DEM-CFD Modeling of Proppant Pillar Deformation and Stability during the Fracturing Fluid Flowback

Zhu, Hehua; Shen, Jiadong; Zhang, Feng-Shou; Huang, Bo; Zhang, Liaoyuan; Huang, Wei; McLennan, John

doi:10.1155/2018/3535817

Cited by 14 publications

(6 citation statements)

References 34 publications

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“…The Young's modulus and Poisson's ratio of the target formation are 30 GPa and 0.28, respectively. The fracture width varies between 5 and 10 mm according to the calculation results of the FRACPRO-PT software (Cleary 1994;Zhu et al 2015). For simplicity, the fracture width is assumed to be 5 mm.…”

Section: Parameter-sensitivity Analysismentioning

confidence: 99%

Modeling of Fracture Width and Conductivity in Channel Fracturing With Nonlinear Proppant-Pillar Deformation

et al. 2019

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Channel fracturing acknowledges that there will be local concentrations of proppant that generate high-conductivity channel networks within a hydraulic fracture. These concentrations of proppant form pillars that maintain aperture. The mechanical properties of these proppant pillars and the reservoir rock are important factors affecting conductivity. In this paper, the nonlinear stress/strain relationship of proppant pillars is first determined using experimental results. A predictive model for fracture width and conductivity is developed when unpropped, highly conductive channels are generated during the stimulation. This model considers the combined effects of pillar and fracture-surface deformation, as well as proppant embedment. The influence of the geomechanical parameters related to the formation and the operational parameters of the stimulation are analyzed using the proposed model. The results of this work indicate the following: 1. Proppant pillars clearly exhibit compaction in response to applied closure stress, and the resulting axial and radial deformation should not be ignored in the prediction of fracture conductivity. 2. There is an optimal ratio (approximately 0.6 to 0.7) of pillar diameter to pillar distance that results in a maximum hydraulic conductivity regardless of pillar diameter. 3. The critical ratio of rock modulus to closure stress currently used in the industry to evaluate the applicability of a channelfracturing technique is quite conservative. 4. The operational parameters of fracturing jobs should also be considered in the evaluation. Conventional Channel fracturing Fig. 1-Schematic of (left) conventional fracturing and (right) channel fracturing (Gillard et al. 2010).

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Section: Parameter-sensitivity Analysismentioning

confidence: 99%

Modeling of Fracture Width and Conductivity in Channel Fracturing With Nonlinear Proppant-Pillar Deformation

et al. 2019

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“…To develop shale gas reservoirs reasonably, it is necessary to determine the stress sensitivity characteristics of artificial fractures and the variation characteristics of fracture conductivity in the stage of the flowback test. Several studies have been conducted on the stress sensitivity characteristics of fractures and the change of fracture conductivity caused by stress sensitivity by means of physical simulation experiments [14][15][16][17][18], numerical simulation [19][20][21][22], and theoretical models [23,24]. Zhang [16] used Barnett shale samples to make physical models to study the influence of fracture conductivity under different pressures and proppant concentrations.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Stress Sensitivity on Artificial Fracture Conductivity in the Flowback Stage of Shale Gas Wells

Yang,

Wu,

Ren

et al. 2023

Processes

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The presence of a reasonable flowback system after fracturing is a necessary condition for the high production of shale gas wells. At present, the optimization of the flowback system lacks a relevant theoretical basis. Due to this lack, this study established a new method for evaluating the conductivity of artificial fractures in shale, which can quantitatively characterize the backflow, embedment, and fragmentation of proppant during the flowback process. Then, the mechanism of the stress sensitivity of artificial fractures on fracture conductivity during the flowback stage of the shale gas well was revealed by performing the artificial fracture conductivity evaluation experiment. The results show that a large amount of proppant migrates, and the fracture conductivity decreases rapidly in the early stage of flowback, and then the decline gradually slows down. When the effective stress is low, the proppant is mainly plastically deformed, and the degree of fragmentation and embedment is low. When the effective stress exceeds 15.0 MPa, the fragmentation and embedment of the proppant will increase, and the fracture conductivity will be greatly reduced. The broken proppant ratio and embedded proppant ratio are the same under the two choke-management strategies. In the mode of increasing choke size step by step, the backflow proppant ratio is lower, and the broken proppant is mainly retained in fractures, so the damage ratio of fracture conductivity is lower. In the mode of decreasing choke size step by step, most of the proppant flows back from fractures, so the damage to fracture conductivity is greater. The research results have important theoretical guiding significance for optimizing the flowback system of shale gas wells.

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“…According to parametric studies, a higher injection rate and lightweight proppants are beneficial for the transport of the proppant through the fracture junctions and to carry proppant in hydraulic fractures and natural fractures [11]. A DEM-CFD (discrete element method-computational fluid dynamics) and the experimental study indicate that during the closure period, the height of the proppants pillar decreases and diameter increases [12]. The proppant flowback could occur easily with a large proppant pillar height or a large fluid pressure gradient.…”

Section: Introductionmentioning

confidence: 99%

“…The proppant flowback could occur easily with a large proppant pillar height or a large fluid pressure gradient. However, the higher bonding strength of the fibers results to improve the stability of the proppant pillar [12]. Propped hydraulic fracture conductivity [2].…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Fracture Conductivity in Shale Reservoirs

Khan¹,

Padmanabhan²,

Haq³

2022

Emerging Technologies in Hydraulic Fracturing and Gas Flow Modelling

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Optimum conductivity is essential for hydraulic fracturing due to its significant role in maintaining productivity. Hydraulic fracture networks with required fracture conductivities are decisive for the cost-effective production from unconventional shale reservoirs. Fracture conductivity reduces significantly in shale formations due to the high embedment of proppants. In this research, the mechanical properties of shale samples from Sungai Perlis beds, Terengganu, Malaysia, have been used for computational contact analysis of proppant between fracture surfaces. The finite element code in ANSYS is used to simulate the formation/proppant contact-impact behavior in the fracture surface. In the numerical analysis, a material property of proppant and formation characteristics is introduced based on experimental investigation. The influences of formation load and resulted deformation of formation are calculated by total penetration of proppant. It has been found that the formation stresses on both sides of fractured result in high penetration of proppant in the fracture surfaces, although proppant remains un-deformed.

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DEM-CFD Modeling of Proppant Pillar Deformation and Stability during the Fracturing Fluid Flowback

Cited by 14 publications

References 34 publications

Modeling of Fracture Width and Conductivity in Channel Fracturing With Nonlinear Proppant-Pillar Deformation

Modeling of Fracture Width and Conductivity in Channel Fracturing With Nonlinear Proppant-Pillar Deformation

Mechanisms of Stress Sensitivity on Artificial Fracture Conductivity in the Flowback Stage of Shale Gas Wells

Hydraulic Fracture Conductivity in Shale Reservoirs

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