Heretofore the concept of EGS heat transport has followed a rigid script dating from the early 70s featuring a mechanically quasi-uniform low-porosity/low-permeability clastic rock matrix that is either naturally or artificially driven by sundry quasi-planar megafractures supporting Poiseuille flow of in situ fluids. The origin and persistence of this EGS fracture/flow concept is likely traceable to the visual identification of large-scale finite-width 'joints' in basement rock outcrops. Three serious problems, however, exist for 'joint' control in situ fluid flow. First, joint expansion seen in mechanical free-surface outcrops does not obviously apply at 3-5km-depth confining pressures. Second, attempts to identify wellbore evidence of 'active' interwell fracture-borne fluid pathways have not been conspicuously successful. Third, there is little evidence in well-log and/or well-core data for large-scale discrete mechanical fractures in an otherwise mechanically quasi-uniform rock matrix. Rather well-log and well-core evidence strongly favours a quite different physical relationship between the rock matrix, rock fractures, and in situ fluid flow. By EGS joint prescription, wellbore microresistivity logs in an EGS volume should record abrupt high-conductivity spikes as the resistivity sensor passes over conductive-fluid-containing joints. The power-spectrum of any spike sequence is essentially flat, S(k) ~ 1/k^0 ~ const. In conspicuous contrast, microresistivity well-log data have, in common with the vast majority of geophysical well logs for most rock types and environments, Fourier power-spectra that scale inversely with wave number, S(k) ~ 1/k^1, over ~ 3 decades of scale range (generally ~1/Km < k < ~1/m, ~1/Dm < k < ~1/cm for microresistivity). The systematic well-log power-law spectral scaling S(k) ~ 1/k phenomenon that negates the matrix + megafracture EGS concept of in situ flow opens the door on a scale-independent physical concept of in situ fractures, fluid flow and heat transport. Power-law scaling phenomena occur notably in thermodynamic binary-population order-disorder continuous phase transitions when an 'order parameter' reaches a 'critical value'. In rock, the plausible critical-valued order parameter is grain-scale fracture density determined by the number of cement-disrupted/percolating grain-grain contact defects with in a host population of intact/non-percolating cement-bonded grain-grain contacts. As tectonic finite-strain continually induces grain-scale failure of cement bonds in (clastic) rock, a critical-state percolation threshold value is maintained, rock volumes become percolation-permeable on scale lengths from mm to km, and well-log geophysical properties such as sonic wave speeds, electrical resistivity, soluble chemical species density, neutron porosity, and mass density fluctuations attain the power-law scaling fluctuation power-spectra S(k) ~ 1/k observed over ~1/Km < k < ~1/cm. At the same time and by a closely related percolating grain-scale-fracture mechanism, in situ clastic rock attains a well-attested ~85% correlation ¥ä¥õ ~ ¥älog(¥ê) recorded for spatial fluctuations in clastic reservoir well-core porosity ¥õ and the logarithm of well-core permeability ¥ê. Both observed physical relations governing in situ fractures and flow, S(k) ~ 1/k for fracture density distributions and ¥ä¥õ ~ ¥älog(¥ê) for fracture-control of permeability, can be straightforwardly incorporated into 2D/3D finite-element flow/transport simulation schemes such as provided by the Sutra USGS open-file code. We use Sutra to demo

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