Time-lapse crosswell seismic tomography for monitoring the CO2injected into an onshore aquifer, Nagaoka, Japan

Abstract. The ice content of the subsurface is a major factor controlling the natural hazard potential of permafrost degradation in alpine terrain. Monitoring of changes in ground ice content is therefore similarly important as temperature monitoring in mountain permafrost. Although electrical resistivity tomography monitoring (ERTM) has proved to be a valuable tool for the observation of ground ice degradation, results are often ambiguous or contaminated by inversion artefacts. In theory, the P-wave velocity of seismic waves is similarly sensitive to phase changes between unfrozen water and ice. Provided that the general conditions (lithology, stratigraphy, state of weathering, pore space) remain unchanged over the observation period, temporal changes in the observed travel times of repeated seismic measurements should indicate changes in the ice and water content within the pores and fractures of the subsurface material. In this paper, the applicability of refraction seismic tomography monitoring (RSTM) as an independent and complementary method to ERTM is analysed for two test sites in the Swiss Alps. The development and validation of an appropriate RSTM approach involves a) the comparison of time-lapse seismograms and analysis of reproducibility of the seismic signal, b) the analysis of time-lapse travel time curves with respect to shifts in travel times and changes in P-wave velocities, and c) the comparison of inverted tomograms including the quantification of velocity changes. Results show a high potential of the RSTM approach concerning the detection of altered subsurface conditions caused by freezing and thawing processes. For velocity changes on the order of 3000 m/s even an unambiguous identification of significant ground ice loss is possible.

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2D time-lapse seismic tomography using an active time-constraint (ATC) approach

The Leading Edge ◽

10.1190/tle34020206.1 ◽

2015 ◽

Vol 34 (2) ◽

pp. 206-212 ◽

Cited By ~ 3

Author(s):

M. Karaoulis ◽

D. D. Werkema ◽

A. Revil

Keyword(s):

Seismic Tomography ◽

Time Lapse ◽

Time Constraint ◽

Active Time

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Characterizing CO2 plumes in deep saline formations: Comparison and joint evaluation of time-lapse pressure and seismic tomography

Geophysics ◽

10.1190/geo2016-0365.1 ◽

2017 ◽

Vol 82 (4) ◽

pp. ID1-ID18 ◽

Cited By ~ 2

Author(s):

Linwei Hu ◽

Joseph Doetsch ◽

Ralf Brauchler ◽

Peter Bayer

Keyword(s):

Seismic Tomography ◽

Structural Information ◽

Geophysical Methods ◽

Time Lapse ◽

P Wave ◽

Shape Identification ◽

Heterogeneous Reservoirs ◽

P Wave Velocity ◽

Direct Linkage ◽

Joint Evaluation

Monitoring the migration of sequestered [Formula: see text] in deep heterogeneous reservoirs is inherently difficult. Geophysical methods have been successfully used, but flow conditions are only indirectly linked to the measured properties. Besides geophysical methods, pressure tomography (PT) is proposed as an alternative method to depict the structure of deep saline formations for [Formula: see text] sequestration and to continuously delineate [Formula: see text] plumes. In contrast to more established geophysical measurements, pressure transients are directly related to flow properties, which allows for the estimation of permeability. We investigate the influence of aquifer heterogeneity on PT performance, and we compare the PT results to crosshole seismic tomography (ST). Multilevel fluid injections and high-frequency P-wave pulses are induced in a simulated deep borehole, and the recorded signals at another well are processed by a traveltime inversion scheme. The reservoir structure is inferred by clustering the inverted hydraulic diffusivity prior to [Formula: see text] injection, and the plume distribution is determined by clustering the tomograms of the inverted mixed-phase diffusivity difference and P-wave velocity difference. The clustered structures are then used for zonal calibration to acquire the saturation within the plumes. Modeling results indicate that PT provides clearer structural information on the [Formula: see text]-free aquifer due to its direct linkage to permeability. However, the plume depicted by PT can be ambiguous, whereas ST is less sensitive to the prevailing heterogeneity of permeability at postinjection and can thus image the plume more clearly. PT and ST can be complementary to each other through the joint clustering to improve plume shape identification and estimation of spatial [Formula: see text] saturation.

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Time-lapse refraction seismic tomography for the detection of ground ice degradation

The Cryosphere ◽

10.5194/tc-4-243-2010 ◽

2010 ◽

Vol 4 (3) ◽

pp. 243-259 ◽

Cited By ~ 36

Author(s):

C. Hilbich

Keyword(s):

Seismic Tomography ◽

Time Lapse ◽

Phase Changes ◽

Swiss Alps ◽

P Wave ◽

Permafrost Degradation ◽

Travel Times ◽

Refraction Seismic ◽

Velocity Changes ◽

Ice Content

Abstract. The ice content of the subsurface is a major factor controlling the natural hazard potential of permafrost degradation in alpine terrain. Monitoring of changes in ice content is therefore similarly important as temperature monitoring in mountain permafrost. Although electrical resistivity tomography monitoring (ERTM) proved to be a valuable tool for the observation of ice degradation, results are often ambiguous or contaminated by inversion artefacts. In theory, the sensitivity of P-wave velocity of seismic waves to phase changes between unfrozen water and ice is similar to the sensitivity of electric resistivity. Provided that the general conditions (lithology, stratigraphy, state of weathering, pore space) remain unchanged over the observation period, temporal changes in the observed travel times of repeated seismic measurements should indicate changes in the ice and water content within the pores and fractures of the subsurface material. In this paper, a time-lapse refraction seismic tomography (TLST) approach is applied as an independent method to ERTM at two test sites in the Swiss Alps. The approach was tested and validated based on a) the comparison of time-lapse seismograms and analysis of reproducibility of the seismic signal, b) the analysis of time-lapse travel time curves with respect to shifts in travel times and changes in P-wave velocities, and c) the comparison of inverted tomograms including the quantification of velocity changes. Results show a high potential of the TLST approach concerning the detection of altered subsurface conditions caused by freezing and thawing processes. For velocity changes on the order of 3000 m/s even an unambiguous identification of significant ice loss is possible.

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Time‐lapse crosswell seismic tomography to characterize flow structure in the reservoir during the thermal stimulation

Geophysics ◽

10.1190/1.1443805 ◽

1995 ◽

Vol 60 (3) ◽

pp. 660-666 ◽

Cited By ~ 12

Author(s):

Doo Sung Lee ◽

Veronica M. Stevenson ◽

Phil F. Johnston ◽

C. E. Mullen

Keyword(s):

Fluid Flow ◽

Flow Structure ◽

Seismic Tomography ◽

Thermal Response ◽

Time Lapse ◽

Tracer Test ◽

Heat Propagation ◽

Oil Field ◽

Thermal Stimulation ◽

Fluid Temperature

Time‐lapse crosswell seismic tomography data, recorded with an interval of six months, indicate a strong directional thermal response in a fractured eolian sandstone reservoir at a five‐spot thermal stimulation site in the South Casper Creek oil field, Wyoming. The seismic thermal response depicted on the tomogram and in conjunction with the geological data from cores and a wireline log, reveals the multichannel flow mechanism in the reservoir formation. The three factors that control steam or heat propagation are the fractures, the directional permeability existing in the rock matrix, and the fault. Crosswell tomograms imply that the primary fluid flow is through fractures oriented north‐south, whereas the secondary fluid flow is through the matrix in the direction of maximum horizontal permeability. The thermal response expressed on the tomogram infers that a fault oriented N80°E offsets flow units and acts as a flow barrier or baffle. The flow structure implied by the crosswell seismic tomography is strikingly different from the initial conjecture, as deduced from engineering perception based on geological reasoning. However, the tomographic implications were supported by both a tracer test and fluid temperature measurements at the four producing wells around the injector.

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