Numerical simulation of proppant directly entering complex fractures in shale gas

Zhang, Tao; Liu, Cong; Shi, Yongbing; Mu, Kefan; Wu, Chuanbin; Guo, Jianchun; Lu, Cong

doi:10.1016/j.jngse.2022.104792

Cited by 16 publications

(8 citation statements)

References 8 publications

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“…Zhang et al used CT scanning technology to study the microstructure changes of the shale hydration process and found that shale hydration can promote the development of secondary pores and fractures, which can lead to changes in shale structure and evolution into macroscopic damage. 14 It is believed that the essence of shale structural failure is the expansion and extension of microcracks. Wang et al found through shale expansion experiments that shale exhibits significant self-absorption and expansion in the initial stage, with minimal changes in the later stage.…”

Section: Introductionmentioning

confidence: 99%

“…Field data have shown that a considerable amount of the fracturing fluid is lost and retained within the shale, resulting in lower overall backflow rates. − Liu et al , found through on-site mine tests that microseismic events can still occur during the process of shutting down the well after fracturing construction, indicating that there is still crack development during the process of shutting down the well. Zhang et al used CT scanning technology to study the microstructure changes of the shale hydration process and found that shale hydration can promote the development of secondary pores and fractures, which can lead to changes in shale structure and evolution into macroscopic damage . It is believed that the essence of shale structural failure is the expansion and extension of microcracks.…”

Section: Introductionmentioning

confidence: 99%

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Distribution Characteristics and Backflow Flow Pattern of a Slickwater Fracturing Fluid in Shale Based on Low-Field Nuclear Magnetic Resonance

Liu,

Zhang,

Yang

et al. 2024

Energy Fuels

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The distribution and characteristics of the fracturing fluid in shales play a crucial role in determining the shale gas production system for the mining field. By use of low-field nuclear magnetic resonance (NMR) technology and an online displacement system, the distribution of the fracturing fluid in shale reservoirs during hydraulic fracturing was investigated. An online monitoring method was established to track the filtration loss, well soaking, and backflow 3 processes of fracturing fluids in shale reservoirs. The full-scale pore-throat size of the shale in the CN block predominantly distributes within the range of 0.4–8.0 nm. Low-field NMR technology accurately captured the variations in the water-phase sorption and flow in different pores within the shale. During the filtration loss stage, the fracturing fluid entered the core in a stepwise manner, indicating the development of microfractures during fluid invasion. During the well soaking stage, the fracturing fluid preferentially entered the small pores under capillary forces with a stable sorption time of approximately 8 h at the standard core scale. The peak value of the T2 spectrum gradually decreased with increasing backflow time. Within 135 min, the liquid in the large pores and microfractures in the shale was predominantly expelled. After 135 min, the fracturing fluid in the small pores became immobile and formed bound water. After 200 min, the backflow of the fracturing fluid reached a stable state. During the backflow stage, the fracturing fluid in the large pores was primarily expelled, making the greatest contribution to the backflow volume. Weighted analysis of 3 major production parameters showed that the order of importance for influencing the backflow rate in shale was backflow pressure difference > soaking time > outlet pressure. To fully flow back the fracturing fluid after fracturing, it is recommended that the pressure difference be gradually increased, the soaking time shortened, and the outlet pressure optimized.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Distribution Characteristics and Backflow Flow Pattern of a Slickwater Fracturing Fluid in Shale Based on Low-Field Nuclear Magnetic Resonance

Liu,

Zhang,

Yang

et al. 2024

Energy Fuels

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“…Tsuji et al [10] first combined CFD and DEM for the numerical simulation of a fluidized bed. Zhang et al [11] investigated the two-phase flow law based on the CFD-DEM model for different fracture widths and angles, and pump discharge and fluid viscosity conditions. Tao Zhang et al [12] use the Eulerian-Eulerian two-fluid model to study the flow of fracturing fluid and proppant in a flat plate fracture under the influence of different inlet velocity and position, proppant concentration, and other parameters, and the simulation results were compared with experiments with high compliance, which verified the validity of the model.…”

Section: Introductionmentioning

confidence: 99%

Study on Proppant Transport and Placement in Shale Gas Main Fractures

Liang,

Xiu,

et al. 2024

Energies

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In this paper, based on the background of a deep shale reservoir, a solid–liquid two-phase flow model suitable for proppant and fracturing fluid flow was established based on the Euler method, and a large-scale fracture model was established. Based on field parameters, a proppant transport experiment was conducted. Then, on the basis of the experimental fracture model, proppant transport simulation under different influencing factors was carried out. The results show that the laboratory experiment was in good agreement with the simulated results. The process of proppant accumulation in fractures can be divided into three stages according to the characteristics of sand banks. The displacement mainly affects the sedimentation distance of the proppant in the first stage, and the viscosity of the fracturing fluid represents the strength of the fluid sand carrying performance. Compared with 40/70 mesh proppant, 70/140 mesh proppant is more easily fluidizable, the fracture width has less influence on proppant migration and placement, and the perforation location only affects the accumulation pattern at the fracture entrance, but has less influence on proppant placement in the remote well zone.

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“…Huang et al (2021) proposed a continuum model for simulating proppant transport and fluid flow in hydraulic fractures. Isaev et al (2023) proposed adaptive seeding/reseeding methods with exact integration of particles trajectories and local time step refinement in the vicinity of injection zones In these studies, equations describing the migration and sedimentation of proppant were derived based on the solid-liquid coupling relationship and sedimentation law during proppant flow (Hu et al, 2023;Li et al, 2023;Shi, 2016), and most of them were simulated with CFD-DEM (Gong et al, 2023;Liu et al, 2019;Lv et al, 2023;Shi, 2016;Tong and Mohanty, 2016;Xiang and Li, 2023;Zhang et al, 2022Zhang et al, , 2023aZhu et al, 2023) or CFD-XFEM software (Brannon et al, 2005;Qu et al, 2022Qu et al, , 2023Zhang et al, 2023b) such as fluent for two-dimensional and pseudo three-dimensional model. Through numerical simulations of parameters (Hang et al, 2023;Suri et al, 2019Suri et al, , 2020b based on different fracturing fluids and proppant morphologies, the velocity, concentration and pressure distribution of the proppant within the fracture were obtained, and proppant migration and sedimentation patterns were also derived for different fracture morphology parameters and proppant and fluid parameters.…”

Section: Introductionmentioning

confidence: 99%

Simulation and solution of a proppant migration and sedimentation model for hydraulically fractured inhomogeneously wide fractures

Peiqi,

Lin,

et al. 2024

Energy Exploration & Exploitation

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The distribution of proppant during hydraulic fracturing may directly contribute to the flow conductivity of the proppant fracture, so research on the migration and sedimentation of proppant in the fracture and the final distribution pattern is of great relevance. The mass conservation equations of proppant solids and fracturing fluid were adopted to describe the distribution of proppant migration and sedimentation in the fracture, improving the additional gravity coefficient by utilizing the density difference between proppant and fracturing fluid and the concentration of proppant, together with the proppant sedimentation velocity at different Reynolds numbers in this study. The flow coefficients were obtained by discretizing the system of equations through the finite volume method combined with the harmonic mean method and the upstream weight method. The concentration additional pressure gradient term was computed by using the Superbee format innovatively to improve the solution convergence of the model. Numerical simulations with identical parameters were compared with indoor test results, which fully verified the correctness of the model and the accuracy of the discrete solution based on the finite volume method. The effects of flow rate of fracturing fluid, ratio of injected sand, viscosity of fracturing fluid, grain size of proppant and density of proppant on proppant migration and sedimentation based on three elliptical fracture morphologies: even-wide, top-wide and bottom-narrow as well as top-narrow and bottom-wide were investigated and analyzed through comparing the rate of proppant front movement, the level of sweeping range and the degree of inhomogeneity in the range under different conditions. Findings of this study suggest that: (1) top-wide and bottom-narrow fractures are more preferable for homogenous sanding in the early stage of proppant injection, and top-narrow and bottom-wide fractures are best for sanding in the later stage; (2) the viscosity of fracturing fluid is the most influential factor on proppant migration and sedimentation, which increases in the range of 100 mPa.s to enhance the sweeping range and homogeneity of proppant sanding and therefore achieve a better fracturing effect.

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Numerical simulation of proppant directly entering complex fractures in shale gas

Cited by 16 publications

References 8 publications

Distribution Characteristics and Backflow Flow Pattern of a Slickwater Fracturing Fluid in Shale Based on Low-Field Nuclear Magnetic Resonance

Distribution Characteristics and Backflow Flow Pattern of a Slickwater Fracturing Fluid in Shale Based on Low-Field Nuclear Magnetic Resonance

Study on Proppant Transport and Placement in Shale Gas Main Fractures

Simulation and solution of a proppant migration and sedimentation model for hydraulically fractured inhomogeneously wide fractures

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