Fracture Spacing Variability and the Distribution of Fracture Patterns in Granitic Geothermal Reservoir: A Case Study in the Noble Hills Range (Death Valley, CA, USA)

Abstract

Scanlines constitute a robust method to better understand in 3D the fracture network variability in naturally fractured geothermal reservoirs. This study aims to characterize the spacing variability and the distribution of fracture patterns in a fracture granitic reservoir, and the impact of the major faults on fracture distribution and fluid circulation. The analogue target named the Noble Hills (NH) range is located in Death Valley (DV, USA). It is considered as an analogue of the geothermal reservoir presently exploited in the Upper Rhine Graben (Soultz-sous-Forêts, eastern of France). The methodology undertaken is based on the analyze of 10 scanlines located in the central part of the NH from fieldwork and virtual (photogrammetric models) data. Our main results reveal: (1) NE/SW, E/W, and NW/SE fracture sets are the most recorded orientations along the virtual scanlines; (2) spacing distribution within NH shows that the clustering depends on fracture orientation; and (3) a strong clustering of the fracture system was highlighted in the highly deformed zones and close to the Southern Death Valley fault zone (SDVFZ) and thrust faults. Furthermore, the fracture patterns were controlled by the structural heritage. Two major components should be considered in reservoir modeling: the deformation gradient and the proximity to the regional major faults.

Effect of Fracture Geometry Parameters on the Permeability of a Random Three-Dimensional Fracture Network

“…Generally, it is commonly assumed that there is no correlation between the aperture and trace length of a fracture. Consequently, the probability density function of the fracture length can be considered as the form of the aperture ground distribution [45]:…”

Editorial of Special Issue “Enhanced Geothermal Systems and Other Deep Geothermal Applications throughout Europe: The MEET Project”

“…Hydrothermal alteration was described for outcrops far from the faults [6] and close to them [7]. The structural characterization of the fracture network that conducted the fluids responsible for the hydrothermal alterations is presented in [8,9].…”

“…Chabani et al [8] proposed a geometrical description and a quantification of the multiscale network organization and its effect on connectivity using a wide-ranging scale analysis. The statistical analyses were performed from regional maps to thin sections.…”

“…During the four years of the project, two main types of exploitations were investigated: Enhanced Geothermal Systems (EGS) and oil-to-geothermal conversion or co-production. The following topics were addressed: the upscaling of thermal power production and optimized operation of EGS plants (papers [1][2][3][4][5]); variscan geothermal reservoirs in granitic and metamorphic rocks (papers [6][7][8][9][10][11][12][13][14][15][16][17]); and technical, economic and environmental assessment for oil-to-geothermal fields and EGS integration into energy systems (papers [18][19][20]). These 20 papers give an overview of some of the work performed in the MEET project, but they are not exhaustive of all the results obtained in this frame.…”

Heat Extraction in Geothermal Systems with Variable Thermo-Poroelastic Fracture Apertures

“…This endeavor is underpinned by the aspiration to unveil the prospective geothermal resources concealed beneath the Earth's surface. Within the structured framework of the EU-H2020 funded MEET (Multidisciplinary and multi-context Engagement for Enabling geothermal Technology) project, an extensive corpus of data, elucidating varying fracture properties, was collected from a set of geographically diverse locales, encompassing Göttingen, Havelange, Cornwall, the arid terrain of Death Valley, and Soultz-sous-Forets [1][2][3][4][5][6][7]. An observation about this data corpus was the discernible variability in the fracture aperture and its potential correlative relationship with the overarching fracture length.…”