Abstract
A better understanding of the process of stimulation by hydraulic fracturing in shale gas and oil reservoirs is necessary for improving resource productivity. However, direct observation of hydraulically stimulated regions including induced fractures has been difficult. In the present study, we develop a new approach for directly visualizing regions of shale specimens impregnated by fluid during hydraulic fracturing. The proposed laboratory method uses a thermosetting resin mixed with a fluorescent substance as a fracturing fluid. After fracturing, the resin is fixed within the specimens by heating, and the cut sections are then observed under ultraviolet light. Based on brightness, we can then distinguish induced fractures and their surrounding regions impregnated by the fluid from other regions not reached by the fluid. Polarization microscope observation clearly reveals the detailed structures of tortuous or branched fractures on the micron scale and interactions between fractures and constituent minerals. The proposed experimental and observation method is useful for understanding the process of stimulation by hydraulic fracturing and its relationship with microscopic rock characteristics, which is important for fracturing design optimization in shale gas and oil resource development.
Highlights
Shale gas is becoming an important alternative energy source as the demand for energy increases.Shale gas has the potential to affect the natural gas market, and the entire global energy mix
We show examples of experimental results using shale samples extracted from three different sites, representing complex propagation patterns resulting from interactions with constituent minerals and preexisting discontinuities in the rocks
Thisaallowed the induced mixed with a fluorescent substance as a fracturing fluid in the laboratory
Summary
Shale gas is becoming an important alternative energy source as the demand for energy increases.Shale gas has the potential to affect the natural gas market, and the entire global energy mix. Shale gas is becoming an important alternative energy source as the demand for energy increases. Since 2000, improvements in gas recovery technologies from shale formations have encouraged the industry to accelerate the development of these resources. A combination of two technologies, horizontal well drilling and multi-stage hydraulic fracturing, has made shale gas production economically feasible [1]. Fractures created around a horizontal well by multi-stage fracturing have worked well for gas production because they increase the permeability of the rock and surface area in contact with resources in tight rock reservoirs. Many unknowns remain with respect to the effects of hydraulic fracturing in production. A better understanding of the fracturing process, especially fracture development patterns, is necessary in order to enhance productivity
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