Energy-Based Brittleness Index and Acoustic Emission Characteristics of Anisotropic Coal Under Triaxial Stress Condition

Zhang, Jun; Ai, Chi; Li, Yuwei; Che, M.; Gao, Rui; Zeng, Jia

doi:10.1007/s00603-018-1535-9

Cited by 106 publications

(39 citation statements)

References 56 publications

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“…Rickman et al [24] reported that a large elastic modulus of rock resulted in high brittleness. Rock with high brittleness breaks down at low strain [46][47][48][49][50][51]. The stress-strain curve in Figure 3 indicated that the elastic modulus of the volcanic rocks was slightly lower than that of shale (around 50.0 GPa) and remarkably higher than that of sandstone (around 10.0 GPa).…”

Section: Experimental Setup and Specimen Preparationmentioning

confidence: 99%

Effect of Multiple Flow Pulses on Hydraulic Fracture Network Propagation in Naturally Fractured Volcanic Rock

et al. 2020

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Exploring engineering methods for increasing fracture network complexity is important for the development of unconventional oil and gas reservoirs. In this study, we conducted a series of fracturing experiments on naturally fractured volcanic samples. An injection method, multiple flow pulses, is proposed to increase fracture complexity. The results show that fluid leaked into the natural fracture network (NFN) when the injection rate was low (0.2 mL/min); hydraulic-fracture-dominant fracture geometry was created with an injection rate of 2 and 5 mL/min. Under the 2 mL/min-injection scheme with 3 pulses, the injection pressure during the intermittent stage was low (<5 MPa), resulting in a limited increase in fracture complexity. When the number of the flow pulses increased to 5, the pressure drop rate in the fourth and fifth intermittent stage significantly increased, indicating an increase in the aperture of natural fractures (NFs) and in the fluid leak-off effect. Under the 5 mL/min injection scheme containing 5 pulses, besides the enhanced fluid leak-off, a sharp injection pressure drop was observed, indicating the activation of NFs. The complexity and the aperture of the ultimate fracture network further increased. The injection method, multiple flow pulses, can be used to create complex fracture networks effectively.

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Section: Experimental Setup and Specimen Preparationmentioning

confidence: 99%

Effect of Multiple Flow Pulses on Hydraulic Fracture Network Propagation in Naturally Fractured Volcanic Rock

et al. 2020

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“…However, most Chinese oil field reservoirs are continental deposits with serious heterogeneity and prominent interlayer contradictions. Under the traditional injection method, 7 ASP solution is injected into high‐permeability reservoirs in large amounts, 8‐10 while it is injected into low‐permeability reservoirs in small amounts, and the compatibility of low‐permeability reservoirs with ASP solution is poor, 11‐13 resulting in a poor production degree and low total oil recovery in low‐permeability reservoirs. Therefore, in order to improve the total oil recovery of heterogeneous oil layers, a layered injection method which is for the different levels of oil permeability is proposed for Daqing Oilfield, and the method is shown in Figure 1 14,15 .…”

Section: Introductionmentioning

confidence: 99%

Experimental evaluation of ASP flooding to improve oil recovery in heterogeneous reservoirs by layered injection approach

Huang

et al. 2020

Energy Science & Engineering

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To improve the oil displacement effect of ASP (alkali/surfactant/polymer) solution in heterogeneous oil reservoirs, layered injection technology is proposed for the first time for Daqing Oilfield. The technology uses partial pressure tools to control the injection amount of ASP solution in high‐permeability oil layers and uses a partial quality tool in low‐permeability oil layers. To study the experimental effect of this layered injection technology, the relationships between the different permeability, molecular weight, and concentration of the ASP solution, as well as the resistance coefficient and residual resistance coefficient, are first established, and then, a layered injection experimental model is established to carry out experimental research on injection capacity and oil displacement capacity. The experimental results show that the smaller the range of the core permeability is, the larger the molecular weight and concentration of the ASP solution are, and the poorer the injection capacity of the ASP solution is. After the action of a partial pressure tool and a partial quality tool, the injection capacity of ASP solution is improved to different degrees, and the oil displacement effect of low‐permeability cores is significantly improved, while the total oil recovery is increased, and the total oil recovery of heterogeneous cores under different conditions is increased by 1.4%‐4.05%. This experiment is of great significance to the study of improving the oil recovery of heterogeneous reservoirs.

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“…The influence of the loading rate on AE through the uniaxial and triaxial compression acoustic emission of the rock has been investigated [5][6][7][8][9]. The rock damage and failure modes are assessed by acoustic emission parameters [10][11][12]. Therefore, the relationship between the rock deformation and failure process and AE parameters is studied in the test to explore the evolution of AE under different stress paths and experimental environment.…”

Section: Introductionmentioning

confidence: 99%

On the Kaiser Effect of Rock under Cyclic Loading and Unloading Conditions: Insights from Acoustic Emission Monitoring

et al. 2019

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The Kaiser effect reflects the memory of the loaded rock to the irreversible damage and deformation. The stress level, loading rate and lithology are the main factors affecting the Kaiser effect of the rock. To identify the accurate stress point of the Kaiser effect, the MTS 816 rock mechanics testing system and the DS5-A acoustic emission testing and analysis system were adopted. The uniaxial cyclic loading–unloading and acoustic emission characteristic test of 90 rock specimens from three types of rocks under different stress level and loading rate was carried out. The evolution of acoustic emission under uniaxial compression of the rock corresponds to the compaction stage, elastic stage, yield stage and post-peak stress drop stage of the rock deformation and failure process and is divided into the quiet period, transition period, active period and decay period of the acoustic emission. The larger the hardness of rock is, the earlier the stress point of the Kaiser effect appears. The loading stress level (σA) has appreciable influence on the Kaiser effect of the rock. When σA ≥ 0.7σc, the Kaiser effect disappears. Usually, the dilatancy stress (crack initiation stress) does not exceed 70% of the uniaxial compressive strength (σc) of the rock, and the stress point can be the threshold to determine whether the Kaiser effect occurs. The influence of loading rate (lr) on Felicity rate (FR) is relatively large when lr < 0.01 mm/s, and FR rapidly grows with increase of the loading rate. When lr ≥ 0.01 mm/s, the influence of the loading rate on FR is relatively small. The findings facilitate the future application of the Kaiser effect and improvement of the accuracy of the acoustic emission data interpretation.

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Energy-Based Brittleness Index and Acoustic Emission Characteristics of Anisotropic Coal Under Triaxial Stress Condition

Cited by 106 publications

References 56 publications

Effect of Multiple Flow Pulses on Hydraulic Fracture Network Propagation in Naturally Fractured Volcanic Rock

Effect of Multiple Flow Pulses on Hydraulic Fracture Network Propagation in Naturally Fractured Volcanic Rock

Experimental evaluation of ASP flooding to improve oil recovery in heterogeneous reservoirs by layered injection approach

On the Kaiser Effect of Rock under Cyclic Loading and Unloading Conditions: Insights from Acoustic Emission Monitoring

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