Brittleness Evaluation of Shale Based on the Brazilian Splitting Test

Hou, Bing; Zeng, Yanjun; Meng, Fan; Li, Dandan

doi:10.1155/2018/3602852

Cited by 14 publications

(6 citation statements)

References 12 publications

(12 reference statements)

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“…Li et al [12] equally reported on the likely occurrences of secondary fractures along laminations and shear failures driven by edge-concentrated compressional loads. Hou et al [23] and Ma et al [13] reported on tensile splitting, tensile-shear, and shear failure patterns. Tensile splitting is synonymous with primary fractures, and tensile-shear failure with a half-moon shaped fracture plane may be caused by the suppression of rock failure due to the high bonding strength between the rock's bedding layers.…”

Section: Thermal Conditioning Effects On Physical Appearances Of Shal...mentioning

confidence: 99%

“…Researchers have investigated (1) burial depth [17,18], (2) total organic carbon (TOC) [19,20], (3) bedding and/or loading orientations [12,[20][21][22][23][24][25][26], and (4) KCl-water saturation [12] effects on shale tensile strength. These established that studies relating to shale tensile failure have focused mainly on bedding and/or loading orientation effects on shale tensile strength.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation of Shale Tensile Failure under Thermally Conditioned Linear Fracturing Fluid (LFF) System and Reservoir Temperature Controlled Conditions

2022

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Linear fracturing fluid (LFF) provides viscosity driven benefits of proppant suspensibility and fluid loss control, and with the use of a breaker agent, flowback recovery can be greatly enhanced. Shale tensile strength is critical in the prediction of fracture initiation and propagation, but its behavior under the interaction with LFF at reservoir temperature conditions remains poorly understood. This necessitated an in-depth investigation into the tensile strengths of Eagle Ford and Wolfcamp shales under thermally conditioned LFF and reservoir temperature controlled conditions. Brazilian Indirect Tensile Strength (BITS) testing was carried out for the quantitative evaluation of shale tensile strength, followed by extensive failure pattern classifications and surface crack length analysis. The thermally conditioned LFF saturation of shale samples led to average tensile strength (ATS) increases ranging from 26.33–51.33% for Wolfcamp. Then, for the Eagle Ford samples, ATS increases of 3.94 and 6.79% and decreases of 3.13 and 15.35% were recorded. The exposure of the samples to the temperature condition of 90 °C resulted in ATS increases of 24.46 and 33.78% for Eagle Ford and Wolfcamp shales, respectively. Then, for samples exposed to 220 °C, ATS decreases of 6.11 and 5.32% were respectively recorded for Eagle Ford and Wolfcamp shales. The experimental results of this research will facilitate models’ development towards tensile strength predictions and failure pattern analysis and quantifications in the LFF driven hydraulic fracturing of shale gas reservoirs.

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Section: Thermal Conditioning Effects On Physical Appearances Of Shal...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Shale Tensile Failure under Thermally Conditioned Linear Fracturing Fluid (LFF) System and Reservoir Temperature Controlled Conditions

2022

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“…85 Hence, discrepancies are expected to be observed in geomechanical properties of the outcrop and subsurface. 123 Hou et al 124 investigated the influence of buried depth, coring angle, and test conditions on the mechanical characteristics of shale by carrying out Brazilian tensile testing using shale samples of the Longmaxi Formation. They found a gradual increase in the shale tensile strength with increasing depth of burial and loading rates, resulting in higher values for downhole shale samples than outcrop samples.…”

Section: Comparison Based On Geomechanicalmentioning

confidence: 99%

Use of Outcrop as Substitute for Subsurface Shale: Current Understanding of Similarities, Discrepancies, and Associated Challenges

et al. 2021

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Full coring in shale reservoirs is challenging, time consuming, and risky due to fragility. Therefore, shale outcrop analogs are often used as an alternative to enhance the understanding of corresponding subsurface reservoir formation multifaceted mineralogy and rock characteristics. As consequence, many researchers perform their fundamental experimental studies on the core samples collected from outcrops when the subsurface unconventional shale samples are scarce. An assumption is often made that the rock composition and properties of outcrop and subsurface samples remain the same which raises some serious concerns and demands a thorough review of published research to check the validity of this approach to characterize shale reservoirs. The high degree of lateral and vertical heterogeneity and anisotropy, weathering, contamination, and postdepositional tectonic activities further add to the major challenges. In this literature-based study, the authors revisit the current understanding and challenges of using shale outcrops to complement the available subsurface samples and use them for the preliminary evaluation of underexploration and undeveloped unconventional shale reservoirs. The similarities and discrepancies of mineralogical, petrophysical, geochemical, and geomechanical properties are discussed. Finally, some concluding remarks and recommendations are presented.

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“…At present, there is no unified standard in the evaluation of rock brittleness [11]. The evaluation of reservoir rock brittleness is mainly from lithology analysis, geophysical methods, and rock mechanics experiments [12][13][14][15][16]. The methods based on lithologic characteristics consider the content of brittle minerals [17,18].…”

Section: Introductionmentioning

confidence: 99%

An Improved Model for Evaluating the Brittleness of Shale Oil Reservoirs Based on Dynamic Elastic Properties: A Case Study of Lucaogou Formation, Jimusar Sag

et al. 2022

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Rock brittleness is a critical factor affecting the stimulation of shale oil reservoirs. For efficient development of the shale oil in Lucaogou Formation, Jimusar Sag, the brittleness of the sweet spots needs to be evaluated. In this paper, the triaxial compression, acoustic wave measurements, and three-point bending tests were carried out on the reservoir cores. Based on the prepeak energy characteristics of the stress-strain curve, the brittleness of different horizons was calculated, with the largest difference of 24.89%. An improved model based on dynamic elastic properties was proposed to evaluate the brittleness along the vertical pay zones, by which the continuous brittleness in the upper sweet spot was found more changeful than that in the lower sweet spot. The linear correlation coefficient between the brittleness from the improved model and that from the laboratory tests is 0.85, improving the accuracy by 21% and 27% respectively, compared with the conventional elastic property methods. From the characteristics of compression fractures and the length of the fracture process zone, it was found that the compression fractures were more complex and the fracture process zone length was shorter in a more brittle rock, verifying the reliability of the improvement model. The improved method based on dynamic elastic properties proposed in this paper is expected to guide the brittleness evaluation in other regions.

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Brittleness Evaluation of Shale Based on the Brazilian Splitting Test

Cited by 14 publications

References 12 publications

Experimental Investigation of Shale Tensile Failure under Thermally Conditioned Linear Fracturing Fluid (LFF) System and Reservoir Temperature Controlled Conditions

Experimental Investigation of Shale Tensile Failure under Thermally Conditioned Linear Fracturing Fluid (LFF) System and Reservoir Temperature Controlled Conditions

Use of Outcrop as Substitute for Subsurface Shale: Current Understanding of Similarities, Discrepancies, and Associated Challenges

An Improved Model for Evaluating the Brittleness of Shale Oil Reservoirs Based on Dynamic Elastic Properties: A Case Study of Lucaogou Formation, Jimusar Sag

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