Elastic properties of microporous cemented grainstones

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. E211-E226 ◽  
Author(s):  
François Fournier ◽  
Philippe Leonide ◽  
Kévin Biscarrat ◽  
Arnaud Gallois ◽  
Jean Borgomano ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Pore Space ◽  
Micropore Volume ◽  
Pore Geometry ◽  
Petrographic Analysis ◽  
S Wave ◽  
Lower Porosity ◽  
Diagenetic History ◽  
Space Architecture ◽  
The Impact

We investigated the effect of porosity, pore geometry, and diagenetic history on the elastic properties of dry, tightly cemented grainstones whose pore space consists dominantly of intragranular microporosity within micritic grains. The integration of laboratory petrophysical measurements (porosity, P- and S-wave velocity), petrographic analysis and scanning electron microscope (SEM) imaging of micropore space of 80 Lower Cretaceous microporous carbonate samples from Provence (south-east France) allows (1) the changes in porosity and pore geometry during the diagenetic history to be related to changes in elastic properties, and (2) the impact of micritic grain diagenesis on the elastic properties of microporous grainstones to be quantified by means of fitting parameters derived from equivalent elastic medium modeling. The Urgonian microporous cemented grainstones are elastically equivalent to a homogeneous calcitic host with spherical calcitic inclusions comprising spheroidal pores. The best fit is obtained when porous spheres are modelled using the differential effective medium (DEM) approach and the whole composite using the self-consistent (SC) method (DEM-SC model). At lower porosity values ([Formula: see text]), when the micropore volume is controlled by intercrystalline cementation processes without compaction, the equivalent pore aspect ratio (EPAR) derived from DEM-SC modelling is nearly constant and averages 0.15. At higher porosities, changes in micropore space architecture related to leaching processes result in slightly increasing EPAR. The recognition of EPAR-preserving versus EPAR-non preserving elastic property evolution is proposed as a tool for diagenetic pattern detection in microporous carbonate reservoirs.

scholarly journals Effective medium modeling of diagenesis impact on the petroacoustic properties of carbonate rocks

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. WA43-WA57 ◽  
Author(s):  
Mathilde Adelinet ◽  
Jean-François Barthélémy ◽  
Elisabeth Bemer ◽  
Youri Hamon
Keyword(s):  
Elastic Properties ◽  
Carbonate Rocks ◽  
Effective Medium ◽  
Petrographic Analysis ◽  
Permeability Evolution ◽  
Data Set ◽  
Microstructural Parameters ◽  
Acoustic Signature ◽  
Extensive Experimental Data ◽  
The Impact

Carbonate formations are highly heterogeneous, and the velocity-porosity relationships are controlled by various microstructural parameters, such as the types of pores and their distribution. Because diagenesis is responsible for important changes in the microstructure of carbonate rocks, we have extended the standard effective medium approach to model the impact of diagenesis on the carbonate elastic properties through a step-by-step effective medium modeling. Two different carbonate rocks deposited, respectively, in lacustrine and marine environments are considered in this study. The first key step is the characterization of the diagenesis, which affected the two studied carbonate sample sets. Effective medium models integrating all of the geologic information accessible from petrographic analysis are then built. The evolution of the microstructural parameters during diagenesis is thoroughly constrained based on an extensive experimental data set, including X-ray diffraction analysis, different porosimetry methods, and ultrasonic velocity measurements. A new theoretical approach including two sources of compliance is developed to model the specific behavior of carbonates. A compliant interface is introduced around the main carbonate grains to represent grain contacts and the different pore scales are taken into account through multiscale modeling. Finally, direct calculations with the model provide elastic wave velocities representative of the different diagenetic stages. An extrapolation to permeability evolution is also introduced. This approach allows the identification of the acoustic signature of specific diagenetic events, such as dolomitization, dissolution, or cementation, and the assessment of their impact on the elastic properties of carbonates.

Pore geometry effects on elastic properties of Opalinus Clay

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. D543-D551 ◽  
Author(s):  
Lukas M. Keller
Keyword(s):  
Elastic Properties ◽  
Volume Fraction ◽  
Water Saturation ◽  
Pore Space ◽  
Ion Beam ◽  
Evaluation Process ◽  
Preferred Orientation ◽  
Opalinus Clay ◽  
Pore Geometry ◽  
Anisotropy Parameters

Regarding the storage of nuclear waste within clay rock formations requires fundamental understanding of elastic properties of this rock type with regard to the risk evaluation process. The influence of the pore geometry on elastic properties of Opalinus Clay is studied on the basis of realistic pore microstructure, which is reconstructed from image data acquired by focused ion beam nanotomography. These microstructures are used as input pore geometries for linear elastic finite-element modeling to determine Thomsen’s [Formula: see text], [Formula: see text], and [Formula: see text] anisotropy parameters and the effective elastic moduli related to the porous material. The presence of fully drained intergranular pores substantially increases the values of [Formula: see text] and [Formula: see text]. For the investigated sample with an expected porosity of approximately 10 vol.%, the anisotropic pore space contributes similarly to the anisotropy parameters when compared with the contribution related to the preferred orientation of minerals. On the other hand, if the pore space is undrained, the effect of pores is smaller and the anisotropy is largely controlled by the preferred orientation of minerals. It is revealed that the value of [Formula: see text] is most sensitive to changes in water saturation. In case water is drained from the pores, the vertical Young’s modulus [Formula: see text] reduces significantly more when compared with the horizontal modulus [Formula: see text]. Presuming that the drainable porosity corresponds to a volume fraction of 10 vol.%, [Formula: see text] reduces by approximately 15%–20%. The effect of drainage is even more pronounced for the Poisson’s ratios, whereas the shear moduli are not much affected by drainage.

Using laboratory data to understand how pore aspect ratio influences elastic parameters and AVO

Geophysics ◽  
2021 ◽  
pp. 1-50
Author(s):  
Kamal Moravej ◽  
Alison Malcolm
Keyword(s):  
Aspect Ratio ◽  
Elastic Properties ◽  
Wave Velocity ◽  
Selective Laser Sintering ◽  
Laboratory Data ◽  
Physical Models ◽  
P Wave ◽  
S Wave ◽  
Water Saturated ◽  
The Impact

Pore geometry is an important parameter in reservoir characterization that affects the permeability of reservoirs and can also be a controlling factor on the impact of pressure and saturation on reservoirs elastic properties. We use SLS (Selective Laser Sintering) 3D printing technology to build physical models to experimentally investigate the impacts of pore aspect ratio on P-, and S- wave velocities and amplitude variation with offset (AVO). We printed six models to study the effects of the pore aspect ratio of prolate and oblate pore structures on elastic properties and AVO signatures. We find that the P-wave velocity is reduced by decreasing the pore aspect ratio (flatter pore structure), whereas the shear wave velocity is less sensitive to the pore aspect ratio. This effect is reduced when the samples are water saturated. We present new experimental and processing techniques to extract realistic AVO signatures from our experimental data and show that the pore aspect ratio has similar effects on AVO as fluid compressibility. This shows that not considering the pore aspect ratio in AVO analysis can lead to misleading interpretations. We further show that these effects are reduced in water-saturated samples.

scholarly journals Diagenetic Trends of Synthetic Reservoir Sandstone Properties Assessed by Digital Rock Physics

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 151
Author(s):  
Maria Wetzel ◽  
Thomas Kempka ◽  
Michael Kühn
Keyword(s):  
Elastic Properties ◽  
Pore Space ◽  
Rock Physics ◽  
Mineral Dissolution ◽  
Ct Scans ◽  
Micro Ct ◽  
Digital Rock Physics ◽  
Gravity Driven ◽  
Stress Dependent ◽  
The Impact

Quantifying interactions and dependencies among geometric, hydraulic and mechanical properties of reservoir sandstones is of particular importance for the exploration and utilisation of the geological subsurface and can be assessed by synthetic sandstones comprising the microstructural complexity of natural rocks. In the present study, three highly resolved samples of the Fontainebleau, Berea and Bentheim sandstones are generated by means of a process-based approach, which combines the gravity-driven deposition of irregularly shaped grains and their diagenetic cementation by three different schemes. The resulting evolution in porosity, permeability and rock stiffness is examined and compared to the respective micro-computer tomographic (micro-CT) scans. The grain contact-preferential scheme implies a progressive clogging of small throats and consequently produces considerably less connected and stiffer samples than the two other schemes. By contrast, uniform quartz overgrowth continuously alters the pore space and leads to the lowest elastic properties. The proposed stress-dependent cementation scheme combines both approaches of contact-cement and quartz overgrowth, resulting in granulometric, hydraulic and elastic properties equivalent to those of the respective micro-CT scans, where bulk moduli slightly deviate by 0.8%, 4.9% and 2.5% for the Fontainebleau, Berea and Bentheim sandstone, respectively. The synthetic samples can be further altered to examine the impact of mineral dissolution or precipitation as well as fracturing on various petrophysical correlations, which is of particular relevance for numerous aspects of a sustainable subsurface utilisation.

scholarly journals Measuring ultrasonic characterisation to determine the impact of TOC and the stress field on shale gas anisotropy

2013 ◽  
Vol 53 (1) ◽  
pp. 245 ◽  
Author(s):  
Yazeed Altowairqi ◽  
Reza Rezaee ◽  
Milovan Urosevic ◽  
Claudio Delle Piane
Keyword(s):  
Elastic Properties ◽  
Shale Gas ◽  
Ultrasonic Transducers ◽  
S Wave ◽  
Gas Reservoirs ◽  
Wave Velocities ◽  
Degree Of Anisotropy ◽  
The Impact ◽  
The Relationship ◽  
Dynamic Elastic Properties

While the majority of natural gas is produced from conventional sources, there is significant growth from unconventional sources, including shale-gas reservoirs. To produce gas economically, candidate shale typically requires a range of characteristics, including a relatively high total organic carbon (TOC) content, and it must be gas mature. Mechanical and dynamic elastic properties are also important shale characteristics that are not well understood as there have been a limited number of investigations of well-preserved samples. In this study, the elastic properties of shale samples are determined by measuring wave velocities. An array of ultrasonic transducers are used to measure five independent wave velocities, which are used to calculate the elastic properties of the shale. The results indicated that for the shale examined in this research, P- and S-wave velocities vary depending on the isotropic stress conditions with respect to the fabric and TOC content. It was shown that the isotropic stress significantly impacts velocity. In addition, S-wave anisotropy was significantly affected by increasing stress anisotropy. Stress orientation, with respect to fabric orientation, was found to be an important influence on the degree of anisotropy of the dynamic elastic properties in the shale. Furthermore, the relationship between acoustic impedance (AI) and TOC was established for all the samples.

scholarly journals Review of the relationship between aggregates geology and Los Angeles and micro-Deval tests

2021 ◽  
Vol 80 (3) ◽  
pp. 1963-1980
Author(s):  
Solomon Adomako ◽  
Christian John Engelsen ◽  
Rein Terje Thorstensen ◽  
Diego Maria Barbieri
Keyword(s):  
Los Angeles ◽  
Crystal Size ◽  
Grain Shape ◽  
Mechanical Performance ◽  
Pore Space ◽  
Construction Material ◽  
Engineering Properties ◽  
Coarse Grained ◽  
The Impact ◽  
The Relationship

AbstractRock aggregates constitute the enormous volume of inert construction material used around the globe. The petrologic description as igneous, sedimentary, and metamorphic types establishes the intrinsic formation pattern of the parent rock. The engineering properties of these rocks vary due to the differences in the transformation process (e.g. hydrothermal deposits) and weathering effect. The two most common mechanical tests used to investigate the performance of aggregates are the Los Angeles (LA) and micro-Deval (MD) tests. This study reviewed the geological parameters (including mineralogy, grain and crystal size, grain shape, and porosity) and the relationship to Los Angeles and micro-Deval tests. It was found that high content of primary minerals in rocks (e.g. quartz and feldspar) is a significant parameter for performance evaluation. Traces of secondary and accessory minerals also affect the performance of rocks, although in many cases it is based on the percentage. Furthermore, some studies showed that the effect of mineralogic composition on mechanical strength is not sufficient to draw final conclusions of mechanical performance; therefore, the impact of other textural characteristics should be considered. The disposition of grain size and crystal size (e.g. as result of lithification) showed that rocks composed of fine-grain textural composition of ≤ 1 mm enhanced fragmentation and wear resistance than medium and coarse grained (≥ 1 mm). The effect of grain shape was based on convex and concave shapes and flat and elongated apexes of tested samples. The equidimensional form descriptor of rocks somehow improved resistance to impact from LA than highly flat and elongated particles. Lastly, the distribution of pore space investigated by means of the saturation method mostly showed moderate (R = 0.50) to strong (R = 0.90) and positive correlations to LA and MD tests.

scholarly journals Air mediates the impact of a compliant hemisphere on a rigid smooth surface

Soft Matter ◽  
2021 ◽  
Author(s):  
Siqi Zheng ◽  
Sam Dillavou ◽  
John M. Kolinski
Keyword(s):  
Elastic Body ◽  
Elastic Properties ◽  
Impact Velocity ◽  
Solid Surface ◽  
High Speed ◽  
Smooth Surface ◽  
High Speed Imaging ◽  
The Impact ◽  
Rigid Smooth

When a soft elastic body impacts upon a smooth solid surface, the intervening air fails to drain, deforming the impactor. High-speed imaging with the VFT reveal rich dynamics and sensitivity to the impactor's elastic properties and the impact velocity.

Modelling the impact of pore space distribution on carbon turnover

2007 ◽  
Vol 208 (2-4) ◽  
pp. 295-306 ◽  
Author(s):  
K. Kuka ◽  
U. Franko ◽  
J. Rühlmann
Keyword(s):  
Pore Space ◽  
Space Distribution ◽  
Carbon Turnover ◽  
The Impact

Trapping patterns during capillary displacements in disordered media

2022 ◽  
Vol 933 ◽  
Author(s):  
Fanli Liu ◽  
Moran Wang
Keyword(s):  
Numerical Simulations ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Disordered Media ◽  
Pore Geometry ◽  
Control Parameters ◽  
Pore Throat ◽  
The Impact ◽  
Theoretical Analyses

We investigate the impact of wettability distribution, pore size distribution and pore geometry on the statistical behaviour of trapping in pore-throat networks during capillary displacement. Through theoretical analyses and numerical simulations, we propose and prove that the trapping patterns, defined as the percentage and distribution of trapped elements, are determined by four dimensionless control parameters. The range of all possible trapping patterns and how the patterns are dependent on the four parameters are obtained. The results help us to understand the impact of wettability and structure on trapping behaviour in disordered media.

Stress Drop Derived from Spectral Analysis Considering the Hypocentral Depth in the Attenuation Model: Application to the Ridgecrest Region, California

2021 ◽  
Author(s):  
Dino Bindi ◽  
Hoby N. T. Razafindrakoto ◽  
Matteo Picozzi ◽  
Adrien Oth
Keyword(s):  
Stress Drop ◽  
Spectral Decomposition ◽  
Epicentral Distance ◽  
Source Parameters ◽  
S Wave ◽  
Qualitative Comparison ◽  
Ground Shaking ◽  
Attenuation Model ◽  
Hypocentral Distance ◽  
The Impact

ABSTRACT We investigate the impact of considering a depth-dependent attenuation model on source parameters assessed through a spectral decomposition. In particular, we evaluate the effect of considering the hypocentral depth as an additional variable for the attenuation model, using as the target the tendency of the average stress drop to increase with depth, as observed in recent studies. We analyze the Fourier spectra of S-wave windows for about 1900 earthquakes with a magnitude above 2.5 recorded in the Ridgecrest region, southern California. Two different parameterizations of the attenuation term are implemented in the spectral decomposition, either as a function of the hypocentral distance alone or as a function of both epicentral distance and depth. The comparison of the spectral attenuation curves shows that, although the hypocentral model describes, on average, the range of values spanned by the attenuation curve for different depths, systematic differences with distance, depth, and frequency are observed. These differences are transferred to the source spectra and, in turn, to the source parameters extracted from the best-fitting ω−2 models. In particular, stress drops for events deeper than 7 km are, on average, almost double even when depth is introduced explicitly in the attenuation model. The increase of stress drop with depth is confirmed also after accounting for the increase of the shear velocity with depth, which absorbs about 30%–40% of the total increase. Moreover, a qualitative comparison with a model for the gradient of the effective normal stress confirms the reliability of the observed trend. Finally, the coherent spatial patterns shown by a simplified 2D tomographic representation of the spectral residuals highlights the impact on ground-shaking variability of the lateral variability of the crustal attenuation properties in the region.

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