Radial Hydraulic Fracturing Experiment: 1 Cycle of Fracture Propagation, Arrest, and Closure in Molasse de Villarlod Sandstone - Sample M03

Overview

This dataset encompasses detailed measurements from a lab-scale radial hydraulic fracturing experiment conducted on a cubic sample of Molasse de Villarlod sandstone, designated as Sample M03. The sandstone, sourced from a quarry in Fribourg, Switzerland, is known for its porosity (18.1%) and permeability, making it an ideal material for studying hydraulic fracture processes. The primary focus of the experiment was to observe and analyze the propagation, arrest, and closure of hydraulic fractures under controlled triaxial stress conditions.

Experimental Setup

The experiment was conducted on a cubic sandstone sample with dimensions of 25 × 25 × 25 cm. The sample was placed in a truetriaxial frame that applied confining stresses in all three principal directions:

Vertical Confining Stress: 7 MPa

Horizontal Confining Stress: 14 MPa

A viscous glucose fluid containing a UV additive was used as the fracturing fluid. This fluid was injected through a 1/8'' high-pressure tube cemented with epoxy into a centrally drilled hole within the sample. An axisymmetric notch was created at the injection point to facilitate fracture initiation and promote the planarity of the fracture.

The experiment was designed to simulate one cycle of fracture initiation, propagation, arrest, and closure. The closure of the fracture was occured by the leakoff of the fracturing fluid into the surrounding porous medium.

Acoustic Monitoring

To capture the dynamics of fracture propagation and closure, the experiment employed both passive and active acoustic monitoring systems:

Passive Acoustic Monitoring:

Sensors: 16 Vallen VS150-M passive piezoelectric sensors were used to capture Acoustic Emissions (AEs) within the frequency range of 50 kHz to 600 kHz.

Signal Processing: Continuous signal analysis and denoising were performed on the captured AE data. The STA/LTA algorithm was applied to the denoised signal to identify potential p-wave arrivals, providing insights into the fracture mechanics.

Active Acoustic Monitoring:

Transducers: A total of 64 piezoelectric transducers were integrated into the loading platens, with 32 acting as sources and 32 as receivers. The array included 10 shear-wave and 54 longitudinal-wave transducers.

Signal Generation and Acquisition: A Ricker excitation signal with a central frequency adjustable between 300 and 750 kHz was generated and amplified using a high-power amplifier. The signal was routed to one of the 32 source transducers via a multiplexer, and the resulting signals were recorded simultaneously by the 32 receiver transducers at a sampling frequency of 50 MHz. Each source was excited 50 times to improve the signal-to-noise ratio, with the complete acquisition sequence taking approximately 2.5 seconds.

Additional Measurements

In addition to acoustic monitoring, several other key measurements were recorded during the experiment:

Fluid Injection Parameters: The pressure and rate of fluid injection were continuously monitored.

Flat-Jack and Piston Parameters: The pressures and volumes exerted by each pair of flat-jacks were recorded at a frequency of 1 Hz.

Fracture Opening Measurement: An eddy current sensor, an electromagnetic inductive device, was placed inside the wellbore at the notch/inlet to directly measure the fracture opening.

All measurements were synchronized using a dedicated LabView application to ensure consistency across the dataset.

Conclusion

This dataset provides a comprehensive view of the hydraulic fracturing behavior of Molasse de Villarlod sandstone under controlled laboratory conditions, with a focus on the processes of fracture propagation, arrest, and closure. The dataset includes raw and processed acoustic data, fluid injection metrics, and direct observations of fracture opening. It is an invaluable resource for researchers and engineers studying hydraulic fracturing, rock mechanics, and related fields. The data is suitable for detailed analysis and modeling of fracture mechanics in porous, permeable sandstones.

Note

Since the fracture did not extend to the boundaries of the sample, the sample was subsequently cut, and a core was extracted. This core was then sent for CT-scan analysis, which was used to reconstruct the residual fracture surfaces and assess their roughness. The dataset from this analysis is available in the Related Work section via the provided URL (Talebkeikhah, M. (2024). CT-Scan Image Dataset of Residual Fluid-Driven Fracture in a Molasse de Villarlod Sandstone Core - Post-Radial Hydraulic Fracture Experiment - M03 Sample [Data set]. Zenodo. https://doi.org/10.5281/zenodo.13358916).

Processing code

Follow the URL repositories below to access to the codes for processing these dataset.

https://github.com/GeoEnergyLab-EPFL/ActiveAcoustiX

https://github.com/GeoEnergyLab-EPFL/FracLowRate

Contact and Support

Email:

Brice Lecampion: [e-mail]

Mohsen Talebkeikhah: [e-mail]