Effect of frequency during cyclic hydraulic fracturing and the process of fracture development in laboratory experiments

Diaz, Melvin; Kim, Kwang Yeom; Jung, Sung Gyu

doi:10.1016/j.ijrmms.2020.104474

Cited by 42 publications

(19 citation statements)

References 28 publications

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“…Thus fracturing is required to connect natural micro-cracks with the goal of forming a complex network of fractures to achieve effective shale gas production. The fractures obtained from hydraulic fracturing are relatively large (on the scale of several microns) (He et al, 2017;Lin et al, 2018;Hu et al, 2020a;Diaz et al, 2020;Wang et al, 2021a;Wang et al, 2021b) and typically develop along the boundaries between mineral particles and organic matter (He et al, 2020). The gases in the nano-scale pores within the matrix do not readily enter the cracks and for this reason do not easily migrate to the well.…”

Section: Effect Of Temperature On Organic-rich Shalementioning

confidence: 99%

Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

Yuan

Yang

2021

Front. Earth Sci.

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Mud shale can serve as source or cap rock but also as a reservoir rock, and so the development of pores or cracks in shale has become of great interest in recent years. However, prior work using non-identical samples, varying fields of view and non-continuous heating processes has produced varying data. The unique hydrocarbon generation and expulsion characteristics of shale as a source rock and the relationship with the evolution of pores or cracks in the reservoir are thus not well understood. The present work attempted to monitor detailed structural changes during the continuous heating of shale and to establish possible relationships with hydrocarbon generation and expulsion by heating immature shale samples while performing in situ scanning electron microscopy (SEM) imaging and monitoring the chamber vacuum. Samples were heated at 20°C/min from ambient to 700°C with 30 min holds at 100°C intervals during which SEM images were acquired. The SEM chamber vacuum was found to change during sample heating as a consequence of hydrocarbon generation and expulsion. Two episodic hydrocarbon expulsion stages were observed, at 300 and 500°C. As the temperature was increased from ambient to 700°C, samples exhibited consecutive shrinkage, expansion and shrinkage, and the amount of structural change in the vertical bedding direction was greater than that in the bedding direction. At the same time, the opening, closing and subsequent reopening of microcracks was observed. Hydrocarbon generation and expulsion led to the expansion of existing fractures and the opening of new cracks to produce an effective fracture network allowing fluid migration. The combination of high-resolution SEM and a high-temperature heating stage allowed correlation between the evolution of pores or cracks and hydrocarbon generation and expulsion to be examined.

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Section: Effect Of Temperature On Organic-rich Shalementioning

confidence: 99%

Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

Yuan

Yang

2021

Front. Earth Sci.

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“…Furthermore, the influence of the stress holding time during CHF has been gradually recognized by scholars. Diaz et al (2020) designed four schemes to study the influence of the peak holding time during CHF, wherein the loading and unloading time was strictly controlled at 20 s (as shown in Fig. 11).…”

Section: Influence Of the Number Of Cycles And Stress Holding Time On...mentioning

confidence: 99%

A critical review of the experimental and theoretical research on cyclic hydraulic fracturing for geothermal reservoir stimulation

Xie

et al. 2021

Geomech. Geophys. Geo-energ. Geo-resour.

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Hydraulic fracturing is necessary to stimulate deep geothermal reservoirs. Compared with traditional hydraulic fracturing (THF), cyclic hydraulic fracturing (CHF) decreases the breakdown pressure (BP), generates a more complex crack network and reduces the induced seismicity; thus, it has attracted increasing attention. In this work, state-of-the-art studies on CHF are comprehensively reviewed for the first time. Six CHF cyclic loading schemes are clarified, and their stimulation results are discussed. It is difficult to assess which loading schemes are the most advantageous because the reservoir boundary conditions and properties of rock specimens vary. The effects of critical influential factors on the stimulation results of CHF are reviewed in detail. A higher confining pressure generally produces longer cracks, and a lower-viscosity fracturing fluid more easily connects micropores and widens cracks. The existing theoretical and numerical models of CHF, which are based mainly on fracture mechanics and damage mechanics, are summarized and discussed. Based on this comprehensive review, some aspects through which the failure mechanism of CHF can be further understood are suggested. This work can benefit the application of CHF to exploit deep geothermal resources. Article Highlights• Six different cyclic hydraulic fracturing schemes are classified, and the corresponding stimulated effects are discussed. • The effects of the primary influencing factors on cyclic hydraulic fracturing are summarized. • Recommendations for further studying cyclic hydraulic fracturing are suggested.

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“…Su et al [18] conducted a true triaxial experimental study and found that under the action of low-frequency periodic disturbance, the threshold values of the axial static stress and amplitude of the disturbance load existed in a rockburst. Moreover, many scholars also have explored the mechanical properties of rocks under cyclic loading from the perspectives of acoustic emission (AE) characteristics, infrared thermography, and energy dissipation [19][20][21][22][23][24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Fracture and Damage Characteristics of Granite under Uniaxial Disturbance Loads

Fei

Wang

et al. 2022

Buildings

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To investigate the mechanical properties and damage characteristics of granite under frequent disturbance loads in the process of underground engineering construction, laboratory uniaxial compression tests were conducted on granite under combined dynamic and static loading conditions. The following conclusions were reached: (1) under a dynamic disturbance, the failure stress of granite grows gradually as the initial stress and disturbance load rise due to the coupling of damage and strain-rate effect; (2) the characteristic stresses of granite specimens grow with the increasing amplitude of disturbance Δσ under the disturbing loads; with the same Δσ, the characteristic stresses show an increase trend with the increasing initial stress σm; (3) the particle size distribution of rock fragments broken under the disturbance load follows the fractal law, and the fractal dimension F gradually enlarges with the growth of Δσ, indicative of an increased degree of fragmentation; and (4) the damage variable grows rapidly at first, then steadily, and, finally, shows a rapid growth trend again under the disturbance loads. The Δσ significantly influences the number of cycles and rate of change of the damage variable during the steady increase. This research has certain theoretical significance and engineering guidance value for dynamic disaster recognition and control.

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Effect of frequency during cyclic hydraulic fracturing and the process of fracture development in laboratory experiments

Cited by 42 publications

References 28 publications

Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

A critical review of the experimental and theoretical research on cyclic hydraulic fracturing for geothermal reservoir stimulation

Fracture and Damage Characteristics of Granite under Uniaxial Disturbance Loads

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