scholarly journals Enhancement of Permeability Activated by Supercritical Fluid Flow through Granite

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Tsuyoshi Nohara ◽  
Masaoki Uno ◽  
Noriyoshi Tsuchiya
Keyword(s):  
Fluid Flow ◽  
Supercritical Fluid ◽  
Open Fracture ◽  
Fracture Network ◽  
Granitic Rocks ◽  
High Permeability ◽  
Angle Fracture ◽  
Sealing Zone ◽  
Flow Through

This geological study utilized electron probe microanalysis of granitic rocks to evaluate traces of hydrothermal fluid activity. Amphibole-plagioclase thermometry was applied to estimate the temperature of a glassy vein as approximately 700°C. The results of mesoscopic and microscopic observations of the rock core obtained through borehole investigations revealed that the track of supercritical fluid flow was microfracture filling with hornblende and plagioclase. Grain-boundary microfractures and parallel microfractures were recognized as traces formed by the limited activity of the supercritical fluid immediately after granite setting in the Late Cretaceous. The current high permeability of a borehole in and around the track of supercritical fluid flow was recognized to be related to the microfracture network. In order to investigate the enhancement of permeability activated by the supercritical fluid flow through granite, the results of this geological study and existing data from in situ permeability tests were analysed. Various fractures in and around the trace of a self-sealing zone were investigated for another borehole rock core. The trace of the self-sealing zone, which was composed of filling textures associated with the supercritical fluid, corresponded to the current low-permeability section of the borehole. Representative types were proposed for simple classification based on the characteristics of fractures and the permeability data of each test section. A high-angle fracture of chlorite filling in combination with an open fracture and the development of a sericite-filling fracture network including a low-angle open fracture were recognized as characteristics of high-permeability types. The results of this study indicate that the enhancement of permeability was activated by supercritical fluid flow through granite.

scholarly journals The Role of In Situ Stress in Organizing Flow Pathways in Natural Fracture Networks at the Percolation Threshold

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Chuanyin Jiang ◽  
Xiaoguang Wang ◽  
Zhixue Sun ◽  
Qinghua Lei
Keyword(s):  
Fluid Flow ◽  
Percolation Threshold ◽  
Fractured Reservoirs ◽  
Fracture Network ◽  
In Situ Stress ◽  
Natural Fracture ◽  
Fracture Aperture ◽  
Dilation Effect ◽  
Stress Dependent

We investigated the effect of in situ stresses on fluid flow in a natural fracture network. The fracture network model is based on an actual critically connected (i.e., close to the percolation threshold) fracture pattern mapped from a field outcrop. We derive stress-dependent fracture aperture fields using a hybrid finite-discrete element method. We analyze the changes of aperture distribution and fluid flow field with variations of in situ stress orientation and magnitude. Our simulations show that an isotropic stress loading tends to reduce fracture apertures and suppress fluid flow, resulting in a decrease of equivalent permeability of the fractured rock. Anisotropic stresses may cause a significant amount of sliding of fracture walls accompanied with shear-induced dilation along some preferentially oriented fractures, resulting in enhanced flow heterogeneity and channelization. When the differential stress is further elevated, fracture propagation becomes prevailing and creates some new flow paths via linking preexisting natural fractures, which attempts to increase the bulk permeability but attenuates the flow channelization. Comparing to the shear-induced dilation effect, it appears that the propagation of new cracks leads to a more prominent permeability enhancement for the natural fracture system. The results have particularly important implications for predicting the hydraulic responses of fractured rocks to in situ stress fields and may provide useful guidance for the strategy design of geofluid production from naturally fractured reservoirs.

Cyclic fluid flow through a regionally extensive fracture network within the Kodiak accretionary prism

1995 ◽  
Vol 100 (B7) ◽  
pp. 12881-12894 ◽  
Author(s):  
Donald M. Fisher ◽  
Susan L. Brantley ◽  
Mark Everett ◽  
Joseph Dzvonik
Keyword(s):  
Fluid Flow ◽  
Accretionary Prism ◽  
Fracture Network ◽  
Flow Through

Modeling of supercritical fluid flow through a yarn package

2000 ◽  
Vol 19 (1) ◽  
pp. 87-99 ◽  
Author(s):  
Brent Shannon ◽  
Walter Hendrix ◽  
Brent Smith ◽  
Gerardo Montero
Keyword(s):  
Fluid Flow ◽  
Supercritical Fluid ◽  
Flow Through

scholarly journals Enhancing fracture-network characterization and discrete-fracture-network simulation with high-resolution surveys using unmanned aerial vehicles

2020 ◽  
Vol 28 (7) ◽  
pp. 2285-2302
Author(s):  
Mahawa Essa Mabossani Akara ◽  
Donald M. Reeves ◽  
Rishi Parashar
Keyword(s):  
Fluid Flow ◽  
Fracture Network ◽  
Pumping Test ◽  
Discrete Fracture Network ◽  
Granitic Rocks ◽  
Equivalent Permeability ◽  
Fracture Length ◽  
Discrete Fracture ◽  
Network Scale ◽  
Aperture Scaling

Abstract A workflow is presented that integrates unmanned aerial vehicle (UAV) imagery with discrete fracture network (DFN) geometric characterization and quantification of fluid flow. The DFN analysis allows for reliable characterization and reproduction of the most relevant features of fracture networks, including: identification of orientation sets and their characteristics (mean orientation, dispersion, and prior probability); scale invariance in distributions of fracture length and spatial location/clustering; and the distribution of aperture values used to compute network-scale equivalent permeability. A two-dimensional DFN-generation approach honors field data by explicitly reproducing observed multi-scale fracture clustering using a multiplicative cascade process and power law distribution of fracture length. The influence of aperture on network-scale equivalent permeability is investigated using comparisons between a sublinear aperture-to-length relationship and constant aperture. To assess the applicability of the developed methodology, DFN flow simulations are calibrated to pumping test data. Results suggest that even at small scales, UAV surveys capture the essential geometrical properties required for fluid flow characterization. Both the constant and sublinear aperture scaling approaches provide good matches to the pumping test results with only minimal calibration, indicating that the reproduced networks sufficiently capture the geometric and connectivity properties characteristic of the granitic rocks at the study site. The sublinear aperture scaling case honors the directions of dominant fractures that play a critical role in connecting fracture clusters and provides a realistic representation of network permeability.

Comparison of discrete fracture network and equivalent continuum simulations of fluid flow through two-dimensional fracture networks for the DECOVALEX–2011 project

2012 ◽  
Vol 76 (8) ◽  
pp. 3179-3190 ◽  
Author(s):  
C. T. O. Leung ◽  
A. R. Hoch ◽  
R. W. Zimmerman
Keyword(s):  
Fluid Flow ◽  
Fracture Network ◽  
Two Dimensional ◽  
Field Scale ◽  
Continuum Approach ◽  
Discrete Fracture ◽  
Grid Block ◽  
Flow Through ◽  
Equivalent Continuum ◽  
Equivalent Continuum Approach

AbstractFluid flow through a two-dimensional fracture network has been simulated using a discrete fracture model. The computed field-scale permeabilities were then compared to those obtained using an equivalent continuum approach in which the permeability of each grid block is first obtained by performing fine-scale simulations of flow through the fracture network within that region. In the equivalent continuum simulations, different grid-sizes were used, corresponding to N by N grids with N = 10, 40, 100 and 400. The field-scale permeabilities found from the equivalent continuum simulations were generally within 10% of the values found from the discrete fracture simulations. The discrepancies between the two approaches seemed to be randomly related to the grid size, as no convergence was observed as N increased. An interesting finding was that the equivalent continuum approach gave accurate results in cases where the grid block size was clearly smaller than the 'representative elementary volume'.

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