Influence of reservoir geology on seismic response during decameter-scale hydraulic stimulations in crystalline rock

Villiger, Linus1; Gischig, Valentin2; Doetsch, Joseph3; Krietsch, Hannes3; Dutler, Nathan4; Jalali, Mohammadreza5; Valley, Benoit4; Selvadurai, Paul A.1; Mignan, Arnaud1,6; Plenkers, Katrin1; Giardini, Domenico1; Amann, Florian5; Wiemer, Stefan1

2020-04-28

10.5194/se-11-627-2020

Solid Earth   影响因子和分区

1869-9510

1869-9529

We performed a series of 12 hydraulic stimulation experiments in a 20 m x 20 m x 20 m foliated, crystalline rock volume intersected by two distinct fault sets at the Grimsel Test Site, Switzerland. The goal of these experiments was to improve our understanding of stimulation processes associated with high-pressure fluid injection used for reservoir creation in enhanced or engineered geothermal systems. In the first six experiments, pre-existing fractures were stimulated to induce shear dilation and enhance permeability. Two types of shear zones were targeted for these hydroshearing experiments: (i) ductile ones with intense foliation and (ii) brittle-ductile ones associated with a fractured zone. The second series of six stimulations were performed in borehole intervals without natural fractures to initiate and propagate hydraulic fractures that connect the wellbore to the existing fracture network. The same injection protocol was used for all experiments within each stimulation series so that the differences observed will give insights into the effect of geology on the seismo-hydromechanical response rather than differences due to the injection protocols. Deformations and fluid pressure were monitored using a dense sensor network in boreholes surrounding the injection locations. Seismicity was recorded with sensitive in situ acoustic emission sensors both in boreholes and at the tunnel walls. We observed high variability in the seismic response in terms of seismogenic indices, b values, and spatial and temporal evolution during both hydroshearing and hydrofracturing experiments, which we attribute to local geological heterogeneities. Seismicity was most pronounced for injections into the highly conductive brittle-ductile shear zones, while the injectivity increase on these structures was only marginal. No significant differences between the seismic response of hydroshearing and hydrofracturing was identified, possibly because the hydrofractures interact with the same pre-existing fracture network that is reactivated during the hydroshearing experiments. Fault slip during the hydroshearing experiments was predominantly aseismic. The results of our hydraulic stimulations indicate that stimulation of short borehole intervals with limited fluid volumes (i.e., the concept of zonal insulation) may be an effective approach to limit induced seismic hazard if highly seismogenic structures can be avoided.

SCI ; EI

英语

其他

Swiss Federal Institute of Technology Zurich[ETH-35 16-1] ; Swiss National Foundation[200021_165677][200021_169178]

Geochemistry & Geophysics

Geochemistry & Geophysics

WOS:000529403800001

COPERNICUS GESELLSCHAFT MBH

20201908635752

Acoustic emission testing ; Crystalline rocks ; Geothermal fields ; Seismic response ; Fault slips ; Fracture ; Hydraulic fracturing ; Sensor networks

Geothermal Phenomena:481.3.1 ; Earthquake Measurements and Analysis:484.1 ; Secondary Earthquake Effects:484.2 ; Petroleum Deposits : Development Operations:512.1.2 ; Geothermal Energy:615.1 ; Acoustic Properties of Materials:751.2 ; Materials Science:951

Web of Science

1.Swiss Fed Inst Technol, Swiss Seismol Serv, Zurich, Switzerland
2.CSD Ingenieure, CH-3097 Bern, Switzerland
3.Swiss Fed Inst Technol, Dept Earth Sci, Zurich, Switzerland
4.Univ Neuchatel, CHYN, Neuchatel, Switzerland
5.Rhein Westfal TH Aachen, Dept Engn Geol & Hydrogeol, Aachen, Germany
6.Southern Univ Sci & Technol, Acad Adv Interdisciplinary Studies, Inst Risk Anal Predict & Management, Shenzhen, Peoples R China

Villiger, Linus,Gischig, Valentin,Doetsch, Joseph,et al. Influence of reservoir geology on seismic response during decameter-scale hydraulic stimulations in crystalline rock[J]. Solid Earth,2020,11(2):627-655.

Villiger, Linus.,Gischig, Valentin.,Doetsch, Joseph.,Krietsch, Hannes.,Dutler, Nathan.,...&Wiemer, Stefan.(2020).Influence of reservoir geology on seismic response during decameter-scale hydraulic stimulations in crystalline rock.Solid Earth,11(2),627-655.

Villiger, Linus,et al."Influence of reservoir geology on seismic response during decameter-scale hydraulic stimulations in crystalline rock".Solid Earth 11.2(2020):627-655.