Types Of Deformation Bands Research Articles

Structural core observations in a siliciclastic reservoir-scale framework

Abstract Detailed knowledge of subseismic structures and their influence on reservoir production performance is important for optimal reservoir management. Predicting subseismic structures from seismic-scale structural interpretations is inherently difficult without the use of core data. Cores allow direct measurements of porosity and permeability of deformed rocks and enable researchers to make detailed investigation of deformation mechanisms and cementation processes. Frequency, distribution and sometimes orientation of planar structures can be constrained. Such observations are then used together with location relative to seismically mapped fault and fold structures, and with respect to lithology and stratigraphy. However, a significant gap exists between the scale of core observation and the size of structures mappable from seismic data. Bridging this gap requires a sound general understanding of the different structures that occur in reservoirs, which, in addition to faults, includes drag folds, veins, fractures and the many types of deformation bands that can exist in porous rocks. Proper understanding of such subseismic structures is primarily based on outcrop-based observations and analyses, aided by physical experiments and numerical modelling. We stress that integrating such cutting-edge knowledge with core, seismic and other case-specific subsurface data in an appropriate tectonic context is paramount for realistic reservoir characterization and successful reservoir management.

The effect of grain size and porosity on the nature of compaction localisation in high-porosity sandstone

Compaction bands are a type of deformation band with negligible shear in porous rocks such as sandstones and are important because they can impede subsurface fluid flow. However, the microstructural properties which favour their growth are not fully understood. We experimentally investigate the effect of porosity and grain size on compaction localisation using synthetic sandstones that permit control of the starting porosity (27%, 32%, 37%) and mean grain size (ranging from 314 to 987 μm). Each sample is subjected to the same triaxial test conditions and shortened by 5% axial strain at an effective confining pressure of 85% of their grain crushing pressure (P*). Discrete compaction bands oriented normal to the axial loading direction are found only in the sample with the lowest starting porosity (27%) and smallest grain size (314 μm), while diffuse bands are observed for the same porosity at a larger grain size of 411 μm. No compaction bands are observed for any grain size in either the 32% or 37% starting porosity samples. Porosity analysis indicates grain size reduction does not necessarily correspond to porosity reduction indicating that compaction by grain rearrangement is as effective as localisation through comminution for these high-porosity synthetic sandstones.

Cyclic deformation and dislocation structure evolution of a copper bicrystal with components rotating gradually along the grain boundary

Abstract The push –pull cyclic deformation of a copper bicrystal with components rotating gradually along the grain boundary (GB) was carried out under constant plastic strain amplitude at room temperature in air. The evolution of slip morphology and dislocation structure was observed by scanning electron microscopy electron channelling contrast technique. It was shown that slip morphology and dislocation structure in one of the grains changed gradually along the GB. This phenomenon can be understood based on the local irreversible rotation of crystals, which exists during the symmetrical push– pull loading. When the secondary slip was localized to form the secondary persistent slip bands, which interacted with the regular walls in the second type of deformation band, then the cell structure was formed. The second type of deformation band is one kind of sites for cell formation.

Deformation Bands and Associated FIP Characteristics From High-Porous Triassic Reservoirs in the Tarim Basin, NW China: A Multiscale Analysis

Deformation bands are widely formed and distributed in Triassic high-porous rocks as a result of multistage tectonic movement. In this research, core observation, the rock thin section (fluorescence and casting thin section), FIB-SEM, X-ray diffraction, Raman laser, and thermometry of fluid inclusions were employed to describe the macro- and micro characteristics of deformation bands and their associated relationship with microfractures. Results indicate that the main types of deformation bands formed in the Lunnan Triassic high-porosity sandstone during the Yanshanian and Himalayan periods under different temperature and pressure conditions are compaction shear bands, and their quantity increases evidently with the distance of thrust faults. The density of deformation bands near the fault is about 15/m; porosity and permeability decrease sharply compared with those of the host rock. Microscopically, two obtained fluid-inclusion planes (FIPs) can be distinguished as 51 samples collected from 12 wells by the cutting relationship and mechanical characteristics. The homogenization temperature of associated aqueous inclusion is generally characterized by two peaks, mainly 70–80°C and 110–120°C, which were formed in the Late Yanshanian and Late Himalayan periods. The formation period of deformation bands induced by the intragranular microfractures improved the reservoir seepage capacity. In the later stage, as the interlayer and barrier with low porosity and low permeability affects the distribution of oil and gas, which is an important factor in this study of the local fluid dynamic field and high-quality reservoir evolution distribution.

Microstructure and petrophysical properties of deformation bands in high porosity carbonates

Deformation bands are one of the most common strain localization structures found in deformed porous rocks. Numerous documented studies on deformation bands in siliciclastics have found that they often experience a reduction in porosity due to pore collapse and cataclasis, as well as post-deformation diagenetic alteration. However, the deformation mechanisms and post-deformation diagenetic processes that affect deformation bands in carbonates are not so well understood. To fill this knowledge gap, deformation bands were studied in porous carbonates from various locations in Europe. The study focused on assessing the deformation mechanisms occurring within deformed carbonates as well as other processes that impact the porosity and permeability of the resulting deformation bands. Varying mechanisms were identified depending on the texture and composition of a host rock, and the stress conditions during deformation. For instance, host rocks dominated by coccoliths, i.e. chalk, appear to be deformed by the collapse of macro-pores within foraminifera, reducing the overall porosity, but having negligible impact on permeability. Conversely, high porosity grainstones deform by multiple mechanisms including: mechanical disintegration of peloids and subsequent aggrading neomorphism, as well as cataclasis. Post-kinematic grain dissolution and cementation are also common in various types of deformation bands.

Effects of pre-existing faults on compaction localization in porous sandstones

The formation of deformation bands can significantly modify the strength and transport properties of porous sedimentary rocks. Among the different types of deformation bands, compaction bands exhibit porosity reduction with little to no shear displacement. Natural compaction bands have previously been reported and studied in only a few areas. They often coexist with faults and other localized deformation structures. We mapped the geometrical relation between compaction bands, shear bands and faults in Lower Cretaceous porous sandstone at Makhtesh Katan, Israel. To understand the effect of pre-existing faults on the formation of compaction bands, we conducted deformation experiments on pre-faulted Bentheim sandstones. These experiments produced compaction bands consistently intersect the pre-existing fault. To gain better mechanical understanding of the observed band geometry, we also carried out three-dimensional (3D) numerical simulations with the input elastic moduli and yield strength well-constrained from the deformation experiments. We demonstrated that the formation of deformation bands is dictated by stress concentrations associated with the pre-existing fault. Frictional slip along the heterogeneous fault plane can produce a local stress concentration that would be responsible for further localized damage and the development of deformation zones. When fault slip is restricted (a possible result of high confinement), compaction bands initiate at high stress concentration sites resulting from geometrical irregularities of the fault. Finally, using a plane-strain two-dimensional (2D) linear-elastic model with the geometry of the faults mapped in the outcrop, we were able to provide a mechanical explanation of the distribution for deformation bands observed at the Makhtesh Katan study area.

Corrosion behavior of thermo-mechanically processed biomedical Ti-29Nb-13Ta-4.6Zr

The effects of thermomechanical processing (TMP) on the corrosion behavior of a titanium based bio-alloy are addressed in the present work. In this regard two distinct temperature regime, i.e. warm compression at two temperatures of 300 and 400 °C along with hot compression at 900 °C, which is above the corresponding β-transus temperature, were contemplated for TMP cycles. The results showed that the corrosion resistant of processed materials was extremely higher than that of as-received one. The electron backscatter diffraction (EBSD) studies characterized two different mechanisms which played important roles in the material corrosion behavior. In the warm worked specimens, the martensite plates were seen at the vicinity of different types of deformation bands. These martensite plates were thought to assist improving the corrosion rate of processed materials through creating a continuous passive surface film. On the contrary, the occurrence of extended dynamic recovery in addition to the partial dynamic recrystallization in the materials processed at 900 °C could raise the intrinsic susceptibility to local attack thereby increasing the corrosion rate. The latter was attributed to the higher dissociation rate of moving dislocations at non-equilibrium serrated grain boundaries (specially at lower strain rate) and higher fraction of high angle grain boundaries (specially at higher strain rate), which could act as preferred sites for corrosion attack initiation.

Sequential growth of deformation bands in carbonate grainstones in the hangingwall of an active growth fault: Implications for deformation mechanisms in different tectonic regimes

Deformation bands in porous sandstones have been extensively studied for four decades, whereas comparatively less is known about deformation bands in porous carbonate rocks, particularly in extensional settings. Here, we investigate porous grainstones of the Globigerina Limestone Formation in Malta, which contain several types of deformation bands in the hangingwall of the Maghlaq Fault: (i) bed-parallel pure compaction bands (PCB); (ii) pressure solution-dominated compactive shear bands (SCSB) and iii) cataclasis-dominated compactive shear bands (CCSB). Geometric and kinematic analyses show that the bands formed sequentially in the hangingwall of the evolving Maghlaq growth fault. PCBs formed first due to fault-controlled subsidence and vertical loading; a (semi-)tectonic control on PCB formation is thus documented for the first time in an extensional setting. Pressure solution (dominating SCSBs) and cataclasis (dominating CCSBs) appear to have operated separately, and not in concert. Our findings therefore suggest that, in some carbonate rocks, cataclasis within deformation bands may develop irrespective of whether pressure solution processes are involved. We suggest this may be related to stress state, and that whereas pressure solution is a significant facilitator of grain size reduction in contractional settings, grain size reduction within deformation bands in extensional settings is less dependent on pressure solution processes.

Temperature and composition of carbonate cements record early structural control on cementation in a nascent deformation band fault zone: Moab Fault, Utah, USA

Fluid-driven cementation and diagenesis within fault zones can influence host rock permeability and rheology, affecting subsequent fluid migration and rock strength. However, there are few constraints on the feedbacks between diagenetic conditions and structural deformation. We investigate the cementation history of a fault-intersection zone on the Moab Fault, a well-studied fault system within the exhumed reservoir rocks of the Paradox Basin, Utah, USA. The fault zone hosts brittle structures recording different stages of deformation, including joints and two types of deformation bands. Using stable isotopes of carbon and oxygen, clumped isotope thermometry, and cathodoluminescence, we identify distinct source fluid compositions for the carbonate cements within the fault damage zone. Each source fluid is associated with different carbonate precipitation temperatures, luminescence characteristics, and styles of structural deformation. Luminescent carbonates appear to be derived from meteoric waters mixing with an organic-rich or magmatic carbon source. These cements have warm precipitation temperatures and are closely associated with jointing, capitalizing on increases in permeability associated with fracturing during faulting and subsequent exhumation. Earlier-formed non-luminescent carbonates have source fluid compositions similar to marine waters, low precipitation temperatures, and are closely associated with deformation bands. The deformation bands formed at shallow depths very early in the burial history, preconditioning the rock for fracturing and associated increases in permeability. Carbonate clumped isotope temperatures allow us to associate structural and diagenetic features with burial history, revealing that structural controls on fluid distribution are established early in the evolution of the host rock and fault zone, before the onset of major displacement.

Contractional deformation of porous sandstone: Insights from the Aztec Sandstone, SE Nevada, USA

Contractional deformation of highly porous sandstones is poorly explored, as compared to extensional deformation of such sedimentary rocks. In this work we explore the highly porous Aztec Sandstone in the footwall to the Muddy Mountain thrust in SE Nevada, which contains several types of deformation bands in the Buffington tectonic window: 1) Distributed centimeter-thick shear-enhanced compaction bands (SECBs) and 2) rare pure compaction bands (PCBs) in the most porous parts of the sandstone, cut by 3) thin cataclastic shear-dominated bands (CSBs) with local slip surfaces. Geometric and kinematic analysis of the SECBs, the PCBs and most of the CSBs shows that they formed during ∼E–W (∼100) shortening, consistent with thrusting related to the Cretaceous to early Paleogene Sevier orogeny of the North American Cordilleran thrust system. Based on stress path modeling, we suggest that the compactional bands (PCBs and SECBs) formed during contraction at relatively shallow burial depths, before or at early stages of emplacement of the Muddy Mountains thrust sheet. The younger cataclastic shear bands (CSBs, category 3), also related to E–W Sevier thrusting, are thinner and show larger shear offsets and thus more intense cataclasis, consistent with the initiation of cataclastic shear bands in somewhat less porous materials. Observations made in this work support earlier suggestions that contraction lead to more distributed band populations than what is commonly found in the extensional regime, and that shear-enhanced compaction bands are widespread only where porosity (and permeability) is high.

Dilatant shear band formation and diagenesis in calcareous, arkosic sandstones, Vienna Basin (Austria)

The present study examines deformation bands in calcareous arkosic sands. The investigated units can be considered equivalent to reservoir units in the Matzen field in the Vienna Basin (Austria), which is one of the most productive oil reservoirs in central Europe. The outcrop exposes carbonate-free and carbonatic sediments of Badenian age separated by a normal fault. Carbonatic sediments in the hanging wall of the normal fault develop single and multistrand dilation bands with minor shear displacements (<2 mm). In contrast, carbonate-free sediments in the footwall exhibit a more pervasive system of cataclastic shear bands, which are frequently accumulated in clusters with up to 70 cm displacement. The cataclastic shear bands show a permeability reduction up to 3 orders of magnitude and strong baffling effects in the vadose zone. Carbonatic dilation bands show a permeability reduction of 1–2 orders of magnitude and no baffling structures. We distinguished two types of deformation bands in the carbonatic units, which differ in deformation mechanisms, distribution and composition. Full-cemented bands form as cataclastic dilation bands with an intense syn-kinematic calcite cementation, whereas the younger loose-cemented bands are cataclastic dilatant shear bands cemented by patchy calcite and clay minerals. All analyzed bands are characterized by a two-staged petrophysical evolution: Porosity increase by dilation and grain fracturing is followed by a porosity and permeability reduction caused by authigenic cementation. The changed petrophysical properties and especially the porosity evolution are closely related to diagenetic processes driven by varying pore fluids in different diagenetic environments. The deformation band evolution and sealing capacity is controlled by the initial host rock composition.

Influence of deformation bands on sandstone porosity: A case study using three-dimensional microtomography

This study presents a qualitative and quantitative analysis of porosity in deformation bands by applying X-ray micro-computed tomography in conjunction with microstructural analysis. Samples of compactional cataclastic bands and shear compactional bands identified in Early Cretaceous aeolian sandstones of the Paraná Basin were analyzed. The application of X-ray micro-computed tomography expanded the view of features in the porous framework of each type of deformation band studied and provided information that are not clear or was not observable with optical microscopy. The compactional cataclastic bands and shear compactional bands differ in geometry, thickness, microstructures and, mainly, in the distribution, shape and orientation of the remaining pores. Porosity analysis was also performed by comparing values of porosity (total, open and closed pores) of the parental rock and the deformation band in each sample. Results of these analyses show a reduction of total porosity and open pores and therefore an increase in the amount of closed pores in all types of deformation bands in relation to parental rock. In addition, it is observed that changes in porosity characteristics are related to the effect of different deformation mechanisms that operated in each type of deformation band.

Effect of Cold Rolling on Microstructure and Mechanical Properties of an Al-Mg-Sc-Zr Alloy

The microstructural evolution and mechanical properties of an Al-5.4Mg-0.4Mn-0.2Sc-0.09Zr alloy subjected to cold rolling with a total strain up to ~1.6 was studied using high resolution EBSD analysis and TEM. It was shown that cold rolling induces elongation of initial grains and the formation of deformation bands along rolling direction in addition to dramatic increase in density of lattice dislocations. Two types of deformation bands evolve. Deformation bands initially bounded by low-angle boundaries (LABs) with misorientation higher than 2o and spacing ranging from 0.8 to 4 μm gradually transform to lamellas delimited by high-angle boundaries (HABs). Thin deformation bands delimited by LABs with misorientation of 2o or less evolve within these coarse bands. First type of deformation bands is subdivided due to mutual intersection with second order deformation bands or shear bands to elongated crystallite evolving to micron scale grains with strain. The thin deformation bands may be also subdivided to nanoscale crystallites. It was shown that the formation of well-defined deformation bands yield very high anisotropy in strength and ductility, while a strong increase in lattice dislocation density with strain diminishes this anisotropy.

The strain accommodation in Ti–28Nb–12Ta–5Zr alloy during warm deformation

The warm deformation behavior of a β-type Ti alloys, composing of Ti–27.96Nb–11.97Ta–5.02Zr %wt, (so called TNTZ alloy), has been investigated in the present work in a warm deformation temperature. A variety of deformation features are characterized in the material microstructure after applied warm deformation scheme. The XRD analysis confirms an enhancement in martensite volume fraction. The electron back scatter diffractometry (EBSD) elucidates that the martensite has been mainly formed by laterally at the vicinity of different types of deformation bands. Both the well-known twining systems in TNTZ series have been occurred during deformation. The micro-shear bands, which are defined as highly concentrated plastic strain regions, are characterized in the deformed microstructure. The micro-shear bands are severely formed in the regions, which accommodate the most amount of applied strain.

AFM-FIB-TEM Combo Analysis of Surface Relief Caused by Various Types of deformation bands in the Ti-Mo-Based Pseudoelastic Alloys

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Mechanical and field studies of deformation localization in rocks

Refining Constitutive Characterization of Geomaterials and Identifying Their Rupture Mechanisms in Natural Conditions; Montpellier, France, 7–8 September 2011 Results from rock testing and geological observations of different types of deformation bands and fractures highlight the problem of understanding the underlying formation mechanisms from granular (micro) to outcrop scale. Particularly puzzling are recently discovered compaction and dilatancy bands that are completely antipodal features. Both are narrow (several grain diameters thick), generally not planar but rather irregular and zigzagging (depending on the observation scale) bands that can form in the uniformly stressed rocks. The difference between them is that the compaction bands form at a relatively high pressure (mean stress) normal to the maximal compressive stress. The material within the compaction bands undergoes volume reduction due to the more dense grain packing and/ or crushing. Conversely, the dilatancy bands form at low pressure and normal to the least compressive stress. The material within them undergoes a volume increase due to grain rearrangements and/or formation of intragranular and intergranular microfractures. The dilatancy bands can become opened fractures with further deformation.

Morphological diagram of Savart-Masson bands of macrolocalized deformation

The dynamics and morphology of Savart-Masson bands of macrolocalized deformation during a tension test of flat samples of aluminum-magnesium alloy Al-6wt.%Mg with a constant stress rate \((\dot \sigma _0 = const)\) have been investigated in situ using high-speed video recording. A phenomenological classification of the Savart-Masson bands according to the morphological and kinetic peculiarities is presented. This classification includes six types of deformation bands which replace each other with an increase in stress. A morphological diagram of Savart-Masson deformation bands is obtained for the first time. These bands differ significantly from the A, B, and C deformation bands during a tension test with a constant strain rate \((\dot \varepsilon _0 = const)\) under the conditions of the Portevin-Le Chatelier effect.

Spatial variation of microstructure and petrophysical properties along deformation bands in reservoir sandstones

A series of deformation bands from various reservoir sandstones deformed at different burial depths have been studied with respect to microstructural and petrophysical variations. In many of the examples explored, the internal microstructure, porosity, and permeability vary along the bands at the centimeter or even millimeter scale, changing and in most cases reducing the ability of the bands to act as barriers to fluid flow. Porosity varies by up to 18% and permeability by up to two orders of magnitude. Such petrophysical variations are found along different types of deformation bands, but the range depends upon the deformation mechanisms, in particular on the degree of cataclasis and dissolution in cataclastic and dissolution bands, and on the phyllosilicate content in disaggregation bands. For cataclastic bands, the grain-size distribution changes along the bands with regard to the degree of cataclasis. Furthermore, the increased specific surface area of the pore-grain interface as a result of cataclasis causes higher permeability reduction in cataclastic bands than in other types of deformation bands. Phyllosilicate content can influence the thickness of phyllosilicate bands. However, no apparent correlation between thickness and intensity of cataclasis in the studied cataclastic deformation bands is observed.

Terminology for structural discontinuities

Strain localization structures such as fractures, stylolites, and deformation bands have important effects on reservoir performance but lack a consistent terminology. Advances in the recognition and interpretation of such structures now motivate a comprehensive framework that stresses their similarities instead of their differences. We review and assess the classical terms for localized geologic structures, followed by a comprehensive nomenclature that accounts for joints, faults, fractures, anticracks, shear zones, and deformation bands in compact and high-porosity rocks. Geologic structural discontinuities are defined by their lengths and by the sense and rate of displacement change across them. For example, structural discontinuities having negligible thickness, and consequently, a discontinuous displacement across them, are called sharp discontinuities. Depending on the sense of displacement (opening, shearing, or closing), these structures are called cracks, faults, or anticracks. However, structural discontinuities having a measurable thickness in outcrop or hand specimen and a continuous change in displacement across them are called tabular discontinuities. Correspondingly, these types of deformation bands are called dilation bands, shear bands, or compaction bands. The class of structural discontinuity, i.e., sharp or tabular, depends on the properties of the deforming rock. Consistent characteristics and patterns of these structural discontinuities, and their displacement-length scaling relations, demonstrate the rich yet consistent varieties of strain localization that are manifested in crustal rocks in general, and reservoir rocks in particular.

90&amp;deg;対称傾角粒界を有するアルミニウム双結晶の引張変形と再結晶

An aluminum bicrystal having a symmetric 90° tilt grain boundary was tensile-deformed at room temperature and subsequently annealed. In the component grains of the bicrystal, two slip systems with almost the same Schmid factor were activated on the primary slip plane. The grains were rotated in the opposite directions, which resulted in the decrease in the tilt angle by 20°. Two different types of deformation bands, i.e. band of secondary slip and kink band were formed in the grains. The deformation was not symmetric about the grain boundary. Recrystallization occurred through strain induced boundary migration predominantly from one of the grains towards the other.