Source Localization of Microseismic Emissions During Pneumatic Fracturing

Turquet, Antoine; Toussaint, Renaud; Eriksen, Fredrik Kvalheim; Daniel, Guillaume; Lengline, Oliver; Flekkøy, Eirik Grude; Måløy, Knut Jørgen

doi:10.1029/2019gl082198

Cited by 9 publications

(5 citation statements)

References 43 publications

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“…both shear and tensile opening at the same time. This is consistent with the pressure gradients which are pointing radially inwards to the finger tips, and is also supported by findings in [64] where the mechanics leading to acoustic emissions are observed (based on the polarisation on the sensors) to have two different types; compaction/relaxation or shearing.…”

Section: Discussionsupporting

confidence: 89%

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Pressure evolution and deformation of confined granular media during pneumatic fracturing

et al. 2018

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By means of digital image correlation, we experimentally characterize the deformation of a dry granular medium confined inside a Hele-Shaw cell due to air injection at a constant overpressure high enough to deform it (from 50 to 250 kPa). Air injection at these overpressures leads to the formation of so-called pneumatic fractures, i.e., channels empty of beads, and we discuss the typical deformations of the medium surrounding these structures. In addition we simulate the diffusion of the fluid overpressure into the medium, comparing it with the Laplacian solution over time and relating pressure gradients with corresponding granular displacements. In the compacting medium we show that the diffusing pressure field becomes similar to the Laplace solution on the order of a characteristic time given by the properties of the pore fluid, the granular medium, and the system size. However, before the diffusing pressure approaches the Laplace solution on the system scale, we find that it resembles the Laplacian field near the channels, with the highest pressure gradients on the most advanced channel tips and a screened pressure gradient behind them. We show that the granular displacements more or less always move in the direction against the local pressure gradients, and when comparing granular velocities with pressure gradients in the zone ahead of channels, we observe a Bingham type of rheology for the granular paste (the mix of air and beads), with an effective viscosity μ_{B} and displacement thresholds ∇[over ⃗]P_{c} evolving during mobilization and compaction of the medium. Such a rheology, with disorder in the displacement thresholds, could be responsible for placing the pattern growth at moderate injection pressures in a universality class like the dielectric breakdown model with η=2, where fractal dimensions are found between 1.5 and 1.6 for the patterns.

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Section: Discussionsupporting

confidence: 89%

“…This spatio-temporal source shape is characteristic of a seismic pulse [63]. Acoustic localization of such events is discussed in [64]. The deformations shown in the snapshots are typical: Initially there is little deformation (compacted stage) until beads in a region in front of the channel rearrange and compact.…”

Section: Compacted Stick-slip Stagementioning

confidence: 96%

Pressure evolution and deformation of confined granular media during pneumatic fracturing

et al. 2018

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“…Recently, a few studies have investigated the boundary forces or seismic signal generated by particle impacts and granular flows using vibration sensors (e.g. Bachelet, Mangeney, De Rosny, et al, ; Barrière et al, ; Farin et al, , ; Hsu et al, ; Huang et al, ; Taylor & Brodsky, ; Turkaya et al, ; Turquet et al, , ; Yohannes et al, ). For example, Yohannes et al () and Hsu et al () measured the distribution of fluctuating forces at the base of dry and saturated granular flows in a rotating drum using force sensors.…”

Section: Introductionmentioning

confidence: 99%

“…Barrière et al () measured the acoustic signal generated at the base of granular flows in a flume with a hydrophone attached under the flume and established an empirical scaling law relating the 50th percentile particle diameter D 50 of the particle distribution in the granular flows to the maximum amplitude A max and average frequency f mean of the generated acoustic signal:

D_{50} \approx 5.0 \cdot 1 0^{4} A_{m a x}^{0.39} false/ f_{m e a n}^{0.86}

. Turkaya et al () and Turquet et al (, ) characterized the acoustic emissions of confined granular material in Hele‐Shaw cells during shear and compaction caused by internal gas flow. Finally, Taylor and Brodsky () conducted granular shearing experiments under constant confining pressure in a torsional rheometer on which a piezoelectric accelerometer was attached.…”

Section: Introductionmentioning

confidence: 99%

Relations Between the Characteristics of Granular Column Collapses and Resultant High‐Frequency Seismic Signals

et al. 2019

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Deducing relations between the dynamic characteristics of landslides and rockfalls and the resultant high‐frequency (>1 Hz) seismic signal is challenging. To investigate relations that can be tested in the field, we conducted laboratory experiments of 3‐D granular column collapse on a rough inclined thin plate, for a large set of column masses, aspect ratios, particle diameters, and slope angles. The dynamics of the granular flows were recorded using a high‐speed camera, and the generated seismic signal was measured using piezoelectric accelerometers. Empirical scaling laws are established between the characteristics of the granular flows and deposits and that of the generated seismic signals. The radiated seismic energy scales with particle diameter as d3, column mass as M and aspect ratio as a1.1. The increase of the radiated seismic energy as slope angle increases correlates with a similar increase in particle agitation. Based on our experimental results, we revisit scaling laws reported in the field and discuss their possible physical origin. The discrepancy between field and experimental observations can be explained by the complex influence of the substrate on seismic signal and the difference of flow initiation in both cases. However, our empirical scaling laws allow us to determine which flow parameters could be inferred from a given seismic characteristic in the field. In particular, by assuming the flow average speed is known, we show that we can retrieve parameters d, M, and a within a factor of two from the seismic signal.

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“…Initially applied in geothermal energy exploration and exploitation [1], it has been widely used to characterize physical processes related to fluid injection and extractions [2], block caving for mining [3] and hydraulic fracturing especially for unconventional oil and gas production [4]. In laboratory, A. L. Turquet et al detected microseismic signals to study the localization of the acoustic emission source with the aim of understanding fluid-induced earthquake nucleation process [5]. By dealing with microseismic point clouds, i.e.…”

Section: Introductionmentioning

confidence: 99%

Downhole Microseismic Monitoring Using Time-Division Multiplexed Fiber-Optic Accelerometer Array

et al. 2020

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Microseismic monitoring is of importance for several geoscience research aspects and for applications in oil and gas industry. For signals generated by the ultra-weak microseismic events, conventional moving-coil geophone systems have reached their limit in detection sensitivity especially at high frequency range. Here we for the first time present a specially tailored fiber-optic sensing system targeting at downhole microseismic monitoring. The system contains 30 individual interferometric accelerometers and 2 reference sensors, which are time-division multiplexed into a 12-level vector seismic sensor array. The multiplexed accelerometers can achieve ∼50 ng/ √ Hz noise equivalent acceleration, which is superior to the commercial available moving-coil geophone systems at frequencies above 200 Hz. The measured sensitivity of the accelerometers can reach ∼200 rad/g from 10 Hz to 1 kHz. The dynamic range is above 134 dB over the same frequency range and is higher than its electronic counterpart in the low frequency band. Moreover, the sensors can function properly under the harsh condition of 120 • C temperature and 40 MPa pressure over the 4-hour test duration. The sensor array along with the interrogator has been running uninterruptedly over 3 weeks in a multi-stage hydraulic fracturing stimulation field test. On-site results show that our system can clearly resolve the vector nature of both compressional and shear waves generated by the microseismic events. INDEX TERMS Fiber-optic accelerometer, Seismic sensor, Time-division multiplexing, Microseismic monitoring II. PRINCIPLE OF THE FIBER-OPTIC SEISMIC SENSOR UNIT A. THE SEISMIC SENSOR UNIT This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2020.3003374, IEEE Access Fei Liu et al.: Downhole microseismic monitoring using time-division multiplexed fiber-optic accelerometer array

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Source Localization of Microseismic Emissions During Pneumatic Fracturing

Cited by 9 publications

References 43 publications

Pressure evolution and deformation of confined granular media during pneumatic fracturing

Pressure evolution and deformation of confined granular media during pneumatic fracturing

Relations Between the Characteristics of Granular Column Collapses and Resultant High‐Frequency Seismic Signals

Downhole Microseismic Monitoring Using Time-Division Multiplexed Fiber-Optic Accelerometer Array

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