Stress-path dependence of ultrasonic and seismic velocities in shale

Holt, R.M.; Bauer, Andreas; Bakk, Audun; Szewczyk, Dawid

doi:10.1190/segam2016-13946568.1

Cited by 9 publications

(12 citation statements)

References 10 publications

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“…Note that the stress path sensitivities both in SPz and RPz are very similar to those shown for a different field shale in Holt et al (2016). Figure 3 Laboratory measured ultrasonic stress and strain sensitivities SPz and RPz for axial P-wave velocity vs stress path parameter with a field shale core having the sample (z-) axis normal to the bedding plane (cf.…”

Section: Also Shown Inmentioning

confidence: 77%

“…For isotropic incremental stress, the ratio C/A plays the role of an effective stress coefficient. Holt et al (2016) demonstrated that laboratory measured P-and S-wave velocities follow a linear trend in in the stress path coefficient  = 3/1:…”

Section: Link To Rock Physicsmentioning

confidence: 99%

“…These parameters may be quantified by geomechanical modeling/simulations, and to some extent verified from in situ measurements, like time-lapse extended leak-off tests (XLOT). They reflect the geometry (aspect ratio and tilt) of the reservoir zone, the elastic contrast between the reservoir zone and the surroundings, and impact of non-elastic processes (Holt et al, 2016). The classical analytical solution assumes no elastic contrast (Geertsma, 1973) and predicts h/v = -½ (i.e.…”

Section: Link To Rock Physicsmentioning

confidence: 99%

“…Assuming that wave velocities in shale under in situ conditions change linearly with changes in stress and pore pressure, the change in P-or S-wave velocities along any direction may be written (Holt et al, 2016):…”

Section: Link To Rock Physicsmentioning

confidence: 99%

“…Eq(3)); which may be derived from laboratory experiments. Ultrasonic data were used in the current work, but there is evidence that stress sensitivities may be different at seismic frequencies (Holt et al, 2016).  The Skempton parameters AS and BS (notice the angular dependence of AS in Eq.…”

Section: Link To Rock Physicsmentioning

confidence: 99%

See 4 more Smart Citations

Overburden pore-pressure changes and their influence on 4D seismic

Holt¹,

Bauer

Bakk

2017

SEG Technical Program Expanded Abstracts 2017

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SummaryChanges in seismic two-way travel time in the overburden can be attributed to pore pressure changes in the underlying reservoir. Since cap rock permeability is very small, these stress changes occur without drainage on short term, which means that, depending on stress path, pore pressure may also change in the overburden. The direct impact of this on 4D seismic has not been thoroughly addressed in the literature. Here, laboratory data with an overburden shale core are presented, showing stress path dependent changes in P-wave velocity and pore pressure. The expected impact on 4D seismic can be significant.

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Section: Also Shown Inmentioning

confidence: 77%

Section: Link To Rock Physicsmentioning

confidence: 99%

Section: Link To Rock Physicsmentioning

confidence: 99%

Section: Link To Rock Physicsmentioning

confidence: 99%

Section: Link To Rock Physicsmentioning

confidence: 99%

See 3 more Smart Citations

Overburden pore-pressure changes and their influence on 4D seismic

Holt¹,

Bauer

Bakk

2017

SEG Technical Program Expanded Abstracts 2017

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Applied techniques for residual oil recovery from source rocks: A review of current challenges and possible developments

Abdulkareem

Padmanabhan

2020

Can J Chem Eng

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Depleted fossil fuel resources have led to an investigation of other promising alternatives such as renewable and unconventional energy sources. Shale formations have limited permeability. Therefore, several extraction techniques have been applied to improve residual oil recovery and production. In this work, the techniques applied above ground to extract the organic fractions from oil/gas shale are discussed. Studies related to compositional fractionation, ultrasonic-assisted, microwave-assisted, supercritical fluids, and surface retorting techniques have been conducted systematically in approximately 150 scholarly articles over the past 10 years. The impacts of each technique as well as the drawbacks and challenges are highlighted in this paper. The fractionation techniques are sufficient in general; however, they are time consuming as they include several stages and use a considerable amount of solvents. Ultrasonic and microwave techniques are highly reliant on formation transparency linked to the organic fraction heterogeneous distribution. The surface retorting method, which is highly efficient with up to 90% recovery, for example, the Galoter and Paraho methods, is still dependent on shale particulate size, generates a massive amount of spent shale as waste, and is prominently emissive. Therefore, assessments that can be used to overcome existing drawbacks are considered. This can provide practical insight about these techniques to overcome limitations and concerns in terms of efficiency, cost, environmental issues, and reliability features. The work highlights the dominant extraction techniques for further development.

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Stress-dependent elastic properties of shales—laboratory experiments at seismic and ultrasonic frequencies

Szewczyk¹,

Bauer

Holt³

2017

Geophysical Journal International

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Knowledge about the stress sensitivity of elastic properties and velocities of shales is important for the interpretation of seismic time-lapse data taken as part of reservoir and caprock surveillance of both unconventional and conventional oil and gas fields (e.g. during 4-D monitoring of CO 2 storage). Rock physics models are often developed based on laboratory measurements at ultrasonic frequencies. However, as shown previously, shales exhibit large seismic dispersion, and it is possible that stress sensitivities of velocities are also frequency dependent. In this work, we report on a series of seismic and ultrasonic laboratory tests in which the stress sensitivity of elastic properties of Mancos shale and Pierre shale I were investigated. The shales were tested at different water saturations. Dynamic rock engineering parameters and elastic wave velocities were examined on core plugs exposed to isotropic loading. Experiments were carried out in an apparatus allowing for static-compaction and dynamic measurements at seismic and ultrasonic frequencies within single test. For both shale types, we present and discuss experimental results that demonstrate dispersion and stress sensitivity of the rock stiffness, as well as P-and S-wave velocities, and stiffness anisotropy. Our experimental results show that the stress-sensitivity of shales is different at seismic and ultrasonic frequencies, which can be linked with simultaneously occurring changes in the dispersion with applied stress. Measured stress sensitivity of elastic properties for relatively dry samples was higher at seismic frequencies however, the increasing saturation of shales decreases the difference between seismic and ultrasonic stress-sensitivities, and for moist samples stress-sensitivity is higher at ultrasonic frequencies. Simultaneously, the increased saturation highly increases the dispersion in shales. We have also found that the stress-sensitivity is highly anisotropic in both shales and that in some of the cases higher stress-sensitivity of elastic properties can be seen in the direction parallel to the bedding plane.

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Stress-path dependence of ultrasonic and seismic velocities in shale

Cited by 9 publications

References 10 publications

Overburden pore-pressure changes and their influence on 4D seismic

Overburden pore-pressure changes and their influence on 4D seismic

Applied techniques for residual oil recovery from source rocks: A review of current challenges and possible developments

Stress-dependent elastic properties of shales—laboratory experiments at seismic and ultrasonic frequencies

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