetic environments.

Carbonate diagenesis is a subject of enormous complexity because of the basic chemical reactivity of carbonate minerals. These carbonate minerals react quickly with natural waters that either dissolve the carbonates, or precipitate new carbonates to bring the water into equilibrium with the host carbonate sediments and rocks. These rock-water interactions either create porosity by dissolution, or destroy porosity by the precipitation of carbonate cements into pore spaces. Carbonate Diagenesis and Porosity examines these important relationships in detail. This volume is published in co-operation with OGCI, and is based on training courses organised by OGCI and taught by Dr. Moore. It is intended to give the working geologist and university graduate student a reasonable overview of carbonate diagenesis and its influence on the evolution of carbonate porosity. It starts with a discussion of the major differences between carbonates and siliciclastics so that the novice will have an appreciation of the basic nature of the carbonate system. Carbonate porosity, its nature and its classification is then discussed so that the relationship between diagenesis and porosity can be established. Environments of diagenesis and their characteristics are outlined, stressing the nature of pore fluids found in each environment. Tools for the recognition of these environments are then discussed with stress on the constraints suffered by each technique. Each major diagenetic environment is then discussed in detail with petrographic, geochemical characteristics outlined, and an in depth discussion of the impact of the environment's diagenetic processes on porosity development and evolution. Diagenetic models are developed where appropriate and criteria for recognition listed. Case histories illustrating these concepts and models are presented for each major diagenetic environment and sub-environment. Over 160 line drawings illustrate the book. Petrographic characteristics of porosity and diagenetic fabrics and textures are illustrated using numerous photomicrographs taken specifically for the book by the author. The book has been extensively indexed, and includes a large, current reference section. This book should be useful to any geologist interested in, or working with, carbonate sediments and rocks. It will be particularly useful to the industrial geologist concerned with the exploration or exploitation of hydrocarbons from carbonate rock sequences where an understanding of porosity development, evolution, and prediction are important. In addition, this book will be a good text for advanced carbonate courses at graduate level, and an appropriate reference book for graduate students working in, or interested in, carbonate rock sequences and sediments.