Mechanism of fracture initiation and propagation using a tri-axial hydraulic fracturing test system in naturally fractured reservoirs

Dehghan, Ali Naghi; Goshtasbi, Kamran; Ahangari, Kaveh; Jin, Yan

doi:10.1080/19648189.2015.1056384

Cited by 45 publications

(18 citation statements)

References 54 publications

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“…With the propagation of the hydraulic fractures, a main fracture is formed perpendicularly to the direction of the minimum principal stress. Moreover, the greater the horizontal principal stress difference is, the more easily the main straight hydraulic fracture will form . The results of in‐situ stress tests of the No.…”

Section: Morphology Of Hydraulic Fractures and Prediction Model Of Pomentioning

confidence: 99%

Postfracturing permeability prediction for CBM well with the analysis of fracturing pressure decline

Zhang

Wang

et al. 2019

Energy Science & Engineering

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Hydraulic fracturing is a widely used reservoir stimulation technique to exploit CBM in China. Compared with the original permeability of coal reservoir, the postfracturing permeability is more critical for the productivity evaluation of CBM wells. Based on hydraulic fracturing, microseismics monitoring, and well test data of the CBM wells in Zhengzhuang block of Qinshui Basin, this paper proposes a simple method to obtain the fitting pressure by the classic fracturing pressure decline analysis theory under the condition of corrected dynamic overall leakoff coefficient. In addition, the postfracturing permeability of coal reservoir is predicted by the injection well testing theory. The morphology of hydraulic fractures in the study area is mainly determined by in‐situ stress, and most fractures are vertical ones propagating along the direction of the maximum principal stress. The fracturing curves of the study area can be classified into stable curves, stably fluctuating curves, descending curves, ascending curves, and fluctuating curves, where the stable and descending fracturing curves represent better fracturing effect. The length of hydraulic fractures is much greater than the height. The PKN model has been selected as the hydraulic fracture propagation model to analyze the fracturing pressure decline. The slope value of liner segment of G(δ,0) curve is proposed as the criterion for the fitting pressure calculation. The postfracturing permeabilities of coal reservoir range from 1.55 to 8.83 × 10−3 μm2, all of which are remarkably higher than that of the original reservoir.

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Section: Morphology Of Hydraulic Fractures and Prediction Model Of Pomentioning

confidence: 99%

Postfracturing permeability prediction for CBM well with the analysis of fracturing pressure decline

Zhang

Wang

et al. 2019

Energy Science & Engineering

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“…NFs and BPs may cause hydraulic fractures to extend along or through the structure surfaces [11,17,18]. Various forms of HF in conditions of different confining pressures, NFs, and crustal stress fields as well as the best boundary conditions for the production of many fracturing cracks have also been investigated [19][20][21]. The extension rule of HF after intersecting with NFs has been very clear [22][23][24][25], but when making contact with BPs of different bedding angles, the extension rule will be more complicated [26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

The Influence of Bedding Planes and Permeability Coefficient on Fracture Propagation of Horizontal Wells in Stratification Shale Reservoirs

et al. 2020

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The complexity of hydraulic fractures (HF) significantly affects the success of reservoir reconstruction. The existence of a bedding plane (BP) in shale impacts the extension of a fracture. For shale reservoirs, in order to investigate the interaction mechanisms of HF and BPs under the action of coupled stress-flow, we simulate the processes of hydraulic fracturing under different conditions, such as the stress difference, permeability coefficients, BP angles, BP spacing, and BP mechanical properties using the rock failure process analysis code (RFPA2D-Flow). Simulation results showed that HF spread outward around the borehole, while the permeability coefficient is uniformly distributed at the model without a BP or stress difference. The HF of the formation without a BP presented a pinnate distribution pattern, and the main direction of the extension is affected by both the ground stress and the permeability coefficient. When there is no stress difference in the model, the fracture extends along the direction of the larger permeability coefficient. In this study, the in situ stress has a greater influence on the extension direction of the main fracture when using the model with stress differences of 6 MPa. As the BP angle increases, the propagation of fractures gradually deviates from the BP direction. The initiation pressure and total breakdown pressure of the models at low permeability coefficients are higher than those under high permeability coefficients. In addition, the initiation pressure and total breakdown pressure of the models are also different. The larger the BP spacing, the higher the compressive strength of the BP, and a larger reduction ratio (the ratio of the strength parameters of the BP to the strength parameters of the matrix) leads to a smaller impact of the BP on fracture initiation and propagation. The elastic modulus has no effect on the failure mode of the model. When HF make contact with the BP, they tend to extend along the BP. Under the same in situ stress condition, the presence of a BP makes the morphology of HF more complex during the process of propagation, which makes it easier to achieve the purpose of stimulated reservoir volume (SRV) fracturing and increased production.

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“…Warpinski et al [5,6] found that the growth and geometry of hydraulic fractures were affected by the stress, joints, faults, interfaces and layer material property. Much research has studied factors affecting HF with the development of laboratory equipment and construction of True-Triaxial test devices [7][8][9][10][11][12]. Zhou et al [7] also studied the interaction between HF and NF through a series of experiments and presented the crossed boundary based on different stress regimes.…”

Section: Introductionmentioning

confidence: 99%

“…Sarmadivaleh et al [8] investigated the influences of interface cohesion and approach angle on the interaction between NF and HF. Dehghan et al [9,10] studied the effect of dip direction of NF on HF propagation as well as stress state and approach angle. Guo et al [11] studied several factors including the type of injecting fracturing fluids, pump flow rate, fracturing pressure curve characteristics, and fracture morphology.…”

Section: Introductionmentioning

confidence: 99%

Discrete Element Simulation of Interaction between Hydraulic Fracturing and a Single Natural Fracture

Basirat

Goshtasbi

Ahmadi

2019

Fluids

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Hydraulic fracturing (HF) treatment is performed to enhance the productivity in the fractured reservoirs. During this process, the interaction between HF and natural fracture (NF) plays a critical role by making it possible to predict fracture geometry and reservoir production. In this paper, interaction modes between HF and NF are simulated using the discrete element method (DEM) and effective parameters on the interaction mechanisms are investigated. The numerical results also are compared with different analytical methods and experimental results. The results showed that HF generally tends to cross the NF at an angle of more than 45° and a moderate differential stress (greater than 5 MPa), and the opening mode is dominated at an angle of fewer than 45°. Two effects of changing in the interaction mode and NF opening were also found by changing the strength parameters of NF. Interaction mode was changed by increasing the friction coefficient, while by increasing the cohesion of NF it was less opened under a constant injection pressure.

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Mechanism of fracture initiation and propagation using a tri-axial hydraulic fracturing test system in naturally fractured reservoirs

Cited by 45 publications

References 54 publications

Postfracturing permeability prediction for CBM well with the analysis of fracturing pressure decline

Postfracturing permeability prediction for CBM well with the analysis of fracturing pressure decline

The Influence of Bedding Planes and Permeability Coefficient on Fracture Propagation of Horizontal Wells in Stratification Shale Reservoirs

Discrete Element Simulation of Interaction between Hydraulic Fracturing and a Single Natural Fracture

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