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3D traveltime computation for quasi-P-wave in orthorhombic media using dynamic programming

Hu Jiangtao, Cao Junxing, Wang Huazhong, Liu Shaoyong and Wang Xingjian
3D traveltime computation for quasi-P-wave in orthorhombic media using dynamic programming
Geophysics (February 2018) 83 (1): C27-C35

Abstract

A fractured area, such as a fault area, usually induces orthorhombic anisotropy. Ignoring orthorhombic anisotropy may degrade the subsurface image by creating a well mistie and blurring the image. Traveltime computation is essential for many processing techniques, such as depth imaging and tomography. Solving the ray-tracing system and eikonal equation are two popular methods for traveltime computation in isotropic media. However, because the ray-tracing system becomes complex and the eikonal equation becomes highly nonlinear, their applications in orthorhombic media become complex. We have developed an alternative 3D traveltime computation method in orthorhombic media based on dynamic programming. To avoid solving the complex ray-tracing system and nonlinear eikonal equation, it adopts an explicitly expressed group velocity from the moveout approximation to describe the propagation of the wavepath and computes the traveltime by Fermat's principle. Similar to depth extrapolation, it computes the traveltime from one depth to the next depth and does not suffer from a shadow zone. Besides, three strategies of traveltime computation are proposed to deal with different geologic scenarios. Because classic dynamic programming (i.e., the first strategy) computes all possible wavepaths (i.e., 24 wavepaths) across one spatial location, it may be computationally intensive. Based on the idea of wavefield decomposition (e.g., upgoing and downgoing), the second and third strategies simplify the traveltime computation and reduce the computational cost. Numerical examples on the vertical and tilted orthorhombic models indicate that the traveltime contour obtained by our method matches well with the wavefront extrapolated from the wave equation. Our method can be applied in depth imaging and tomography.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 83
Serial Issue: 1
Title: 3D traveltime computation for quasi-P-wave in orthorhombic media using dynamic programming
Affiliation: Chengdu University of Technology, Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu, China
Pages: C27-C35
Published: 201802
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 44
Accession Number: 2019-003320
Categories: Applied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Secondary Affiliation: Tongji University, CHN, ChinaChina University of Geosciences, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 201902
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