Acoustic waves in finely layered media

Hovem, Jens M.

doi:10.1190/1.1443850

Cited by 41 publications

(44 citation statements)

References 4 publications

(7 reference statements)

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“…Stovas and Ursin, 2007). According to Hovem (1995), for a large ratio between wavelength (λ) and thickness (d) of one cycle in the layering, the layered sector behaves as a homogeneous, effective medium (Backus, 1962). For low ratio, the alternate layers may be replaced by a thicker single layer using a time-average or ray velocity for the total depth range.…”

Section: Discussionmentioning

confidence: 99%

Characterization of a complex near-surface structure using well logging and passive seismic measurements

Benjumea¹,

Macau²,

Gabàs³

et al. 2016

Solid Earth

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Abstract. We combine geophysical well logging and passive seismic measurements to characterize the near-surface geology of an area located in Hontomin, Burgos (Spain). This area has some near-surface challenges for a geophysical study. The irregular topography is characterized by limestone outcrops and unconsolidated sediments areas. Additionally, the near-surface geology includes an upper layer of pure limestones overlying marly limestones and marls (Upper Cretaceous). These materials lie on top of Low Cretaceous siliciclastic sediments (sandstones, clays, gravels). In any case, a layer with reduced velocity is expected. The geophysical data sets used in this study include sonic and gamma-ray logs at two boreholes and passive seismic measurements: three arrays and 224 seismic stations for applying the horizontal-to-vertical amplitude spectra ratio method (H/V). Well-logging data define two significant changes in the P -wave-velocity log within the Upper Cretaceous layer and one more at the Upper to Lower Cretaceous contact. This technique has also been used for refining the geological interpretation. The passive seismic measurements provide a map of sediment thickness with a maximum of around 40 m and shear-wave velocity profiles from the array technique. A comparison between seismic velocity coming from well logging and array measurements defines the resolution limits of the passive seismic techniques and helps it to be interpreted. This study shows how these low-cost techniques can provide useful information about near-surface complexity that could be used for designing a geophysical field survey or for seismic processing steps such as statics or imaging.

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Section: Discussionmentioning

confidence: 99%

Characterization of a complex near-surface structure using well logging and passive seismic measurements

Benjumea¹,

Macau²,

Gabàs³

et al. 2016

Solid Earth

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“…If the wavelength is less then 10 times of the layer thickness then ray theory should be used. Other investigators have found slightly different relationships but all IRXQG D WUDQVLWLRQ DW d ≅ 5-20 (Hovem, 1995).…”

Section: Short Summary Of Ray Theory and Effective Medium Theorymentioning

confidence: 96%

Calibration of Seismic Attributes for Reservoir Characterization

Pennington¹

2002

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The project, "Calibration of Seismic Attributes for Reservoir Calibration," is now complete. Our original proposed scope of work included detailed analysis of seismic and other data from two to three hydrocarbon fields; we have analyzed data from four fields at this level of detail, two additional fields with less detail, and one other 2D seismic line used for experimentation. We also included time-lapse seismic data with ocean-bottom cable recordings in addition to the originally proposed static field data. A large number of publications and presentations have resulted from this work, inlcuding several that are in final stages of preparation or printing; one of these is a chapter on "Reservoir Geophysics" for the new Petroleum Engineering Handbook from the Society of Petroleum Engineers.Major results from this project include a new approach to evaluating seismic attributes in timelapse monitoring studies, evaluation of pitfalls in the use of point-based measurements and facies classifications, novel applications of inversion results, improved methods of tying seismic data to the wellbore, and a comparison of methods used to detect pressure compartments. Some of the data sets used are in the public domain, allowing other investigators to test our techniques or to improve upon them using the same data.From the public-domain Stratton data set we have demonstrated that an apparent correlation between attributes derived along 'phantom' horizons are artifacts of isopach changes; only if the interpreter understands that the interpretation is based on this correlation with bed thickening or thinning, can reliable interpretations of channel horizons and facies be made. From the publicdomain Boonsville data set we developed techniques to use conventional seismic attributes, including seismic facies generated under various neural network procedures, to subdivide regional facies determined from logs into productive and non-productive subfacies, and we developed a method involving cross-correlation of seismic waveforms to provide a reliable map of the various facies present in the area. The Wamsutter data set led to the use of unconventional attributes including lateral incoherence and horizon-dependent impedance variations to indicate regions of former sand bars and current high pressure, respectively, and to evaluation of various upscaling routines. The Teal South data set has provided a surprising set of results, leading us to develop a pressure-dependent velocity relationship and to conclude that nearby reservoirs are undergoing a pressure drop in response to the production of the main reservoir, implying that oil is being lost through their spill points, never to be produced. Additional results were found using the public-domain Waha and Woresham-Bayer data set, and some tests of technologies were made using 2D seismic lines from Michigan and the western Pacific ocean.

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“…The first case is that the wavelength is smaller than, or close to, the spatial periodicity of heterogeneity. For this case the ray theory is a proper way to describe the propagation velocity (Hovem 1995). In contrast, for the second case where the wavelength is much longer than the scale of heterogeneity, the effective medium theory is the most appropriate way to characterize wave propagation (Hovem 1995).…”

Section: Calulations Of Em Wave Velocity and Dielectric Constantmentioning

confidence: 96%

<title>Dielectric property of asphalt pavement specimens in dry, water-saturated, and frozen conditions</title>

Liu¹,

Guo²

2002

SPIE Proceedings

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A series of experiments on asphalt pavement specimens with l-GHz GPR system was conducted in the Connecticut Advanced Pavement (CAP) Laboratory. The objectives of these experiments are as follows. (1) Determining the dielectric property of the asphalt specimens; and (2) Correlating electromagnetic (EM) properties with void ratio and asphalt binder content ratio of asphalt pavement specimens. Results of this study can be used as the baseline to calibrate GPR field surveys for pavement assessment, as well as an indirect means to monitor the compaction process.The travel time for direct and reflected phases are the fundamental information for computing EM wave velocity.Supplemented by pre-existing information on geometry, void ratio, composition measured by other means, we were able to compute the dielectric constant of 30 pavement specimens.The major conclusions from these experiments are as follows.(1) In general EM wave velocity is highest in dry conditions, intermediate in frozen, and lowest in watersaturated conditions; Correspondingly, the dielectric constant is smallest in dry conditions, intermediate in frozen, and highest in water-saturated conditions. (2) EM wave velocity increases slightly with the increase of void ratio for dry samples. In contrast, it decreases significantly with a void ratio increase in water-saturated conditions.Correspondingly, the dielectric constant decreases noticeably with an increasing void ratio in dry conditions, and increases appreciably in saturated conditions. (3) The changes of EM velocity and dielectric constant for dry and saturated conditions can be predicted by the effective medium theory for porous media. (4) When the dielectric constant of the pore material is taken as the value of fresh water ice, the change of EM velocity and dielectric constant for the asphalt pavement specimens in frozen conditions cannot be correctly predicted with the effective medium theory. This implies that the pore water was not completely frozen when GPR measurement was taken. There are no significant changes in dielectric constant for dry and frozen conditions. (5) Variations in EM velocity and dielectric constant with asphalt binder ratio imply that a low asphalt ratio corresponds to a high void ratio so that in the lower end of the asphalt ratio, EM velocity has maximum fluctuation among the different conditions.

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Acoustic waves in finely layered media

Cited by 41 publications

References 4 publications

Characterization of a complex near-surface structure using well logging and passive seismic measurements

Characterization of a complex near-surface structure using well logging and passive seismic measurements

Calibration of Seismic Attributes for Reservoir Characterization

<title>Dielectric property of asphalt pavement specimens in dry, water-saturated, and frozen conditions</title>

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