Anisotropy of Strength and Elastic Properties of Lower Paleozoic Shales from the Baltic Basin, Poland

Wilczyński, Przemysław; Domonik, Andrzej; Łukaszewski, Paweł

doi:10.3390/en14112995

Cited by 11 publications

(3 citation statements)

References 66 publications

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“…The Sasino Shales are more siliceous, with an average to 45% clay minerals, 52% QFP, and only 3.5% carbonates. As indicated in [32], the mechanical and deformation properties of rocks from different units differ significantly. The results of the performed XRD analyses and petrophysical properties of the analyzed rocks were presented in detail in [32][33][34].…”

Section: Characteristics Of the Materialsmentioning

confidence: 99%

Viscoelastic Strains of Palaeozoic Shales under the Burger’s Model Description

Wilczynski,

Cieslik,

Domonik

et al. 2023

Applied Sciences

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This article presents the results of creep studies of Palaeozoic shales from the Baltic Basin in which the exploitation of shale gas in Poland was planned. Knowledge of instantaneous and long-term properties investigated in triaxial stress conditions is important from the point of view of exploitation techniques related to hydraulic fracturing. Rheological phenomena also play an important role in the analysis of the initial stress in shales, the knowledge of which is indispensable in the hydraulic fracturing process. The tests were carried out on samples representing four siltstone–claystone lithostratigraphic units occurring in the Baltic Basin. The studies and analyses were aimed at determining the character of creep in shales, selection of the appropriate rheological model for the analyzed rocks, and determination of the threshold of the linear creep under triaxial compression conditions. An original approach together with analysis results are presented here, which enable the separation and monitoring of shear and volume creep effects, and on this basis, the determination of the significance of the contribution of volume creep in the entire creep process. A relatively simple methodology for determination of the parameters of the Burgers model using this division is presented. The original value of the article is also due to the test results themselves and the parameter values of the analyzed model for triaxial creep of shales, which are not numerous in the literature. The investigations were performed at various loading levels in relation to the triaxial strength of the shales. Depending on the load, at its low values up to 0.7 (σ1 − σ3)max, creep had a determined character and did not show features of progressive creep. The linear creep threshold was also analyzed in this range. The loading level of 0.7 (σ1 − σ3)max was the limit of linear creep. Exceeding this load resulted in the loss of the linear character of creep, which in consequence lead to the subsequent third creep phase ending with rock damage. Parameters of the Burger’s model for gas shales from the Baltic Basin (northern Poland) were identified. There are significant differences in the behavior of shales depending on the lithostratigraphic unit from which the samples were collected. The mineral composition of the shales also influenced their behavior.

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Section: Characteristics Of the Materialsmentioning

confidence: 99%

Viscoelastic Strains of Palaeozoic Shales under the Burger’s Model Description

Wilczynski,

Cieslik,

Domonik

et al. 2023

Applied Sciences

Self Cite

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“…Mayr et al [24] proposed the porosity deformation approach (PDA) to the elastic anisotropy of shale under triaxial loading and found that the velocity change due to hydrostatic loading can be used to predict elastic anisotropy under additional axial loading. Wilczynski et al [25] studied the anisotropy of strength and elastic properties of lower Paleozoic shales from the Baltic basin, Poland, and found that the shale was characterized by VTI type (vertical transverse isotropy) internal anisotropy. Xu et al [26] adopted a finite-element-based continuum damage mechanics model to capture sample size effects and the influence of intrinsic anisotropy on the stressstrain response of shale and investigated deformation and stiffness anisotropy induced by damage propagation in a rock brittle deformation regime.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Anisotropic Mechanical Characteristics of Shale under Triaxial Loading

Dong,

Kang,

Sun

et al. 2024

Applied Sciences

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Shale is composed of a rock matrix and bedding planes with a layered structure, resulting in significant anisotropy in its mechanical properties. In order to study the anisotropic mechanical properties of shale, the shale samples were prepared in different orientations with respect to the bedding planes, and the composition and microstructure of shale were first analyzed by X-ray diffractometer (XRD) and scanning electron microscope (SEM), and then the uniaxial and triaxial compression experiment on shale samples with five different bedding angles (the angle between the loading direction and the normal direction of the bedding planes, 0°, 30°, 45°, 60°, and 90°) were conducted under five confining pressures (0, 10, 20, 30, and 40 MPa), respectively; meanwhile, the acoustic emission (AE) test was carried out in the uniaxial test. The results indicate that the mechanical properties and parameters of shale have obvious anisotropy, and the AE characteristics of shale samples with different bedding angles are significantly different during uniaxial loading. Furthermore, the compressive strength and elastic modulus of the shale samples first decrease and then increase with the increase in the bedding angle under different confining pressures. Moreover, according to the anisotropic grade of compressive strength, the shale has moderate anisotropy. In addition, the failure mode of the shale samples is also anisotropic, and varies with the bedding angle and confining pressure.

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“…Organic matter within the rock matrix directly controls organic porosity and adsorbed gas [2,13,14]. Additionally, TOC affects mechanical anisotropy (Sone and Zoback, 2013a), geomechanical properties [15][16][17][18][19], and brittleness [3,4,20]. In the global perspective, better gross estimation of shale reservoir requires the importance of a more precisely defined TOC model for future development activity.…”

Section: Introductionmentioning

confidence: 99%

Ensemble Learning for Predicting TOC from Well-Logs of the Unconventional Goldwyer Shale

2021

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Precise estimation of total organic carbon (TOC) is extremely important for the successful characterization of an unconventional shale reservoir. Indirect traditional continuous TOC prediction methods from well-logs fail to provide accurate TOC in complex and heterogeneous shale reservoirs. A workflow is proposed to predict a continuous TOC profile from well-logs through various ensemble learning regression models in the Goldwyer shale formation of the Canning Basin, WA. A total of 283 TOC data points from ten wells is available from the Rock-Eval analysis of the core specimen where each sample point contains three to five petrophysical logs. The core TOC varies largely, ranging from 0.16 wt % to 4.47 wt % with an average of 1.20 wt %. In addition to the conventional MLR method, four supervised machine learning methods, i.e., ANN, RF, SVM, and GB are trained, validated, and tested for continuous TOC prediction using the ensemble learning approach. To ensure robust TOC prediction, an aggregated model predictor is designed by combining the four ensemble-based models. The model achieved estimation accuracy with R2 value of 87%. Careful data preparation and feature selection, reconstruction of corrupted or missing logs, and the ensemble learning implementation and optimization have improved TOC prediction accuracy significantly compared to a single model approach.

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Anisotropy of Strength and Elastic Properties of Lower Paleozoic Shales from the Baltic Basin, Poland

Cited by 11 publications

References 66 publications

Viscoelastic Strains of Palaeozoic Shales under the Burger’s Model Description

Viscoelastic Strains of Palaeozoic Shales under the Burger’s Model Description

Experimental Study on Anisotropic Mechanical Characteristics of Shale under Triaxial Loading

Ensemble Learning for Predicting TOC from Well-Logs of the Unconventional Goldwyer Shale

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