Study on anisotropy of Longmaxi shale using hydraulic fracturing experiment

Zhai, Hongchen; Chang, Xu; Zhu, Wei; Lei, Xinglin; Xue, Ziqiu

doi:10.1007/s11430-020-9691-2

Cited by 15 publications

(3 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Weijers et al (2000); McClure and Horne (2013); Lu et al (2015); Ju et al (2019) optimized the fracturing parameter using numerical simulation and found that the stimulated reservoir volume (SRV) and oil-gas production after fracturing are closely positively correlated. With the improvement of experimental technology, some scholars have carried out many new experiments on hydraulic fracturing in recent years, including experiments with new similar materials (Abe et al, 2021;Wang et al, 2021;Zhai et al, 2021;Yang et al, 2022;Zheng et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Experimental study on the hydraulic fracture propagation of laminar argillaceous limestone continental shale

et al. 2023

View full text Add to dashboard Cite

Laminar argillaceous limestone continental shale is an important oil reservoir in Jiyang Depression, Bohai Bay Basin of China. Affected by the laminar structure, the spatial propagation morphology of hydraulic fracturing is not clear. To reveal the propagation law of hydraulic fracturing pathway in laminar marl continental shale, the mineral content and basic rock mechanics test are firstly carried out on the cores from the wells in Jiyang Depression. Secondly the similar material cores with standard-size and large-size are manufactured and processed. Finally, combined with physical model experiments, acoustic emission and moment tensor inversion techniques, the hydraulic fracturing experiments on the large-size cores under different stress differences are conducted. The experimental results show that the in situ stress (confining stresses), laminar structure, and lithological distribution jointly affect the propagation mode of fractures. As the horizontal stress difference increases, the stimulated reservoir volume gradually decreases, and the number of shear fractures decreases accordingly. Macroscopically, the pump pressure curve shows obvious fluctuation in the case with lower horizontal stress difference, which is the external performance of hydraulic fracture initiation–obstruction–turning–penetrating–obstruction–turning. The content of brittle and plastic minerals has a significant impact on the fracture complexity, particularly the layers with high argillaceous content have a significant inhibitory effect on fracture propagation. The weakly cemented lamination or bedding plane is easy to capture the fracture and make it propagate along the bedding plane, thereby increasing the complexity of fracture network. The research results are expected to provide a theoretical reference for design and optimization of hydraulic fracturing parameter in continental shale oil exploration and development.

show abstract

Section: Introductionmentioning

confidence: 99%

Experimental study on the hydraulic fracture propagation of laminar argillaceous limestone continental shale

et al. 2023

View full text Add to dashboard Cite

show abstract

“…Deng et al [21] found that the P-and S-wave velocities increase with an increasing bedding angle or axial stress. Zhai et al [22] conducted differential rock physics experiments on the Longmaxi Formation shale through pseudo triaxial stress loading experiments and concluded that applied isotropic stress to the shale can increase its P-and S-wave velocity, elastic modulus, and Poisson's ratio; however, the anisotropy degree also weakens.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Stress Sensitivity of Elastic Wave Velocities for Anisotropic Shale in Wufeng–Longmaxi Formation

Feng,

Tang,

Tang

et al. 2023

Processes

View full text Add to dashboard Cite

The shale of the Wufeng–Longmaxi formation in the Sichuan Basin is the preferred layer for shale gas exploration in China, and its petrophysical characteristics are the key to geological and engineering sweet spot prediction. However, the characteristics and impact mechanisms of its acoustic wave velocity and elastic anisotropy are currently unclear. In this paper, the Wufeng–Longmaxi shale is taken as the research object, and the P-wave and S-wave velocities of the samples are tested under the loading and unloading processes of confining pressure. The stress sensitivity variations in parameters such as wave velocity, wave velocity ratio, and anisotropy are discussed. P-wave and S-wave anisotropy parameters are correlated under different pressure conditions. X-ray diffraction, casting thin sections, scanning electron microscopy, micron CT scanning, and other analytical techniques are used to explore the mechanisms of stress sensitivity of elastic parameters. The research results indicate that: (1) the acoustic velocities of samples from different angles are V90° > V45° > V0°, and there is a positive correlation between the wave velocity and the confining pressure. After unloading the confining pressure, irreversible plastic deformation occurs due to the closure of some microfractures in the rock core, causing the wave velocity to be higher than the initial value. (2) The stress sensitivity coefficient of the P-wave (The mean is 3.00 m·s−1·MPa−1) is higher than that of the S-wave (the mean is 1.23 m·s−1·MPa−1), and the stress sensitivity coefficient of the compacted stage (the mean is 3.02 m·s−1·MPa−1) is higher than that of the elastic stage (the mean is 1.21 m·s−1·MPa−1). (3) The anisotropy of the P-wave and S-wave is negatively correlated with the confining pressure. When the confining pressure is loaded to 65 MPa, the change rate of the P-wave anisotropy coefficient is 23%, and its stress sensitivity is higher than that of S-wave anisotropy coefficient (the change rate is 13.7%). After unloading the confining pressure, the degree of anisotropy is reduced due to the closure of some microfractures. The empirical formula of P-wave and S-wave anisotropy parameters under different pressures is established through linear regression, which can provide a reference for mutual predictions. (4) The variation in wave velocity anisotropy with stress can be divided into stress and material anisotropy, which are related to the directional arrangement of microfractures and clay minerals, respectively. The quantitative characterization of shale anisotropy can be realized by evaluating the development degree of reservoir fractures and mineral components, providing a reference for logging interpretations, sweet spot prediction, and fracturing construction of shale gas reservoirs.

show abstract

“…Effective stress, porosity, permeability, fluid saturation, mineralogical compositions, pore type, and rock strength of sandstone and carbonate samples have been extensively investigated by several researchers (Anselmetti and Eberli 1993;Chang et al 2006;Freund 1992;Khaksar et al 1999;Khazanehdari and Sothcott 2003;Miller 1992;Rafavich et al 1984;Shakouri et al 2019;Soete et al 2015). Several studies have investigated the effects of many parameters, such as gas transport and adsorption effect, pyrolysisinduced thermal maturation, water content, the relationship between static and dynamic properties, temperature, anisotropy, and bedding orientation effects using shale samples (Aljamaan et al 2017;Aljamaan et al 2013;Allan et al 2016;Alnoaimi* et al 2014;Guo et al 2013;He et al 2019;Holt et al 2015;Holt et al 2012;Kim et al 2020;Kuila et al 2011;Lai et al 2016;Masri et al 2014;Sone and Zoback 2013a;Sone and Zoback 2013b;Zhai et al 2021). However, few studies have conducted to examine the rock physical and/or dynamic elastic properties of shale formations (Badrouchi et al 2019;Cho et al 2016;He and Ling 2016;Heller et al 2014;Khalil et al 2019;Ramezanian and Emadi 2020;Sun et al 2016).…”

Section: Introductionmentioning

confidence: 99%

An experimental study to investigate the physical and dynamic elastic properties of Eagle Ford shale rock samples

Altawati

Emadi

Khalil

2021

J Petrol Explor Prod Technol

View full text Add to dashboard Cite

Unconventional resources, such as Eagle Ford formation, are commonly classified for their ultra-low permeability, where pore sizes are in nano-scale and pore-conductivity is low, causing several challenges in evaluating unconventional-rock properties. Several experimental parameters (e.g., diffusion time of gas, gas injection pressure, method of permeability measurement, and confining pressure cycling) must be considered when evaluating the ultra-low permeability rock's physical and dynamic elastic properties measurements, where erroneous evaluations could be avoided. Characterizing ultra-low permeability samples' physical and elastic properties helps researchers obtain more reliable information leading to successful evaluations. In this study, 24 Eagle Ford core samples' physical and dynamic elastic properties were evaluated. Utilizing longer diffusion time and higher helium injection pressure, applying complex transient method, and cycling confining pressure were considered for porosity, permeability, and velocities measurements. Computerized tomography (CT) scan, porosity, permeability, and ultrasonic wave velocities were conducted on the core samples. Additionally, X-ray Diffraction (XRD) analysis was conducted to determine the mineralogical compositions. Porosity was measured at 2.07 MPa injection pressure for 24 h, and the permeability was measured using a complex transient method. P- and S-wave velocities were measured at two cycles of five confining pressures (up to 68.95 MPa). The XRD analysis results showed that the tested core samples had an average of 81.44% and 11.68% calcite and quartz, respectively, with a minor amount of clay minerals. The high content of calcite and quartz in shale yields higher velocities, higher Young's modulus, and lower Poisson's ratio, which enhances the brittleness that is an important parameter for well stimulation design (e.g., hydraulic fracturing). The results of porosity and permeability showed that porosity and permeability vary between 5.3–9.79% and 0.006–12 µD, respectively. The Permeability–porosity relation of samples shows a very weak correlation. P- and S-wave velocities results display a range of velocity up to 6206 m/s and 3285 m/s at 68.95 MPa confining pressure, respectively. Additionally, S-wave velocity is approximately 55% of P-wave velocity. A correlation between both velocities is established at each confining pressure, indicating a strong correlation. Results illustrated that applying two cycles of confining pressure impacts both velocities and dynamic elastic moduli. Ramping up the confining pressure increases both velocities owing to compaction of the samples and, in turn, increases dynamic Young's modulus and Poisson's ratio while decreasing bulk compressibility. Moreover, the results demonstrated that the above-mentioned parameters' values (after decreasing the confining pressure to 13.79 MPa) differ from the initial values due to the hysteresis loop, where the loop is slightly opened, indicating that the alteration is non-elastic. The findings of this study provide detailed information about the rock physical and dynamic elastic properties of one of the largest unconventional resources in the U.S.A, the Eagle Ford formation, where direct measurements may not be cost-effective or feasible.

show abstract

Study on anisotropy of Longmaxi shale using hydraulic fracturing experiment

Cited by 15 publications

References 52 publications

Experimental study on the hydraulic fracture propagation of laminar argillaceous limestone continental shale

Experimental study on the hydraulic fracture propagation of laminar argillaceous limestone continental shale

Experimental Investigation of Stress Sensitivity of Elastic Wave Velocities for Anisotropic Shale in Wufeng–Longmaxi Formation

An experimental study to investigate the physical and dynamic elastic properties of Eagle Ford shale rock samples

Contact Info

Product

Resources

About