Irregular and stepwise behaviour of hydraulic fracturing: insights from linear cohesive crack modelling with maximum stress criterion

Khoei, A.R.; Mortazavi, Saeed; Simoni, L.; Schrefler, Bernhard A.

doi:10.1016/j.compgeo.2023.105570

Cited by 13 publications

(5 citation statements)

References 70 publications

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“…The processor used for model solving is Intel (R) Core (TM) i7-10700 CPU @ 2.60 GHz, and the calculation time of the model is 1.6 h. The model was solved by the Newton-Raphson method. We treated the hydraulic fracture propagation as a quasi-static process [20,31]. In the calculatio with the injection of fracturing fluid, the pressure in the fracture increased, an on the reservoir rock increased.…”

Section: Finite Element Modelmentioning

confidence: 99%

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Numerical Simulation of Hydraulic Fracture Propagation in Conglomerate Reservoirs: A Case Study of Mahu Oilfield

Pan

et al. 2023

Processes

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Mahu conglomerate oilfield has strong heterogeneity. Currently, large-scale hydraulic fracturing is commonly used for reservoir reconstruction. The geometry of hydraulic fractures is influenced by gravel. By referring to the scanning and logging results of a conglomerate reservoir, and considering the characteristics of gravel development in the Mahu Oilfield reservoir, python programming is used to establish a finite element model containing a matrix, bonding interface, and gravel, which considers the random distribution of gravel position and size. The model uses cohesive element global embedding to study the geometry of a hydraulic fracture. The results show that the hydraulic fracture in the gravel reservoir mainly spreads around the gravel, and the propagation path of the hydraulic fracture is affected by the horizontal stress difference. When the interfacial bonding strength is greater than 2 MPa, the conglomerate is more likely to be penetrated by hydraulic fractures, or the hydraulic fractures stop expanding after entering the conglomerate. The strength of the conglomerate largely determines whether hydraulic fractures can pass through it. When the strength of gravel is greater than 7 MPa, hydraulic fractures will stop expanding after entering the gravel. During the hydraulic fracturing process of conglomerate reservoirs, using a large injection rate can result in longer hydraulic fractures and larger fracture volumes.

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Section: Finite Element Modelmentioning

confidence: 99%

“…The model was solved by the Newton-Raphson method. We treated the process of hydraulic fracture propagation as a quasi-static process [20,31]. In the calculation process, with the injection of fracturing fluid, the pressure in the fracture increased, and the load on the reservoir rock increased.…”

Section: Model Accuracy Verificationmentioning

confidence: 99%

Numerical Simulation of Hydraulic Fracture Propagation in Conglomerate Reservoirs: A Case Study of Mahu Oilfield

Pan

et al. 2023

Processes

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“…Extreme low permeability limits the effectiveness of gas drainage on preventing gas hazards in coal mines. 4,5 Chemical stimulation has been found to be an economical method to improve rock permeability and largely enhance the performance of the hydraulic fracturing in gas/oil production. 6−9 But the mechanism of chemical stimulation is still unclear, which has not been widely accepted by the industry and public.…”

Section: Introductionmentioning

confidence: 99%

“…Coalbed methane (CBM) is an unconventional gas resource as well as a hazardous source in coal mines, which could cause gas explosions and outbursts costing many lives. − Gas extraction has been a primary technique to control the gas emission in mining spaces; however, problems still exist in the elimination of potential gas hazards. Extreme low permeability limits the effectiveness of gas drainage on preventing gas hazards in coal mines. , Chemical stimulation has been found to be an economical method to improve rock permeability and largely enhance the performance of the hydraulic fracturing in gas/oil production. − But the mechanism of chemical stimulation is still unclear, which has not been widely accepted by the industry and public. It often causes public concern about environmental safety and contamination.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Analysis of the Effect of NaClO Stimulation in Anthracite and Bituminous Coal with FTIR and LF-NMR

Chen,

Zhai,

et al. 2024

Energy Fuels

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Oxidant stimulation is increasingly used to enhance gas and oil production. Unlike acid stimulation, which dissolves minerals, oxidant stimulation modifies coal microstructures through reactions with the coal matrix. However, the stimulating effect of oxidation on coal lacks quantitative characterization. This study investigates the effects of NaClO stimulation on anthracite and bituminous coal microstructures. Various measurements, including LF-NMR, FTIR, SEM, and 3D-XRM, assess the physical and chemical changes in coal. Results indicate that NaClO stimulation significantly alters coal's molecular and porous structures. FTIR reveals notable changes in coal's chemical composition, such as increased hydroxyl groups, aromatic hydrocarbons, and oxygen functional groups with rising NaClO concentration, while aliphatic hydrocarbons decrease. Coal hydrophilicity and aromaticity gradually increase due to enhanced hydrogen bonds and aromatic structures. Four indexes (I, DOC, H al /H, and A(CH 2 )/A(CH 3 )) quantitatively characterize modifications in the four typical functional groups. LF-NMR T 2 spectra show an increase of over 50% in mesopore and macropore volume after 10% NaClO stimulation. Multiscale-fractal analysis yields fractal dimensions for adsorption pores, seepage pores, and microfractures. The fractal dimension of seepage pores decreases with rising NaClO concentration, while adsorption pores and microfractures do not exhibit fractal characteristics. Findings indicate that bituminous coal is more suitable than anthracite for NaClO oxidation stimulation to enhance permeability.

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“…The latter has the advantage of avoiding the decrease in computational convergence caused by mesh refinement due to stress concentration and the ability to simulate fracture propagation direction changes. However, its computational efficiency is not high, and it cannot form intersecting fractures [21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Factors Influencing Three-Dimensional Multi-Cluster Hydraulic Fracturing Considering Interlayer Effect

Zhou,

Liu,

Liang

2024

Applied Sciences

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This study establishes a three-dimensional cohesive model of multi-cluster hydraulic fracturing using finite element method (FEM). It fully considers the interaction between the interlayer and the reservoir and analyzes the key factors influencing fracture propagation. The results show that during the initial stage of hydraulic fracturing, the width of the edge fracture is greater than that of the mid fracture, while the situation is reversed for the fracture length. A larger cluster spacing leads to less interaction between fractures, while a greater number of clusters increases the interaction between fractures. With an increase in displacement, the lost fracturing fluid entering the formation enhances the interaction between fractures. An increase in elastic modulus results in a decrease in the width and height of edge fractures but an increase in their length, with little impact on mid fractures. As Poisson’s ratio increases, there is little change in the fracture morphology of edge fractures, while the width and height of mid fractures increase significantly. With an increase in permeability, the influx of fracturing fluid into the interlayer decreases, leading to a reduction in the interaction between fractures. Finally, the study analyzes and discusses the impact of these parameters on the SRV (stimulated reservoir volume) in both the reservoir and the interlayer. These findings provide new insights for hydraulic fracturing and contribute to improving its productivity.

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Irregular and stepwise behaviour of hydraulic fracturing: insights from linear cohesive crack modelling with maximum stress criterion

Cited by 13 publications

References 70 publications

Numerical Simulation of Hydraulic Fracture Propagation in Conglomerate Reservoirs: A Case Study of Mahu Oilfield

Numerical Simulation of Hydraulic Fracture Propagation in Conglomerate Reservoirs: A Case Study of Mahu Oilfield

Quantitative Analysis of the Effect of NaClO Stimulation in Anthracite and Bituminous Coal with FTIR and LF-NMR

Analysis of Factors Influencing Three-Dimensional Multi-Cluster Hydraulic Fracturing Considering Interlayer Effect

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