Nondestructive measurements and evaluation has great significance in various domains of science, engineering and technology. The objective of this research is to investigate the anisotropic behavior in a sandstone sample from non-invasive tests using Laser Doppler Vibrometer coupled with Piezoelectric Transducer and to validate these results using a laboratory scale controlled hydraulic fracturing arrangement. High-resolution 3-component single-point seismograms were generated for the core sample using a combination of 1 MHz Piezoelectric Transducer as a source of elastic waves that travel within the reservoir rock sample and Laser Doppler Vibrometer as the receiver. Hilbert transforms of the 3-component data were calculated to obtain the complex signal. Shear wave splitting phenomenon due to anisotropy in rock was examined and the resultant S H and S V wave polarizations were measured. Elastic tensor for the core sample was subsequently determined from the velocity picks within the Hilbert energy envelope followed by the estimation of Thomsen's parameters. The hodogram analysis was performed to assess the process of shear wave splitting in the rock sample that detects the anisotropy of the medium and this, in turn, specifies the characteristics of weakness planes. Laboratory scale controlled hydraulic fracturing was performed to verify whether the fractures propagate along the anisotropic planes of weakness. Real-time fracture detection was carried out during this process and its propagation features were studied. The fractured core sample was imaged under the slice Computed Tomography scan machine to perceive the mode and propagation of fractures in the rock specimen.

Natural gas hydrates are unconventional abundant hydrocarbon energy resources that can guarantee energy sustainability with little environmental impact. The solid nature of the resource, distinct thermodynamic characteristics, and accumulations at shallow depths make the existing conventional production techniques unviable. Among all the currently explored production techniques, the hydrate-based carbon capture and sequestration (HBCCS) technique is expected to improve production, proven to be geomechanically safer, and conceptualized to be environmentally friendly. In this carbon-neutral production concept, carbon emissions are effectively sequestered for the long-term. This review presents a comprehensive overview and perspective of the CO 2 exchange-based approach to extract methane (CH 4 ) from naturally occurring gas hydrate reserves, emphasizes its prospect as a suitable alternative according to the current energy demands and climate concerns, establishes its environmental and production challenges, and demonstrates the recent developments. This review focuses on the production aspect and discusses the mechanism of the exchange process, experimental and modeling studies, various in situ production tests using different techniques on multiple sediments, and production challenges associated with the exchange process. The aspects of geomechanics and possibilities of fracturing in hydrate reservoirs are also discussed elaborately. A suitable and effective technique is yet to be established to produce natural gas commercially by addressing the existing challenges like sand production, seafloor stability concerns, marine ecosystem problems, low production rate, uncontrolled dissociation, water production, etc. Although the CO 2 exchange-based method is thermodynamically favorable, rapid crystallization of CO 2 restricts mass transfer and prevents continuous exchange. The exchange process is also influenced by heat, salinity, residual water saturation, exchange gas composition, injection phase, injection pressure, sediment properties, etc. There is a need to study the CO 2 −CH 4 exchange process at a fundamental level and at a larger scale, to understand its intricacies. In tandem with comprehensively discussing the subject, this review has listed the issues that require tenable solutions, which shall be helpful to readers who wish to work on production from CH 4 hydrates using the CO 2 exchange process. Methane hydrates shall be one of the strategic energy sources to meet our growing energy requirements for a sustainable future.

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