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Huang, F., Bergmann, P., Juhlin, C., Ivandic, M., Lüth, S., Ivanova, A., . . . Zhang, F. (2018). The first post-injection seismic monitor survey at the Ketzin pilot CO2 storage site: results from time-lapse analysis. Geophysical Prospecting, 66(1), 62-84.
Open this publication in new window or tab >>The first post-injection seismic monitor survey at the Ketzin pilot CO2 storage site: results from time-lapse analysis
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2018 (English)In: Geophysical Prospecting, ISSN 0016-8025, E-ISSN 1365-2478, Vol. 66, no 1, 62-84 p.Article in journal (Refereed) Published
Abstract [en]

The injection of CO2 at the Ketzin pilot CO2 storage site started in June 2008 and ended in August 2013. During the 62 months of injection, a total amount of about 67 kt of CO2 was injected into a saline aquifer. A third repeat 3D seismic survey, serving as the first post-injection survey was acquired in 2015, aiming to investigate the recent movement of the injected CO2. Consistent with the previous two time-lapse surveys, a predominantly WNW migration of the gaseous CO2 plume in the up-dip direction within the reservoir is inferred in this first post-injection survey. No systematic anomalies are detected through the reservoir overburden. The extent of the CO2 plume west of the injection site is almost identical to that found in the 2012 second repeat survey (after injection of 61 kt), however there is a significant decrease in its size east of the injection site. Assessment of the CO2 plume distribution suggests that the decrease in the size of the anomaly may be due to multiple factors, such as limited vertical resolution, CO2 dissolution and CO2 diffusion, in addition to the effects of ambient noise. 4D seismic modelling based on dynamic flow simulations indicates that a dynamic balance between the newly injected CO2 after the second repeat survey and the CO2 being dissolved and diffused was reached by the time of the first post-injection survey. Considering the considerable uncertainties in CO2 mass estimation, both patchy and non-patchy saturation models for the Ketzin site were taken into consideration.

Keyword
Seismic processing, Monitoring, 3D time-lapse (4D), CO2 sequestration
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-301005 (URN)10.1111/1365-2478.12497 (DOI)000418349700006 ()
Funder
Vattenfall ABSwedish Research Council, 2010-3657
Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2018-01-17Bibliographically approved
Yan, P., Garcı́a Juanatey, M. A., Kalscheuer, T., Juhlin, C., Hedin, P., Savvaidis, A., . . . Kück, J. (2017). A magnetotelluric investigation of the Scandinavian Caledonides in western Jämtland, Sweden, using the COSC borehole logs as prior information. Geophysical Journal International, 208(3), 1465-1489.
Open this publication in new window or tab >>A magnetotelluric investigation of the Scandinavian Caledonides in western Jämtland, Sweden, using the COSC borehole logs as prior information
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2017 (English)In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 208, no 3, 1465-1489 p.Article in journal (Refereed) Published
Abstract [en]

In connection with the Collisional Orogeny in the Scandinavian Caledonides (COSC) project, broad-band magnetotelluric (MT) data were acquired at 78 stations along a recent ca. 55km- long NW-SE directed reflection seismic profile (referred to as the COSC Seismic Profile; CSP), with the eastern end located similar to 30 km to the west of the orogenic Caledonian front. The MT component of the project aims at (i) delineating the highly conductive (similar to 0.1 Omega . m) alum shales that are associated with an underlying main decollement and (ii) calibrating the MT model to borehole logs. Strike and distortion analyses of the MT data show a 3-D structure in the western 10 km of the profile around the 2.5 km deep COSC-1 borehole (IGSN: ICDP5054EHW1001) and a preferred strike angle of N34 degrees E in the central and eastern parts of the profile. 2-D modelling of MT impedances was tested using different inversion schemes and parameters. To adjust the resistivity structure locally around the borehole, resistivity logging data from COSC-1 were successfully employed as prior constraints in the 2-D MT inversions. Compared with the CSP, the model inverted from the determinant impedances shows the highest level of structural similarity. A shallow resistor (> 1000 Omega . m) in the top 2-3 km depth underneath the western most 10 km of the profile around COSC-1 corresponds to a zone of high seismic reflectivity, and a boundary at less than 1 km depth where the resistivity decreases rapidly from > 100 to < 1 Omega . m in the central and eastern parts of the profile coincides with the first seismic reflections. The depth to this boundary is well constrained as shown by 1-D inversions of the MT data from five selected sites and it decreases towards the Caledonian front in the east. Underneath the easternmost part of the profile, the MT data show evidence of a second deeper conductor (resistivity < 1 Omega . m) at > 3 km depth. Based upon the COSC-1 borehole logs, the CSP reflection seismic image, and the surface geologic map, the MT resistivity models were interpreted geologically. In the vicinity of COSC-1, the resistor down to 2-3 km depth pertains to the metamorphic Middle Allochthon. The up to 1000-m-thick shallow resistor in the central and eastern parts of the profile is interpreted to overly an imbricated unit at the bottom of the Lower Allochthon that includes the alum shales. In the MT resistivity model, the 300-500 m thick imbricated unit masks the main Caledonian decollement at its bottom. A second possible interpretation, though not favoured here, is that the decollement occurs along a much deeper seismic reflection shallowing from 4.5 km depth in the west to similar to 600 m depth in the east. An additional borehole (COSC-2) is planned to penetrate the Lower Allochthon and the main decollement surface in the central part of the profile and can provide information to overcome this interpretational ambiguity. Using a synthetic study, we evaluate how resistivity logs from COSC-2 can improve the 2-D inversion model.

Keyword
Inverse theory, Downhole methods, Magnetotellurics, Continental tectonics: compressional, Europe
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-303495 (URN)10.1093/gji/ggw457 (DOI)000396818900016 ()
Funder
Swedish Research Council, 2013-5780The Geological Survey of Sweden (SGU)
Available from: 2016-09-20 Created: 2016-09-20 Last updated: 2017-04-27Bibliographically approved
Brodic, B., Malehmir, A. & Juhlin, C. (2017). Bedrock and Fracture Zone Delineation UsingDifferent Near-surface Seismic Sources. In: : . Paper presented at Near Surface Geoscience 3-7 September 2017, Malmö, Sweden. Amsterdam, Netherlands: European Association of Geoscientists and Engineers (EAGE).
Open this publication in new window or tab >>Bedrock and Fracture Zone Delineation UsingDifferent Near-surface Seismic Sources
2017 (English)Conference paper, Published paper (Other academic)
Abstract [en]

To delineate the bedrock surface and a fracture zone intersected by a well at c. 50 m depth, a seismic survey wasconducted using four different near-surface seismic sources. These were a 5-kg sledgehammer, a metal I-beamhit laterally, an accelerated weight drop and a prototype source tested for the first time called Udarnik. TheUdarnik source has two hammers whose impacts are initiated by an electromagnetic force of the stable coilexciting its inner moving part. Two hammers separated by a distance of approximately 50 cm successively hittwo contact plates mounted on the bottom of the source. The sweep length is adjustable and maximum 18 hitscan be made per second. In this study, we compare the performance of every source used and present reflectionseismic sections and tomography results from the high-fold (star-type acquisition was used) combinedlandstreamer and wireless recorder survey. Preliminary results indicate that bedrock was well delineated both ontomography results and stacked sections for all sources and some weak reflectivity is observed where thefracture zone is expected with most of the sources used showing the potential of the seismic methods forfracture zone imaging and near-surface characterization

Place, publisher, year, edition, pages
Amsterdam, Netherlands: European Association of Geoscientists and Engineers (EAGE), 2017
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-327950 (URN)10.3997/2214-4609.201702068 (DOI)
Conference
Near Surface Geoscience 3-7 September 2017, Malmö, Sweden
Projects
TRUST Geoinfra
Available from: 2017-08-14 Created: 2017-08-14 Last updated: 2017-08-22Bibliographically approved
Brodic, B., Malehmir, A. & Juhlin, C. (2017). Delineating fracture zones using surface-tunnel-surfaceseismic data, P-S, and S-P mode conversions. Journal of Geophysical Research - Solid Earth, 122(7), 5493-5516.
Open this publication in new window or tab >>Delineating fracture zones using surface-tunnel-surfaceseismic data, P-S, and S-P mode conversions
2017 (English)In: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 122, no 7, 5493-5516 p.Article in journal (Refereed) Published
Abstract [en]

A surface-tunnel-surface seismic experiment was conducted at the Äspö Hard Rock Laboratoryto study the seismic response of major fracture systems intersecting the tunnel. A newly developedthree-component microelectromechanical sensor-based seismic landstreamer was deployed inside the noisytunnel along with conventional seismic receivers. In addition to these, wireless recorders were placed on thesurface. This combination enabled simultaneous recording of the seismic wavefield both inside the tunneland on the surface. The landstreamer was positioned between two geophone-based line segments, alongthe interval where known fracture systems intersect the tunnel. First arrival tomography produced a velocitymodel of the rock mass between the tunnel and the surface with anomalous low-velocity zones correlatingwell with locations of known fracture systems. Prominent wave mode converted direct and reflected signals,P-S and S-P waves, were observed in numerous source gathers recorded inside the tunnel. Forward traveltime and 2-D finite difference elastic modeling, based on the known geometry of the fracture systems, showthat the converted waves are generated at these systems. Additionally, the landstreamer data were used toestimate Vp/Vs, Poisson’s ratio, and seismic attenuation factors (Qp and Qs) over fracture sets that havedifferent hydraulic conductivities. The low-conductivity fracture sets have greater reductions in P wavevelocities and Poisson’s ratio and are more attenuating than the highly hydraulically conductive fracture set.Our investigations contribute to fracture zone characterization on a scale corresponding to seismicexploration wavelengths.

National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-327949 (URN)10.1002/2017JB014304 (DOI)000409366700040 ()
Available from: 2017-08-14 Created: 2017-08-14 Last updated: 2017-12-20Bibliographically approved
Doughty, C., Tsang, C.-F., Rosberg, J.-E., Juhlin, C., Dobson, P. F. & Birkholzer, J. T. (2017). Flowing fluid electrical conductivity logging of a deep borehole during and following drilling: estimation of transmissivity, water salinity and hydraulic head of conductive zones. Hydrogeology Journal, 25(2), 501-517.
Open this publication in new window or tab >>Flowing fluid electrical conductivity logging of a deep borehole during and following drilling: estimation of transmissivity, water salinity and hydraulic head of conductive zones
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2017 (English)In: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 25, no 2, 501-517 p.Article in journal (Refereed) Published
Abstract [en]

Flowing fluid electrical conductivity (FFEC) logging is a hydrogeologic testing method that is usually conducted in an existing borehole. However, for the 2,500-m deep COSC-1 borehole, drilled at re, central Sweden, it was done within the drilling period during a scheduled 1-day break, thus having a negligible impact on the drilling schedule, yet providing important information on depths of hydraulically conductive zones and their transmissivities and salinities. This paper presents a reanalysis of this set of data together with a new FFEC logging data set obtained soon after drilling was completed, also over a period of 1 day, but with a different pumping rate and water-level drawdown. Their joint analysis not only results in better estimates of transmissivity and salinity in the conducting fractures intercepted by the borehole, but also yields the hydraulic head values of these fractures, an important piece of information for the understanding of hydraulic structure of the subsurface. Two additional FFEC logging tests were done about 1 year later, and are used to confirm and refine this analysis. Results show that from 250 to 2,000 m depths, there are seven distinct hydraulically conductive zones with different hydraulic heads and low transmissivity values. For the final test, conducted with a much smaller water-level drawdown, inflow ceased from some of the conductive zones, confirming that their hydraulic heads are below the hydraulic head measured in the wellbore under non-pumped conditions. The challenges accompanying 1-day FFEC logging are summarized, along with lessons learned in addressing them.

Place, publisher, year, edition, pages
SPRINGER, 2017
Keyword
Hydraulic testing, Fractured rock, Hydraulic head, Well logging, Drilling
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-320848 (URN)10.1007/s10040-016-1497-5 (DOI)000395001300015 ()
Funder
Swedish Research Council, 2013-94
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2018-01-13Bibliographically approved
Brodic, B., Malehmir, A., Bastani, M., Mehta, S., Juhlin, C., Lundberg, E. & Wang, S. (2017). Multi-component digital-based seismic landstreamer and boat-towed radio-magnetotelluric acquisition systems for improved subsurface characterization in the urban environment. First Break, 35(8), 41-47.
Open this publication in new window or tab >>Multi-component digital-based seismic landstreamer and boat-towed radio-magnetotelluric acquisition systems for improved subsurface characterization in the urban environment
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2017 (English)In: First Break, ISSN 0263-5046, E-ISSN 1365-2397, Vol. 35, no 8, 41-47 p.Article in journal (Other academic) Published
Abstract [en]

It is estimated that urban life will be the norm for around 60% of the world’s population by 2040, leading to a more centralized distribution of people and making the city as the main place of residence (Whiteley, 2009). This population centralization inherently implies rapidly expanding cities and imposes the need for more infrastructure within, around and between the present city boundaries. However, infrastructure projects nowadays have to follow strict civil engineering standards that require detailed knowledge of subsurface conditions during different stages of the construction processes. Since direct methods conventionally used for site characterization (e.g., drilling and/or core testing) are still relatively expensive the focus in the last two decades has been on non-invasive, geophysical methods. However, geophysical site characterization in urban areas is not an easy task owing to numerous challenges and various types of noise sources. Challenges such as electric/electromagnetic (EM) noise, pipelines and other subsurface objects (sometimes even unknown or undocumented), the inability to properly couple sensors because of pavement, traffic noises and limited space are common in urban environment. Since geophysical surveys need to be done with the least amount of disturbances to the environment, residents and traffic, new geophysical techniques for fast, non-invasive and high-resolution site characterization are needed. To overcome some of these challenges, a nationwide joint industry-academia project was launched in 2012 TUST GeoInfra, www.trust-geoinfra.se). As a component in the project, Uppsala University developed two new data acquisition systems. These are a fully digital MEMS-based (Micro-machined Electro-Mechanical Sensor) three component (3C) seismic landstreamer and a boat-towed radio-magnetotelluric (RMT) acquisition system. Both systems were specifically designed to address urban environments with the RMT system particularly aiming at efficient and cost-effective geophysical surveying on shallow-water bodies, which constitute 7% of Scandinavia. In this article, we will describe the two systems and present two case studies illustrating their potential. A number of published accounts are now available from the two systems showing what type of problems they can address (e.g., Bastani et al., 2015; Brodic et al., 2015; Malehmir et al., 2015a, 2015b, 2016a, 2016b, 2017; Dehghannejad et al., 2017; Maries et al., 2017; Mehta et al., 2017; Brodic et al., 2017).

Place, publisher, year, edition, pages
Amsterdam, Netherlands: , 2017
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-327951 (URN)
Projects
TRUST Geoinfra
Available from: 2017-08-14 Created: 2017-08-14 Last updated: 2017-12-10Bibliographically approved
Malehmir, A., Bellefleur, G., Koivista, E. & Juhlin, C. (2017). Pros and cons of 2D vs 3D seismic mineral exploration surveys. First Break, 35(8), 49-55.
Open this publication in new window or tab >>Pros and cons of 2D vs 3D seismic mineral exploration surveys
2017 (English)In: First Break, ISSN 0263-5046, E-ISSN 1365-2397, Vol. 35, no 8, 49-55 p.Article in journal (Refereed) Published
Abstract [en]

While the economic downturn in the mineral industry is improving, exploring for economically feasible deposits to sustain our economy and the global growth in the long term remains a great challenge. Exploring giant deposits (> 30-50 Mt) at depth is believed to be a solution. However, the answers are only likely to be found using a multi-disciplinary approach involving improved field geological mapping, improved conceptual models (e.g., mineral system approach) for deep targeting, and a combination of physical property measurements together with 2D and 3D geophysical surveys. Most metallic deposits have favourable physical properties to be targeted using various geophysical methods (Figure 1), but many of these methods do not have sufficient sensitivity and resolution at great depth (> 500 m). Encouraging examples of the use of surface seismic methods for deep mineral exploration and mine planning are available (e.g., Eaton et al., 2003 and references therein; Malehmir et al., 2012 and references therein; Buske et al., 2015 and references therein). 

National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-328039 (URN)
Projects
StartGeoDelineation, Vinnova
Funder
VINNOVA, 2014-06238
Available from: 2017-08-16 Created: 2017-08-16 Last updated: 2017-08-17Bibliographically approved
Sattar, N., Juhlin, C., Koyi, H. & Ahmad, N. (2017). Seismic stratigraphy and hydrocarbon prospectivity of the Lower, Cretaceous Knurr Sandstone lobes along the southern margin of Loppa High, Hammerfest Basin, Barents Sea. Marine and Petroleum Geology, 85, 54-69.
Open this publication in new window or tab >>Seismic stratigraphy and hydrocarbon prospectivity of the Lower, Cretaceous Knurr Sandstone lobes along the southern margin of Loppa High, Hammerfest Basin, Barents Sea
2017 (English)In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 85, 54-69 p.Article, review/survey (Refereed) Published
Abstract [en]

The Lower Cretaceous Knurr Sandstone deposited along the southern slope of Loppa High and overlain by the Kolje and Kolmule seals forms an attractive play in the Hammerfest Basin of the Barents Sea. Late Jurassic organic-rich Hekkingen shale directly underlies the Knurr Sandstone and acts as a source to provide effective charge. Three wells, 7120/2-2, 7122/2-1 and 7120/1-2, have proven the Knurr-Kolje play in structural traps, with an oil discovery in 7120/1-2. Prospectivity related to stratigraphic traps is, however, highly under-explored. In order to document and map the reservoir distribution and stratigraphic-trap fairway, the Lower Cretaceous sedimentary package containing the Knurr Sandstone is divided into a number of depositional sequences and systems tracts using key regional seismic profiles calibrated with logs. Mapping of the key surfaces bounding the Knurr sandstone has been carried out using all the seismic vintages available from Norwegian Petroleum Directorate (NPD).The thick massive nature of the sandstone (123 m in well 7122/2-1), sedimentary features characteristic of gravity flow deposits, high-resolution internal seismic reflections and stratal geometries (truncations and lapout patterns), and sequence stratigraphic position of the Knurr Sandstone on seismic profiles confirm that the lobes identified on the seismic section are gravity driven base of the slope lobes. These Knurr lobes and slope aprons were formed as a result of uplift of the Loppa paleo-high in the Late Jurassic to Early Cretaceous times which caused subaerial exposure and incision. The characteristic mounded, lobate geometry evident on the seismic can be mapped along the toe-of-slope and records multiple stacked lobes fed by multiple feeder canyons. Lateral partitioning and separation of the lobes along the toe-of-slope could potentially create strati graphic traps. The existing 2D seismic coverage is, however, not sufficient to capture lateral stratigraphic heterogeneity to identify stratigraphic traps. 3D seismic coverage with optimum acquisition parameters (high spatial and vertical resolution, appropriate seismic frequency and fold, long offsets and original amplitudes preserved) can allow for the reconstruction of 3D geomorphologic elements to de-risk potential stratigraphic traps prior to exploratory drilling.

Keyword
Barents sea, Knurr sandstone, Seismic stratigraphy, Turbidite lobes, Hammerfest basin
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-333820 (URN)10.1016/j.marpetgeo.2017.04.008 (DOI)000403983300004 ()
Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2017-11-29Bibliographically approved
Hedin, P., Almqvist, B., Berthet, T., Juhlin, C., Buske, S., Simon, H., . . . Alm, P.-G. (2016). 3D reflection seismic imaging at the 2.5 km deep COSC-1 scientific borehole, central Scandinavian Caledonides. Tectonophysics, 689, 40-55.
Open this publication in new window or tab >>3D reflection seismic imaging at the 2.5 km deep COSC-1 scientific borehole, central Scandinavian Caledonides
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2016 (English)In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 689, 40-55 p.Article in journal (Refereed) Published
Abstract [en]

The 2.5 km deep scientific COSC-1 borehole (ICDP 5054-1-A) was successfully drilled with nearly complete core recovery during spring and summer of 2014. Downhole and on-core measurements through the targeted Lower Seve Nappe provide a comprehensive data set. An observed gradual increase in strain below 1700 m, with mica schists and intermittent mylonites increasing in frequency and thickness, is here interpreted as the basal thrust zone of the Lower Seve Nappe. This high strain zone was not fully penetrated at the total drilled depth and is thus greater than 800 m in thickness.

To allow extrapolation of the results from downhole logging, core analysis and other experiments into the surrounding rock and to link these with the regional tectonic setting and evolution, three post-drilling high-resolution seismic experiments were conducted in and around the borehole. One of these, the first 3D seismic reflection land survey to target the nappe structures of the Scandinavian Caledonides, is presented here. It provides new information on the 3D geometry of structures both within the drilled Lower Seve Nappe and underlying rocks down to at least 9 km.

The observed reflectivity correlates well with results from the core analysis and downhole logging, despite challenges in processing. Reflections from the uppermost part of the Lower Seve Nappe have limited lateral extent and varying dips, possibly related to mafic lenses or boudins of variable character within felsic rock. Reflections occurring within the high strain zone, however, are laterally continuous over distances of a kilometer or more and dip 10–15° towards the southeast. Reflections from structures beneath the high strain unit and the COSC-1 borehole can be followed through most of the seismic volume down to at least 9 km and have dips of varying degree, mainly in the east–west thrust direction of the orogen.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
3D reflection seismic, continental scientific deep drilling, borehole geophysics, collisional orogeny in the Scandinavian Caledonides, Seve Nappe Complex, shear zones
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-261087 (URN)10.1016/j.tecto.2015.12.013 (DOI)000387522100005 ()
Projects
Collisional Orogeny in the Scandinavian Caledonides (COSC)
Funder
Swedish Research Council, 2013-5780Swedish Research Council, 2013-94German Research Foundation (DFG), BU1364/10-1German Research Foundation (DFG), GI982/2-1
Available from: 2015-08-29 Created: 2015-08-29 Last updated: 2017-12-04Bibliographically approved
Zhang, F., Juhlin, C., Niemi, A., Huang, F. & Bensabat, J. (2016). A feasibility and efficiency study of seismic waveform inversion for time-lapse monitoring of onshore CO2 geological storage sites using reflection seismic acquisition geometries. International Journal of Greenhouse Gas Control, 48, 134-141.
Open this publication in new window or tab >>A feasibility and efficiency study of seismic waveform inversion for time-lapse monitoring of onshore CO2 geological storage sites using reflection seismic acquisition geometries
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2016 (English)In: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 48, 134-141 p.Article in journal (Refereed) Published
Abstract [en]

Monitoring of the CO2 distribution at depth is imperative for onshore geological storage of CO2. Seismic methods are effective monitoring tools during and after the injection process, but are generally expensive and time consuming to perform. In this paper we perform a series of synthetic experiments in order to compare the seismic waveform inversion method with conventional seismic monitoring methods for time-lapse monitoring at CO2 geological storage sites. We mainly focus our study on seismic data sets with typical reflection acquisition geometries that is far offset limited. Two synthetic seismic data sets (consisting of one baseline and repeat) were generated by a third party 2D forward modeling code to compare the waveform inversion method with a conventional time-lapse procedure. The velocity models are based on a simplified structure of the Heletz site in Israel. The area into which CO2 is injected is on the order of a few hundred meters wide and a few 10 s of meters high. We compare the waveform inversion results and conventional time-lapse results to determine how sparse spatial sampling affects the results by increasing both the shot and receiver spacing. We test the waveform inversion method for a synthetic time-lapse data set with different inversion strategies. First, we invert each data set independently by using both phase and amplitude information. Then we invert them by using only phase information. We also test the influence of the starting model. Finally, we test the double difference inversion method which is equivalent to only inverting the difference between the baseline and repeat data sets. During the test a relative coarse starting model and higher starting frequency were used in order to better represent real seismic reflection data. Our results show that, under certain noise conditions, it may be possible to use a combination of sparse spatial sampling geometries and seismic waveform inversion to monitor the velocity changes caused by CO2 injection. We conclude that seismic waveform inversion may be a good complement to standard CDP processing when monitoring CO2 injection.

Keyword
CO2 monitoring, CO2 sequestration, Time-lapse seismic, Seismic waveform inversion
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-299609 (URN)10.1016/j.ijggc.2015.11.015 (DOI)000378004200011 ()
Funder
EU, FP7, Seventh Framework Programme, 227286EU, European Research Council
Note

Följande post har en snarlik titel, men syfter möjligtvis till en annan post: http://uu.diva-portal.org/smash/record.jsf?pid=diva2:573803

Available from: 2016-07-25 Created: 2016-07-25 Last updated: 2017-11-28Bibliographically approved
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