Passive Acoustic Metamaterial Proppants for Advanced Fracture Diagnostics

Ineffective fracture design and practices in unconventional oil and natural gas wells present environmental risks and reduce the production efficiency of hydraulic fracturing, largely due to the inability to measure propped fracture geometry and behavior using current proppants and available tools. In this project, a unique proppant detection technology based on acoustic metamaterials is being developed that allows distinct detection of proppant location and environmental conditions away from the wellbore using industry standard acoustic logging tools. Development of the smart proppant and related detection technology is accomplished through design and scaled-up production of metamaterial proppant particles, proppant characterization including effects of mechanical stress on acoustic response, pilot deployment of downhole acoustic logging tool to detect proppant geometry and behavior, and development of advanced data analysis techniques to locate proppant in fractures away from the wellbore. In Phase I, a composite particle structure with specific geometries and mechanical properties was designed based on acoustic modeling and simulation and a production system was engineered to produce the smart proppant. Laboratory acoustic testing using ultrasonic transducers was employed to test control and experimental proppants in various environmental and geometric configurations. Mixtures of control and experimental proppants were used to determine the concentration dependence of the acoustic response. Mechanical load was applied to the proppants and mixtures during acoustic testing and the change in response under stress was measured. A pilot field trial was conducted in which proppant packets were buried around a cemented casing pipe and the simulated wellbore was logged using a monopole, full waveform triple sonic logging tool. In Phase II, an improved smart proppant with smaller size and acoustic signatures in the middle of the frequency range of a monopole sonic logging tool will be produced in scaled-up quantity, characterized, and tested in a pilot field study. This effort will greatly expand the understanding and utility of the smart proppant and related detection systems by improving discrimination and contrast of proppant position and determination of closure stress at the proppant location. Alternative acoustic detection methods will be explored along with advanced data analysis techniques for determining the character of propped fractures. Increased information about hydraulic fracturing operations directly benefits environmental health and safety. It can lead to increased stimulation efficiency, zonal isolation, and production control. Knowledge of proppant distribution and flowback helps to better understand the geomechanical forces and operational requirements of hydraulic fracturing. The ultimate result of this enhanced awareness is safer and more economical production techniques and processes that contribute to US energy independence.