Study on rock brittleness characteristics of deep volcanic reservoir under different confining pressures

Qiu, Guozhou; Chang, Xin; Li, Jing; Guo, Yintong; Wang, Lei; Ma, Hongling; Guo, Wuhao; Bi, Zhenhui

doi:10.1007/s13202-023-01717-z

Cited by 4 publications

(2 citation statements)

References 21 publications

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“…The current research on true triaxial fracturing experiments can already consider the influence of natural bedding in reservoirs and the propagation of multiple clusters of fractures. However, the current size of cube specimens in the laboratory is usually 100 mm × 100 mm × 100 mm or 300 mm × 300 mm × 300 mm, with few experimental specimens reaching the meter level in size, far smaller than the actual reservoir modification area (Shang et al, 2018;Liu et al, 2021;Qiu et al, 2023). Therefore, there are still significant size limitations in the physical simulation research of multi-cluster fracturing based on indoor experiments (Wang, et al, 2022;Yang et al, 2023b).…”

Section: Introductionmentioning

confidence: 99%

Study on multi-cluster fracturing simulation of deep reservoir based on cohesive element modeling

Wu,

Guo

et al. 2024

Front. Energy Res.

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With the depletion of conventional reservoir development, reservoir fracturing under deep high geo-stress and high geo-stress difference conditions is receiving increasing attention. Deep reservoirs typically require multi-cluster fracturing to achieve efficient reservoir transformation and development. In this paper, considering the relevant geological parameters of a certain reservoir in the southwest, three-dimensional multi-cluster reservoir fracturing models were established based on cohesive element modeling. Then, the propagation law of artificial fractures in reservoirs under the influence of the different number of fracturing clusters, injection displacement, and Young’s modulus in different regions of the 60 m fracturing well section is analyzed, and the quantitative law of parameters such as fracture length, maximum fracture width, injection point fracture width, fracture area, and tensile failure ratio during multi-cluster fracturing construction, as well as the propagation law of fracture morphology are revealed. The simulation results show that using multi-cluster fracturing can significantly improve the effectiveness of reservoir reconstruction, but as the number of fracturing clusters increases, it is also easy to form some small opening artificial fractures. These small opening artificial fractures may not be conducive to the transportation of proppants and fluids. During single cluster fracturing, the interface stiffness and rock Young’s modulus have a significant impact on the propagation of artificial fractures in the reservoir. As the number of fracturing clusters increases, the competition between artificial main fractures expands significantly, which may reduce the impact of interface stiffness and rock Young’s modulus. The fluid injection rate has a significant impact on reservoir fracturing, and in the same area, using high displacement injection can significantly increase the volume of reservoir reconstruction. This study can provide some reference for multi-cluster fracturing construction in deep reservoirs.

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Section: Introductionmentioning

confidence: 99%

Study on multi-cluster fracturing simulation of deep reservoir based on cohesive element modeling

Wu,

Guo

et al. 2024

Front. Energy Res.

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“…With the deepening of fracturing research, the assumption of homogeneous rocks in theoretical derivation has made it difficult to meet the current research needs. Meanwhile, although indoor experiments are an excellent method for fracturing research (Qiu, et al, 2023;Tan, et al, 2023), they are limited by sample size and cost, making it difficult to conduct more targeted on-site numerical simulation studies. As an accurate, efficient and convenient research method, numerical simulation can take into account some special factors in the actual reservoir, such as irregular natural fractures, random lithology mutants, and even complex ground stress states, and it is very suitable for studying the fracture propagation mechanism of deep shale reservoirs (Wei, et al, 2015;Liu, et al, 2018;Wu M. et al, 2018;Zheng, et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Study on the fracture propagation law of deep shale reservoir under the influence of different number of fracturing clusters

Zeng,

Wu,

et al. 2024

Front. Energy Res.

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Deep reservoirs have a large difference in geo-stress, and compared to shallow reservoirs, multiple clusters of fracturing are usually required to effectively improve the quality of reservoir reconstruction. In this paper, considering the relevant geological parameters of a certain reservoir in the southwest, multi-cluster reservoir fracturing models under three-dimensional conditions based on the cohesive element modelling method are established. Then, the quantitative rules of fluid pressure, fracture length, fracture aperture, fracture area, tensile failure rate, and the fractal dimension of fracture morphology under different fracturing cluster numbers were revealed. The results show that compared to conventional fracturing, multi-cluster fracturing can significantly increase the number of main fractures and improve the effectiveness of reservoir reconstruction. As the number of clusters increases, the number of main fractures in the reservoir increases, but it can also lead to the increase of small opening fractures, which may be unfavourable for the pumping of proppant and subsequent mining. Meanwhile, based on the fractal dimension results of fracture morphology, it was found that under this simulation condition, the number of fracturing clusters had a significant impact on the fractal dimension of fracturing fractures before the fracturing of six clusters, while after the fracturing of six clusters, the impact of the number of fracturing clusters on the fractal dimension of fracturing fractures decreased. Therefore, when considering factors such as the complexity of fractures, multi-cluster fracturing does not necessarily result in more fracturing clusters being better but should be comprehensively considered for optimization. This study has certain reference significance for selecting the spacing between multiple fracturing clusters.

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Study on the influence of vertical stress difference coefficient on fracture characteristics of shale under high stress

Chang,

Qiu,

et al. 2024

Energy Science & Engineering

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To study the effect of vertical stress difference coefficient on fracture characteristics of shale fracturing, high stress true triaxial hydraulic fracturing test was carried out. By analyzing the profile after fracturing, it was found that the area of hydraulic fracture increased with the increase of vertical stress difference coefficient, and the probability of shear fracture will increase when the stress difference coefficient was high. A high vertical stress differential coefficient exerts a strong control over the direction of crack propagation, while a low vertical stress difference coefficient is beneficial to improve the roughness of hydraulic fracture surface and promote the formation of complex fracture network. By analyzing the pump pressure curves of different tests, it was found that with the increase of vertical stress difference coefficient, the formation and expansion of hydraulic fractures were more difficult. The surface characteristics of hydraulic fractures were quantified based on three‐dimensional topography scanning technology, combined with fractal dimension and fracture area calculation method, the results showed that with the increase of vertical stress difference coefficient, the fractal dimension and fracture area decreased. Since shale is stratified, and the transformation of reservoir is mainly reflected in the enhancement of fracture complexity through tensile failure, Xsite discrete grid method was used to study the influence of fracture propagation behavior with different bedding strengths. The results showed that when the bedding tensile strength was high, hydraulic fractures were easy to pass through the bedding, and when the bedding tensile strength was low, hydraulic fractures were easy to be captured by natural fractures. In addition, tensile cracks were easy to form when the tensile strength of bedding was low, shear cracks were easy to form when the strength of bedding was high, and the fracture volume was larger when the strength of bedding was low. This study provides a theoretical basis for hydraulic fracturing in engineering.

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Study on rock brittleness characteristics of deep volcanic reservoir under different confining pressures

Cited by 4 publications

References 21 publications

Study on multi-cluster fracturing simulation of deep reservoir based on cohesive element modeling

Study on multi-cluster fracturing simulation of deep reservoir based on cohesive element modeling

Study on the fracture propagation law of deep shale reservoir under the influence of different number of fracturing clusters

Study on the influence of vertical stress difference coefficient on fracture characteristics of shale under high stress

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