Microseismic Emissions During Pneumatic Fracturing: A Numerical Model to Explain the Experiments

Abstract

Modeling of fluid injection processes into a deformable porous medium is a challenging area of physics that has a wide range of applications like the food, construction, and petroleum industries. In this research, we investigate pneumatic fracturing of a porous medium experimentally and numerically in a Hele‐Shaw cell. In the experiments, we inject air into the porous medium (initially random loose packed) to create compaction, channeling, and fracturing while monitoring the cell with accelerometers and a high‐speed camera. Furthermore, we develop a numerical model in two steps: (1) a poroelastoplasticity‐based model to explain dynamic fluid pressure variations and (2) a solid stress model based on Janssen's theory. The contributions of the different pressure sources air in channels and solid stress in the experiments, and the simulations are compared with respect to amplitude and frequency. Afterward, the variations of the normal stress exerting on the plates are convolved with a Lamb Wave green function to generate acoustic emissions numerically. The physics behind the evolution of the experimentally recorded power spectrum of the out‐of‐plane plate vibrations are explained using numerical models. The frequency bands (in the simulated power spectra) are influenced by the size of the opened channels and the Hele‐Shaw cell and are in the same range with the experimentally measured peaks of the acoustic emissions.

Source Localization of Microseismic Emissions During Pneumatic Fracturing

“…The aerofracturing experiments analyzed here are conducted in a Hele-Shaw cell made of two glass plates 80 cm × 40 cm × 1 cm with an aperture of 1 mm between them-see details in Turkaya et al (2015), Eriksen et al (2017), Eriksen et al (2018), and Turquet et al (2018). The experimental setup is shown in Figure 1a.…”

“…The main reason behind using a Hele-Shaw cell is to optically record the deformations associated with the microseismic event while recording the vibrations on the glass plate with accelerometers. This work is based on an experimental approach similar to Turkaya et al (2015), Eriksen et al (2017), Eriksen et al (2018), and Turquet et al (2018).…”

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

“…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.…”

“…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: . 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.…”

Seismic and Microseismic Signatures of Fluids in Rocks: Bridging the Scale Gap

“…Fluid substitution can also be conveniently studied in 2‐D analog experiments like the Hele‐Shaw cell, a transparent 2‐D experimental model. Using a high speed camera and accelerometers, Turquet et al () follow the pressure‐driven compaction of initially loose sphere packings when injecting air into the cell. They show that solid‐fluid interactions lead to the generation of acoustic events similar to microseismicity.…”