This document provides an overview of fracture characterisation from borehole image logs. It discusses how fractures of different sizes, apertures, and mineral infills can be imaged using various borehole tools. Direct measurements that can be taken from images include fracture location, orientation, morphology, continuity and apparent aperture. Fracture descriptions should be ground-truthed with core data. The impact of fractures on reservoir performance can be both positive and negative. Analysis of fracture image data involves displaying and separating fractures into sets, analyzing factors like density and spacing, and developing a conceptual fracture model.
1) Seismic interpretation uses acoustic waves to image the subsurface by measuring the two-way travel time and amplitude of reflections. 2) A seismic source generates wavefronts that travel through the subsurface, reflecting or transmitting at interfaces between rock layers. 3) The amount of reflection depends on the relative difference in physical properties across interfaces, defined by reflection coefficients. Layers thinner than 1/4 the wavelength cannot be resolved individually.
Seismic data interpretation aims to tell the geologic story contained in seismic data by correlating seismic features with known geological elements. The summary outlines key concepts including:
1. Reflection, velocity, P and S waves, polarity, phase, resolution and detectability which influence seismic interpretation.
2. Depositional environments, rock types, faults and folds are interpreted from seismic data to understand the subsurface petroleum system.
3. Structural and stratigraphic interpretation including seismic attributes, multi-attribute logging, direct hydrocarbon indicators, and AVO/impedance inversion are used to characterize reservoirs.
The document discusses the basics of well logging design. It includes an agenda for a one-day course that covers basic logging theory, interpretation, logging program design, and a workshop. The objectives are to familiarize participants with various log measurements, well evaluation strategies, and approaches to well logging design. Key logging topics covered include definitions, history, measurement principles for resistivity, spontaneous potential, gamma ray, density, neutron, and acoustic logs. Interpretation applications and limitations are also discussed.
The fundamental part of the trap which is low-permeable to impermeable rock with a capillary entry pressure large enough to prevent the petroleum from migrating further is termed as Seal.
This document discusses rock typing, which involves classifying reservoir rocks into unique units based on their depositional environment and subsequent diagenetic changes that result in distinct porosity-permeability relationships. The document outlines the rock typing methodology, which includes selecting key wells, identifying rock types in those wells, predicting rock types in uncored sections, and modeling rock type distribution between wells. The document also discusses common pitfalls in rock typing and provides an example case study where rock typing was used to investigate high water cuts during production.
Quantitative and Qualitative Seismic Interpretation of Seismic Data Haseeb Ahmed
This document discusses quantitative and qualitative seismic interpretation techniques used to analyze seismic data and map subsurface geology. It compares traditional qualitative techniques to more modern quantitative techniques. It then focuses on unconventional seismic interpretation techniques used for unconventional reservoirs with low permeability, including AVO analysis, seismic inversion, seismic attributes, and forward seismic modeling. These techniques can help identify tight gas, shale gas, and gas hydrate reservoirs that conventional methods cannot easily detect. The document provides details on how each technique works and its advantages.
1) Seismic interpretation uses acoustic waves to image the subsurface by measuring the two-way travel time and amplitude of reflections. 2) A seismic source generates wavefronts that travel through the subsurface, reflecting or transmitting at interfaces between rock layers. 3) The amount of reflection depends on the relative difference in physical properties across interfaces, defined by reflection coefficients. Layers thinner than 1/4 the wavelength cannot be resolved individually.
Seismic data interpretation aims to tell the geologic story contained in seismic data by correlating seismic features with known geological elements. The summary outlines key concepts including:
1. Reflection, velocity, P and S waves, polarity, phase, resolution and detectability which influence seismic interpretation.
2. Depositional environments, rock types, faults and folds are interpreted from seismic data to understand the subsurface petroleum system.
3. Structural and stratigraphic interpretation including seismic attributes, multi-attribute logging, direct hydrocarbon indicators, and AVO/impedance inversion are used to characterize reservoirs.
The document discusses the basics of well logging design. It includes an agenda for a one-day course that covers basic logging theory, interpretation, logging program design, and a workshop. The objectives are to familiarize participants with various log measurements, well evaluation strategies, and approaches to well logging design. Key logging topics covered include definitions, history, measurement principles for resistivity, spontaneous potential, gamma ray, density, neutron, and acoustic logs. Interpretation applications and limitations are also discussed.
The fundamental part of the trap which is low-permeable to impermeable rock with a capillary entry pressure large enough to prevent the petroleum from migrating further is termed as Seal.
This document discusses rock typing, which involves classifying reservoir rocks into unique units based on their depositional environment and subsequent diagenetic changes that result in distinct porosity-permeability relationships. The document outlines the rock typing methodology, which includes selecting key wells, identifying rock types in those wells, predicting rock types in uncored sections, and modeling rock type distribution between wells. The document also discusses common pitfalls in rock typing and provides an example case study where rock typing was used to investigate high water cuts during production.
Quantitative and Qualitative Seismic Interpretation of Seismic Data Haseeb Ahmed
This document discusses quantitative and qualitative seismic interpretation techniques used to analyze seismic data and map subsurface geology. It compares traditional qualitative techniques to more modern quantitative techniques. It then focuses on unconventional seismic interpretation techniques used for unconventional reservoirs with low permeability, including AVO analysis, seismic inversion, seismic attributes, and forward seismic modeling. These techniques can help identify tight gas, shale gas, and gas hydrate reservoirs that conventional methods cannot easily detect. The document provides details on how each technique works and its advantages.
Formation evaluation and well logging are processes used to determine the properties of subsurface reservoirs and identify commercially viable oil and gas fields. Key logging tools developed over time include resistivity logs in the 1920s, dipmeters in the 1940s, gamma ray and neutron logs in the 1940s, sonic logs in the 1950s, density logs in the 1960s, and logging while drilling was introduced, allowing real-time data acquisition. The document provides a historical overview of the development of various openhole well logging tools and techniques.
This document provides an overview of formation evaluation techniques used in petroleum exploration and development. It discusses various logging methods like mud logging, coring, open-hole logging using electrical, nuclear and acoustic tools, logging while drilling, formation testing including wireline formation testing and drill stem testing, and cased-hole logging techniques. The goal of formation evaluation is to detect and quantify oil and gas reserves using measurements taken inside the wellbore and interpret physical properties of rocks and contained fluids.
Using 3-D Seismic Attributes in Reservoir Characterizationguest05b785
The document discusses using 3D seismic attributes for reservoir characterization. It provides an overview of seismic reflection methods and defines seismic attributes as any measurement derived from seismic data. Common types of attributes are described including time, complex trace, window, Fourier and multi-trace attributes. The document gives examples of attributes like envelope, phase, frequency and coherence that can provide information on lithology, thickness, faults and fractures. Methods of interpreting attribute data from 3D volumes are outlined. The document concludes by providing examples of how attributes can be used for reservoir characterization tasks like fault interpretation and porosity estimation.
This document provides information on using borehole images to analyze in-situ stress indicators. It discusses how breakouts and drilling-induced fractures in borehole images can reveal the orientation of the present-day stress field. Breakouts typically occur parallel to Shmin and indicate the minimum horizontal stress, while induced fractures occur parallel to SHmax and indicate the maximum horizontal stress. The document also covers how tools like microresistivity imagers, acoustic televiewers, and LWD tools can be used to directly observe these stress indicators and make stress orientation measurements. Additional indirect evidence from hole shape, tool motion, and defocused image pads can also provide insight into the in-situ stress field.
1. The document discusses various well logging tools and concepts used in petrophysical interpretation. It describes tools such as the spontaneous potential (SP) log, gamma ray (GR) log, resistivity logs including induction and lateral logs, and porosity logs.
2. Key concepts covered include the logging environment and factors that impact tool measurements like borehole conditions and mud properties. Interpretation techniques for evaluating permeable zones, formation resistivity, water saturation, and porosity are also summarized.
3. The document provides examples of using tools and concepts like the Archie formula to calculate water resistivity, determine hydrocarbon presence, and evaluate clean versus shaly formations. It also discusses corrections that must be applied to well log
Modern oil and gas field management is increasingly reliant on detailed and precise 3D reservoir characterisation, and timely areal monitoring. Borehole seismic techniques bridge the gap between remote surface-seismic observations and downhole reservoir evaluation: Borehole seismic data provide intrinsically higher-resolution, higher-fidelity images than surface-seismic data in the vicinity of the wellbore, and unique access to properties of seismic wavefields to enhance surface-seismic imaging. With the advent of new, operationally-efficient very large wireline receiver arrays; fiber-optic recording using Distributed Acoustic Sensing (DAS); the crosswell seismic reflection technique, and advanced seismic imaging algorithms such as Reverse Time Migration, a new wave of borehole seismic technologies is revolutionizing 3D seismic reservoir characterization and on-demand reservoir surveillance. New borehole seismic technologies are providing deeper insights into static reservoir architecture and properties, and into dynamic reservoir performance for conventional water-flood production, EOR, and CO2 sequestration – in deepwater, unconventional, full-field, and low-footprint environments. This lecture will begin by illustrating the wide range of borehole seismic solutions for reservoir characterization and monitoring, using a diverse set of current- and recent case study examples – through which the audience will gain an understanding of the appropriate use of borehole seismic techniques for field development and management. The lecture will then focus on DAS, explaining how the technique works; its capability to deliver conventional borehole seismic solutions (with key advantages over geophones); then describing DAS’s dramatic impact on field monitoring applications and business-critical decisions. New and enhanced borehole seismic techniques – especially with DAS time-lapse monitoring – are ready to deliver critical reservoir management solutions for your fields.
well logging tools and exercise_dileep p allavarapuknigh7
Logging is a process that provides comprehensive formation information through continuously recording parameter measurements with depth. It plays an important role in exploration and production by obtaining resistivity, porosity, and lithology logs to identify hydrocarbon-bearing zones. Different disciplines like drilling, logging, core analysis, and reservoir modeling are interrelated and provide both open and cased hole data. Logs are interpreted to calculate parameters like water saturation, hydrocarbon saturation, and effective porosity, with the goal of determining hydrocarbon saturation multiplied by effective porosity in reservoir units. Accurate interpretation requires integration of log data with core analysis and rock physics studies.
The Fullbore Formation MicroImager (FMI) instrument provides high resolution images of bedding and fractures in borehole walls. It uses electrical resistivity contrasts to image features around the borehole at vertical resolutions of 5 mm. FMI data is processed using Schlumberger software to correct speed, equalize histograms, and enhance images. FMI can be used for structural analysis, reservoir characterization of natural fractures and porosity, thin bed detection, and other applications. It images features like dips, fractures, vugs, laminations, and other sedimentological structures.
image logs were introduced by schlumberger in 1980.
these logs are advanced and most widely use in industry.
Image logs can provide detailed picture of the wellbore that represent the geological and petro physical properties of the section being logged.
The formation density tool provides a continuous record of a formation's bulk density along the length of a borehole. It works by emitting gamma rays into the formation, which are scattered via Compton scattering. The density measurement is used to derive porosity, with the main advantages being it compensates for mudcake and minor borehole issues. When combined with neutron logs, it provides one of the best ways to identify lithologies in a borehole. The tool has good vertical resolution but can be impacted by borehole quality, drilling mud properties, and shale content.
The document describes a high-definition formation microimager tool called the FMI-HD. It has new electronics and signal processing that provide clearer images in challenging environments like wells drilled with salt-saturated or oil-based muds. Case studies show it can image small fractures in carbonates drilled with oil-based mud and clearly identify structures in a well with very high resistive formations drilled with hyper saline water-based mud. The improved clarity allows better reservoir characterization.
Sonic logs measure the travel time of sound waves through formations to determine properties like porosity. There are four main wave types measured: compressional, shear, Stoneley, and mud waves. Early sonic tools had issues, but later tools like dual receiver and borehole compensated tools overcame problems by using multiple receivers and transmitters. Sonic logs can be used to calculate porosity through a simple relationship between travel time and porosity. They also provide qualitative insights into lithology, texture, compaction, and identifying fractures. Sonic logs help calibrate seismic data by providing very high resolution formation measurements.
Well logging involves lowering instruments into boreholes to record properties of rock formations. It provides critical information for oil and gas, groundwater, and mineral exploration. Key logs measure natural gamma radiation, electrical resistivity, acoustic properties, and nuclear properties like neutron count. Together these logs characterize porosity, lithology, fluid content and other formation features. Well logging has evolved significantly since the first electric log in 1927, with new tools, digital acquisition, and measurement-while-drilling capabilities. It remains a core technology for understanding subsurface geology.
The document discusses geomechanics applications throughout the lifecycle of oil and gas fields. It covers determining stress states, wellbore stability, fluid flow in fractured reservoirs, and 3D/4D geomechanical modeling. The author is Mark Zoback, a professor of geophysics at Stanford University who has published extensively on in situ stress measurements and their implications for wellbore stability, fault sealing, and induced seismicity from fluid injection.
The document describes seismic interpretation workflows, including conventional and unconventional techniques. Conventional techniques involve horizon interpretations, fault picking, and tying seismic data to well logs to understand subsurface geology. Unconventional techniques analyze seismic attribute variations like amplitudes to identify hydrocarbon indicators. The workflow includes generating synthetics from well logs, interpreting horizons on seismic sections, identifying structures like faults and gas chimneys, and determining direct hydrocarbon indicators.
The document provides an overview of principles of seismic data interpretation. It discusses fundamentals of seismic acquisition and processing such as seismic response, phase, polarity, reflections, and resolution. It also covers topics like structural interpretation pitfalls, seismic interpretation workflows involving building databases and time-depth relationships, and structural styles. The document includes sections on depth conversion, subsurface mapping techniques, and different types of velocities.
Well log interpretation involves using well log data to estimate reservoir properties. It has been used since the 1920s to qualitatively identify hydrocarbons and is now a quantitative tool. A key figure was Gustavus Archie who in the 1940s established the field of petrophysics by relating well logs to core data. His work allowed properties like porosity, permeability and fluid saturation to be estimated. A presentation on well log interpretation outlined the workflow including editing logs, estimating properties like shale volume, porosity, permeability and fluid saturation, and presented two case studies analyzing different carbonate reservoirs.
Migration from source to reservoir rocks is not fully understood. Hydrocarbons must replace water in reservoir pores during migration. Formation waters are usually ancient waters trapped during deposition. Salinity of formation waters generally increases with depth from 35,000 ppm to over 350,000 ppm. Primary migration out of low permeability source rocks is debated, with mechanisms including diffusion, microfractures, and oil-phase migration along organic-rich pathways.
This document outlines the process for reservoir characterization, which involves multi-disciplinary analyses including: 1) geological analyses of core data, well logs, and cross sections; 2) analysis of geological databases; 3) evaluation of source rock and rock mechanics; 4) geophysical evaluation and interpretation of seismic data; and 5) reservoir engineering analyses including completion and drilling evaluations. The results of these analyses will be integrated into reservoir models to identify potential infill locations and "sweet spots" with greater producibility potential.
Fractures can be imaged on borehole logs if they have sufficient contrast with the host rock and are intersected by the borehole. Fracture data from logs needs to be processed and analyzed to characterize fracture properties like orientation, density, spacing, and distribution. Fractures are classified and their properties like aperture are described based on direct measurements from logs. However, log interpretations of properties like open/closed need to be ground-truthed with core data, as logs can provide an incomplete picture on their own. Integrating fracture data from multiple logs and other data sources is important for fracture reservoir modeling and simulation.
The document discusses fracture analysis from borehole image logs. It describes how fractures appear on different types of logs and the limitations of using logs to characterize fractures. Fractures may be resolved if they are wider than the log's resolution and have sufficient contrast from the surrounding rock. The document also discusses classifying fractures based on their appearance, orientation, and other attributes observed from logs. Relating fractures to flow requires integrating log data with other data sources like core and production tests.
Formation evaluation and well logging are processes used to determine the properties of subsurface reservoirs and identify commercially viable oil and gas fields. Key logging tools developed over time include resistivity logs in the 1920s, dipmeters in the 1940s, gamma ray and neutron logs in the 1940s, sonic logs in the 1950s, density logs in the 1960s, and logging while drilling was introduced, allowing real-time data acquisition. The document provides a historical overview of the development of various openhole well logging tools and techniques.
This document provides an overview of formation evaluation techniques used in petroleum exploration and development. It discusses various logging methods like mud logging, coring, open-hole logging using electrical, nuclear and acoustic tools, logging while drilling, formation testing including wireline formation testing and drill stem testing, and cased-hole logging techniques. The goal of formation evaluation is to detect and quantify oil and gas reserves using measurements taken inside the wellbore and interpret physical properties of rocks and contained fluids.
Using 3-D Seismic Attributes in Reservoir Characterizationguest05b785
The document discusses using 3D seismic attributes for reservoir characterization. It provides an overview of seismic reflection methods and defines seismic attributes as any measurement derived from seismic data. Common types of attributes are described including time, complex trace, window, Fourier and multi-trace attributes. The document gives examples of attributes like envelope, phase, frequency and coherence that can provide information on lithology, thickness, faults and fractures. Methods of interpreting attribute data from 3D volumes are outlined. The document concludes by providing examples of how attributes can be used for reservoir characterization tasks like fault interpretation and porosity estimation.
This document provides information on using borehole images to analyze in-situ stress indicators. It discusses how breakouts and drilling-induced fractures in borehole images can reveal the orientation of the present-day stress field. Breakouts typically occur parallel to Shmin and indicate the minimum horizontal stress, while induced fractures occur parallel to SHmax and indicate the maximum horizontal stress. The document also covers how tools like microresistivity imagers, acoustic televiewers, and LWD tools can be used to directly observe these stress indicators and make stress orientation measurements. Additional indirect evidence from hole shape, tool motion, and defocused image pads can also provide insight into the in-situ stress field.
1. The document discusses various well logging tools and concepts used in petrophysical interpretation. It describes tools such as the spontaneous potential (SP) log, gamma ray (GR) log, resistivity logs including induction and lateral logs, and porosity logs.
2. Key concepts covered include the logging environment and factors that impact tool measurements like borehole conditions and mud properties. Interpretation techniques for evaluating permeable zones, formation resistivity, water saturation, and porosity are also summarized.
3. The document provides examples of using tools and concepts like the Archie formula to calculate water resistivity, determine hydrocarbon presence, and evaluate clean versus shaly formations. It also discusses corrections that must be applied to well log
Modern oil and gas field management is increasingly reliant on detailed and precise 3D reservoir characterisation, and timely areal monitoring. Borehole seismic techniques bridge the gap between remote surface-seismic observations and downhole reservoir evaluation: Borehole seismic data provide intrinsically higher-resolution, higher-fidelity images than surface-seismic data in the vicinity of the wellbore, and unique access to properties of seismic wavefields to enhance surface-seismic imaging. With the advent of new, operationally-efficient very large wireline receiver arrays; fiber-optic recording using Distributed Acoustic Sensing (DAS); the crosswell seismic reflection technique, and advanced seismic imaging algorithms such as Reverse Time Migration, a new wave of borehole seismic technologies is revolutionizing 3D seismic reservoir characterization and on-demand reservoir surveillance. New borehole seismic technologies are providing deeper insights into static reservoir architecture and properties, and into dynamic reservoir performance for conventional water-flood production, EOR, and CO2 sequestration – in deepwater, unconventional, full-field, and low-footprint environments. This lecture will begin by illustrating the wide range of borehole seismic solutions for reservoir characterization and monitoring, using a diverse set of current- and recent case study examples – through which the audience will gain an understanding of the appropriate use of borehole seismic techniques for field development and management. The lecture will then focus on DAS, explaining how the technique works; its capability to deliver conventional borehole seismic solutions (with key advantages over geophones); then describing DAS’s dramatic impact on field monitoring applications and business-critical decisions. New and enhanced borehole seismic techniques – especially with DAS time-lapse monitoring – are ready to deliver critical reservoir management solutions for your fields.
well logging tools and exercise_dileep p allavarapuknigh7
Logging is a process that provides comprehensive formation information through continuously recording parameter measurements with depth. It plays an important role in exploration and production by obtaining resistivity, porosity, and lithology logs to identify hydrocarbon-bearing zones. Different disciplines like drilling, logging, core analysis, and reservoir modeling are interrelated and provide both open and cased hole data. Logs are interpreted to calculate parameters like water saturation, hydrocarbon saturation, and effective porosity, with the goal of determining hydrocarbon saturation multiplied by effective porosity in reservoir units. Accurate interpretation requires integration of log data with core analysis and rock physics studies.
The Fullbore Formation MicroImager (FMI) instrument provides high resolution images of bedding and fractures in borehole walls. It uses electrical resistivity contrasts to image features around the borehole at vertical resolutions of 5 mm. FMI data is processed using Schlumberger software to correct speed, equalize histograms, and enhance images. FMI can be used for structural analysis, reservoir characterization of natural fractures and porosity, thin bed detection, and other applications. It images features like dips, fractures, vugs, laminations, and other sedimentological structures.
image logs were introduced by schlumberger in 1980.
these logs are advanced and most widely use in industry.
Image logs can provide detailed picture of the wellbore that represent the geological and petro physical properties of the section being logged.
The formation density tool provides a continuous record of a formation's bulk density along the length of a borehole. It works by emitting gamma rays into the formation, which are scattered via Compton scattering. The density measurement is used to derive porosity, with the main advantages being it compensates for mudcake and minor borehole issues. When combined with neutron logs, it provides one of the best ways to identify lithologies in a borehole. The tool has good vertical resolution but can be impacted by borehole quality, drilling mud properties, and shale content.
The document describes a high-definition formation microimager tool called the FMI-HD. It has new electronics and signal processing that provide clearer images in challenging environments like wells drilled with salt-saturated or oil-based muds. Case studies show it can image small fractures in carbonates drilled with oil-based mud and clearly identify structures in a well with very high resistive formations drilled with hyper saline water-based mud. The improved clarity allows better reservoir characterization.
Sonic logs measure the travel time of sound waves through formations to determine properties like porosity. There are four main wave types measured: compressional, shear, Stoneley, and mud waves. Early sonic tools had issues, but later tools like dual receiver and borehole compensated tools overcame problems by using multiple receivers and transmitters. Sonic logs can be used to calculate porosity through a simple relationship between travel time and porosity. They also provide qualitative insights into lithology, texture, compaction, and identifying fractures. Sonic logs help calibrate seismic data by providing very high resolution formation measurements.
Well logging involves lowering instruments into boreholes to record properties of rock formations. It provides critical information for oil and gas, groundwater, and mineral exploration. Key logs measure natural gamma radiation, electrical resistivity, acoustic properties, and nuclear properties like neutron count. Together these logs characterize porosity, lithology, fluid content and other formation features. Well logging has evolved significantly since the first electric log in 1927, with new tools, digital acquisition, and measurement-while-drilling capabilities. It remains a core technology for understanding subsurface geology.
The document discusses geomechanics applications throughout the lifecycle of oil and gas fields. It covers determining stress states, wellbore stability, fluid flow in fractured reservoirs, and 3D/4D geomechanical modeling. The author is Mark Zoback, a professor of geophysics at Stanford University who has published extensively on in situ stress measurements and their implications for wellbore stability, fault sealing, and induced seismicity from fluid injection.
The document describes seismic interpretation workflows, including conventional and unconventional techniques. Conventional techniques involve horizon interpretations, fault picking, and tying seismic data to well logs to understand subsurface geology. Unconventional techniques analyze seismic attribute variations like amplitudes to identify hydrocarbon indicators. The workflow includes generating synthetics from well logs, interpreting horizons on seismic sections, identifying structures like faults and gas chimneys, and determining direct hydrocarbon indicators.
The document provides an overview of principles of seismic data interpretation. It discusses fundamentals of seismic acquisition and processing such as seismic response, phase, polarity, reflections, and resolution. It also covers topics like structural interpretation pitfalls, seismic interpretation workflows involving building databases and time-depth relationships, and structural styles. The document includes sections on depth conversion, subsurface mapping techniques, and different types of velocities.
Well log interpretation involves using well log data to estimate reservoir properties. It has been used since the 1920s to qualitatively identify hydrocarbons and is now a quantitative tool. A key figure was Gustavus Archie who in the 1940s established the field of petrophysics by relating well logs to core data. His work allowed properties like porosity, permeability and fluid saturation to be estimated. A presentation on well log interpretation outlined the workflow including editing logs, estimating properties like shale volume, porosity, permeability and fluid saturation, and presented two case studies analyzing different carbonate reservoirs.
Migration from source to reservoir rocks is not fully understood. Hydrocarbons must replace water in reservoir pores during migration. Formation waters are usually ancient waters trapped during deposition. Salinity of formation waters generally increases with depth from 35,000 ppm to over 350,000 ppm. Primary migration out of low permeability source rocks is debated, with mechanisms including diffusion, microfractures, and oil-phase migration along organic-rich pathways.
This document outlines the process for reservoir characterization, which involves multi-disciplinary analyses including: 1) geological analyses of core data, well logs, and cross sections; 2) analysis of geological databases; 3) evaluation of source rock and rock mechanics; 4) geophysical evaluation and interpretation of seismic data; and 5) reservoir engineering analyses including completion and drilling evaluations. The results of these analyses will be integrated into reservoir models to identify potential infill locations and "sweet spots" with greater producibility potential.
Fractures can be imaged on borehole logs if they have sufficient contrast with the host rock and are intersected by the borehole. Fracture data from logs needs to be processed and analyzed to characterize fracture properties like orientation, density, spacing, and distribution. Fractures are classified and their properties like aperture are described based on direct measurements from logs. However, log interpretations of properties like open/closed need to be ground-truthed with core data, as logs can provide an incomplete picture on their own. Integrating fracture data from multiple logs and other data sources is important for fracture reservoir modeling and simulation.
The document discusses fracture analysis from borehole image logs. It describes how fractures appear on different types of logs and the limitations of using logs to characterize fractures. Fractures may be resolved if they are wider than the log's resolution and have sufficient contrast from the surrounding rock. The document also discusses classifying fractures based on their appearance, orientation, and other attributes observed from logs. Relating fractures to flow requires integrating log data with other data sources like core and production tests.
This document discusses fracture interpretation from borehole images. It covers which fractures can be imaged, how fractures are described and classified from images, and how fracture properties like aperture and distribution are analyzed. Key points made include that fractures must have sufficient contrast to be imaged, different classification schemes exist (e.g. by response and morphology), and that ground-truthing like core calibration is important for interpretation. Flow patterns and equations for relating resistivity measurements to fracture aperture are also summarized.
- Fractures will appear on borehole images if they have sufficient contrast with the host rock in properties like density, resistivity, or texture, and are intersected by the borehole.
- Fracture interpretation from images involves describing attributes like location, orientation, morphology, aperture, and relationships to other fractures and features. It also involves classifying fractures and relating them to flow or reservoir properties.
- Accurately resolving fracture width and orientation from images requires accounting for tool resolution and effects of current channeling around conductive fractures that can make them appear larger.
Lyapichev. Analysis, design & behavior of CFRDsYury Lyapichev
This document provides information on the analysis, design, behavior, and seismic resistance of concrete face rockfill dams (CFRDs). It discusses numerical modeling of CFRDs, stresses in the concrete face and underlying transition zones, and the effects of high compressibility of rockfill materials. It also summarizes general recommendations for dynamic analysis and design of high CFRDs in seismic regions, including use of roller compacted concrete to reduce concrete face deformation. A new design for the 275m high Kambarata-1 CFRD in Kyrgyzstan incorporates this technique to improve seismic safety.
Lyapichev: Analysis, design & behavior of CFRDsYury Lyapichev
Comprehensive numerical analysis, design & behavior of some high concrete face rockfill dams (CFRDs) are given including recommendations for improvement their safety in seismic regions .
Cracks on concrete.
How to catergorized cracks on newly poured concrete
Thermal cracks
Mass concrete
Fresh concrete
Cracks on concrete have many causes. They may affect appearance only, or it may indicate significant structural distress
This document discusses different methods for classifying rock discontinuities based on their genesis and mechanical properties. There are two main bases for classification - geological genetic classification which specifies the type of discontinuity, and classification based on mechanical characteristics. Several rock mass classification systems are also presented, including the South African Geomechanics Classification system which divides rock masses into units with similar properties and assigns ratings to parameters like strength, fracturing and groundwater to determine an overall rock quality. While useful, no single system is applicable to all rock types and conditions.
1. The document discusses understanding the role of damage mechanisms and kinematics in large landslides.
2. Damage occurs both externally in the slope and internally through fracturing, and there are various types of damage related to factors like slope geometry and lithology.
3. Kinematics influence the failure mechanism and volume, and both damage and kinematics must be considered and modeled to understand landslide mechanics.
non destructive testing review for detection of creep damage in power plant s...Pintu Kumar
This document discusses non-destructive techniques for detecting creep damage in power plant steels. It describes creep as time-dependent deformation of materials under high stress and temperature. Several techniques are examined, including replication, ultrasonics, positron annihilation, magnetic methods, eddy current, potential drop, and X-ray diffraction. Ultrasonics using backscatter and Barkhausen emission/magneto-acoustic emission show potential for localizing creep damage in ferromagnetic materials. Potential drop techniques may be able to detect creep damage earlier than conventional methods. No single technique is ideal and limitations exist for subsurface defect detection and distinguishing creep damage from other microstructural changes.
Underground rock reinforcement and supportBalraj Joshi
This document discusses underground excavation stability and rock reinforcement. It begins by explaining that rock mass behavior is simplified for analysis by treating it as continuous, homogeneous, isotropic and linearly elastic, rather than its actual discontinuous, non-homogeneous, anisotropic and nonlinearly elastic properties. It then discusses how excavation affects stress conditions by removing rock and requiring loads to transfer elsewhere. Various numerical modeling approaches are presented for analyzing stresses, displacements and failed zones, including continuum and discontinuous methods. The document concludes by emphasizing that rock support design requires an engineering judgment approach due to the complexities involved.
Rocks mechanics and its application in mining geology.
It aims at enhancing the mining process and higher yielding by reducing the chance of failures by providing information about the rocks of the mining area.
Geomechanical Modeling Abu Dhabi Commentsssuser886c55
Fractured reservoirs can be categorized into four types based on how fractures impact porosity and permeability. Type 1 reservoirs have fractures providing essential porosity and permeability since the rock matrix has little. Type 2 reservoirs have fractures providing essential permeability with the matrix providing porosity. Type 3 reservoirs have fractures providing additional permeability to an already productive matrix. Type 4 reservoirs have fractures creating barriers rather than improving flow. Recognition of the reservoir type is important for evaluating reserves, predicting production behavior, and designing development plans.
Rock mechanics for engineering geology part 1Jyoti Khatiwada
Rock mass classification systems are used to characterize rock masses for engineering design and stability analysis. The key systems discussed include the Rock Mass Rating (RMR) system, Q-system, Slope Mass Rating (SMR), and the New Austrian Tunnelling Method (NATM) classification. These systems aim to identify significant rock mass parameters, divide rock masses into classes of similar quality, and provide guidelines for design and communication between engineers and geologists. The advantages and limitations of each system are reviewed.
1) The document discusses structural damage detection in concrete slabs using a wavelet approach. It covers different types of slabs and common failures like cracking, crazing, curling.
2) It introduces yield line analysis and non-destructive testing methods to analyze slabs. Finite element software ANSYS and MATLAB toolbox are used to model and analyze slabs under static and dynamic loads.
3) Wavelet analysis is discussed as an approach to analyze time history responses of structures subjected to dynamic loads, which can provide information about the structure and loads in the signal.
The document discusses building maintenance, common defects, and remedial methods for RCC structures. It describes three main common defects: foundations, walls, and concrete/RCC frames. For foundations, common issues include differential settlement, uplift of shrinkage soil, and dampness. For walls, issues include cracking, dampness penetration, and failure during cyclones. For concrete frames, common problems discussed are seepage/leakage, spalling of concrete, and corrosion of steel reinforcement. The document provides detailed remedial methods and guidelines for investigating and classifying structural damage to determine appropriate restoration methods.
The document discusses building maintenance, common defects, and remedial methods for RCC structures. It describes three main common defects: foundations, walls, and concrete/RCC frames. For foundations, common issues include differential settlement, uplift of shrinkage soil, and dampness. For walls, issues include cracking, dampness penetration, and failure during cyclones. For concrete frames, common problems discussed are seepage/leakage, spalling of concrete, and corrosion of steel reinforcement. The document provides detailed remedial methods for addressing each of these defects.
This document discusses the importance of geomechanics in understanding unconventional reservoirs. It covers topics such as natural fractures, mechanical rock properties, stress regimes, and how they impact horizontal drilling, hydraulic fracturing, and reservoir productivity. Natural fractures are especially important in tight formations as they can provide permeability and introduce anisotropy. The document also provides classifications of fractured reservoirs and naturally occurring fractures.
Assessing the Collapse Hazard of Base Isolated Buildings Considering Pounding...EERI
This document discusses assessing the collapse hazard of base isolated buildings considering pounding to moat walls using the FEMA P695 methodology. Key points:
1) Experimental shake table tests were conducted on a 1/4 scale base isolated model with different concrete wall thicknesses to examine the effect of wall stiffness on pounding behavior.
2) Numerical models were developed including a simplified moat wall model, isolator models, and 3D superstructure model.
3) Nonlinear static (pushover) and dynamic (response history) analyses were performed and collapse evaluation was conducted in accordance with FEMA P695, calculating parameters like period-based ductility and spectral shape factor.
M.Sc. Thesis of Gokturk Mehmet Dilci
Effect of Load Path on Mode of Failure at the Brittle-Ductile Transition İn Well-Sorted Aggregates of St Peters Sand
Similar to 6a - Fracture characterisation.ppt (20)
The document summarizes hydrocarbon exploration activities offshore Cyprus and plans for developing a natural gas discovery. It notes that Noble Energy discovered an estimated 7 trillion cubic feet gas field in 2011 (Block 12) and plans to conduct appraisal drilling in 2013. It outlines next steps for upstream development, pipelines to transport gas to Cyprus by 2017-2018, and plans to establish an onshore LNG plant by 2019 to export gas to Europe and beyond. The discovery could significantly change Cyprus' energy profile if additional discoveries are made through a second offshore licensing round.
This document discusses key concepts related to ore deposits and ore-forming processes. It defines mineralization as the geological formation of economic minerals in a lithological unit through natural earth processes. For a mineralization to be considered a mineral deposit, it must meet minimum thresholds for metal quantity and grade. Ore deposits are classified based on characteristics like host rock, mineral assemblage, size, and geological formation process. Metals are sourced from crustal or mantle rocks, transported by aqueous fluids complexed with ligands, and concentrated at deposition sites where drastic changes in pressure, temperature, or fluid composition occur. Driving forces include heat from volcanic or plutonic activity and fluid flow influenced by topography or geothermal gradients.
The document discusses subaerial unconformities visible in outcrops and provides examples from various locations around the world. Key criteria to identify subaerial unconformities include evidence of exposure like paleosols, erosion and truncation of underlying strata, paleotopography, and onlap of overlying strata. Photos show unconformities with regolith development, karst features, and basal conglomerates that onlap eroded surfaces. Forced regressive surfaces of marine erosion are also discussed and depicted in outcrops showing scoured contacts and shoreface sandstone wedges.
The document describes several landforms produced by wave erosion along coastlines, including headlands, bays, wave-cut notches, wave-cut platforms, arches, caves, stacks, and blowholes. Headlands are areas that jut out into the sea, often ending in cliffs, while bays are wide curved inlets. Wave action can erode cliffs from below, forming platforms, notches, arches that eventually collapse into stacks and stumps. Blowholes form through joints in cliff rocks exposed to hydraulic action inside wave-eroded caves.
Waves eroding a coastline of varying rock resistance will form headlands of harder rock separated by bays in weaker rock. Landforms produced by wave erosion include headlands, bays, stacks, caves, arches, pillars, and wave-cut platforms and notches. Caves can develop into blowholes if joints in the rock connect the cave to the cliff top.
The document describes several landforms produced by wave erosion along coastlines including:
- Stacks, which are pillars of rock isolated from the cliff due to wave erosion.
- Headlands, which are parts of the coastline that jut out into the sea, often ending in cliffs.
- Bays, which are wide curved inlets formed along coastlines with weaker, more erodible rock.
- Arches and caves, which are openings formed when waves erode through headlands or into cliffs.
Waves erode cliffs and headlands through various processes, forming different coastal landforms. Caves form where waves attack both sides of headlands. Arches may form if caves erode all the way through. Stacks and stumps are left when arches and stacks eventually collapse. Over time, this differential erosion of harder and weaker rocks creates a series of alternating headlands and bays along the coastline.
This document describes several landforms produced by wave erosion along coastlines:
- Headlands jut out into the sea at the end of cliffs. Bays form sheltered inlets in weaker coastal rocks between headlands.
- Arches form when waves erode caves completely through headlands. Stacks are isolated pillars that remain when arches collapse.
- Other landforms include caves undercut at the base of cliffs, wave-cut platforms of gently sloping land left after cliff retreat, and blowholes which form when joints in cliff rocks connect eroded caves to the surface.
The document describes various landforms produced by wave erosion along coastlines including headlands, bays, wave-cut notches, wave-cut platforms, arches, caves, stacks, and blowholes. It explains how waves erode harder and softer rocks at different rates, forming headlands in harder rocks and sheltered bays in weaker rocks. Arches form when waves erode caves through headlands, and stacks remain when arches collapse, eventually becoming stumps.
Stratigraphic principles and sequence stratigraphy are methods used to analyze sedimentary rock layers and impose a temporal dimension. Key concepts include:
- Steno's laws of superposition, original horizontality, and lateral continuity which describe how sedimentary layers are deposited.
- Sequence stratigraphy subdivides strata using surfaces that represent changes in relative sea level, including sequence boundaries, maximum flooding surfaces, and systems tracts like transgressive and highstand.
- Facies describe the characteristics of sediment deposited in different environments, and sequence stratigraphy studies the geometric relationships between facies belts to interpret depositional history.
Submarine canyons cut across continental shelves and slopes, carrying sediment from rivers and coastal areas to deep ocean basins. Submarine fans form at the mouths of canyons, accumulating sediment across the continental slope in a fan-shaped pattern. Sediment transport within submarine fans occurs through various mechanisms like debris flows, density currents, and turbidity currents, resulting in deposition of turbidite sequences that can be studied to understand ancient submarine fan environments.
This document summarizes a study of the Floridan Aquifer/Chipola River System funded by the USGS and FDEP. The objectives are to identify nutrient sources to the aquifer, characterize hydrologic transport processes using modeling, and match nitrate concentrations in springs using the model. The study area includes the Dougherty Karst Plain where the Floridan Aquifer is recharged through sinkholes and rivers. A MODFLOW model is being used to simulate nitrate tracking from recharge areas and calibrate to spring discharge concentrations. Local grid refinement is being added to improve flow path and travel time estimates in key springs.
Sediments form through the weathering and erosion of rocks, followed by transportation and deposition. There are three main types of sediments: mechanical (clastic), chemical, and organic. Sedimentary rocks form through the compaction and cementation of sediments via the process of diagenesis. Sedimentology involves the study of sediment formation and depositional environments, while stratigraphy examines the temporal and spatial relationships between sedimentary strata. Key methods used in sedimentology include facies analysis, particle size and shape analysis, lithological analysis, and stratigraphic mapping and description.
This document discusses key petrophysical properties of hydrocarbon-bearing reservoir rocks including porosity, permeability, saturation, and capillarity. It defines porosity as the ratio of pore space to total volume, permeability as the ability of rocks to allow fluid flow through interconnected pores, saturation as the volume of pore space occupied by a fluid, and capillarity as the pressure difference between fluids across curved interfaces in rock pores. Accurate analysis and modeling of these petrophysical properties is important for estimating petroleum reserves and recovery efficiency from reservoirs.
This document provides an overview of facies analysis and depositional environments in sedimentary geology. It discusses different facies interpretations of successive units in non-marine sandstones, including planar and trough cross-bedding, asymmetric scour surfaces, and rippled sandstone and mudstone. It also examines a transect of a Permian reef margin and hierarchy of depositional units, including migrating dunes, changes in hydraulic regime, lag accumulation, bar migration, channel erosion, and allogenic events driven by tectonics, eustasy, climate. Adjacent environments can result in vertical successions with different sedimentary structures.
The document discusses reservoir petrophysics, which is the study of rock properties and interactions with fluids. It describes a course on reservoir petrophysics that systematically studies physical rock properties including porosity, permeability, fluid saturation, and fluid-rock interactions. The course objectives are to define key concepts and demonstrate techniques for determining properties like porosity, permeability, and fluid saturation through experiments and calculations.
The document discusses various methods used to prevent sloughing during well drilling operations. Specifically:
1. Circulating refrigerating fluid through the well below the freezing point of the formation to freeze it and prevent sloughing.
2. Circulating brine through the well below the freezing point of water to freeze the formation.
3. Circulating mud-laden fluid through the well below the freezing point of water to freeze the formation.
4. Circulating an emulsion through the well below the freezing point of water to freeze the formation.
5. Causing fluid to flow into the well to seep into the formation, then circulating it below the freezing point of water to freeze the formation
The document discusses methods for drilling wells through formations containing sloughing shale to prevent borehole collapse.
It describes 6 methods:
1. Circulating refrigerated fluid through the well to freeze the formation, with the refrigerant having a freezing point below that of the formation fluid.
2. Circulating brine through the well and cooling it to freeze the formation, with the brine's freezing point below that of water.
3. Circulating mud-laden fluid through the well in the same way as method 2.
4. Circulating an emulsion through the well in the same way as methods 2 and 3.
5. Causing fluid to flow into the well to contact
The document discusses the problem of sloughing shale during drilling operations. Sloughing shale occurs when the mud weight is not adequate to control subsurface pressure or the mud salinity causes undesirable osmotic pressure, leading to borehole collapse and stuck drill pipes or bottom hole assembly (BHA). It states that sloughing shale is one of the mechanical issues that can cause stuck pipes. The author provides a personal anecdote about experiencing BHA getting stuck in sloughing shale for the first time and seeing large cuttings, which was shocking. While shale formations can be drilled quickly when conditions are right, sloughing shale turns it into a stressful problem similar to kicks, losses, and other drilling hazards. Close
This document discusses carbonate sedimentology and classification. It summarizes two early carbonate classification systems by Dunham (1962) and Folk (1962). It also notes that while interpretation techniques used for clastic reservoirs can be applied to carbonates, carbonates differ in their importance of biogenic processes and susceptibility to diagenesis. The document stresses that the ultimate goal is understanding carbonate lithofacies and correlating them with well log and core data.
TIME DIVISION MULTIPLEXING TECHNIQUE FOR COMMUNICATION SYSTEMHODECEDSIET
Time Division Multiplexing (TDM) is a method of transmitting multiple signals over a single communication channel by dividing the signal into many segments, each having a very short duration of time. These time slots are then allocated to different data streams, allowing multiple signals to share the same transmission medium efficiently. TDM is widely used in telecommunications and data communication systems.
### How TDM Works
1. **Time Slots Allocation**: The core principle of TDM is to assign distinct time slots to each signal. During each time slot, the respective signal is transmitted, and then the process repeats cyclically. For example, if there are four signals to be transmitted, the TDM cycle will divide time into four slots, each assigned to one signal.
2. **Synchronization**: Synchronization is crucial in TDM systems to ensure that the signals are correctly aligned with their respective time slots. Both the transmitter and receiver must be synchronized to avoid any overlap or loss of data. This synchronization is typically maintained by a clock signal that ensures time slots are accurately aligned.
3. **Frame Structure**: TDM data is organized into frames, where each frame consists of a set of time slots. Each frame is repeated at regular intervals, ensuring continuous transmission of data streams. The frame structure helps in managing the data streams and maintaining the synchronization between the transmitter and receiver.
4. **Multiplexer and Demultiplexer**: At the transmitting end, a multiplexer combines multiple input signals into a single composite signal by assigning each signal to a specific time slot. At the receiving end, a demultiplexer separates the composite signal back into individual signals based on their respective time slots.
### Types of TDM
1. **Synchronous TDM**: In synchronous TDM, time slots are pre-assigned to each signal, regardless of whether the signal has data to transmit or not. This can lead to inefficiencies if some time slots remain empty due to the absence of data.
2. **Asynchronous TDM (or Statistical TDM)**: Asynchronous TDM addresses the inefficiencies of synchronous TDM by allocating time slots dynamically based on the presence of data. Time slots are assigned only when there is data to transmit, which optimizes the use of the communication channel.
### Applications of TDM
- **Telecommunications**: TDM is extensively used in telecommunication systems, such as in T1 and E1 lines, where multiple telephone calls are transmitted over a single line by assigning each call to a specific time slot.
- **Digital Audio and Video Broadcasting**: TDM is used in broadcasting systems to transmit multiple audio or video streams over a single channel, ensuring efficient use of bandwidth.
- **Computer Networks**: TDM is used in network protocols and systems to manage the transmission of data from multiple sources over a single network medium.
### Advantages of TDM
- **Efficient Use of Bandwidth**: TDM all
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELgerogepatton
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
International Conference on NLP, Artificial Intelligence, Machine Learning an...gerogepatton
International Conference on NLP, Artificial Intelligence, Machine Learning and Applications (NLAIM 2024) offers a premier global platform for exchanging insights and findings in the theory, methodology, and applications of NLP, Artificial Intelligence, Machine Learning, and their applications. The conference seeks substantial contributions across all key domains of NLP, Artificial Intelligence, Machine Learning, and their practical applications, aiming to foster both theoretical advancements and real-world implementations. With a focus on facilitating collaboration between researchers and practitioners from academia and industry, the conference serves as a nexus for sharing the latest developments in the field.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
2. Structure 2/2
• Introduction
• Which fractures might be imaged?
• Direct measurement and description
of fractures from borehole images
• Ground-truthing with core or outcrop
• Analysis of results
• Data integration
Outline
3. Structure 2/3
The impact of fractures on reservoir performance
Good
• Fractured reservoirs can be
prolific (e.g. Asmari Fm, Iran)
• Open fractures may sustain
high flow rates (e.g. Ekofisk
Fm, Norwegian North Sea)
• Hydrocarbons found in
basement where otherwise
unproducable (e.g. granitic
basement in Vietnam)
• Closed fractures can
increase sweep tortuosity
and so improve overall
sweep effectiveness
• Sealing faults can produce
structural traps
Bad
• Sealing faults lead to reservoir
compartmentalisation and
unswept oil
• Closed fractures baffle
perpendicular flow
• Open fractures act as thief zones
within injectors – early water
breakthrough
• Dual porosity systems – initial
fracture contribution may be high
but subsequent matrix
contribution slow; injector
planning critical to later
production
• Fractures and faults may
adversely affect well stability
5. Structure 2/5
Where do images fit?
15
m
1
cm
Borehole
images
and
dipmeters
3D seismic
Core
Fault throw (m)
Cumulative
fault
density
(faults
per
km)
0.01
1
100
10000
10000
100
1
0.01
Real geology and
limitless resolution
but limited coverage
& hard to see large
structure
VSP
Fractures detected
down to 10s of mm
and imaged to 5
mm, runs of 1000s
of metres, allows
large structure to be
inferred
Fractures unlikely
to be detected; only
faults and fracture
corridors over 10
metres wide.
Provides large-
scale structure
Seismic at a finer
scale, sees smaller
faults but scale too
coarse to image
fracture network
6. Structure 2/6
Increased compartmentalisation
Permeability barriers, baffles
Increased communication
Permeability conduits
Add to understanding of structural trends which are
significant within the reservoir.
Generally un-resolved on seismic (<10m throw), but
seen in core.
GO
The importance of sub-seismic faults
7. Structure 2/7
Images & core
Fracture model
Reservoir simulation
mapped seismic
faults
Cemented
Partially cemented;
vuggy
Closed
Mudstone
shear
Open
Unlithified
breccia
Cement
fault seals
Phyllosilicate
fault seals
Cataclastic
fault seals
Cataclastic
Fracture types and properties
The impact of images
8. Structure 2/8
Data processing
Quality control
Fracture effect on flow
• Visual appearance
• Match with direct/indirect flow indicators
Fracture distribution
• Raw fracture density
• Corrected fracture density
• Fracture spacing
• Fracture distribution statistics
Image description
• Fracture identification
• Classification
• Orientation
• Additional attributes
Upscaling/prediction
• Damage zone widths
• Recognition of seismic and
subseismic scale faults
• Relationship to major structures
FRACTURED RESERVOIR MODELLING
Raw image
log data
Core
Log data
Stratigraphy
Seismic sections
and maps
Core
Mudloss
Sonic waveforms
Dynamic data
Stage 1
Stage 2 Stage 3
Fracture interpretation workflow
10. Structure 2/10
A fracture will be imaged if…
• It is broader than the minimum intrinsic tool
resolution
• It has sufficiently contrasting properties compared
to the host rock; density and/or textural contrast
for acoustic tools and resistivity contrast for
electrical tools
• Due to the presence of a mineral infill, reduction in
grain size and/or preferential cementation around
closed fractures
• Due to the difference in properties between the drilling
fluid and the host rock across open fractures
• It is intersected by the borehole
11. Structure 2/11
Resolving fractures
• Function of tool sample rate
• Sensor size (electrical tools)
• Beam spot size (acoustic tools)
• For electrical images operating under ideal conditions, resolution
approaches button size.
• Current distortion by strong contrast features has the following effects:-
• Features below the intrinsic tool resolution down to around 10 μm may
dominate the pixel response of a sample and therefore be detected but
their true width and location within the image pixel is unresolved
• Conductive fractures draw in current and so appear larger than they really
are, with a resistive halo surrounding the fracture
• Conductive fractures have a greater depth of penetration than the
surrounding matrix and so may be steeper than they appear from images
• Resistive fractures repel current and so appear smaller than they really are
• These issues may be reduced by running acoustic and electrical tools
together (STAR-CBIL and Earth Imager-CBIL)
14. Structure 2/14
Fracture description from borehole images
Direct measurements and observations
• Location of fracture, measured depth
• Fracture attitude as dip and dip direction
• Fracture category based on characteristics listed below
• Interpretation confidence
• Tool response: resistive/conductive if microresistivity, high/low
amplitude and long/short transit time if acoustic.
• Morphology, e.g. irregular, vuggy, etc.
• Continuity: continuous, terminates within borehole, discontinuous
within borehole (discrete segments), etc.
• Apparent aperture & thickness
• Relationship to bedding and other fractures: cross-cutting
relationships, offsets, terminations, intersection orientations
15. Structure 2/15
Terminology
Fracture
Natural
Induced
Fault
Microfault
Joint
Failure plane accommodating
strain resulting from tectonism,
thermal stresses, compaction, etc.
Present in the pristine,
formation and relating to
geological phenomena
Formed in response
to drilling operations
and not geological
Fracture with no
offset of wall rocks
and often due to
dilation
Fracture with shear offset
displacing hanging- and foot-walls
Occasionally used to denote
faults with a small offset on
a centimetre scale
16. Structure 2/16
Fracture categories
Descriptive schemes
• Response only
high, amplitude fracture
• Response and offset
resistive microfault
• Response, offset and morphology
discontinuous low-amplitude fracture
thick continuous conductive fracture
Interpretive schemes
• Inferred aperture (caution!)
thick open fracture, cemented fracture
• Geological interpretation (following core calibration)
granulation seam, vuggy fracture
FIT FOR PURPOSE
18. Structure 2/18
Resistive fault
Resistive fracture
Conductive fractures
Resistive fractures?
M M
Continuous
Irregular trace
Width mm-cm?
Offset circa 8-10 cm
Splays (riedel/antiriedel?)
No displacement
Hairline
Regular trace (planar)
Discontinuous
Terminates at fault
Discontinuous
Layer-bound?
Form connected network
Variable width
Weak fabric
Resistive
Fracture description
19. Structure 2/19
Fracture morphologies in a carbonate reservoir
Luthi, 2000
Planar
Variable
width ‘blebs’
Bedding-
confined
Wide
conductive Breccia
20. Structure 2/20
• Resistivity images in a water-based mud system (traditional):
• Conductive (dark image) =/= open?
• Resistive (light) =/= closed?
• Resistivity images in an oil-base mud system
(new tools; Earth Imager, OBMI):
• Conductive (dark image) =/= closed?
• Resistive (light) =/= open?
• Acoustic Images:
• Low amplitude (dark) =/= open?
Check transit time image to confirm aperture
• high amplitude (light) =/= closed?
• Core calibration should be used to confirm type.
• Image logs can provide an interpretive insight only.
• Only dynamic data provide true insight into fracture “producibility”.
Open versus closed
21. Structure 2/21
Cemented
Partially cemented;
vuggy
Closed
Mudstone
shear
Open
Unlithified
breccia
Cement
fault seals
Phyllosilicate
fault seals
Cataclastic
fault seals
Cataclastic
Cemented
Cemented
Partially cemented;
vuggy
Partially cemented;
vuggy
Closed
Closed
Mudstone
shear
Mudstone
shear
Open
Open
Unlithified
breccia
Unlithified
breccia
Cement
fault seals
Cement
fault seals
Phyllosilicate
fault seals
Phyllosilicate
fault seals
Cataclastic
fault seals
Cataclastic
fault seals
Cataclastic
Cataclastic
This needs local calibration to
core!
Fracture Microfault Fault
Resistive FRAC RES MF RES FAULT RES
Mixed FRAC MIX MF MIX FAULT MIX
Conductive FRAC CON MF CON FAULT CON
Fracture classification schemes
22. Structure 2/22
The importance of ground-truthing
Resistive fracture swarm
Braided – may relate to shear?
Strain hardening?
Closed? Cemented?
Microfaults?
Granulation seams
Core or outcrop
23. Structure 2/23
Flow zone 2
Flow zone 1
Flowmeter data Acoustic images Manual dips
Vuggy fracture
27. Structure 2/27
Flow paths around fractures
Resistive fracture
Current is repelled
away from the
fracture.
Current-lines at B are
compressed, giving
elevated resistivity
(low current).
Current lines at C are
more separated,
producing a more
conductive response.
Conductive fracture
Current is drawn into
the fracture.
Current is increased
across the fracture,
giving a conductive
response at b, B and C.
The fracture mid point
may therefore be higher
than the true fracture
location
28. Structure 2/28
• If fluid is flowing through fractures, then fracture
aperture (open width) influences flow rate. Flow rate
is proportional to the cube of the aperture
• Aperture may be measured and ranked from resistivity
images (although conductive fractures might not be
open) and acoustic transit time images
• Aperture readings may be misleading as fractures may
change in width along their trace, be damaged and
enlarged at their interface with the borehole wall, and
be affected by the effects of mud invasion. Readings
vary between the water, oil and gas legs and must be
corrected
• Aperture does not necessarily correlate with flow as
flow requires connected volume rather than isolated
fractures
0 mm
0.64 mm
1.27 mm
Fracture aperture assessment
29. Structure 2/29
b
xo
b
mR
cAR
W
1
W fracture width /mm
A excess conductance
(right)
Rm mud resistivity
Rxo formation resistivity
c,b tool-specific constants
derived from forward
modelling
Relationship between fracture width and excess
conductance due to the presence of the fracture.
dz
I
z
I
V
A bm
z
z
b
e
n
}
)
(
{
1
0
Ve voltage difference across tool
Ib button current, fracture
Ibm button current, matrix
z vertical position
0,n base, top
Luthi-Souhaité equation
30. Structure 2/30
Pros and cons of imaging technologies for fracture characterisation
WBM electrical imagers
• Highest intrinsic resolution so detects
finest fractures & mechanical layers
• Sees slightly into the formation
through the mudcake
• May be used to derive apertures
• Limited coverage; may miss some
fractures between the pads
• Gives a relative resistivity only
OBM electrical imagers
• Works in oil-base muds that are
commonly used for operational reasons
• Provides true resistivity values
• Limited coverage
• Low resolution as fewer, larger buttons
than WBM electrical imagers
• Poor in conductive formation e.g. shales.
Acoustic televiewers
• 100% borehole coverage so only
misses fractures unresolved
• High intrinsic resolution
• ‘Caliper image’ may see open fractures
• Allows reliable identification and
orientation of in-situ stress features
• Only sees the skin of the borehole wall
and cannot see through mudcake
LWD tools
• Macroresistivity devices see well into
formation, sometimes several depths;
may see behind hole artefacts
• Run close behind bit, before time
dependent damage occurs
• Used for geosteering horizontal wells;
may intersect steep fractures
• Generally lower resolution than wireline
tools by over 1 order of magnitude – will
only see broad fractures
Electrical tools are prone to stick and pull
Acoustic tools are poor in bad hole
All tools work best in smooth hole and fractures and faults often
facilitate spalling and thus hole damage; the tools often work least
well where the well bore is most fractured.
32. Structure 2/32
Consistent bedding
orientation; clear lamination
evident in SHDT images.
Parallel resistive fractures, thin
(under 1 inch), bed continuity
uncertain across fractures.
RESISTIVE FRACTURES
Probable mineralised fractures
and therefore likely to be
baffles. Four fractures in 8
feet – 0.5 fractures/foot
uncorrected density. Spacing
circa 0.5 feet.
Anomalously shallow bedding
at top of resistive unit.
Return to bed orientation at top
of image.
33. Structure 2/33
RESISTIVE FRACTURE
FMS of previous SHDT
example.
Consistent bedding
orientation; clear lamination.
RESISTIVE FRACTURES
(SHDT orientations dotted)
Parallel resistive fractures, thin
(under 1 inch), bed continuity
uncertain across fractures but
there may be bed offset.
Single conjugate fracture
present.
Probable mineralised fractures
and therefore likely to be
baffles. Seven fractures in 8
feet (main set)
– 0.87
fractures/foot uncorrected
density. Spacing
circa0.5
feet.
More fractures are identified
when compared to the SHDT;
conjugate feature not seen at
all in dipmeter.
All resistive and thus no
aperture likely; not stress
-
enhanced.
35. Structure 2/35
Analysing the fracture data
Fracture display
• Tadpole plots
• Strike histograms
• Dip sticks (section view)
• Stereoplots
• Strike bars (map view)
• Data listings
• Fracture density curve
Fracture analysis
1. Separation into sets by
character and orientation
2. Borehole sampling bias
analysis
3. Data analysis by set
• Mean orientation (R&C)
• Fracture density (R&C)
• Damage zones or fracture
corridors
• Fracture spacing (C)
• Damage zone width (C)
4. Analysis by mechanical
stratigraphy
5. Likely geological significance
6. Construction of
conceptual model
37. Structure 2/37
Coloured dots distinguish different fracture
Sets. Lines represent fracture set strikes.
N
15
30
45
60
75
90
15
30
45
60
75
90
15
30
45
60
75
90
15
30
45
60
75
90
15
30
45
60
75
90
15
30
45
60
75
90
Sets are defined on the basis of:-
• Fracture dip-type.
• Orientation (clusters on
stereonet).
• Association, i.e. conjugate sets
are identified, secondary
structures recorded (e.g. Riedel
shears) – may require core
calibration.
• Orientations recorded and effect
of borehole sampling bias
considered.
• Fracture spacing statistics
generated by fracture set, hence
key to defining subsurface
network.
Fracture sets
38. Structure 2/38
N
15
30
45
60
75
90
15
30
45
60
75
90
15
30
45
60
75
90
15
30
45
60
75
90
15
30
45
60
75
90
15
30
45
60
75
90
Orientation 88°/158°
Count 461
Type Discontinuous, conductive - set A
Sampling bias Low
Critically-stressed? Yes; evidence for propping, low angle to
SHmax
Interpretation Stress-enhanced open fracture; probably
mode-II, early; appears to be conjugate to
set B (orange) , subsequently rotated in
main tilt event.
0
20
40
60
80
100
120
140
160
180
200
Orthogonal fracture spacing
Frequency
Mean 0.30
Standard Error 0.03
Median 0.14
Mode 0.07
Standard Deviation 0.56
Sample Variance 0.32
Kurtosis 54.22
Skewness 6.27
Range 6.84
Minimum 0.00
Maximum 6.84
Count 461
Spacing statistics, set A
Fracture set statistics
39. Structure 2/39
Strike histogram
Green Set
Red set
q
q
Fracture plane
Borehole
Apparent Weighted
Weighted Apparent frequency
Frequency cos q
=
Borehole sampling bias
40. Structure 2/40
0
5
10
15
20
25
30
35
0 20 40 60 80
Angle between fracture and borehole (q)
Derived weighting factor
Bias correction factor
Weighting
factor
(1/cos
q)
q
=
84.2°
Weighting factor = 10
• Weighting to emphasise fractures that are not orthogonal to the well bore
• Cut-off applied to prevent fractures parallel to wellbore skewing the data-set
• Provides a better estimation of the true subsurface fracture network
Terzaghi correction factor
42. Structure 2/42
S
q reciprocal of corrected
fracture density
Fracture spacing
• Distribution of fracture spacing is used to infer larger-scale significance:
• Random
• Regularly-spaced
• Clustered
43. Structure 2/43
T
Fractures at
limits of
damage zone
q
0.001
0.01
0.1
1
10
100
1000
0.0001 0.001 0.01 0.1 1 10 100
Fault zone thickness, m
Fault
throw,
m
After Knott 1996.
et al.
Sandstone/sandstone
Sandstone/shale
Minimal throw estimates:-
• rule of thumb (e.g. fault throw = 2.5 x damage zone width for
brittle failure)
• drag zone analysis based on splines (for more plastic
deformation) and graphical cross-section approach.
Fault damage zone width
45. Structure 2/45
Matrix block 5m x 5m x 3m
North
N-S red fracture set
5 m spacing
N-S blue fracture set
3 m spacing
E-W green fracture set
5 m spacing
Matrix block size
46. Structure 2/46
• Lithology – changes in fracture type, morphology
and density often occur at lithological boundaries.
Joints are layer-bound within mechanical units
• Curvature – fracture intensity is often proportional
to the degree of structural curvature due to outer-
arc extension and inner-arc compression
• Localisation – fracture intensity may be
proportional to distance from a fault, forming a
‘damage-zone’
• Present-day in-situ stress field; enhances some
fractures whilst closing others, causing an
apparent variation in intensity
Influences upon fracture distribution
47. Structure 2/47
• Well and fracture orientations
• Division into fracture sets (combining orientation
and fracture type information)
• Fracture density
• Core density calibration
• Borehole corrected fracture density
• Fracture spacing
• Fracture distribution
• 3D modelling
Fracture distribution analysis
49. Structure 2/49
Fracture description from wireline logs?
If thick, high-contrast fractures:
• Subtle in most conventional logs unless many inches thick and
highly contrasting fracture fill
• Separations of shallow and deep laterolog curves due to current
path effects
• Events on photoelectric effect curve in barite muds
• Spikes of increased delta-T sonic if fractures are large and open
• Cycle skipping in older-generation sonic logs
• Caliper events Full waveform sonic logs: Stoneley waveforms,
fast versus slow directions and magnitude of anisotropy from
shear sonic
• Nuclear magnetic resonance logs
50. Structure 2/50
• Use an array of receivers
which, under the right
conditions gather Stoneley
wave arrivals
• Stoneley tube wave
sensitive to lithological
changes, borehole
enlargements, faults and
open fractures
• Azimuthal anisotropy
(slow/fast directions)
identify in-situ stress
directions and fracture
strikes
Full waveform sonic data
53. Structure 2/53
Fracture description: what else can we use?
Core:
• Full geological description, ground-truth with resolution to electron
microscope scale but over limited intervals and it can be difficult to
see the larger structure
Dynamic data:
• Mud losses may identify open fractures
• Production logs may quantify producibility and fluid entry points
• Dual packer systems can be used test the producibility of imaged
fractures but are costly and time consuming
Seismic data:
• 3D volumes may identify, orientate and locate large faults and
fracture corridors but cannot image fine-scale detail
• VSP surveys may resolve features a few metres wide
54. Structure 2/54
Flow zone 2
Flow zone 1
Flowmeter data Acoustic images Manual dips
Calibration of log and core data
56. Structure 2/56
000
Fractures per 10 ft interval
0 250
Resistive fracture
Conductive fracture
Cumulative fracture density
Depth
Production log data
(red – flow, blue – temperature)
0 100
Integration of images and spinner data
57. Structure 2/57
Time slice Seismic section
Filtered dip data overlaid on top of
seismic section. Green=bedding,
red=fractures
Rendered seismic horizon
Up-scaling to seismic data
60. Structure 2/60
Fault seal interpretation workflow
Fault zone recognised
on images as
discordant feature
Lithology difference
across fault?
JUXTAPOSITION
FAULT SEAL
CEMENTED
FAULT SEAL
GRAIN SIZE
REDUCTION
FAULT SEAL
CLAY LINED
FAULT SEAL
OPEN
FAULT
Fault is resistive
or high amplitude?
Fault is conductive
or low amplitude
Mud losses or
increased
transit time?
Fault shows
shale response on
open hole logs?
Argillaceous
lithology?
Strong image
response?
Cementation
indicators on
open hole logs?
Y
N
Y
N N Y Y
N
Y
Y
Y
N
N
N Y
N
Electrical responses assume water-base mud;
reverse resistive and conductive for oil-base mud
Adams & Dart 1998
67. Structure 2/67
Fault
orientation
Fault density & clustering
relationship to bedding
Fault seal type
Fault rock type
Host rock lithology
In-situ stress
Damage zone
- dimension
- fault clustering
- fault offset populations
Deformation history
Fault seal influences
68. Structure 2/68
Fault
damage
zone
Look at all scales!
Core to seismic
Borehole images allow conceptual models to be made which may
be refined and extended using other available data: up-scaling to
seismic and field analogues, down-scaling and ground-truthing to
core and quantifying flow with production data
69. Structure 2/69
Orientation
Density & clustering
relationship to bedding
Fracture size
(length)
Abutting
relationships
Sealing or open?
Aperture
In-situ stress
FRACTURE MODEL
Fracture modelling input data
70. Structure 2/70
Images & core
Fracture model
Reservoir simulation
mapped seismic
faults
Cemented
Partially cemented;
vuggy
Closed
Mudstone
shear
Open
Unlithified
breccia
Cement
fault seals
Phyllosilicate
fault seals
Cataclastic
fault seals
Cataclastic
Fracture types and properties
The impact of images
71. Structure 2/71
Why use borehole images for fracture
characterisation?
• Data is gathered over a long interval, allowing large-scale
structure to be inferred
• Borehole images give fracture orientations
• Borehole images are cost effective when compared to coring
and production tests
• Scale bridge between core and seismic
• The effect of well operations on fractures may be inferred
72. Structure 2/72
• Well design to maximise intersections with flowing
fractures and enter fault compartments by crossing
sealing faults
• Inputs to developing discrete fracture model
• Inputs to geological models and reservoir simulations
• To plan wells where reservoir units are offset by faults
• As an input in multi-attribute analysis of 3D seismic
data and derived acoustic impedance and coherence
volumes, allowing fractured reservoir units to be imaged
Applications