Title: 
Permeabilityspecific Spatial Correlation Systematics for UtahForge EGS Stimulation Meqs 
Authors: 
Peter LEARY and Peter MALIN 
Key Words: 
EGS, Meqs, crustal permeability, spatial correlation flow, modeling 
Conference: 
Stanford Geothermal Workshop 
Year: 
2023 
Session: 
Enhanced Geothermal Systems 
Language: 
English 
Paper Number: 
Leary 
File Size: 
1605 KB 
View File: 

Recent UtahForge well 16A(78)32 stimulation Meq XYZM (location/magnitude) data show two spatial correlation features observed in ambient crust Meqs: lognormal moment distributions and eventpair spatial correlation scaling with interevent offset r, G(r) ~ 1/r^p, p ~ 1. Neither spatial correlation feature is compatible with the uncorrelated randomness that is typically assumed for crustal fluid flow modeling via spatially averaged heterogeneity and/or DFN distributions. Both UtahForge Meq spatial correlation features are, however, congruent with rockfluid interaction spatialcorrelation empirics attested by ambient crust welllog, wellcore, and wellflow data worldwide. UtahForge Meq spatial correlation features are seen to apply equally to ambient crustal Meqs recorded at tectonic, convective geothermal, and crystalline basement EGS stimulation sites. More specifically, the UtahForge Meq spatial correlations are latent in the ambient crust poropermeability relation κ(x,y,z) ~ exp(αφ(x,y,z)), where porosity 0 less than φ(x,y,z) less than 1 is a pinknoise random powerlaw scaling volumetric distribution and α a poroconnectivity parameter with empirical value range 23 less than mean(αφ) less than 56 for crustal formations with mean porosities 0.003 less than mean(φ) less than 0.3. The poropermeability relation κ(x,y,z) ~ exp(αφ(x,y,z)) is inherently lognormal for the empirical αφ condition, with highend permeability sites spatially correlated as G(r) ~ 1/r^p, p ~ 1. It follows that many if not most UtahForge stimulation Meqs, in line with ambient crust Meqs elsewhere, arise from lowvelocity seismic slip within high permeability poroconnectivity structures rather than as high velocity slip on planar fault surfaces. Meq moment distributions thus reflect ambient crust permeability structures, while hectohertz seismic emission waveform spectra and coda scattering of crustal basement EGS stimulation Meqs provide support evidence for seismic slip on poropermeability structures given by the κ(x,y,z) ~ exp(αφ(x,y,z)) ambient crust rockfluid interaction empiric. Crustal flow models for EGS stimulation processes require systematic computational means for representing the powerlaw scaling spatial correlation properties of ambient crust permeability distributions.
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