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  • Physics  (4)
  • UA 4068.4  (4)
  • 1
    Online Resource
    Online Resource
    An enhanced accuracy method to determine oil saturation by carbon/oxygen logging in tight reservoirs
    Society of Exploration Geophysicists ; 2022
    In:  GEOPHYSICS Vol. 87, No. 2 ( 2022-03-01), p. D21-D31
    Details
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 87, No. 2 ( 2022-03-01), p. D21-D31
    Abstract: The low porosity and permeability characteristics of tight oil reservoirs have brought challenges to monitoring oil saturation recently. Although carbon/oxygen logging is effective for oil saturation evaluation, the statistical fluctuations of the measured energy spectrum in tight reservoirs make it impossible to distinguish the different signals between oil and water. Thus, noise adjusted singular-value decomposition (NASVD) is applied to denoise the raw energy spectrum and evaluate the oil saturation quantitatively. The energy spectrum matrix, which is composed of the energy spectrum of the measurement point and its adjacent depth points, is decomposed and reconstructed to remove noninformative signals and improve the signal-to-noise ratio of the raw energy spectrum. The parameter K evaluates the smoothness of the logging curves, reflecting the influence of the number of energy spectra and singular values on NASVD. Meanwhile, the NASVD, Savitzky-Golay filtering, and depth averaging methods are compared for calculating the accuracy of C/O, Si/Ca, and oil saturation with the Monte Carlo method, indicating that the NASVD is better than the other two methods for eliminating the statistical fluctuations of the raw energy spectrum. A simulation example indicates that the NASVD can control the calculation errors of tight reservoir oil saturation to within 15%, which significantly improves the accuracy of the estimated oil saturation. An oil field example indicates that the oil saturation interpretation result for tight reservoirs is in good agreement with the oil saturation from open-hole log analysis, signifying that the NASVD energy spectrum denoising method can provide a quantitative estimate of oil saturation in tight oil reservoirs.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    URL: Article
    DOI: 10.1190/geo2021-0309.1
    RVK:
    UA 4068.4
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2022
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Building large-scale density model via a deep-learning-based data-driven method
    Society of Exploration Geophysicists ; 2021
    In:  GEOPHYSICS Vol. 86, No. 1 ( 2021-01-01), p. M1-M15
    Details
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 86, No. 1 ( 2021-01-01), p. M1-M15
    Abstract: As a rock-physics parameter, density plays a crucial role in lithology interpretation, reservoir evaluation, and description. However, density can hardly be directly inverted from seismic data, especially for large-scale structures; thus, additional information is needed to build such a large-scale model. Usually, well-log data can be used to build a large-scale density model through extrapolation; however, this approach can only work well for simple cases and it loses effectiveness when the medium is laterally heterogeneous. We have adopted a deep-learning-based method to build a large-scale density model based on seismic and well-log data. The long short-term memory network is used to learn the relation between seismic data and large-scale density. Except for the data pairs directly obtained from well logs, many velocity and density models randomly generated based on the statistical distributions of well logs are also used to generate several pairs of seismic data and the corresponding large-scale density. This can greatly enlarge the size and diversity of the training data set and consequently leads to a significant improvement of the proposed method in dealing with a heterogeneous medium even though only a few well logs are available. Our method is applied to synthetic and field data examples to verify its performance and compare it with the well extrapolation method, and the results clearly display that the proposed method can work well even though only a few well logs are available. Especially in the field data example, the built large-scale density model of the proposed method is improved by 11.9666 dB and 0.6740, respectively, in peak signal-to-noise ratio and structural similarity compared with that of the well extrapolation method.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    URL: Article
    DOI: 10.1190/geo2019-0332.1
    RVK:
    UA 4068.4
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2021
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Matrix-fluid decoupling-based joint PP-PS-wave seismic inversion for fluid identification
    Society of Exploration Geophysicists ; 2019
    In:  GEOPHYSICS Vol. 84, No. 3 ( 2019-05-01), p. R477-R487
    Details
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 84, No. 3 ( 2019-05-01), p. R477-R487
    Abstract: Seismic fluid identification is the main goal of current prestack seismic inversion. Various kinds of fluid indicators are used for fluid detection in industry today. However, the existing methods cannot always provide reliable fluid prediction owing to the insensitivity to fluid response and the lack of converted wave constraints. The equivalent fluid bulk modulus is an effective fluid factor based on matrix-fluid decoupling, which can provide persuasive evidence for fluid detection. Combining poroelasticity theory and matrix-fluid decoupling theory, we have deduced a new PS-wave linear amplitude versus offset approximation equation that provides estimations of equivalent fluid bulk modulus, rigidity, porosity, and density. Then, the joint inversion of PP- and PS-waves based on matrix-fluid decoupling was executed in a Bayesian framework with constraints from rock physics and well-log data obtaining elastic parameter estimation of high precision directly. We tested the new method on a synthetic example and field multicomponent data, and the results indicated that the estimated fluid factor matched with well-data interpretation and geology information because of adding converted wave information and avoiding indirect inversion error. This demonstrated that the new method can enhance the quality of fluid detection and provide reliable geophysical evidence for reservoir characterization.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    URL: Article
    DOI: 10.1190/geo2017-0376.1
    RVK:
    UA 4068.4
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2019
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Location Call Number Limitation Availability
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Electrical properties and its correlation to the petrology of the Upper Yangtze organic shales
    Society of Exploration Geophysicists ; 2017
    In:  GEOPHYSICS Vol. 82, No. 4 ( 2017-07-01), p. D199-D209
    Details
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 82, No. 4 ( 2017-07-01), p. D199-D209
    Abstract: Shale gas is a particularly important research target on Chinese energy resources, especially in the Upper Yangtze region. Complex topography and geologic conditions challenge seismic exploration of shale gas in this area, and ground-based electromagnetic (EM) methods are used to aid recognition of the best reservoirs. However, the electrical properties of organic shale (EPOS) and its correlation to shale-gas petrology remain poorly understood. We studied EPOS and their correlation to shale petrology by measuring and analyzing the petrochemical features and complex impedance of rock samples from the Silurian Longmaxi and Cambrian Niutitang Formations in the Upper Yangtze, southwest China. Our study indicates that the organic shale in the Upper Yangtze features low resistivity and high polarizability in terms of a high negative phase, but no obvious low resistivity is observed among shaly sandstone and shales with lower and higher total organic carbon. Pyrite and quartz contents in the organic shale dominantly contribute to the EPOS with different mechanisms. Our result indicates that the EPOS bear relations to the petrology parameters of organic shale, which is essential for shale-gas evaluation and exploration. The correlation between EPOS and the shale-gas petrology promoted a new way for shale-gas exploration with complex geology, topography, and surface conditions in China, especially in the Upper Yangtze region, by using the ground-based EM method to evaluate the parameters of shale gas and to aid to delimit the productive reservoirs (“sweet spots”).
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    URL: Article
    DOI: 10.1190/geo2016-0203.1
    RVK:
    UA 4068.4
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2017
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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