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Fusion of Active and Passive Waveform Measurements for Mapping the Hydraulic Fractures
  • Aditya Chakravarty,
  • Siddharth Misra
Aditya Chakravarty
Texas A&M University

Corresponding Author:[email protected]

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Siddharth Misra
Texas A&M University
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Abstract

Fracture characterization is essential to hydrocarbon and geothermal exploration and production as well as carbon geo-sequestration. Active and passive measurements have been extensively applied to map fractures across various scales. Active and passive measurements have inherent advantages and limitations that complement each other. In this study, to improve the mapping of embedded fractures and the surrounding geomechanically altered regions, we integrate active shear-wave transmission measurement with passive acoustic-emission measurement collected during a lab-scale hydraulic-fracturing experiment. The proposed approach leverages the advantages of the two modalities of measurements, while minimizing the limitations. Polarized shear-wave transmission (active) measurement was collected before and after the hydraulic fracturing, and the acoustic emission (passive) measurement was collected during hydraulic fracturing. Two sets of two-dimensional maps of fracture and fracture-induced damage in axial, median and frontal planes were obtained by separately processing the physics-informed transformations of active and passive measurements. These 2D maps are then fed to wavelet-based image-fusion technique to integrate the two sources of information for the reliable mapping/imaging of the embedded fractures and the surrounding geomechanically altered regions. Plain word summary Fractures and geomechanical alterations embedded in a solid material can be characterized using active or passive measurements. Signal type, timing, duration and location of the source is controlled during an active measurement to allow optimal interactions of the propagating wave and the fractured material, whereas the signals due to waves generated by the processes of fracturing and geomechanical alterations are captured during a passive measurement. Active and passive measurements have advantages and limitations that complement each other. In this study, physics-informed transformations and wavelet-based image fusion are used to integrate the active and passive measurements to get the best of the two measurement modalities for purposes of reliable imaging of fractures and the surrounding geomechanically altered regions. Key points  Integration of active and passive measurements will leverage their strengths and minimize the limitations of individual measurement techniques.  To the best of authors’ knowledge, no reference exists where the two modalities are combined to characterize the fractures either in the field or laboratory scale.  We integrate active ultrasonic measurements with passive acoustic-emission measurements using physics-informed transformations and data fusion techniques.  The proposed method improves the imaging of embedded fractures and the surrounding geomechanically altered regions.  Two-dimensional maps of fracture and fracturing-induced damage is generated in axial, median and frontal planes.