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.
Highlights
Published: 17 December 2021In deep geothermal systems, many studies have been undertaken to better understand the importance of the natural fractures in various contexts [1,2]
The present work is part of MEET project and focused on the Noble Hills (NH) range, considered as a paleo geothermal reservoir analogue, which offers a general overview of the structural organization of the fracture networks at outcrop and wider scales
This study aims at understanding the fracture spacing variability and the distribution of fracture patterns in granitic rocks, and the impact of the proximity of major faults on fracture distribution and fluid circulation
Summary
Published: 17 December 2021In deep geothermal systems, many studies have been undertaken to better understand the importance of the natural fractures in various contexts [1,2]. The low rock matrix permeability and porosity allow the fluid flow within fracture networks [9,10,11]. A fracture network is characterized by geometrical parameters such as lengths, spacings, widths, orientations, fracture distributions, and the relationships between them significantly affect the connectivity within the reservoir [9,14,15,16,17]. Among these parameters, spacing between fractures is a well-considered parameter, because it controls the probability of intersecting fractures during drilling [18]. Statistic parameters that describe fracture spacing include: (1) The mean, which characterizes the global expected frequency of fracture intersection, and (2) the standard deviation, which describes the distribution of the fractures around the mean
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