ORCID Profile
0000-0002-3074-5535
Current Organisation
Delft University of Technology
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Publisher: Elsevier BV
Date: 03-2015
Publisher: Society of Exploration Geophysicists
Date: 2020
Abstract: Mudstones are often anisotropic, which complicates depth conversion in seismic exploration and monitoring subsurface reservoirs during injection or production. In addition, the physical and mechanical properties of mudstones are highly sensitive to their water content. The elastic anisotropy of mudstones is not well understood because of their complex nature and the lack of laboratory experiments performed on well-preserved s les. Triaxial deformation tests were performed on mudstone core plugs to investigate the impact of water saturation on the elastic anisotropy of the Whitby Mudstone (United Kingdom). The mechanical and physical properties of the Whitby Mudstone were estimated from stress-strain and ultrasonic wave velocity data obtained on core plugs with different water saturations under isotropic and anisotropic stress conditions. The Whitby Mudstone has extremely high intrinsic elastic anisotropy (0.3–0.4) due to its composition and lamination. This elastic anisotropy increases with decreasing water content. There are three competing mechanisms that play a key role in the anisotropy increase due to dehydration such as (1) density contrast in the pore space (i.e., the presence of purely brine or a mixture of brine and air in the pore space), (2) formation of dehydration fractures, and (3) frame stiffening. Increasing the mean effective stress leads to a decrease in Thomsen’s anisotropy parameters [Formula: see text] and [Formula: see text] because of the closure of defects, such as natural and dehydration fractures, and the formation of stress-induced fractures. The relationship between the wavefront anellipticity factor [Formula: see text] and the mean effective stress is nonmonotonic and can be related to the onset of inelastic deformation.
Publisher: Copernicus GmbH
Date: 18-02-2021
Abstract: Abstract. In experiments designed to understand deep shear zones, we show that periodic porous sheets emerge spontaneously during viscous creep and that they facilitate mass transfer. These findings challenge conventional expectations of how viscosity in solid rocks operates and provide quantitative data in favour of an alternative paradigm, that of the dynamic granular fluid pump model. On this basis, we argue that our results warrant a reappraisal of the community's perception of how viscous deformation in rocks proceeds with time and suggest that the general model for deep shear zones should be updated to include creep cavitation. Through our discussion we highlight how the integration of creep cavitation, and its Generalised Thermodynamic paradigm, would be consequential for a range of important solid Earth topics that involve viscosity in Earth materials like, for ex le, slow earthquakes.
Publisher: Elsevier BV
Date: 08-2011
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-7156
Abstract: & & Understanding rock failure is key for the safe and efficient development of the subsurface. Gas storage (CO& sub& & /sub& , H& sub& & /sub& or CH& sub& & /sub& ), production of geothermal energy and the traditional extraction of hydrocarbons means fluid injection or extraction. These processes change the local stress state, but also local temperature or chemistry. Such use of the subsurface is about either keeping fluid where it is (storage) or making sure fluids come out with a sufficient but still safe rate. Since fault rocks are in many cases important fluid transport pathways, this needs a careful and complete understanding of how rocks fail. Therefore, a thorough understanding of the stages of deformation leading to failure is key, as well as any potential differences for different rock types and failure modes. We performed uniaxial compressive and triaxial experiments on limestone and sandstone to investigate the hydro-mechano-chemical coupling in rock failure, using active and passive acoustics to monitor the failure behaviour. All experiments are done at room temperature.& & & & Using active acoustics for first arrival times is an established technique. We use here the more novel coda-wave interferometry technique to track deformation in triaxial tests at different confining pressures in sandstones and limestone, which deform respectively in a fully brittle or a semi-ductile manner. This shows that the first signs of failure can be picked up before the yield point, i.e. before the time it is picked up by any of the traditional bulk stress-strain signals used in experimental rock deformation. In uniaxial compressive experiments on the same brittle sandstone s les we show that the loading pattern can affect the final strength but also the maximum acoustic emission litude. Cyclic loading tends to systematically reduce the magnitude of the largest induced seismic event, whilst simultaneously also promoting more complex fracture patterns and disintegration. This implies that the risk of induced seismicity can be mitigated by changing the loading pattern in subsurface operations. Finally, we show that for reactive rocks under the right pressure and temperature conditions, changing the chemistry can have an effect on rock strength, where the effects depend on the internal rock structure. This research increases the understanding of rock failure and show the potential of monitoring for a safe and efficient development of the subsurface.& &
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-5890
Abstract: & & Active use of the subsurface alters the in-situ pore-fluid composition. For limestone, chemical interaction between the pore fluid and the rock has been shown to alter some of the mechanical parameters, though the exact nature of this mechano-chemical interaction is not yet fully understood. To address this, we performed tri-axial compressive experiments on two highly pure (& % CaCO& sub& & /sub& ) and well documented limestones: Indiana Limestone and Edwards White, which were saturated with different fluid compositions. We selected our s les to have a porosity within a narrow range: 23.2 & #177 0.3% for Edwards White and 12.9 & #177 0.5% for Indiana Limestone. Prior to testing, the rock s les were saturated under vacuum with a fluid solution, and left to equilibrate under vacuum at room temperature for 18 hours. The fluids used in our experiments are 1) CaCO& sub& & /sub& -saturated water, 2) a brine which has a composition representative for the Dutch subsurface, and 3) a solution of industrial corrosion inhibitor. S les were tested at room temperature and confining pressures of 2.5, 5 and 10 MPa. In addition to the stress and strain data observed from these experiments, thin sections were made from the deformed s les to perform micro-structural analysis on the damage zone.& & & & Our results show no mechano-chemical effects for Edwards White. However, the rock strength of the Indiana limestone s les changes due to the different pore fluids: At a confining pressure of 2.5 MPa the s le saturated with to CaCO& sub& & /sub& solution failed at 49 MPa, compared to 47 MPa and 54 MPa for the s les that were saturated with the brine and the inhibitor solution respectively. At a confining pressure of 5 MPa both the s le tested with the CaCO& sub& & /sub& solution and the brine solution failed at 57 MPa and the s le exposed to the inhibitor solution failed at 56 MPa. The s les tested at a confining pressure of 10 MPa respectively failed at: 76, 79 and 73 MPa. & These differences of 5 to 10% lead to a shift in the resulting failure envelopes depending on the pore fluid used in the experiments when describing the failure behaviour of these s les using the Mohr-Coulomb failure criterion: The group tested with CaCO& sub& & /sub& solution had a cohesion of 11 MPa and the coefficient of friction of 0.67. For the s les tested with brine solution these values are 10 MPa and 0.71 respectively. For the group tested with inhibitor solution these values equal 15 MPa and 0.47 respectively. The experiments presented here serve as a baseline from which we can further determine which ions or compounds interact with the rock, and the nature of this interaction. For our follow-up work, we will continue by performing a detailed microstructural analysis to better understand the overall controls on the mechano-chemical interactions or the lack thereof. In follow-up experiments, we will narrow down the complexity of the fluid solutions so we can identify the effect of specific ionic species.& &
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-13656
Abstract: & & Reactivation of pre-existing faults/fractures in the reservoir due to the deep injection is a key concern in designing and running geothermal and water/CO& sub& & /sub& injection projects. Therefore, we investigate potential methods to manage injection-induced seismicity. Recent laboratory and field studies recommend that changes in injection pattern (e.g., cyclic injection) might trigger less seismicity than monotonic injection. This study presents results from uniaxial compressive laboratory experiments performed on high porosity Red Felser sandstone that provide new information about the effect of loading pattern and rate on injection& #8208 driven seismicity. Red Felser sandstone s les with identical porosity and dimensions were subjected to three different loading patterns, including cyclic recursive (CR), cyclic progressive (CP), and monotonic loading. Besides, three different loading rates (displacement control) were applied for each loading pattern: low, medium, and high rates that are 10& sup& -4 & /sup& mm/s, 5& #215 & sup& -4& & /sup& mm/s, and 5& #215 & sup& -3 & /sup& mm/s, respectively. Microseismicity analysis shows that (i) the maximum magnitude of seismic events and seismic radiated energy at failure decrease for lower loading rates and during the cyclic loading scenario, (ii) the b-value (magnitude-frequency distribution of events) increases on average 40% for a low-rate cyclic recursive loading in comparison with high-rate cyclic recursive and monotonic loading at different rates. The largest b-value resulted from a low-rate cyclic recursive (LCR) loading pattern. The b-value was estimated and compared using different methods, including a least-square regression on either an incremental frequency distribution or a cumulative frequency distribution, and with the maximum likelihood method (MLM) to provide a reliable b-value estimation. The analyses indicate that by considering the accurate magnitude of completeness, MLM, and, with a least-square regression, the incremental frequency distribution, both result in a reliable b-value. From a mechanical perspective, a low loading rate reduces the s le's final strength by 19%. Moreover, s les subjected to cyclic loading display more complex fracture patterns and more disintegration. In our laboratory study, a combination of low-rate loading and a recursive cyclic loading pattern resulted in reduced seismicity through decreasing the maximum seismicity magnitude and increasing the b-value.& &
Publisher: Elsevier BV
Date: 04-2007
Publisher: Wiley
Date: 07-2000
DOI: 10.1002/GJ.858
Abstract: Non‐silicate solid inclusions in garnet from ultra‐deep garnet peridotites, Otrøy, Western Gneiss Region, Norway, have been studied using light‐optical, scanning and analytical electron microscopic techniques. Texturally, the investigated garnets reveal protogranular, porphyroclastic and equigranular microstructures. Protogranular and porphyroclastic garnets contain microstructural evidence of the former existence of ‘super‐titanic’ garnet. The microstructural evidence consists of exsolution textures involving rutile and ilmenite needles // Grt as well as interstitial rutile grains. This exsolution microstructure is similar to the relict majoritic garnet microstructures found in the same peridotite. Some garnets contain both pyroxene and rutile exsolution. Other non‐silicate mineral inclusions in protogranular and porphyroclastic garnet consist of nickel‐iron alloys (Ni 99 Fe 01 ) and Cr‐rich spinel. In addition, some protogranular, porphyroclastic and equigranular garnets contain composite Ni‐Fe‐Cu sulphide inclusions. The latter represent immiscible sulphide melt trapped within cracks that have healed. The original melting temperature of Ni‐Fe‐Cu sulphides was determined as being ≥ 1000°C and contrasts with temperatures derived from garnet–olivine–pyroxene mineral compositions using conventional geothermobarometry ( c . 800°C/3 GPa). This contradiction is explained by the decoupling of microstructures and mineral chemistry the microstructures were formed at higher temperatures than indicated by the current mineral chemistry. The decoupling of microstructures and current mineral chemistry has important applications for geodynamic models. Copyright © 2000 John Wiley & Sons, Ltd.
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-7596
Abstract: Rising demand for energy and green energy has led to increasing subsurface activities, such as geothermal energy sites. These increasing human activities in the subsurface have caused substantial induced earthquakes in more densely populated areas, increasing the risks of operating safely. Well-known ex les of induced seismicity, due to geothermal sites, are the M5.4 earthquake in Pohang (South Korea) or the M3.4 earthquake in Basel (Switzerland). & Monitoring and forecasting earthquakes have been a topic of interest for years. Predictions are often made by production scenarios, probabilistic models, or average earthquake size distribution (b-value). Only a few studies focus on predicting fluid-induced seismicity by using seismic monitoring methods. Pore fluid changes play an important role in the reactivation of the fault strength and stability. Variations in pore pressure can cause a drop in the stresses along the fault plane and cause fault instability and movement resulting in induced seismicity.& Monitoring and predicting the stress changes along the fault planes can therefore be essential in forecasting induced seismicity and mitigation, potentially reducing the risks of operating (in denser populated areas). However, monitoring the degree of these changes remains challenging. Most studies using seismic methods to monitor induced seismicity on a field scale or laboratory scale focus on either passive monitoring or active monitoring. This study combines the two methods and shows how they complement each other in monitoring and mitigation of fault reactivation in the laboratory. We have performed pore fluid injection experiments on faulted sandstones to reactivate the faults while monitoring both actively (active seismic) and passively (acoustic emission).These results show that both acoustic monitoring techniques can be used to detect the different fault reactivation stages: linear strain build-up, early creep (pre-slip), stress drop (main slip), and continuous sliding phase. However, using active monitoring the early creep phase is detected slightly earlier than using passive monitoring. Combining the methods shows that the stress changes along the fault can be detected with more detail in more accuracy. As a result, the combination of passive and active techniques may be useful for monitoring faulted or critically stressed reservoirs that experience pore pressure changes.
Publisher: Wiley
Date: 07-09-2021
Publisher: Springer Science and Business Media LLC
Date: 05-12-2010
Publisher: Elsevier BV
Date: 03-2012
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-18114
Abstract: & & Our understanding of the behavior of the geomagnetic field arises from magnetic signals stored in geological materials, e.g. lavas. Almost all experiments to determine the past state of the Earth& #8217 s magnetic field use bulk s les (typically 1 - 10 cc) and measure their magnetic moment after series of laboratory treatments. Lavas, however, consist of mixtures of different iron-oxide grains that vary in size, shape, and chemistry. Some of these grains are good recorders of the Earth& #8217 s magnetic field others are not. Only a small amount of adverse behaved magnetic grains in a s le already h ers all classical experiments to obtain paleointensities success rates as low as 10-20% are common, i.e. for 80-90% of all lavas vital information on paleointensities is lost before it can be uncovered.& & & & Recently, we showed that it is possible to determine the magnetization of in idual grains inside a synthetic s le using a new technique: Micromagnetic Tomography. The in idual magnetizations of grains are determined by inverting scanning magnetometry data from the surface on the s le onto the known locations, sizes and shapes of the magnetic grains that are obtained from a microCT scan of the s le. The synthetic s le used for our proof-of-concept, however, was optimized for success: the dispersion of magnetic markers was low, and the magnetite grains had a well-defined grain size range. Furthermore, the scanning SQUID microscope used requires the s le to be at 4 K, below the Verweij transition of the magnetite grains.& & & & Here we present the first Micromagnetic Tomography results from natural s les. We used two magnetic scanning techniques that operate at room temperature, a Magnetic Tunneling Junction set-up and a Quantum Diamond Magnetometer, to acquire the magnetic surface scans from a Hawaiian lava and calculated magnetic moments of in idual grains present. We show that it is possible to acquire rock magnetic information as function of grain size from these natural s les and reveal the first results of interpreting a paleomagnetic direction from selected subsets of grains in our s les. These are the first steps towards deriving rock magnetic and paleomagnetic information from subsets of known good recorders inside lava s les, a technique that will revolutionize our field of research.& &
Publisher: American Geophysical Union (AGU)
Date: 10-2021
DOI: 10.1029/2020JB021469
Abstract: The hydraulic performance and mechanical stability of open fractures are crucial for several subsurface applications including fractured geothermal reservoirs or nuclear waste repositories. Their hydraulic and mechanical properties (fluid flow and fracture stiffness) are both strongly dependent on the fracture geometry. Any change in effective stress impacts aperture and thus the ability of fractures to promote flow. Here, we carried out flow experiments with shear displaced tensile fractures in pre‐loaded, low‐permeability sandstones with two different cyclic loading scenarios with up to 60 MPa hydrostatic confining pressure. During “constant cyclic loading” (CCL) experiments, the fracture was repeatedly loaded to the same peak stress (up to 60 MPa). During “progressive cyclic loading” (PCL) experiments, the confining pressure was progressively increased in each cycle (up to 15, 30, 45, and 60 MPa). The matrix and fracture deformation was monitored using axial and circumferential LVDT extensometers to obtain the fracture stiffness. The fracture geometry before and after the experiment was compared by calculating the aperture distribution from 3D surface scans. Initial loading with confining pressure of the fracture leads to a linear fracture specific stiffness evolution. For any subsequent stress cycles fracture stiffness shifts to a nonlinear behavior. The transition is shown to be related to a stress memory effect, similar to the “Kaiser Effect” for acoustic emissions. Progressive loading of fractures possibly leads to less permeability reduction compared to continuous cyclic loading.
Publisher: Oxford University Press (OUP)
Date: 11-02-2202
Publisher: American Geophysical Union (AGU)
Date: 06-04-2020
DOI: 10.1029/2019GL086172
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-4177
Abstract: & & Over the last few decades, it has become apparent that different human activities in the subsurface, such as water waste injection, hydraulic fracturing, and geothermal energy production can lead to induced seismicity. Understanding the effects of fluid injection-related parameters on seismic response or evolution of it is essential for finding a method to manage and minimize the induced seismicity risk. Experimental and numerical studies indicate that varying injection patterns and rates can be used to effect and/or mitigate seismicity. However, most of the studies are for intact rock medium, and the mechanism of injection-induced seismicity of faulted rock medium is not clear yet. In this study, we performed fault reactivation experiments on faulted (saw-cut) Red Pfaelzer sandstones to provide new insight into the effect of stress ressure cycling and rate on fault slip behavior and seismicity evolution. The saw-cut s les were subjected to two different reactivation mechanisms: 1) stress-driven and 2) injection-driven fault reactivation. Three different reactivation scenarios were performed during the stress-driven fault reactivation experiments: continuous sliding, cyclic sliding, and under-threshold cycling sliding. Ten AE transducers were used to detect microseismicity during the fault reactivation experiments, and consequently, different microseismic parameters, such as frequency-magnitude distribution (b-value), AE energy, and AE rate were estimated. Stress-driven fault reactivation experiments showed that (i) a below-threshold cycling scenario prevents seismicity and pure shear slip however if the shear stress exceeds the previous maximum shear stress, seismicity risk increases drastically in terms of b-value, maximum AE energy, and magnitude. (ii) Compared to continuous sliding, cyclic sliding triggers less seismicity in terms of total b-value and large AE events due to the uniform reduction in roughness and asperity on the fault plane. (iii) By increasing the number of cycles, in general, the number of generated events and AE energy per cycle is reduced. Nevertheless, there is a risk of generating large AE events during the first cycles. In addition, results from the injection-driven fault reactivation experiments demonstrated that high injection rate results in higher peak slip velocity. Compared to the stepwise injection pattern, the cyclic recursive injection scenario showed higher peak slip velocity, due to the high hydraulic energy budget and fault compaction. A proper injection strategy needs to consider various factors, such as fault drainage, critical shear stress, injection rate, and injection pattern (frequency and litude). Our results demonstrate that selecting proper stress ressure litude, and pressurization rate for the injection design strategy can help to reduce seismicity risk.& & & &
Publisher: American Geophysical Union (AGU)
Date: 05-2019
DOI: 10.1029/2018JB016617
Publisher: American Geophysical Union (AGU)
Date: 10-2021
DOI: 10.1029/2021JB022364
Abstract: Our understanding of the past behavior of the geomagnetic field arises from magnetic signals stored in geological materials, e.g., (volcanic) rocks. Bulk rock s les, however, often contain magnetic grains that differ in chemistry, size, and shape some of them record the Earth's magnetic field well, others are unreliable. The presence of a small amount of adverse behaved magnetic grains in a s le may already obscure important information on the past state of the geomagnetic field. Recently it was shown that it is possible to determine magnetizations of in idual grains in a s le by combining X‐ray computed tomography and magnetic surface scanning measurements. Here we establish this new Micromagnetic Tomography (MMT) technique and make it suitable for use with different magnetic scanning techniques, and for both synthetic and natural s les. We acquired reliable magnetic directions by selecting subsets of grains in a synthetic s le, and we obtained rock‐magnetic information of in idual grains in a volcanic s le. This illustrates that MMT opens up entirely new venues of paleomagnetic and rock‐magnetic research. MMT's unique ability to determine the magnetization of in idual grains in a nondestructive way allows for a systematic analysis of how geological materials record and retain information on the past state of the Earth's magnetic field. Moreover, by interpreting only the contributions of known magnetically well‐behaved grains in a s le, MMT has the potential to unlock paleomagnetic information from even the most complex, crucial, or valuable recorders that current methods are unable to recover.
Publisher: Elsevier BV
Date: 11-2010
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-1787
Abstract: & & The SHARP project was launched in late 2021 as a collaboration between 16 research institutions and commercial companies in Norway, UK, the Netherlands, Denmark, and India under the ACT3 Programme. The project is interdisciplinary with a strong focus on understanding and reducing the uncertainties related to subsurface CO& sub& & /sub& storage containment risk focusing on the geomechanical aspects of CO& sub& & /sub& storage.& & & & The geomechanical response to CO& sub& & /sub& injection is one of the key uncertainties in assessing proposed storage sites. The main aim of the SHARP project is to mature the technology for quantification of subsurface deformation by the development and integration of models for subsurface stress, rock mechanical failure and seismicity. Key activities for the project include: developing basin-scale geomechanical models that incorporate tectonic and deglaciation effects and use newly developed constitutive models of rock/sediment deformation (WP1) & improving knowledge of the present-day stress field in the North Sea from integrated earthquake catalogues and developing a database of earthquake focal mechanisms (WP2) quantifying rock strain and identifying failure attributes suitable for monitoring and risk assessment using experimental data (WP3) developing more intelligent methods for in situ monitoring of rock strain and failure as part of the overall monitoring programmes (WP4) quantifying containment risks using geomechanical models and observations from the field and laboratory (WP5) and communicating technology development on containment risk to industry and regulators (WP6).& & & & The SHARP project is expected to accelerate the maturation of six sites from the North Sea region and India. The case study sites range from very mature projects such as the Northern Lights CO& sub& & /sub& storage project in the Horda area (N) to emerging storage prospects such as the Endurance site (UK) and the Hanstholm structure (DK). Furthermore, application of the methods to well-characterised offshore depleted oil and gas fields as Nini (DK) and Aramis (NL) will accelerate their transformation into viable and safe CO& sub& & /sub& storage sites. India has high focus on emission reduction including development of CCUS and an onshore case study for CO& sub& & /sub& injection will be matured using lessons learned from the European projects in order to kick-start CO& sub& & /sub& injection and storage projects in India.& & & & Involvement of international CO& sub& & /sub& storage operators in the consortium ensures that the SHARP project has a high impact on CCS development in Europe and India, as well as globally. New technologies for quantification of subsurface deformation and strategies for monitoring deformation and fluid flow will provide cost-efficient tools for CO& sub& & /sub& subsurface risk management. The results of the project will be communicated to storage site operators and regulators to increase confidence in storage safety and seismicity risk assessment.& &
Publisher: American Geophysical Union (AGU)
Date: 2011
DOI: 10.1029/2010GC003290
Publisher: Oxford University Press (OUP)
Date: 12-04-2013
DOI: 10.1093/GJI/GGT099
Publisher: Springer Science and Business Media LLC
Date: 2001
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-14277
Abstract: A successful energy transition requires effective storage options. Using underground energy storage (UES), such as depleted porous reservoirs, can help balance the production and demand for renewable energy. Because of the production and injection operations sequence, all underground energy storage systems, including compressed air and hydrogen energy storage, are subject to cyclic loading. To design and operate underground storage facilities, it is essential to understand the geomechanical behavior of porous reservoir rock under cyclic loading. We present the results of the triaxial cyclic laboratory experiments conducted on Red Phaelzer sandstone at 10 MPa confining pressure. By considering three frequencies (F1=0.014 Hz, F2=0.0014 Hz, and F1=0.0002 Hz), two litudes (A1=20 MPa and A2=5.9 MPa) and two stress regimes (38 MPa and 85 MPa), 12 triaxial cyclic tests were performed. In total, eight triangular stress cycles were applied for each test, and at the same time, six piezoelectric sensors recorded the acoustic emission (AE) activities during these experiments. Results showed that the total axial inelastic deformation increases when the stress regime and litude of cycles are increased. However, this parameter reduces by increasing the frequency of cycles. In addition, Young& #8217 s modulus computed from the loading r s of the cycles increased significantly from the first cycle to the second cycle for all the tests. For tests in the brittle regime, the relation is that the larger the litude of cycles, the lower the increase in Young& #8217 s modulus. In addition, the AE analysis showed that major events were recorded in the first cycle. By increasing the number of cycles, the number of events, the maximum AE, and the average AE litude decreased. Our experimental results highlight that major mechanical changes and AE activities occur during the first cycle, and the stress regime influences the intensity of AE and mechanical changes. These outcomes can benefit studies about subsidence, uplift, fault reactivation, and other physical phenomena impacting the reservoir& #8217 s storage capacity, which is affected by cyclic sandstone deformation.
Publisher: Elsevier BV
Date: 02-2023
Publisher: American Geophysical Union (AGU)
Date: 06-04-2018
DOI: 10.1002/2017GL076634
Publisher: Wiley
Date: 13-07-2021
Publisher: Copernicus GmbH
Date: 19-08-2020
DOI: 10.5194/SE-2020-137
Abstract: Abstract. In experiments designed to understand deep shear zones, we show that periodic porous sheets emerge spontaneously during viscous creep, forming a hydro-mechanical anisotropy that influences mass transfer. These findings challenge the current paradigm of viscosity in solid rocks. In particular, they showcase how shear zones may actively focus mass transport and highlight the possibility that viscous rocks could locally transition from flow to fracture. Our work demonstrates that viscosity in solids is not directly comparable to viscosity in fluids and this is consequential for a range of important solid Earth topics, like slow earthquakes, the flow of glacial ice and the tectonics of exoplanets.
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-2670
Abstract: & & In response to the growing geo-societal challenges of our densely populated planet, current research frequently requires convergence of multiple research disciplines, and optimized use of openly available data, research facilities and funds. Such optimization is the main aim of many research infrastructures developing both at the national and international level. In the Netherlands, the European Plate Observing System & #8211 Netherlands (EPOS-NL) was formed, as the Dutch research infrastructure for solid Earth sciences. EPOS-NL aims to further develop world-class facilities for research into georesources and hazards, and to provide international access to these facilities and derived data. It is a partnership between Utrecht University, Delft University of Technology and the Royal Netherlands Meteorological Institute (KNMI) and is funded by the Dutch Research Council. EPOS-NL facilities include: 1) The Earth Simulation Lab at Utrecht University, 2) The Groningen gas field seismological network and the ORFEUS Data Center at KNMI, 3) The deep geothermal doublet (DAPwell), to be installed on the Delft university c us, and 4) A distributed facility for multi-scale imaging and tomography (MINT), shared between the Utrecht and Delft universities. EPOS-NL provides financial, technical and scientific support for access to these facilities. To get facility access, researchers can apply to a bi-annual call, with 2021 calls planned in Q1 and Q3. EPOS-NL further works with researchers, data centers and industry to provide access to essential data and models (e.g. pertaining to the seismogenic Groningen gas field) within the framework of the European infrastructure EPOS, conforming to FAIR (Findable, Accessible, Interoperable and Reusable) data principles. In that way, EPOS-NL contributes directly to a globally developing trend to make research facilities and data openly accessible to the international community. This supports cost-effective and multi-disciplinary research into the geo-societal challenges faced by our densely populated planet. See www.EPOS-NL.nl for more information.& &
Publisher: Elsevier BV
Date: 2007
Publisher: Elsevier BV
Date: 10-2011
Publisher: Wiley
Date: 02-02-2022
Publisher: Mineralogical Society of America
Date: 10-2008
DOI: 10.2138/AM.2008.2874
Publisher: Wiley
Date: 02-02-2022
Publisher: American Geophysical Union (AGU)
Date: 07-2020
DOI: 10.1029/2020JB020042
Abstract: Using active ultrasonic source survey data, coda wave decorrelation (CWD) time‐lapse imaging during the triaxial compression of Whitby Mudstone cores provides a 3‐D description of the evolution and redistribution of inelastic strain concentrations. Acoustic emissions (AEs) monitoring is also performed between any two consecutive surveys. From these data, we investigate the impact of initial water saturation S w on the onset, growth, and reactivation of inelastic deformation, compared to the postdeformation fracture network extracted from X‐ray tomography scans. Our results indicate for the applied strain rate and degree of initial water saturation, and within the frequency range of our ultrasonic transducers (0.1 to 1 MHz), that inelastic strain localization and propagation in the Whitby Mudstone does not radiate AEs of sufficient magnitude to be detected above the average noise level. This is true for both the initial onset of inelasticity (strain localization) and during macroscopic failure. In contrast, the CWD results indicate the onset of what is interpreted as localized regions of inelastic strain at less than 50% of the peak differential stress the Whitby Mudstone can sustain. The seemingly aseismic nature of these clay‐rich rocks suggests the gradual development of inelastic strain, from the microscopic diffuse damage, up until the macroscopic shear failure.
Publisher: Elsevier BV
Date: 07-2005
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-10115
Abstract: & & Not all rocks are perfect. Frequently heterogeneities will be present, either in the form of pre-existing fractures, or in the form of sealed fractures. Tensile strength and strength anisotropy of rocks has been investigated for strongly layered rocks, such as shales, sandstones and gneisses, but data is lacking on the effect of single planar heterogeneities, such as pre-existing fractures or stylolites. We have performed Brazilian Disc tests on limestone s les containing pre-existing fractures and stylolites, investigating Brazilian test Strength (BtS) and fracture orientation. We used Indiana limestone s les, pre-fractured with the Brazilian Disc method, and Treuchtlinger Marmor s les which contained central stylolites. All experiments were filmed. The planar discontinuity was set at different rotation angles of approximately 0& #8211 & #8211 & #8211 & #8211 & #8211 & #8304 , where 90& #8304 is parallel to the principal loading direction, and 0& #8304 to the horizontal axis of the s le. Pre-fracturing Indiana limestone s les results in a cohesion-less planar discontinuity, whereas the stylolites in the Treuchtlinger Marmor s les are discontinuities which have some strength.& & & & The results show that our imperfect s les with a planar discontinuity are always weaker than an intact s le. For the Indiana limestone, with a cohesion-less interface, there is 10 to 75% of weakening, which is angle-dependent. Once the angle is 30 or lower there is no influence from the initial fracture for the orientation of the new fracture. The stress-displacement pattern followed the expectation for Brazilian Disc testing. However, in the s les with a stylolite, strength is isotropic and between 25 and 65% of the strength of an intact s le. For all cases several new cracks appeared, of which the orientation is influenced by the orientation of the stylolite. The fracture pattern and associated stress drops are more complex for high angles. Interestingly, in the s les with stylolites, always more than one fracture was formed, whereas in the s les with a cohesionless interface usually only one new fracture formed, which for natural settings suggests a potential for higher fracture density when hydrofracturing a stylolite-rich interval.& & & & A second difference between these datasets is the litude of the pre-existing interface. The effect of litude will be qualitatively investigated with a 2D Comsol model, to investigate the location of the first fracture occurring, which can then be compared to the camera data of the experiments.& &
Publisher: Elsevier BV
Date: 05-2004
Publisher: Elsevier BV
Date: 2010
Publisher: Wiley
Date: 03-2000
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-5250
Abstract: & & We revisit large shear strain deformation experiments on Carrara marble and observe that anisotropic porous domains develop spontaneously during shearing. Specifically, as s les are deformed periodic porous sheets are documented to emerge and are found to transfer mass. These results imply that viscous shear zones may naturally partition fluids into highly anisotropic bands. As this hydro-mechanical anisotropy is produced by creep, each porous sheet is interpreted to represent a transient dynamic pathway for fluid transport. It is unclear how long each porous domain is uniquely sustained but it is clear that sheets are persistently present with increasing strain. Our results forward the idea that viscous shear zones have dynamic transport properties that are not related to fracturing or chemical reaction. We believe these new results provide experimental foundation for changing the paradigm of viscosity in rocks to include dynamic permeability. In our view making this change in perspective could alter many classical interpretations in natural banded mylonite zones, for ex le shear zone parallel syn-kinematic veining may be the result of& ore sheet instability and ductile fracturing.& &
Publisher: Society of Exploration Geophysicists
Date: 07-2018
Abstract: The transition from recoverable elastic to permanent inelastic deformation is marked by the onset of fracturing in the brittle field. Detection of this transition in materials is crucial to predict imminent failure/fracturing. We have used an ultrasonic pulse transmission method to record the change in waveform across this transition during fracturing experiments. The transition from elastic to inelastic deformation coincides with a minimum in ultrasonic attenuation (i.e., maximum wave litude). Prior to this attenuation minimum, the existing microfractures close. After this minimum, new microfractures form and attenuation increases until peak stress conditions, at which point, larger fractures form leading to complete s le failure. In our experiments, velocity changes are not sensitive enough to be indicative for the transition from elastic to inelastic deformation. Analysis of attenuation, not velocity, may thus detect imminent failure in materials. Our results may help detect fracturing in borehole casings or the near-wellbore area, or they may help predict imminent release of energy by seismic rupture.
Publisher: Elsevier BV
Date: 2009
Publisher: Wiley
Date: 06-2020
Publisher: Elsevier BV
Date: 15-12-2005
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-4396
Abstract: & & This work is conducted within the framework of SUCCEED, a research consortium with the aim to validate the utilization of produced CO& sub& & /sub& , from the Hellishei& #240 i geothermal plant in Iceland, for re-injection into the field for: i) pressure maintenance, and thus promoting geothermal production, and ii) permanent storage in basaltic formations through CO& sub& & /sub& mineralisation.& The objective of work carried out at Hellishei& #240 i in SUCCEED is to provide a state-of-the-art, cost-effective, and low-environmental impact coupled geothermal-CO& sub& & /sub& storage monitoring technique.& In this work, a detailed seismic-velocity and mechanical behaviour-characterisation study was carried out on various rock formations present at the outcrops near the Hellishei& #240 i geothermal site.& & & & Laboratory experiments include well-controlled active-source acoustic-assisted unconfined (UCS) and confined (CCS) compressive strength tests. Where the former, i.e., UCS, allow for investigating the mechanical behaviour, or static elastic properties, of the assessed rock formations, the latter, i.e., CCS, shed light on the seismic velocities at field-representative stress conditions (up to 70 MPa). The abovementioned experiments were conducted at ambient temperature and at dry pore-space conditions. For studying pore-scale phenomena (e.g., number of connected pores, mineralogy, etc.), several thin sections were prepared and micro computed tomography (micro-CT) scans were taken.& & & & The studied rock formations included basalts with varying porosities (ranging from 22 to 51 %), i.e., the main reservoir formation, hyaloclastites, and dykes. Micro-CT scan analyses, conducted on the basaltic reservoir formation in Hellishei& #240 i, revealed that its pore structure is highly heterogeneous. Active-source acoustic-assisted UCS tests showed similar velocity & #8211 stress trends: a rapid increase in velocity at low stress levels, related to closure of potential microcracks (and thus compaction), followed by a more modest increase at higher levels of axial stress. The pyroclastic hyaloclastite appeared to be the weakest material assessed, revealing relatively low seismic velocities, a static Young modulus of 2.54& #177 .09 GPa, and an ultimate strength of around 4.3 MPa. On the contrary, the igneous intrusion, i.e., dyke, is by far the stiffest material studied, yielding a Young modulus of 34.85& #177 .39 GPa and an ultimate strength of more than 200 MPa. The investigated basalt s les indicated a porosity-dependent Young modulus and compressional-wave velocity, where both the modulus and velocity decrease significantly with increasing (connected) porosity following a power-law function. & & & &
Publisher: Wiley
Date: 2020
Publisher: Wiley
Date: 15-01-2020
Publisher: Wiley
Date: 06-2020
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-5959
Abstract: & & Not all rocks are perfect. Frequently heterogeneities will be present, either in the form of pre-existing fractures, or in the form of sealed fractures. To date, investigation of s le heterogeneity, specifically tensile strength and strength anisotropy has focused on layered rocks, such as shales, sandstones and gneisses. Data is lacking on the effect of single planar heterogeneities, such as pre-existing fractures or stylolites, even though these frequently occur in geo-energy settings.& & & & We have performed Brazilian Disc tests on limestone s les containing planar heterogeneities, investigating Brazilian test Strength (BtS) and the effects of orientation on strength. We used prefractured Indiana limestone to represent a planar heterogeneity without cohesion and Treuchtlinger Marmor s les with central stylolites to represent a planar heterogeneity of unknown strength (as an ex le of a sealed fracture). The planar discontinuity was set at different rotation angles of approximately 0& #8211 & #8211 & #8211 & #8211 & #8211 & #8304 , where 90& #8304 (steep angle) is parallel to the principal loading direction, and 0& #8304 (low angle) to the horizontal axis of the s le. All experiments were filmed, and where possible Particle Image Velocimetry was used to determine internal particle motion. Moreover, we used a 2D Comsol model in which we simplified the stylolite surface as a sinusoid. The model was used to qualitatively determine how i) a different period of the sinusoid and ii) relative strength of sinusoid/matrix affect the results.& & & & Our results show that all imperfect s les are weaker than intact s les. The 2D Comsol model indicates that the qualitative results remain unaffected by changing the period (assumed to be representative of roughness) of the cohesive heterogeneity, nor by the relative strength contrast: the location of the first fracture remains unaffected. For both heterogeneity types, the fracture patterns can be ided into four categories, with two clear endmembers, and a more diffusive sub ision in between.& & & & For a cohesion-less heterogeneity:& & & ul& & li& steep angles lead to frictional sliding along the interface, and only a small hypothesized permeability increase.& /li& & li& Intermediate angles lead to a combination of tensile failure of the matrix and sliding along the interface, where for steeper angles more new fractures form which follow the path of the existing fracture.& /li& & li& Low angles lead to closure of the old fracture and new tensile failure.& /li& & /ul& & & For a cohesive heterogeneity of unknown cohesion:& & & ul& & li& Steep angles lead to intensive failure of the heterogeneous zone, attributed to the presence of a stress concentrator.& /li& & li& Intermediate angles lead to partial failure along the heterogeneous zone, and the formation of new fractures in the matrix, potentially instigated by mode II failure to accommodate motion.& /li& & li& Low angles lead to the formation of a new fracture plus opening within the heterogeneous zone.& /li& & /ul& & & These results imply that hydrofracture (i.e. creating tensile stresses) of a stylolite-rich zone will lead to more fractures than fractures in a homogeneous zone, where the orientation of the stylolites and bedding will control the orientation of the permeable pathways.& &
Publisher: American Geophysical Union (AGU)
Date: 27-04-2022
DOI: 10.1029/2021WR030743
Abstract: Fracture networks are abundant in subsurface applications (e.g., geothermal energy production, CO 2 sequestration). Fractured reservoirs often have a very complex structure, making modeling flow and transport in such networks slow and unstable. Consequently, this limits our ability to perform uncertainty quantification and increases development costs and environmental risks. This study provides an advanced methodology for simulation based on Discrete Fracture Model approach. The preprocessing framework results in a fully conformal, uniformly distributed grid for realistic 2D fracture networks at a required level of precision. The simplified geometry and topology of the resulting network are compared with input (i.e., unchanged) data to evaluate the preprocessing influence. The resulting mesh‐related parameters, such as volume distributions and orthogonality of control volume connections, are analyzed. Furthermore, changes in fluid‐flow response related to preprocessing are evaluated using a high‐enthalpy two‐phase flow geothermal simulator. The simplified topology directly improves meshing results and, consequently, the accuracy and efficiency of numerical simulation. The main novelty of this work is the introduction of an automatic preprocessing framework allowing us to simplify the fracture network down to required level of complexity and addition of a fracture aperture correction capable of handling heterogeneous aperture distributions, low connectivity fracture networks, and sealing fractures. The graph‐based framework is fully open‐source and explicitly resolves small‐angle intersections within the fracture network. A rigorous analysis of changes in the static and dynamic impact of the preprocessing algorithm demonstrates that explicit fracture representation can be computationally efficient, enabling their use in large‐scale uncertainty quantification studies.
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-12929
Abstract: & & In conjunction with a deep geothermal project which is being implemented on the TU Delft c us in the Netherlands, a high temperature aquifer thermal energy storage (HT-ATES) is being considered. An initial feasibility study suggests that this could significantly reduce CO& sub& & /sub& emissions from heating and be financially beneficial. As part of the research associated with the implementation of the geothermal well, a 500 m deep monitoring and exploration well has been drilled to further investigate two target layers for HT-ATES and to allow for scientific records before, during and after the production phase of the geothermal project. With this drilling, the potential for HT-ATES of multiple layers is investigated by means of innovative exploration methods. An extensive set of downhole geophysical logging tools was used, many cores from both consolidated and unconsolidated layers were taken and a pumping test was carried out in the deepest layer. This work presents an initial overview of the work carried out and provides insights into the initial results of this innovative exploration drilling. The Delft geothermal project is therefore a great ex le of a beneficial interplay of economic and societal interest (i.e. city heating, CO& sub& & /sub& -neutral c us) and scientific innovation.& &
Publisher: Wiley
Date: 18-04-2022
No related grants have been discovered for Auke Barnhoorn.