Quantitative Diagenesis

This book is both a review and a look to the future, highlighting challenges for better predicting quantitatively the impact of diagenesis on reservoir rocks. Classical diagenesis studies make use of a wide range of descriptive analytical techniques to explain specific, relatively time-framed fluid-rock interaction processes, and deduce their impacts on reservoir rocks. Future operational workflows will consist of constructing a conceptual diagenesis model, quantifying the related diagenetic phases, and modelling the diagenetic processes. Innovative approaches are emerging for applied quantitative diagenesis, providing numerical data that can be used by reservoir engineers as entry (input) data, and for validating results of numerical simulations. Geometry-based, geostatistical and geochemical modelling do not necessarily mimic natural processes, they rather provide reasonable solutions to specific problems.

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 research is the foundation of hydrocarbon reservoir characterization and exploration. Reactive transport modeling (RTM) is an emerging approach for diagenesis research, with unique capability of quantification and forward modeling of the coupled thermo-hydro-chemical processes of diagenesis. Using TOUGHREACT simulator, this thesis investigates the two most important fluid-rock interactions in carbonate rocks, i.e., dolomitization and karstification, based on generic model analyses and a case study in the Ordos Basin, China. In particular, this study attempts to quantitatively characterize the diagenetic processes and to reconstruct the diagenesis-porosity evolution of carbonate reservoirs. Some controversies in carbonate diagenesis research, which cannot be well explained by classical geological methods, have also been discussed. The results are helpful to better understand the spatial-temporal distribution and co-evolution of diagenesis-mineral-porosity during the complicated diagenetic processes with their potential controlling factors, and to reduce the uncertainty of reservoir quality prediction.

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.

This advanced text treats the transformation of sediment into rock, a fundamental process which directly determines the storage and transmissibility properties of reservoirs and seals in hydrocarbon and groundwater systems and in strata-bound mineralization. Attention is paid to diagenetic data from classical petrography and geochemistry and the statistical techniques required to establish its significance and assist in its interpretation. Historically under-used methodologies such as mass balance calculations and the study of modern aquifer systems for understanding rock properties below ancient unconformities are also emphasised. New ground is broken by discussing physico-chemical processes and controls against a background of geological and hydrological evolution of sedimentary basins. In particular, this reconciles the importance of chemical kinetics in shallow, low temperature environments with that of equilibrium thermodynamics in deep, high temperature environments for the evolution of diagenetic products. It also allows detailed treatment of the economically important topic of the loss of porosity with depth. Throughout, the emphasis is on the quantitative description and evaluation of the time-variant parameters controlling heat, fluid and mass transport in porous rock, and upon their integration using mathematics. A full mathematical background is provided and all the basic equations are rigorously derived. Audience: This book will prove essential reading for postgraduate academics and industrial professionals whose work involves predicting rock properties for basin evaluation, and is expected to stimulate new diagenetic research.

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.

This book provides a comprehensive overview of the parameters and factors that cause heterogeneity in carbonate reservoirs, and examines how they interact with one another. It explores the various scales of heterogeneity, how they are caused, and how they can be minimized, as well as how the scales affect each other, providing practical examples in each chapter. The book concludes by discussing the effect of heterogeneity on petrophysical evaluations. As reducing heterogeneity is the only way to obtain accurate carbonate reservoir characteristics at the regional scale, the book offers an important reference guide for all geologists, engineers, and modelers working with subsurface data.