Understanding the micro to macro behaviour of rock fluid systems

Understanding the Micro to Macro Behaviour of Rock-Fluid Systems Geological Society Special Publications Society Book Editors R J PANKHURST (CHIEF EDITOR) P DOYLE F J GREGORY J S GRIFFITHS A J HARTLEY R E HOLDSWORTH J A HOWE P T LEAT A C MORTON N S ROBINS J P TURNER Special Publication reviewing procedures The Society makes every effort to ensure that the scientific and production quality of its books matches that of its journals Since 1997, all book proposals have been refereed by specialist reviewers as well as by the Society's Books Editorial Committee If the referees identify weaknesses in the proposal, these must be addressed before the proposal is accepted Once the book is accepted, the Society has a team of Book Editors (listed above) who ensure that the volume editors follow strict guidelines on refereeing and quality control We insist that individual papers can only be accepted after satisfactory review by two independent referees The questions on the review forms are similar 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BLOOMFIELD, J P & BARKER, J A 2005 MOPOD: a generic model of porosity development In: SHAW, R P (ed.) 2005 Understanding the Micro to Macro Behaviour of Rock-Fluid Systems Geological Society, London, Special Publications, 249, 73-77 GEOLOGICAL SOCIETY SPECIAL PUBLICATION NO 249 Understanding the Micro to Macro Behaviour of Rock-Fluid Systems EDITED BY R P SHAW British Geological Survey, UK 2005 Published by The Geological Society London THE GEOLOGICAL SOCIETY The Geological Society of London (GSL) was founded in 1807 It is the oldest national geological society in the world and the largest in Europe It was incorporated under Royal Charter in 1825 and is Registered Charity 210161 The Society is the UK national learned and professional society for geology with a worldwide Fellowship (FGS) of 9000 The Society has the power to confer Chartered status on suitably qualified Fellows, and about 2000 of the Fellowship carry the title (CGeol) Chartered Geologists may also obtain the equivalent 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Tama-shi, Tokyo 206-0034 Japan Orders: Tel +81 (0)423 57-7650 Fax +81 (0)423 57-7651 E-mail geokanda@ ma.kcom.ne.jp Contents Preface SHAW,R P Understanding the Micro to Macro Behaviour of Rock-Fluid Systems: vii introduction HEFFER,K J The NERC Micro to Macro Programme: implications for fluid resource management LIu, E., CHAPMAN,M., HUDSON, J A., TOD, S R., MAULTZSCH, S & Li, X-Y Quantitative determination of hydraulic properties of fractured rock using seismic techniques 29 ODLING, N E., HARRIS,S D., VASZI,A Z & KNIPE,R J Properties of fault damage zones in siliclastic rocks: a modelling approach 43 XIE, Z., MACKAY,R & CLIFFE,K A Precise numerical modelling of physical 61 transport in strongly heterogeneous porous media BLOOMFIELD,J P & BARKER,J A MOPOD: a generic model of porosity development 73 SELLERS,S & BARKER,J A Anomalous diffusion in simulations of pumping tests on fractal lattices 79 JOHNSTON,P B., ATKINSON,T C., ODLING,N E & BARKER,J A Models of tracer breakthrough and permeability in simple fractured porous media 91 WORDEN, R H., CHARPENTIER,D., FISHER, Q J & APLIN,A C Fabric 103 development and the smectite to illite transition in Upper Cretaceous mudstones from the North Sea: an image Analysis Approach CASSIDY, R., MCCLOSKEY,J & MORROW,P Fluid velocity fields in 115 2D heterogeneous porous media: empirical measurement and validation of numerical prediction BRYDIE, J R., WOGELIUS, R A., MERRIFIELD, C M., BOULT, S., GILBERT, P., ALLISON, D & VAUGHAN,D J The ix2M project on quantifying the effects of biofilm growth on hydraulic properties of natural porous media and on sorption equilibria: an overview 131 SHAW, R P Overview of the NERC 'Understanding the Micro to Macro Behaviour of Rock-Fluid Systems' 145 Index 163 Preface Understanding how fluids flow through rocks is very important in a number of fields Almost all of the world's oil and gas are produced from underground reservoirs and knowledge of how these energy resources got where they are, what keeps them there and how they migrate through the rock, is very important in the search for new resources as well as for extracting as much of the contained oil/gas as possible Similar understanding is important for managing groundwater resources and also for predicting how hazardous or radioactive wastes and carbon dioxide will behave if they are stored or disposed of underground Unravelling the complex behaviour of fluids as they flow through rock is difficult We can't see through rock, so we need to predict how and where fluids flow and at what rates This requires an understanding of the type of rock, its porosity, and the character and pattern of fractures within it Fluid flow can vary with time and over a range of scales, from microscopic pores and cracks to major fault zones Some of Micro to Macro researchers have been studying rocks from boreholes, excavations and elsewhere, and gathering information from seismic surveys, in an attempt to understand how fluids flow in real rocks in real situations Others have been working on computer models and laboratory simulations of fluid flow through porous and/or fractured rocks Put together, these approaches have yielded very useful results, many of which are discussed in this volume Industries whose resources lie in the subsurface, base most of their planning and investment decisions on models of their sites that require numerical descriptions of the geology The commercial consequences of poor geological modelling can be particularly severe where fluid flow is involved because fluid flow is governed by the spatial arrangement of extremes in the range of permeabilities The Micro to Macro Programme has been focused on developing our understanding of the relationships between measured and modelled sub-surface fluid flows spanning the range of spatial and temporal scales relevant to fluid resource management The programme was motivated by observations and emerging theories of how geological heterogeneities vary across these ranges in scale, and the consequences for extrapolating fluid behaviour both in time and space; the aim was to provide a clearer physical understanding on which to base more effective geofluid management, and to allow better integration of data for reservoir characterization and improved models for fluid flow The scope of the programme necessarily involved workers with backgrounds in the hydrocarbon, water, radioactive waste, mining, and geothermal industries and a major objective was to foster communication between disciplines and communities to their mutual benefit As a result many of the projects funded by the Programme will be of considerable interest to those looking at upscaling issues in the hydrocarbon, groundwater resource and waste disposal (including radioactive waste) industries In order to highlight some of the results of the Programme to industry, the Steering Committee commissioned Kes Heifer to provide a review of the results of the Programme with implications for the management of fluid resources which forms the basis of Chapter of this volume While this review is focused on the hydrocarbon industry, it is equally applicable to other sectors where understanding fluid flow is important One of the purposes of this volume is to disseminate the principal results of the Natural Environment Research Council's (NERC) thematic programme 'Understanding the Micro to Macro Behaviour of Rock Fluid Systems', commonly referred to as 'p~2M', and it forms part of the dissemination strategy of the Programme This s programme ran from 1998 to 2004 and provided funding to 17 projects following two calls for proposals In common with other NERC thematic programmes, this Programme was overseen by a steering committee with representatives from industry and academia with expertise and experience in the topics covered by the Programme and knowledge of their potential application An overview of the Micro to Macro Programme is provided in the last paper of this volume As well as this book a principal means of disseminating information arising from the Micro to Macro Programme is via a web site, vii viii PREFACE maintained by the data managers, the British Geological Survey, at http://www.bgs.ac.uk/ micromacro/about.html (or linked from http:// www.nerc.ac.uk/funding/thematics/m2m/) where project updates on most individual projects and links to some of the research departments can be found) This site will be accessible for at least three years after publication of this volume Richard Shaw British Geological Survey, Nottingham Understanding the Micro to Macro Behaviour of R o c k - Fluid Systems: introduction RICHARD SHAW Scientific Co-ordinator, Micro to Macro, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK The purpose of this volume is to disseminate the principal results of the Natural Environment Research Council's (NERC) thematic programme 'Understanding the Micro to Macro Behaviour of Rock-Fluid Systems', commonly referred to as 'tx2M', and it forms part of the dissemination strategy of the programme This s programme ran from 1998 to 2004 and provided funding to 17 projects following two calls for proposals In common with other NERC thematic programmes, this programme was overseen by a steering committee with representatives from industry and academia with expertise and experience in the topics covered by the programme and knowledge of their potential application An overview of the Micro to Macro Programme is provided in the last paper in this volume Understanding how fluids flow through though rocks is very important in a number of fields Almost all of the world's oil and gas are produced from underground reservoirs and knowledge of how these energy resources got where they are, what keeps them there and how they migrate through the rock is very important in the search for new resources as well as for extracting as much of the contained oil/gas as possible Similar understanding is important for managing groundwater resources and also for predicting how hazardous or radioactive wastes and carbon dioxide will behave if they are stored or disposed of underground Unravelling the complex behaviour of fluids as they flow through rock is difficult We cannot see through rock, so we need to predict how and where fluids flow and at what rates This requires an understanding of the type of rock, its porosity and the character and pattern of fractures within it Fluid flow can vary with time and over a range of scales, from microscopic pores and cracks to major fault zones Some of the researchers in the Micro to Macro Programme have been studying rocks from boreholes, excavations and elsewhere, and gathering information from seismic surveys, in an attempt to understand how fluids flow in real rocks in real situations Others have been working on computer models and laboratory simulations of fluid flow through porous and/or fractured rocks Put together, these approaches have yielded very useful results, many of which are discussed in this volume Industries whose resources lie in the subsurface base most of their planning and investment decisions on models of their sites that require numerical descriptions of the geology The commercial consequences of poor geological modelling can be particularly severe where fluid flow is involved because fluid flow is governed by the spatial arrangement of extremes in the range of permeabilities The Micro to Macro Programme has been focused on developing our understanding of the relationships between measured and modelled subsurface fluid flows, spanning the range of spatial and temporal scales relevant to fluid resource management The programme was motivated by observations and emerging theories of how geological heterogeneities vary across these ranges in scale and the consequences of extrapolating fluid behaviour both in time and space; the aim was to provide a clearer physical understanding on which to base more effective geofluid management and to allow better integration of data for reservoir characterization and improved models for fluid flow The scope of the programme necessarily involved workers with backgrounds in the hydrocarbon, water, radioactive waste, mining and geothermal industries and a major objective was to foster communication between disciplines and communities to their mutual benefit As a result, many of the projects funded by the programme will be of considerable interest to those interested in upscaling issues in the hydrocarbon, groundwater resource and waste disposal (including radioactive waste) industries As well as this book, a principal means of disseminating information arising from the Micro to Macro Programme is via a website, maintained by the data managers - the British Geological Survey - at http://www.bgs.ac.uk/micromacro/ about.html (or linked from http://www.nerc ac.uk/funding/thematics/mZm/) where project From: SHAW,R P (ed.) 2005 Understanding the Micro to Macro Behaviour of Rock-Fluid Systems Geological Society, London, Special Publications, 249, 1-3 0305-8719/05/$15.00 The Geological Society of London 2005 OVERVIEW OF THE NERC ix2M PROGRAMME 153 Numerical results have been performed to investigate the effects of scale length (sizes) and spatial distributions of fractures on the characteristics of propagating waves These show that the wavefronts can be affected significantly by the presence of fractures with different scales or lengths relative to the wavelength, and also show that different spatial distributions of fractures can give characteristic features on the wavefields, implying that the information about the fracture distributions in natural rock may be obtained from seismic data to the direction of the hydraulic gradient that dictates the type of curve produced and not necessarily the type of fracture pattern Two-set patterns, on the other hand, produce a more restricted range of curve types A breakthrough curve classification scheme, using principal component analysis (PCA), was devised and linked to fracture pattern properties There are two approaches to classifying additional breakthrough curve data using PCA A8 Tracer tests, hydraulic properties and fracture networks at sub-continuum scales in aquifers (Johnston, P (University College London)) Fractures spaced at c.0.1 m to c 10 m impart continuum scales to fractured aquifers which may exceed the size of many practical problems Sub-continuum flow models often use statistical simulations of explicit fracture networks, which can lead to serious problems of system identification and uniqueness To address this problem, the aim of the research was to determine whether tracer breakthrough curves could be used to characterize fracture topology at subcontinuum scales The approach used in this project was one of forward modelling, starting with a prescribed fracture network in a homogeneous permeable medium The flow field and tracer transport were simulated for each network in turn, using a 2D finite difference numerical code (Odling & Webman 1991; Odling & Roden 1997) in which advection was the only dispersive process Both one-set and two-set patterns were simulated The output from the model - the tracer breakthrough curve - is a record of the fracture geometry, flow field and bulk equivalent permeability of the model and of the chosen injection pattern Linear and radial flow fields were simulated, allowing the results to be compared with natural and forced gradient tracer tests conducted in field experiments By repeating the modelling procedure for different networks, the combinations of bulk permeability and breakthrough curves that each produced were explored Over 3000 patterns were simulated Results indicate that 2D fractured porous media can produce a large variety of tracer breakthrough curves, including two patterns rather commonly seen in field data: the backward-tailed unimodal, non-Fickian type; and the Fickian For the one-set case, it is the combination of the spacing, aperture and angle The breakthrough curves are added to the raw dataset and a new covariance matrix is determined The raw dataset is considered to be definitive, giving a fixed set of orthogonal functions in terms of which any further function can be determined as a linear sum with coefficients representing the principal components In this study the latter was assumed Given a breakthrough curve, produced by a previously un-modelled pattern, it is shown that, using PCA and permeability as constraints, one can reduce the number of possibilities of fracture spacing, aperture, angle of rotation to the hydraulic gradient and pattem responsible for producing that curve A9 Novel flow and transport models for systems exhibiting non-integer flow dimensions (Sellers, S & Barker, J (University College London)) The original project aim was to investigate the possibility of developing novel methods for modelling transport in heterogeneous systems This was based partly on the increasing number of hydraulic tests, mainly in fractured rocks, that exhibit non-integer dimensional flow (i.e not linear, cylindrical or spherical flow) Further motivation came from the fact that observations of fractal dimensions have become quite common: typical measurements refer to pore geometry, surface roughness, fault traces and relationship between fault number, lengths and widths An underlying fractal structure appears consistent with non-integer flow dimensions and, as a pumping test is modelled by a diffusion equation (pressure diffusion), the work came to focus on (generic) diffusion on fractals An initial literature search indicated that there are numerous models for diffusion on fractals, with no agreement as to the correct one The approach taken here was to construct simple fractals with known characteristics (such as fractal dimension) and then simulate diffusion with random walks Sierpinski carpets were chosen 154 R.P SHAW as they are flexible enough to generate arbitrary fractal dimensions Although rather special cases, they have been proposed as a means of constructing porous media Random walks of up to ten million time steps were simulated on ninth generation Sierpinski carpets discretized with a 19 683 x 19 683 lattice The resulting displacements as a function of time were averaged over up to 100000 particles with the same initial starting point The standard procedure in the literature is to average the results over initial conditions to obtain results independent of the starting conditions The goal, however, was to simulate a boundary value problem on a specific fractal as might occur in an experimental situation Main results The presence of intemal boundaries at all scales significantly affects the behaviour of the random walks In fact, the graph of displacement squared versus time often shows significant deviations from a straight line on the standard log-log plot for the investigated time-scales The deviations due to the intemal boundaries are oscillations about a straight line, with periods that can last several decades, thus making difficult or impossible the determination of the asymptotic slope and, hence, the random-walk dimension The random walks can show anisotropic behaviour in that random-walk dimensions for horizontal displacement and vertical displacements can be unequal The dimension results are strongly dependent on the origin In fact, one origin can yield isotropic response whereas a nearby origin of the same fractal yields anisotropic response Equivalent points corresponding to different generation levels of the fractal, however, yield identical dimensions Thus, the random-walk dimensions have an anisotropic, multifractal structure with respect to origin The dependence of the random walks on the origin does not decay in the simulated timescales, indicating a long-term memory effect This result differs from that in Euclidean lattices where the effect of the origin decays exponentially in time Conclusions and significance Random walks have been used to show that very simple fractals such as Sierpinski carpets can exhibit complex and surprising behaviour In particular, the characteristic linear graph on a log-log plot of displacement against time may not be observable for data collected on a limited time-scale Any underlying fractal structure may, therefore, not be readily observable through pumping tests All known diffusion models based on differential equations assume isotropy and attribute a single random-walk dimension to a fractal The results from the simulations are inconsistent with these models and cast doubt on the applicability of a single differential equation for the entire fractal Further, the dependence on the initial conditions indicates that fractals are heterogeneous, so that data collected at one point of the fractal may not be valid for another point of the fractal If the differential equations were modified to allow for anisotropy, then they would be expected to hold at most at a fixed point Also, it is not clear how to relate the observed random-walk dimensions with the underlying fractal dimension A10 Modelling porosity development in heterogeneous fracture networks (Bloomfield, J.P (British Geological Survey) & Barker, J.A (University College London)) The objective of the project has been to produce a model of coupled flow and porosity development in heterogeneous porous media and to use the model to investigate scaling phenomena A code, MOPOD, has been produced and the task of computing porosity development has been formulated as an 'initial value problem' The model is highly flexible: it is capable of modelling 2D and 3D arrays with both regular and random structures, a wide range of initial aperture distributions and flexible boundary conditions, including constant head or flow conditions In addition, codes for visualizing the arrays and for simulating particle transport, which reveals the effects of filtering in relation to particle size, have also been developed Even though the model is formulated in terms of a simple system, evolved arrays can be highly complex and parameterization and prediction of their evolution is not trivial Consequently, investigation has focused on a very simple porosity growth law of the form dai/dt = v~, where ai(t ) is the aperture of pore i at time t, vi is the magnitude of the volumetric flow rate in pore i, and e is the aperture growth rate exponent The evolved structures are highly sensitive to initial porosity distributions, growth-rate exponents and hydraulic boundary conditions; they range from relatively uniform porosity development, through complex anastomosing geometries, to the development of preferentially enlarged OVERVIEW OF THE NERC [z2M PROGRAMME array-spanning paths with long-range correlations A limited study of percolation in the arrays has been undertaken; however, because the porosity fields become highly structured as they evolve, the assumption of a random porosity field required for analysis using percolation methods - becomes invalid There is no evidence for scaling of either the porosity or flow fields in the evolved arrays for the growth laws investigated Although spatial correlations develop in the porosity distribution, pore structures evolve towards a final state and selforganization phenomena are not observed because periodic or cyclic behaviour is not inherent in the simple growth laws investigated The MOPOD code has been used to characterize variations in transmissivity and to investigate the breakthrough characteristics as the porosity field develops The effective transmissivity of the arrays is sensitive to the growth-rate exponent and is a power-law-like function of time The form of the tracer breakthrough is also dependent on the evolved pore structure and, hence, the growth-rate exponent For example, porosity fields with preferentially enlarged array-spanning paths are associated with high concentrations of tracer breakthrough at relatively early times The principal outcomes of the work and their significance are: a flexible, generic, model of coupled flow and porosity development in heterogeneous media has been developed that produces porosity structures with long-range correlations without relying on process-specific assumptions The model provides an alternative to current methods: stochastic methods that not readily reproduce such long-range correlations or pathways; and process-specific approaches that may grossly oversimplify the field situation and that can require significant computational effort New insights have been gained into the development of secondary porosity It has been demonstrated that complex porosity fields can develop from even simple porosity growth laws, that critical exponents are associated with phase changes in the geometry of the evolved structures and that porosity fields develop dynamically stable configurations during an initial phase of growth followed by simple amplification of porosity at later times This work provides a better understanding of how secondary porosity 155 is likely to develop in aquifers and hydrocarbon reservoirs and will enable more realistic prediction of flow and transport A l l Localized flow in fractured rock masses: mechanisms, modelling and characterization (Sanderson, DJ., Zhang, X (Imperial College) & Barker, A.J (Southampton University)) This project mainly involved coupled mechanical/hydraulic modelling of the effects of stress on fracture networks using distinct element numerical methods The main achievements of the research are noted below Numerical modelling has demonstrated that deformation and flow exhibit critical behaviour in terms of stress, with both increasing nonlinearly to become highly localized (Zhang & Sanderson 2001, 2002a; Sanderson & Zhang 2004) At the critical stress state, rock deformation is enhanced by slip on fractures, with rock friction being the main controlling factor The material properties (e.g stiffness) control the geometry of the resulting structures Flow becomes highly localized at the critical stress state and can be described in terms of multifractals The critical stress state may be described in terms of a driving stress ratio R = (fluid p r e s s u r e - m e a n stress)/l(differential stress) Instability occurs where the R-ratio exceeds some critical value, Re, in the range - to - This result may be used to evaluate in situ stress in the crust, which appears to be close to the critical state throughout much of the upper crust Models with fractures and smaller polygonal discontinuities (grains) have demonstrated the importance of dilational shearing on deformation and flow, providing discrete dual porosity/dual permeability simulations of flow (Zhang & Sanderson 2002b; Zhang et al 2002) Models demonstrate sensitivity to fracture geometry, grain texture and stress, and to cyclic loading Simulated well tests have been conducted, including slug tests (Zhang et al 2002) and changes in flow during excavation of a shiplock in China have been simulated (Zhang & Sanderson 2002c) Permeability/depth variations in fractured rock have been simulated and compared with borehole data Results indicate heterogeneous permeability and localized flow similar to that modelled at the critical stress state Near-borehole effects have been modelled and a new type of 'block loosening' deformation identified (Zhang & Sanderson 2002d), which is quite different to traditional 'wellbore breakout' 156 R.P SHAW Fieldwork has allowed quantification of damage around faults and has established a power-law distribution of vein opening from decimetre to micro- (10lxm) scales At the micro-scale, grain processes dominate; at the macro-scale, reactivation of slip on fractures is most important range of heterogeneous media types For this library to be useful, several factors had to be addressed These included 9 A12 Quantifying fluid movements in heterogeneous formations at different scales and their contribution to physical transport (Xie, Z., Mackay, R (Birmingham University) & Cliffe, K.A (Serco Assurance)) The use of numerical models to predict subsurface flow and transport has received much attention in the fields of water resources, petroleum engineering and waste disposal While modelling is important, the predictions made with the available models are often highly inaccurate, particularly for transport problems The cause of this inaccuracy is attributed primarily to the unknown fine-scale heterogeneity of the flow paths and secondarily to weak determination of the fluid stresses on the system New data collection strategies have made little progress in improving accuracy, but significant progress has been made towards bounding the errors by exploring the prediction uncertainty using Monte Carlo simulation methods These methods employ stochastic descriptions of aquifer heterogeneity However, to model at the space- and time-scales of relevance to decision making, averaged process equations are adopted and the stochastic properties of the geological domain are typically characterized at a scale much greater than the scale of heterogeneity affecting the migration patterns This leads to a serious question about how good the large-scale equations and the supporting property distributions are at capturing the transport behaviour and the prediction uncertainty Many papers have been produced that address this question but most adopt either simplified models of geological heterogeneity or consider only short space- and time-scales Results that are relevant to more realistic geological models and large space- and time-scales are needed A rigorous numerical modelling study is presently being undertaken that aims to bridge the apparent gap between practice and theory The foundation for this work has been the preparation of a library of reliable, large space and time simulations for two-dimensional domains encapsulating detailed descriptions of the finescale flow paths and flow velocities through a 9 the minimization of numerical artefacts introduced to generate the media and simulate fluid movement; the production of highly accurate flow and transport simulations; the control of boundary influences on flow geometry and transport behaviour; and, importantly; validation against analytical solutions for known heterogeneity An iterative Choleski decomposition technique has been developed for generating Gaussian random fields obeying standard covariance functions This technique is computationally efficient for generating large numbers of alternative realizations with the same spatial statistical model Importantly, ensemble statistical behaviour is well reproduced over a large number of realizations generated by this method Nonparametric transformations of the Gaussian fields permit the production of more geologically realistic structures One thousand realizations have been produced for several spatial statistical models A mixed finite element discretization of the steady-state groundwater flow equation has been used for the numerical simulation of the flow paths This formulation allows exact calculation of particle trajectories considering advection only Initial work to implement periodic boundary conditions perpendicular to the major flow direction was abandoned when particle migration patterns were found to also degrade to a periodic form Periodicity parallel to the major flow direction proved not to suffer from the same restriction Exploitation of this condition has allowed the domain width perpendicular to flow to be considerably less than the domain length Sensitivity analyses have been performed to determine the optimal rectangular domain size for the random fields Domains corresponding to 40 correlation lengths parallel to flow by 12 correlation lengths perpendicular to flow employing a grid resolution of not less than 50 elements per correlation length were eventually adopted as optimal for the library Validation of the combined suite of media generation model, flow model, particle migration model and chosen domain size has been undertaken by comparison of the numerical results against the analytical results for ensemble spreading parallel and perpendicular to the flow direction developed by Dagan (1990) OVERVIEW OF THE NERC I,z2M PROGRAMME The results are accurate for low variance media for short to intermediate times but deviate significantly for larger times The causes of this deviation are currently being explored but are partly contributed by boundary interference, which seems unavoidable However, not all of the deviation can be explained in this way and a re-examination of the flow model approximations as well as the approximations exploited in the development of Dagan's analytical model is underway A13 Analysis of reaction and flow in stochastically heterogeneous porous media (Huppert, H.E (Cambridge University) & Bonnecaze, R.T (University of Texas at Austin)) Reaction and flow in porous media occur in a variety of situations These include orebody mineralization, use of acids in oil wells to enhance oil recovery and the movement of non-aqueous phase liquids and aqueous contaminants in rocks and soils In homogeneous porous media, these systems lead to an instability that, in turn, leads to the development of fingering of the reaction and flow front created by the positive feedback between flow and reaction Real porous media are not homogeneous and it is unclear how their heterogeneities affect the instability Details of the heterogeneities are usually unknown but they can be described statistically This pilot study has examined the stability of a reactive front in a sinusoidal and stochastically heterogeneous porous medium by both analytical and computational methods It has the aim of predicting the characteristics of the instability from the statistical description of the heterogeneous porous media A model of reaction and flow for two types of heterogeneous porous media has been analysed The first model considered flow in a porous media with two-dimensional sinusoidal variation in permeability that is altered by advected solute with the rock This model system can be analysed to understand flow and reaction in nonhomogeneous porous media This heterogeneity generally enhances the instability and rate of growth of the fingers and creates a preferred mode for growth roughly corresponding to the frequency of the heterogeneity Based on the understanding gained from this model, a model for reaction and flow in a stochastically heterogeneous porous media was developed This model provides a means to predict the statistics of the instability in such porous media 157 AI4 The scaling behaviour of fluid flow in rough rock fractures (Ogilvie, S., Isakov, E & Glover, P (Aberdeen University)) Fluid flow through natural fractures depends upon the scaling behaviour of their fractually rough surfaces Techniques have been developed for imaging fluid flow in natural rock fractures themselves, by using high fidelity physical models (HFPM) and high-resolution numerical simulations These advances have been used to examine the scaling behaviour of miscible/nonmiscible fluid flow in fractures, paying particular attention to: 9 9 channelling, fingering, dispersion and flow stability; surface wettability; normal and shear deformation; and nature and development of fractural fracture matching Digital optical imaging techniques Techniques have been developed fully to either observe a HFPM fracture pair during fluid flow through the rough fracture or, on a single fracture surface covered with dyed fluid, to enable pointwise determination of fracture surface topography The result is a high resolution optical determination of fracture surfaces and apertures with topographies of the two fracture surfaces for all project samples now determined to within 15 txm in the fracture plane (640 x 480 pixel image) and to within 15 ~xm vertically This method provides a faster, higher resolution and cheaper technique than the more commonly used stylus profilometry A further advance in optical profiling is the robust use of devices to calibrate the dyed fluids and equipment used in the imaging process Previous studies arbitrarily scaled the resulting surface heights Profiles of fracture surfaces and aperture maps have been determined for all samples Fracture parameterization and creation of synthetic fractures This experimental work has led to the in-house development of software (SynFracTM), which creates suites of 'digital' fractures whose characteristics are finely tuned to those of the measured fractures It is important to have such a program for generating synthetic fractures because fluid flow modelling is best carried out on a suite of fracture data that share the same characteristics to enable the derived parameters to be a reasonable average rather than depending upon one 158 R.P SHAW implementation that may not be representative as a result of its specific structure Clearly, such a dataset is impossible to obtain from real rocks because it would be too time consuming and different rock fractures may differ in their basic structural parameters Using SynFracT M it is possible to create synthetic fractures at five different resolutions, from 64 x 664 to 1024 • 1024 Three different synthesis methods can be used, the simple Brown (1995) method, the Glover et aL (1998) method and a new, improved method (Ogilvie et al 2003; Isakov et al 2001) that allows high quality partial correlation of random deviates There is also a choice of three different extremely high quality random number generation methods The synthetic fractures can be simply analysed for mean fracture aperture and surface height information in the program, which also enables the operator to view the resulting synthetic rock fractures and apertures both in greyscale plan view and along any mouse-click chosen perpendicular profiles The program outputs in jpeg, tiff, usgs, table text and triple column text formats for use in documents or in fluid flow modelling programs Fluid flow experiments Fluid flow experiments have been carried out on the HFPMs of all samples at a wide range of flow rates using a flow rig and imaging equipment This involves releasing water, then dyed water from fluid reservoirs on the rig, moving the output position which controls flow velocity and recording pressure difference on manometers For each measurement, a Reynold's number is calculated and a series of flow images versus time are captured using Adobe Premier 5.1TM video capture software 2D flow models All data from previously described stages of the project provide boundary condition input into 2D fluid flow models in the plane of the fracture surface The modelling was performed in a FemLabTMenvironment, fracture geometries from SynFracT M 'digital' fractures and Reynold' s numbers from experimental fluid flow This combined experimental-numerical approach is very successful in enabling the physical constraints upon fluid flow in rough rock fractures to be well characterized The Reynold's equation does not account for fracture surface roughnesses, therefore the Femlab modelling involved the solution of the Navier-Stokes, Diffusion and other partial differential equations for an incompressible fluid confined by the complex boundary conditions set by the rough fracture walls The preliminary stages of this work have already been published (Ogilvie et al 2001) and are about to be published (Ogilvie et aL in press) A15 Measurement of complete fluid velocity fields in 2D heterogeneous porous media (Cassidy, R., McCloskey, J & Morrow, P (Ulster University, Coleraine)) The ubiquitous scale invariance of geological material and the consequent absence of a length scale on which to base the upscaling of measurements made on geological samples, represent a serious challenge to the understanding of fluid behaviour in rock Numerical simulation is an important tool for understanding and predicting the movement of fluid in geological materials and current discrete fluid models, in which complex boundary conditions present no serious challenge to the modeller, have the potential for testing many possible upscaling schemes At present, however, there is no accurate empirical data on the distributions of fluid velocities in complex, scale-invariant geometries and models can only be tested against analytical solutions in simple geometries or against bulk experimental measurements The assumption that a model that successfully passes these two tests is able to solve accurately the flow problem in more realistic media remains untested The project set out to measure fluid velocities everywhere in complex 2D media with fractal heterogeneity First, digital models with scale-invariant geometries were created and then translated into physical form The two models described here are: 9 rough fracture, defined by two self-affine fractal surfaces, which is cut from a sheet of aluminium using wire erosion machining and; digital combination of rock matrix and fracture porosity produced by the superposition of the void space from a discrete-element model and from a fracture model containing a fracture set with a fractal length distribution This model is cast in resin using selective hardening of photosensitive polymer; a technique known as stereolithography These models were then enclosed between parallel sheets of glass and Perspex forming a Hele-Shaw cell The cells were permeated with water, doped with small neutrally buoyant spheres and pumped at accurately steady and OVERVIEW OF THE NERC ~2M PROGRAMME reproducible velocities using a high precision HPLC pump Local velocity vectors were estimated by the analysis of sequential images of the spheres over areas of about 0.25 mm z using a high-resolution video camera Precision digital control systems were used to move the cell and measure the fluid velocity; repeated measurements allow the construction of full 2D velocity fields The accuracy of the technique was assessed by comparison between automated and manual measurements, confirming the accuracy over approaching three orders of magnitude in velocity Results for a variety of media and formats for the storage of the void space geometry and measured velocity fields have been obtained These results have been compared to the output of lattice Boltzmann (LB) simulations of flow in identical geometries The results show that: 9 9 the LB model successfully predicts the velocity field for simple geometries; the correlation between predicted and observed velocity fields is strongly dependent on optimization of the simulation viscosity (incorrect viscosities result in incorrect predictions); this LB scheme is incapable of simulating correct viscosities for complex geometries a systematic de-correlation is observed for increasing viscosity mismatch; some important effects relating to interactions between matrix and fracture flow are strongly viscosity dependent Some simulations may be able to predict successfully the behaviour of high viscosity fluids only Non-linear effects between fracture and matrix flow are likely to be more important in these cases A16 Crack damage and permeability evolution near the percolation threshold in a near-perfect crystalline rock (Meredith, P.G., Clint, O.C., Ngwenya, B (University College London); Main, I.G., Odling, N.W.A (Leeds University) & Elphick, S.C (Edinburgh University)) The importance of the evolution of crack networks during deformation is now becoming widely recognized as one of the key factors that control important processes involving fluid flow in rocks of low permeability, for example, hydrothermal circulation at mid-ocean ridges, energy recovery from geothermal reservoirs and accelerating deformation preceding volcanic eruptions Hence, this project has been investigating the scaling properties of crack 159 populations near the percolation thresholds for fracture and fluid flow in Ailsa Craig Microgranite (ACM) with increasing levels of damage The work has shown the ACM to be a nearideal material for this investigation: it is almost perfectly isotropic, with P- and S-wave velocity anisotropy much less than 1%; and the fluid permeability of the undeformed rock is remarkably low at 1.5 • 10 -23 m 2, determined at an effective pressure of 10 MPa No pre-existing microcracking could be observed either by optical or scanning electron microscopy In the first phase of the study, thermal stressing at temperatures up to 800~ was used to induce crack damage in cores of ACM Elastic wave velocities and fluid permeability were measured at room temperature before and after each thermal treatment cycle A reduction of 48% in P-wave velocity and 32% in S-wave velocity was found with thermal stressing up to 800~ indicative of the high level of induced microcracking However, the velocity measurements showed that this new damage was isotropically distributed at all temperatures investigated Fluid permeability was found to have increased by seven orders of magnitude over the same treatment range The increase in permeability is very non-linear, as induced cracks increasingly link up to create more pathways for fluid flow In the second phase, the study was extended by examining the relationship between slow mechanical deformation, microcrack growth and permeability in ACM close to the fracture interconnection percolation threshold To examine these interrelationships, creep experiments were undertaken on cores of ACM during which acoustic emissions, solute breakthrough curves and electrical impedance (EI) were measured at a strain rate of 10- s- The initial network of distributed damage was generated by heating samples at 1~ min-1 to 900~ then cooling to room temperature at the same rate The treated core was then placed in a Hasler cell and initially loaded to 20 MPa To measure breakthrough curves, solutions of deionized/distilled/ degassed water were alternated with a degassed M NaC1 solution Initial 'breakthrough' tests under hydrostatic conditions showed that the EI response detects first a linear change in impedance as the solute front advances through the core followed by a more gradual decrease as the front 'breaks out' of the core end The El response, therefore, describes both the advecfion and dispersion terms associated with the solute front in the core The data allow the interrelationship between crack generation/growth, effective cumulative aperture, permeability and hydraulic dispersion to be examined during the 160 R.P SHAW process of creep deformation Of particular interest is the behaviour of the system close to failure, where rapid changes in fracture network characteristics occur A17 Quantifying the effects of biofilm growth on hydraulic properties and on sorption equilibria: micro to macro measurements (Vaughan, D.J., Wogelius, R.A., Boult, S., Merrifield, C., Brydie, J.R (Manchester University) & Large, D (Nottingham University)) The objectives of this project were to undertake experiments, relevant to microscopic, mesoscopic and macroscopic scales, on the growth of bacterial biofilms, and to study their influence on both the hydraulic properties of geological systems (porous sediments, fractured rocks) and on the sorption of major and trace metals in introduced aqueous fluids In the microscopic experiments, biofilms have been grown in various media using artificial groundwaters under both oxic and anoxic conditions; the rates of biofilm growth have been measured by studying the rate of reduction in discharge through a porous medium, and the biofilms themselves characterized using advanced imaging methods (environmental scanning electron microscopy, confocal laser scanning microscopy) Important information on the structure of immature and mature biofilms has been obtained from the study of model systems, notably the incomplete coverage of the substrate surface, even in mature biofilms, and the influence of fluid flow, seen in imbricate and in shear structures Sorption and precipitation phenomena were studied by the addition of iron and lead to biofilm-conditioned surfaces, with rates of iron hydroxide precipitation being studied using imaging and spectroscopic methods (atomic force microscopy, X-ray photoelectron spectroscopy, etc.) Mesoscopic experiments (e.g involving columns packed with quartz sand) have enabled the effects of biofilm growth on hydraulic conductivity at the centimetre scale to be determined Continuous logging of discharge rate from a column as a function of biomass accumulation has demonstrated reductions in hydraulic conductivity of two to three orders of magnitude during the course of experiments When iron was introduced, the optimum conditions of hydroxide precipitation were found to be when the mineral surfaces are conditioned by biofilm The macroscopic studies have involved design, construction and commissioning of novel equipment to mount in a 500 g geotechnical centrifuge (radius 3.2 m) in the Manchester School of Engineering This enables the scaling up of hydraulic conductivity tests to the - 0 m range, bridging the gap between laboratory and field measurements and enabling field-scale studies in a highly controlled environment Centrifuge experiments involving 600 mm high columns of a porous medium (Congleton Sand) encountered problems due to sloughing of the biofilm at higher g-levels Greater success was achieved following addition of iron in solution with subsequent hydroxide precipitation Changes in hydraulic conductivity observed in the scaled-up centrifuge system experiments again show potential reductions of two to three orders of magnitude following biofilm development, and comparable further reductions following iron hydroxide precipitation A model fracture system has also been constructed for use in centrifuge experiments and is still being commissioned Overall, a great deal of new information has been acquired concerning biofilms, their structures and related characteristics, their importance in controlling the hydraulic properties of sediments and fractured rocks, and their role in the migration of minor/trace impurities in waters Indeed, the importance of biofilms has been demonstrated and quantified over a wide range of scales for the first time The compiler acknowledges the contributions from all the Principal Investigators of the NERC Micro to Macro Programme and their teams that have been used to compile this introduction and summary of the programme This paper is published with the permission of the Executive Director of the British Geological Survey (NERC) References ANI"ONELLIN~,M & AYDIN,A 1994 Effect of faulting on fluid flow in porous sandstones: Petrophysical properties, American Association of Petroleum Geologists Bulletin, 78, 355-377 BLAKEMAN, R.J., ASHTON, J.H., BOYCE, A.J., FALLICK, A.E & RUSSELL,M.J 2002 Timing of interplay between hydrothermal and surface fluids in the Navan Zn + Pb orebody, Ireland; evidence from metal distribution trends, mineral textures, and delta (super 34) S analyses Economic Geology, 97, 73-91 BROWN, S 1995 Simple mathematical model of a rough fracture Journal of Geophysical Research, 100, 5941-5952 DAGAN, G 1990 Transport in heterogeneous porous formations: spatial moments, ergodicity and effective dispersion Water Resources Research, 26, 1281 - 1290 FUNG, L.S., HIEBERT, A.D & NGHIEM, L 1992 Reservoir simulation with a control volume finite- OVERVIEW OF THE NERC ix2M PROGRAMME element method SPE Reservoir Engineering, 7, 349-357 GLOVER,P., MATSUKI,K., HIKIMA,R & HAYASHI,K 1998 Synthetic rough fractures in rocks Journal of Geophysical Research, 103, 9609-9620 HARRIS, S.D., McALHSTER, E., KNIFE, R.J & ODLtNG, N E 2003 Predicting the threedimensional population characteristics of fault zones: a study using stochastic models Journal of Structural Geology, 25, 1281-1299 ISAKOV, E., OGILVIE,S.R., TAYLOR,C.W & GLOVER, P.W.J 2001 Fluid flow through rough fractures in rocks I: High resolution aperture determinations Earth and Planetary Science Letters, 191, 267-282 KNIPE, R.J., FISHER, Q.J., JONES, G et aL 1997 Fault seal analysis: successful methodologies,application and future directions In: MOLLER-PEDERSEN,P KOESTLER, A.G (eds) Hydrocarbon Seals: Importance for Exploration and Production Norwegian Petroleum Society (NPF) Special Publication, 7, 15-40 MACAULAY,C., GRAHAM,C.M & HASZELDINE,R.S 2000a Palaeo-hydrogeology in oil reservoir sandstones from multi-tracer micro-analysis of mineral cements Paper presented at Geoscience 2000, Manchester, 175, Geological Society, London MACAULAY,C., HASZELDINE,R.S., GRAHAM,C.M & FALLICK, A.E 2000b Silicon isotopes identify sponge spicules as source of silica cement in North Sea oilfield sandstones Paper presented at the American Association of Petroleum Geologists Annual Meeting, New Orleans ODLING, N.E & RODEN, J 1997 Contaminant transport in fractured rocks with significant matrix permeability, using natural fracture geometries Journal of Contaminant Hydrology, 27, 263 -283 ODL1NG, N.E & WEBMAN, I 1991 A 'conductance' mesh approach to the permeability of natural and simulated fracture patterns Water Resources Research, 27, 2633-2643 ODLING, N.E., HARRIS, S.D & KNIPE, R.J 2004 Permeability scaling properties of fault damage zones in siliclastic rocks Journal of Structural Geology, 26, 1727-1747 OGILVlE, S.R., ISAKOV, E., GLOVER, P.W.J & TAYLOR, C.W 2001 Use of Image Analysis and Finite Element Analysis to Characterise Fluid Flow in Rough Rock Fractures and their Synthetic Analogues Proceedings of the 8th European Congress for Stereology and Image Analysis Image Analysis and Stereology, 20(2) suppl 1,504-509 OGmVIE, S.R., ISAKOV,E., TAYLOR,C.W 8r GLOVER, P.W.J 2003 Characterisation of rough fractures in crystalline rocks In: PETFORD, N & MCCAFEREY (eds) Hydrocarbons in Crystalline Rocks Geological Society, London, Special Publications, 214, 125-141 OGILVIE, S.R., ISAKOV,E., TAYLOR,C.W & GLOVER, P.W.J in press Fluid flow through rough fractures in rocks III: (Single phase) flow experimentation and modelling Earth and Planetary Science Letters PECHER, R., HARRIS, S.D., KNIPE, R.J., ELLIOTT, L & INGHAM,D.B 2001 New formulation of the Green 161 element method to maintain its second-order accuracy Engineering Analysis with Boundary Elements, 25, 211-219 SANDERSON,D.J & ZHANG,X 2004 Stress controlled localization of deformation and fluid flow in fractured rocks In: COSGROVE, J & ENGELDER, T (eds) The Initiation, propagation and Arrest of Joints and Other Fractures Geological Society, London, Special Publications, 231, 299-314 SmPTON, Z.K & COWIE,P.A 2001 Damage zone and slip-surface evolution over um to km scales in high-porosity Navajo sandstone, Utah Journal of Structural Geology, 23, 1825-1844 SIBSON, R.H 1994 Crustal stress, faulting and fluid flow In: PARNELL, J (ed.) Geofluids: Origin, Migration and Evolution of Fluids in Sedimentary Basins Geological Society, London, Special Publications, 78, 69-84 TAmBENU, A.E 1999 The Green element method Kluwer, Dordrecht VERMA, S.K 1996 Flexible grids for reservoir simulation PhD thesis, Stanford University VLASTOS, S., LIU, E., MAIN, I.G & LL X.-Y 2003 Numerical simulation of wave propagation in media with discrete distributions of fractures: effects of fracture sizes and spatial distributions Geophysical Journal International, 152, 649-668 ZHANG, X & SANDERSON, D.J 2001 Evaluation of instability in fractured rock masses using numerical analysis methods: Effects of fracture geometry and loading direction Journal of Geophysical Research, 106, 26 689-26 706 ZHANG, X & SANDERSON,D.J 2002a Instability and associated localisation of deformation and fluid flow in fractured rocks In: ZHANG, X & SANDERSON, D.J (eds) Numerical Modelling and Analysis of Fluid Flow and Deformation of Fractured Rock Masses Pergamon Press, Elsevier Science, London, 155-186 ZHANG, X & SANDERSON, D.J 2002b Grain scale flow of fluid in fractured rocks In: ZHANG, X & SANDERSON, D.J (eds) Numerical Modelling and Analysis of Fluid Flow and Deformation of Fractured Rock Masses Pergamon Press, Elsevier Science, London, 187-210 ZHANG, X • SANDERSON, D.J 2002c Changes of permeability due to the excavation of ship-locks of the Three Gorges Project, China In: ZHANG, X & SANDERSON,D.J (eds) Numerical Modelling and Analysis of Fluid Flow and Deformation of Fractured Rock Masses Pergamon Press, Elsevier Science, London, 211-231 ZHANG, X & SANDERSON, D.J 2002d Wellbore instability due to 'block loosening' in fractured rock masses In: ZHANG, X & SANDERSON, D.J (eds) Numerical Modelling and Analysis of Fluid Flow and Deformation of Fractured Rock Masses Pergamon Press, Elsevier Science, London, 232-254 ZHANG, X., SANDERSON,D.J & BARKER, A.J 2002 Numerical study of fluid flow of deforming fractured rocks using dual permeability model Geophysics Journal International, 151, 452-468 Index Page numbers in italic refer to figures advection dispersion equation 91 Ailsa Craig microgranite 13, 159 anisotropy fracture surface 10 mudstone 104, 109-110, 112, 113 seismic 29-40 frequency dependence 32, 37 vertical seismic profile 35, 36, 37, 38 shear-wave 19, 20, 33, 36 well-logs 8, antipersistence apertures fracture 15-16, 95-96, 97, 100, 119 growth rate 10, 74-75 bacteria see biofilms, bacterial barriers, flow 43, 50-51 bioclogging 131, 132, 137, 143 biofilms, bacterial effect on fluid flow 131-143, 160 birefringence, shear-wave see splitting, shear-wave Bluebell-Altamont gas field, shear-wave anisotropy 36, 38 Boltzmann simulation, lattice 11, 116, 126-129, 159 Brae oil field cementation of sandstone 148 porosity/permeability correlation breakthrough curves see tracer experiments, breakthrough curves Brownian motion, fractional 6, 7, 8, 118 Cajon Pass well, fracture apertures 16 carpet, Sierpinski see Sierpinski carpets carpet, random 81-82, 82, 83 cementation, quartz 9, 147-148 chalk Cretaceous, tracer test 92, 93, 95 MOPOD model 76 as oil reservoir, porosity/permeability 149-150 channelling, flow 93 Cholesky Decomposition 63, 156 clay minerals fabric evolution 112-113 matrix 109-110, 111 reaction mechanisms 103-104 see also illite, transformation; smectite, illitization CO2 sequestration 22 conductivity hydraulic 62, 66, 67, 134, 135-136, 136, 141, 143 see also fractures, conductivity connectivity, fracture 14, 44 contaminants see transport, contaminants control volume finite element model 151 coupling, fluid 6, 10, 11, 14 crack damage, in crystalline rock 159 crack model 32, 152 Cretaceous, Upper Shetland Group mudstones 104-114, 150151 see also mudstone, Upper Cretaceous Shetland Group critical point 6, 12, 13, 14, 20, 23 criticality and coupled modelling 14-18 in fracture permeability 13-18 in hydrocarbon development 16 intermittent 23 self-organized 7-8, 23 terminology 23-24 Darcy's Law 50, 52, 74, 135 deformability 14-18 deformation, and fluid flow 14-15, 155-156 deformation bands 44, 52 density crack 19 fractures 14-18, 23-24, 29, 30-31, 31 164 minor faults 44 diagenesis effect on fracture systems - effect on scaling mudstone 103-104, 110, 112 diffusion anomalous, fractal lattices 79-89 matrix 93 molecular 93 directionality 17 discrete fracture flow model 151 discrete fracture network model 38-39 dispersivity 91 displacement Ekofisk field, criticality 16 elastic response 31, 32 equant pore model 32 failure equilibrium 23 faults damage zones 3D extrapolation 46-47 barriers to fluid-flow 43-57 efficiency 53-54 flow modelling 12, 50-57, 151 minor fault characteristics 44-45 in siliclastic rock 43-45 stochastic model 45-46 sub-sampling 46-50 upscaled bulk permeability 51-57 hydraulic properties 43-57 main slip zone 55-57 minor, characteristics 6, 44-45 spatial distribution 45-46 sub-seismic FEMLAB modelling 10 flow channelling 73, 93 flow, fluid barriers 43, 50-51 complex geology, scaling 151 - 152 effect of biofilms 131 - 143 in fault damage zone 12, 50-57, 151 in fractures 10, 15, 31, 151 in heterogeneous porous media 11, 18, 61-70, 115-129, 157, 158-159 INDEX matrix-fracture interaction 11, 93, 118, 125 modelling 5, 10, 18, 19, 116 in fault damage zones 50-57 generalized radial flow 18, 79 geomechanical 14-17 in multiscale fractures 32-35 Navan zinc-lead deposit 17-18, 148-149 path analysis 148-149 velocity field measurement 116 - 129, 158-159 flowcell 116-117, 119-122, 128, 158 numerical model 116 flowcell, Hele-Shaw 116-117, 119-122, 120, 128, 158 fractals 10 dynamic transport equations 18 effect on hydraulic properties 79 generalized radial flow model 18, 79 lattices anomalous diffusion models 80-89, 153-154 internal boundaries 87 random walk simulation 83-88, 154 sedimentary versus crystalline rock well-logs see also Sierpinski carpets fracture patterns 97, 98, 99, 100 fractures apertures 10, 15-16, 74-75, 95-96, 97, 100, 119 biofilm development 137-138, 139 cemented 29 characterization 30 conductive/non-conductive 17 connectivity 14, 18 density 14-18, 30-31, 31, 36-38 critical 24 P-wave azimuthal AVO analysis 36-37 shear-wave splitting 35- 36 discrete flow model 151 discrete network model 38-39 effect of diagenesis - en echelon, tracer tests 94-95, 96, 100 fluid flow matrix-fracture interaction 11 scaling 151-152, 157-158 localized flow in rock masses 155-156 multiscale 32- 35 INDEX open 29 orientation estimation 35- 37 parameterization 30, 31, 157-158 permeability 10-18 roughness 10, 117, 157-158 size estimation 37-38 synthetic, modelling 10, 157-158 theoretical models 31-35 frequency dependence, anisotropy 37-38 Gassmann model 19 Gaussian noise 6, geomechanics, flow modelling 14-16 geothermal power 6, 17, 22 granite tracer test 93, 95 unflawed 13, 159 Green element model 151-152 groundwater 5, 22 artificial, biofilm growth 132, 133, 160 transport 61 Gulf of Mexico, Miocene mudstone 150-151 head gradient 74, 76 heterogeneity, geological 115 modelling - physical transport 61-71, 156 tracer experiments 91 - 101 well-logs - High Fidelity Polymer Model 10 hydrocarbons criticality 16 reservoir modelling scaling problems 115-116 illite cement, North Sea oil fields 148 correlation with permeability/porosity 9, 112 illite/smectite ratio 104-105, 108-109, 110, 112, 112, 113 transformation 103-105, 150-151 iron oxyhydroxide precipitate 137, 142, 143 165 LaSTLib-2D 67, 70 lattice Boltzmann simulation 11, I6, 126-129, 159 lattices see fractals, lattices lead see zinc-lead orebody p.2M see Micro to Macro Programme Magnus oil field, cementation of sandstone 148 matrix chalk 149-150 clay 109-110 diffusion 93 permeability 11, 91-92, 93 porosity 32, 115, 118 matrix-fracture flow 11, 118, 125 Micro to Macro Programme 5-24, 145-147 mining 6, 22 Miocene, Gulf of Mexico mudstone 150-151 modelling Boltzmann 11, 116, 126-129, 159 coupled 14-18 dynamic 6, 13 fluid velocity fields 116, 129 geological heterogeneity current practice - scaling particle transport mixed finite element approximation 62, 64-67 velocity field measurement 116, 119-129 static 6, 13 monitoring, seismic 18-20 Monte Carlo simulation diffusion in fractal lattices 80 MOPOD 77 transport in heterogeneous porous media 62, 156 MOPOD model of porosity development 10, 73-77, 154-155 areas of application 75-77 MOPOD code 74 Moray Firth, fault cementation 9, 148 mud diagenesis 103 porosity 103 166 INDEX mudstone Miocene, Gulf of Mexico, microstructure evolution 150-151 Upper Cretaceous Shetland Group 104-114 anisotropy 104, 109-110, 112, 113 clay matrix 109-110, 111, 112-113 illite/smectite ratio 104-105, 108-109, 110, 112, 113 image analysis 105-107 microstructure evolution 150-151 mineralogy 107-108, 110 petrography 107-108 porosity 104, 107, 108, 112-113 Navan mine, palaeo-fluid flow 17-18, 148-149 Ninety Fathom fault, fault frequency distribution 45, 46 North Sea sandstone cementation 147-148 Upper Cretaceous Shetland Group mudstones 104-114, 105, 150-151 oil, chalk reservoirs 149-150 orientation fractures 35-37 minor faults 44 P-waves, azimuthal AVO analysis 29, 35, 36-37 particle transport see transport, particles percolation 13-14, 15, 17, 24, 75, 155, 159 threshold 11, 13-14, 19, 159 permeability bulk upscaled 147 fault damage zones 51-57 effect of diagenesis 9-10 effective 11 - 13 evolution in crystalline rock 159 fractures 10-18 matrix 11, 23, 30, 50, 91-92, 93 non-additive 11 persistence phyllosilicates, in mudstone 104 polymers, extracellular 131 - 132, 137-138, 140 poroelastic model 32-35 porosity development in fractures 10 development model (MOPOD) 73-77, 154-155 fractal dimension growth phenomena 74-75 matrix 32 mudstone 103-104, 107, 108, 112, 113 oil field sandstones 147-148 Pseudomonas aeruginosa PA01 133, 140, 142 pumping tests, Sierpinski carpets 79, 88, 153-154 quartz cementation 9, 147 see also sand, quartz random carpets 81-82, 82, 83 random field generation 62, 63, 156 random walks diffusion modelling 18, 79, 80, 81, 82, 83-88, 83, 154 effect of internal boundaries 87 Sierpinski carpets 82-88, 84, 85, 86, 154 reservoirs hydrocarbon chalk 149-150 criticality 24 modelling 6, discrete fracture network model 38-39 flow simulation 43, 51-57 monitoring 18- 21 sandstone cementation 147-148 sand, quartz, biofilm growth experiments 134, 135, 137 sandstone contaminant transport 43 quartz cementation 9, 147-148 Triassic, tracer test 92, 92, 93 scaling bulk permeability, fault damage zones 51-57 effect of diagenesis INDEX fluid flow in rough fractures 157-158 through complex geology 151-152 problems of extrapolation 115-116 well-log measurements 6-9 see also upscaling schist, fractured, tracer test 92, 92 Scott oil field, cementation of sandstone 148 seismic surveys 6, 152-153 see also anisotropy, seismic shear-wave splitting see splitting, shear wave Shetland Group mudstones 104-114, 105, 150-151 see also mudstone, Upper Cretaceous Shetland Group Sierpinski carpets 18, 80-88, 153-154 generation 80, 81 random walks 82-88, 84, 85, 86 smectite illite/smectite ratio 104-105, 108-109, 110, 112, 113 illitization 103-105, 113, 150-151 splitting, shear-wave 19, 29, 32, 35-36 squirt-flow 19, 32-34 stereolithography 119 stiffness, elastic 8, 32-33 strain, and effective bulk permeability 13 stress critical 15, 17, 24 effective 19 tailing behaviour 92-93, 101 Tara Mine, Navan, fluid flow paths 148-149 thermodynamics, equilibrium throw, fault damage zone 44, 47, 48, 50 tracer experiments 91,153 breakthrough curves 91-101, 97, 98, 99, 100-101, 153 167 transport contaminants 43, 73 dynamic 18 fluid, numerical modelling 61-70, 116 mass, advective 94 molecular diffusion 93 particles heterogeneous porous media 64-67 velocity fields 115-129 trace metal 143 upscaling bulk permeability 51-57 physical transport 61-70 Valhall field criticality 16 oil analysis 150 trace water analysis 16 velocity fields 2D measurement 122-129, 158-159 flowcell 116-117, 119-122 fractured-porous models 118, 124-125 self-affine fractures 117, 125-126 viscosity, fluid flow in fractured rock 11 waste, radioactive 6, 22 well tests see pumping tests well-log measurements, scaling - well-rate, fluctuation 20- 21 Yellow River Delta oil field, P-wave azimuthal AVO analysis 37 zinc-lead orebody, Navan, flow path analysis 148-149 Understanding the Micro to Macro Behaviour of Rock-Fluid Systems Edited by R P Shaw Understanding how fluids flow through though rocks is very important in a number of fields Almost all of the world's oil and gas are produced from underground reservoirs Knowledge of how they got where they are, what keeps them there and how they migrate through the rock is very important in the search for new resources, as well as for maximising the extraction of as much of the contained oil/gas as possible Similar understanding is important for managing groundwater resources and for predicting how hazardous or radioactive wastes or carbon dioxide will behave if stored or disposed of underground Unravelling the complex behaviour of fluids as they flow through rock is difficult, but important We cannot see through rock, so we need to predict how and where fluids flow Understanding the type of rock, its porosity, the character and pattern of fractures within it and how fluid flows through it are important Some contributors to this volume have been trying to understand real rocks in real situations and others have been working on computer models and laboratory simulations Put together, these approaches have yielded very useful results, many of which are discussed in this volume Visit our online bookshop: http://www.geolsoc.org.uk/bookshop Geological Society w e b site: http://www.geolsoc.org.uk !!1!!!!!1!11 ISBN fl-862S9- 86-6 Cover illustration: Background image is a section through a septarian nodule from the Oxford Clay, Latton, Wiltshire (Richard Shaw), top left image is calcite veins in LiassicLimestoneat Kilve, Somerset(Dave Sanderson), centre image is the cliffs at Burton Bradstock, Dorset (Neville Hollingworth) and lower right is an extract of a 3D seismic image of Sleipner, Norwegian sector of the North Sea (Andy Chadwick) ... purposes of this volume is to disseminate the principal results of the Natural Environment Research Council's (NERC) thematic programme 'Understanding the Micro to Macro Behaviour of Rock Fluid Systems' ,... Council's (NERC) thematic programme 'Understanding the Micro to Macro Behaviour of Rock- Fluid Systems' , commonly referred to as 'tx2M', and it forms part of the dissemination strategy of the programme... results of such profiling new software is able to derive statistical parameters of the profiles of fracture surfaces and of the aperture between pairs of surfaces, in order to relate these to fluid