scholarly journals On the evolution of the elastic properties of organic-rich shale upon pyrolysis-induced thermal maturation

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. D263-D281 ◽  
Author(s):  
Adam M. Allan ◽  
Anthony C. Clark ◽  
Tiziana Vanorio ◽  
Waruntorn Kanitpanyacharoen ◽  
Hans-Rudolf Wenk
Keyword(s):  
Elastic Properties ◽  
Elastic Anisotropy ◽  
Time Lapse ◽  
Source Rocks ◽  
Thermal Maturity ◽  
Thermal Maturation ◽  
Confining Pressures ◽  
Acoustic Velocities

The evolution of the elastic properties of organic-rich shale as a function of thermal maturity remains poorly constrained. This understanding is pivotal to the characterization of source rocks and unconventional reservoirs. To better constrain the evolution of the elastic properties and microstructure of organic-rich shale, we have studied the acoustic velocities and elastic anisotropy of samples from two microstructurally different organic-rich shales before and after pyrolysis-induced thermal maturation. To more physically imitate in situ thermal maturation, we performed the pyrolysis experiments on intact core plugs under applied reservoir-magnitude confining pressures. Iterative characterization of the elastic properties of a clay-rich, laminar Barnett Shale sample documents the development of subparallel to bedding cracks by an increase in velocity sensitivity to pressure perpendicular to the bedding. These cracks, however, are not visible through time-lapse scanning electron microscope imaging, indicating either submicrometer crack apertures or predominant development within the core of the sample. At elevated confining pressures, in the absence of pore pressure, these induced cracks close, at which point, the sample is acoustically indistinguishable from the prepyrolysis sample. Conversely, a micritic Green River sample does not exhibit the formation of aligned compliant features. Rather, the sample exhibits a largely directionally independent decrease in velocity as load-bearing, pore-filling kerogen is removed from the sample. Due to the weak alignment of minerals, there is comparatively little intrinsic anisotropy; further, due to the relatively directionally independent evolution of velocity, the evolution of the anisotropy as a function of thermal maturity is not indicative of aligned compliant features. Our results have indicated that horizons of greater thermal maturity may be acoustically detectable in situ through increases in the elastic anisotropy of laminar shales or decreases in the acoustic velocities of nonlaminar shales, micritic rocks, or siltstones.

scholarly journals An instrumented sample holder for time-lapse microtomography measurements of snow under advective airflow

2014 ◽  
Vol 3 (2) ◽  
pp. 179-185 ◽  
Author(s):  
P. P. Ebner ◽  
S. A. Grimm ◽  
M. Schneebeli ◽  
A. Steinfeld
Keyword(s):  
Structural Changes ◽  
Time Lapse ◽  
Temperature Gradients ◽  
Sample Holder ◽  
Experimental Characterization ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Snow Samples

Abstract. An instrumented sample holder was developed for time-lapse microtomography of snow samples to enable in situ nondestructive spatial and temporal measurements under controlled advective airflows, temperature gradients, and air humidities. The design was aided by computational fluid dynamics simulations to evaluate the airflow uniformity across the snow sample. Morphological and mass transport properties were evaluated during a 4-day test run. This instrument allows the experimental characterization of metamorphism of snow undergoing structural changes with time.

scholarly journals In-situ characterization of growth of isothermal ω phase in metastable β-Ti alloy TIMETAL LCB

2020 ◽  
Vol 321 ◽  
pp. 11037
Author(s):  
J. Nejezchlebova ◽  
L. Bodnarova ◽  
M. Janovska ◽  
P. Sedlak ◽  
H. Seiner ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Elastic Constants ◽  
Elastic Anisotropy ◽  
Solid Phase ◽  
In Situ Observation ◽  
Ω Phase ◽  
Resonant Ultrasound ◽  
Isothermal Ageing

Metastable β-Ti alloys exhibit various solid-solid phase transitions. Our study is focused on the characterization of the diffusion controlled β→ωiso phase transition. The particles of ω phase play an important part in thermomechanical treatment since they serve as heterogeneous nucleation sites for precipitation of finely dispersed particles of hexagonal α phase. The in-situ observation of the growth of particles of ω phase could be difficult by conventional techniques. However, it was shown recently that the ω phase significantly influences the elastic constants of the material, and the different forms of ω phase have different effects on the elastic anisotropy, as well as on the internal friction coefficients. Therefore, the β→ω phase transformation could be in-situ observed by the precise measurement of the tensor of elastic constants. In this contribution, we present the study of the kinetics of the β→ωiso phase transformation by resonant ultrasound spectroscopy. The polycrystalline samples of TIMETAL LCB alloy were in-situ examined by this technique during isothermal and non-isothermal ageing at temperatures up to 300 °C.

The influence of confining pressure and water saturation on dynamic elastic properties of some Permian coals

Geophysics ◽  
1993 ◽  
Vol 58 (1) ◽  
pp. 30-38 ◽  
Author(s):  
Gang Yu ◽  
Keeva Vozoff ◽  
David W. Durney
Keyword(s):  
Elastic Properties ◽  
Water Saturation ◽  
Elastic Anisotropy ◽  
Confining Pressure ◽  
S Wave ◽  
Bedding Planes ◽  
Confining Pressures ◽  
Mine Development ◽  
Water Saturated ◽  
Dynamic Elastic Properties

Laboratory measurements are described on Permian coals from Wollongong, New South Wales, Australia related to the dependence of ultrasonic P‐ and S‐wave velocities, attenuation, anisotropy and the dynamic elastic moduli on confining pressure, water saturation, and pore pressure. Five independent stiffness constants are used to represent the elastic anisotropy of the specimens as a function of confining pressure and water saturation. The anisotropy is believed to be controlled mainly by the internal structure of the coals, while the pressure dependence of the constants is controlled mainly by randomly oriented cracks. P‐ and S‐wave dispersions were measured on water‐saturated specimens as confining pressures increased from 2 MPa to 40 MPa. The samples represented cores taken both parallel and perpendicular to bedding planes. Velocities along bedding planes are marginally higher than those across bedding planes. This anisotropy is insensitive to confining pressure. Attenuation was also measured, both normal and parallel to bedding planes, on dry and water‐saturated specimens from 2 MPa to 40 MPa confining pressures. The experimental results show that dynamic elastic properties are potential indicators of the states of stress and saturation in coal seams, and provide necessary information for computer modeling and interpreting seismic surveys carried out to assist mine development.

scholarly journals Form and function in hillslope hydrology: in situ imaging and characterization of flow-relevant structures

2017 ◽  
Vol 21 (7) ◽  
pp. 3749-3775 ◽  
Author(s):  
Conrad Jackisch ◽  
Lisa Angermann ◽  
Niklas Allroggen ◽  
Matthias Sprenger ◽  
Theresa Blume ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Hydraulic Conductivity ◽  
Soil Water ◽  
Time Lapse ◽  
Saturated Hydraulic Conductivity ◽  
Form And Function ◽  
And Function ◽  
Hillslope Scale

Abstract. The study deals with the identification and characterization of rapid subsurface flow structures through pedo- and geo-physical measurements and irrigation experiments at the point, plot and hillslope scale. Our investigation of flow-relevant structures and hydrological responses refers to the general interplay of form and function, respectively. To obtain a holistic picture of the subsurface, a large set of different laboratory, exploratory and experimental methods was used at the different scales. For exploration these methods included drilled soil core profiles, in situ measurements of infiltration capacity and saturated hydraulic conductivity, and laboratory analyses of soil water retention and saturated hydraulic conductivity. The irrigation experiments at the plot scale were monitored through a combination of dye tracer, salt tracer, soil moisture dynamics, and 3-D time-lapse ground penetrating radar (GPR) methods. At the hillslope scale the subsurface was explored by a 3-D GPR survey. A natural storm event and an irrigation experiment were monitored by a dense network of soil moisture observations and a cascade of 2-D time-lapse GPR trenches. We show that the shift between activated and non-activated state of the flow paths is needed to distinguish structures from overall heterogeneity. Pedo-physical analyses of point-scale samples are the basis for sub-scale structure inference. At the plot and hillslope scale 3-D and 2-D time-lapse GPR applications are successfully employed as non-invasive means to image subsurface response patterns and to identify flow-relevant paths. Tracer recovery and soil water responses from irrigation experiments deliver a consistent estimate of response velocities. The combined observation of form and function under active conditions provides the means to localize and characterize the structures (this study) and the hydrological processes (companion study Angermann et al., 2017, this issue).

Thermal characterization of coal using piezoelectric photoacoustic microscopy

1986 ◽  
Vol 64 (9) ◽  
pp. 1184-1189 ◽  
Author(s):  
A. Biswas ◽  
T. Ahmed ◽  
K. W. Johnson ◽  
K. L. Telschow ◽  
J. C. Crelling ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Characterization ◽  
Photoacoustic Signal ◽  
Photoacoustic Microscopy ◽  
Piezoelectric Detection ◽  
Theoretical Predictions ◽  
Coal Macerals

The organic constituents that make up the heterogeneous coal mass are called macerals. Vitrinite and pseudovitrinite are two of the most abundantly occurring macerals in North American coals. Photoacoustic microscopy using piezoelectric detection offers a useful technique for probing the thermal-elastic properties of these coal macerals. The experimental and theoretical conditions under which photoacoustic microscopy can be used to characterize the in situ thermal-elastic properties of macerals, as a function of the percentage of carbon or "rank" of coal, are investigated in this paper. Existing piezoelectric photoacoustic theory has been applied to our sample–transducer configuration to arrive at an expression for the voltage measured from the piezoelectric transducer. The theory indicates that the photoacoustic signal is related to the following sample properties: coefficient of thermal expansion a, bulk modulus B, density ρ, and specific heat c. These properties are coupled together into a dimensionless parameter given by aB/ρc, to which the measured voltage is proportional. Some experimental results used to test the validity of the theoretical predictions are presented. Photoacoustic data gathered on 10 Appalachian Basin coals are plotted as a function of the coal rank. These results are shown to compare favourably with a calculated curve, constructed using independently measured values of a, B, ρ, and c.

Microcrack‐induced versus intrinsic elastic anisotropy in mature HC‐source shales

Geophysics ◽  
1993 ◽  
Vol 58 (11) ◽  
pp. 1703-1706 ◽  
Author(s):  
Lev Vernik
Keyword(s):  
Elastic Anisotropy ◽  
Crack Density ◽  
Experimental Studies ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Clay Particles ◽  
Velocity Anisotropy ◽  
Vsp Data ◽  
Intrinsic Anisotropy

Recent experimental studies of ultrasonic velocity anisotropy in kerogen‐rich shales indicate that these rocks are characterized by a very strong anisotropic response related to a very fine, bedding‐parallel lamination of organic matter and preferred orientation of clay particles in the rock matrix (Vernik and Nur, 1992). This intrinsic anisotropy is further enhanced in thermally mature shales by bedding‐parallel microcracks caused by the processes of hydrocarbon generation (Vernik, paper in preparation). However, the potential of recognizing mature source‐rocks in situ using downhole sonic, crosshole seismic, or VSP data clearly depends on our ability to discriminate between these two major causes of elastic anisotropy, remove the effect of the intrinsic anisotropy, and estimate crack density and crack porosity from velocity measurements.

The effect of kerogen on the elastic anisotropy of organic-rich shales

Geophysics ◽  
2013 ◽  
Vol 78 (2) ◽  
pp. D65-D74 ◽  
Author(s):  
Colin M. Sayers
Keyword(s):  
Elastic Properties ◽  
Trajectory Optimization ◽  
Elastic Anisotropy ◽  
In Situ Stress ◽  
Hydraulic Fractures ◽  
Deformation And Failure ◽  
Reservoir Rocks ◽  
Stress Changes ◽  
Shale Anisotropy

The elastic properties of reservoir rocks are important for geomechanics applications; the most important of which are: analysis of stress changes due to production, analysis of rock deformation and failure, wellbore trajectory optimization, and the design of hydraulic fractures. Organic-rich shales are often observed to be strongly anisotropic due to the partial alignment of anisotropic clay minerals and the bedding-parallel lamination of organic material within the shale. Neglecting shale anisotropy may lead to incorrect estimates of the in situ stress or stress changes resulting from production. As a result, isotropic models may fail to describe geomechanical behavior correctly. The distribution of the organic phase plays an important role in determining the elastic properties of organic-rich shales, and this has a significant effect on production-induced stress changes. The presence of kerogen leads to a decrease in all of the elastic moduli, and has a significant effect on the geomechanical behavior of shales. The change in horizontal effective stress for a given change in pore pressure resulting from production is greater for kerogen-rich shales, and the neglect of anisotropy in predicting such stress changes may lead to significant errors.

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