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The Microwave-Induced Fracturing of Hard Rock
A new, high-efficiency technology for fracturing and breaking rocks is required. Due to various advantages including high efficiency, energy-saving, and having no secondary pollution, the technology of microwave-induced fracturing of hard rock has been considered as a potential method for rock fracturing and breaking. Aiming at the realisation of two engineering applications: microwave-assisted mechanical rock breaking and stress release from rock masses in deep underground engineering works to prevent geological disasters caused by high-stress concentrations such as rockbursts, a novel (open-type) microwave-induced fracturing apparatus (OMWFA) for fracturing hard rocks was developed. On this basis, the two modes of microwave-induced subsurface fracturing and microwave-induced borehole fracturing of hard rocks were proposed. Due to removal of the restraint of the microwave cavity, OMWFA can be used to fracture large-size rock samples and engineering-scale rock masses. Using the apparatus, the fracturing effects of the two fracturing modes on different dimensions of cuboidal basalt samples were investigated. By combining the microwave-induced fracturing apparatus with a press machine to explore the influence of unidirectional stress on the fracturing effect of microwave treatment on basalt. Moreover, field tests were carried out on rock masses encountered in underground engineering works at Baihetan Hydropower Station in Sichuan Province, China, and the fracturing effects were evaluated by applying a digital borehole televiewer and conducting acoustic wave testing. The results show that the apparatus had favourable fracturing effects on the subsurface and borehole samples of basalt. When no stress was applied, the cracks radially expanded from the approximate centre of the radiant surface and unidirectional stress promoted fracturing. The number and depth of cracks increased with prolonged microwave exposure. After microwave treatment, the P-wave velocity of the samples declined, and the longer the microwave exposure, the more significant the reduction in P-wave velocity was. The results of field test reveal that borehole fracturing can exhibit a favourable effect around boreholes. The sound velocity around the borehole and between the boreholes both declined to some extent. Microwave-induced hard rock fracturing offers guiding significance to those exploring and developing new rock breaking and tunnelling methods, and generally enhances construction safety in deep underground engineering works.
Journal Article
Influencing Factors Analysis and Optimization of Hydraulic Fracturing in Multi-Layered and Thin Tight Sandstone Gas Reservoir
With the deepening of exploration and development of tight sandstone gas reservoirs, the remaining recoverable reservoirs gradually become thinner with the vertical stratigraphic structure. The geomechanical properties become complex, and development based on conventional hydraulic fracturing methods often leads to serious problems, such as difficult control of fracture height, penetrating interlayers, too short fracture length, and inadequate proppant filling. In view of the above problems, we conducted a numerical investigation on a hydraulic fracturing scheme in a multi-layered and thin tight sandstone gas reservoir. According to the dataset from wells in a real gas reservoir in China’s Ordos Basin, the relevant geomechanical characteristics of the gas layers, together with the interlayers in the main production interval, were obtained, based on which, a fine numerical model was developed. By using the PL3D fracture propagation algorithm, a 3D hydraulic fracture propagation model was produced, and then using microseismic monitoring and production data matching, a high-precision hydraulic fracture model of the multi-layered and thin tight sandstone gas reservoir was obtained. On this basis, the influence of different geomechanical parameters and fracturing operational parameters on hydraulic fracture propagation was analyzed. Finally, an optimized hydraulic fracturing scheme that fitted the characteristics of the multi-layered and thin tight sandstone gas reservoir was proposed. Using a typical reservoir example, the optimized scheme enabled control of the fracture height in thin layers and the creation of long fractures with better proppant filling, so that the productivity of the fracture was significantly improved.
Journal Article
When Fracking Comes to Town
When Fracking Comes to Town
traces the response of local communities to the shale gas
revolution. Rather than cast communities as powerless to
respond to oil and gas companies and their landmen, it shows that
communities have adapted their local rules and regulations to meet
the novel challenges accompanying unconventional gas extraction
through fracking. The multidisciplinary perspectives of this
volume's essays tie together insights from planners, legal
scholars, political scientists, and economists. What emerges is a
more nuanced perspective of shale gas development and its impacts
on municipalities and residents.
Unlike many political debates that cast fracking in
black-and-white terms, this book's contributors embrace the
complexity of local responses to fracking. States adapted legal
institutions to meet the new challenges posed by this energy
extraction process while under-resourced municipal officials and
local planning offices found creative ways to alleviate pressure on
local infrastructure and reduce harmful effects of fracking on the
environment. The essays in When Fracking Comes to Town
tell a story of community resilience with the rise and decline of
shale gas production.
Contributors: Ennio Piano, Ann M. Eisenberg, Pamela A. Mischen,
Joseph T. Palka, Jr., Adelyn Hall, Carla Chifos, Teresa Córdova,
Rebecca Matsco, Anna C. Osland, Carolyn G. Loh, Gavin Roberts,
Sandeep Kumar Rangaraju, Frederick Tannery, Larry McCarthy, Erik R.
Pages, Mark C. White, Martin Romitti, Nicholas G. McClure, Ion
Simonides, Jeremy G. Weber, Max Harleman, Heidi Gorovitz
Robertson
eBook
Fracking : a reference handbook
The use of fracking is a tremendously important technology for the recovery of oil and gas, but the advantages and costs of fracking remain controversial. This book examines the issues and social, economic, political, and legal aspects of fracking in the United States.
Book
Acoustic Emission Evolution and Hydraulic Fracture Morphology of Changning Shale Stressed to Failure at Different Injection Rates in the Laboratory
Hydraulic fracturing has been widely used to enhance reservoir permeability during the extraction of shale gas. As one of the external input parameters, injection rate has a significant impact on formation breakdown pressure and the complexity of hydraulic fractures. To gain deeper insights into the effect of injection rate on breakdown pressure and fracture morphology, we conducted five hydraulic fracturing experiments on Changning shale in the laboratory. We used five different injection rates between 3 and 30 mL/min to fracture cylindrical core samples with 50 mm in diameter and 100 mm in length. We monitored acoustic emissions and surface displacements during the tests, and analyzed the fracture pattern post mortem by using a fluorescent tracer. We find a semi-logarithmic relationship between the breakdown pressure and the injection rates. Second, we find that it is the injection rate that dictates sample deformation and crack formation during breakdown rather than the fluid volume injected during the whole process. The analysis of amplitudes and frequency of acoustic signals indicates that hydraulic fracturing of Changning shale is overall dominated by tensile fractures (> 60%). However, at low injection rates, shear events are facilitated before rock breakdown. On the other hand, high injection rates result in reducing fracture tortuosity and surface roughness due to limited fluid infiltration in the relatively short injection window. We close this study with a conceptual model to explain the difference between fluid infiltration (low injection rates) and the loading rate effect (high injection rate) in low-permeability shale rocks. The findings obtained in this study can help to adjust injection rates in the field to economically and safely produce gas from shale.HighlightsRock expansion upon breakdown is dominated by instantaneous crack opening caused by injection rates.Low injection rates reduce the breakdown strength by activating shear cracks in a larger fluid infiltration zone.High injection rates have limited effects on fracture morphology.A theoretical model is proposed to elucidate the competing mechanism between fluid infiltration and the loading rate effect.
Journal Article