Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Joint inversion for microseismic event positions and velocity structures by combining multiscale deformable-layer tomography and master station earthquake location method
Wei, Zhili (University of Houston) | Zheng, Yingcai (University of Houston) | Zhou, Hua-Wei (University of Houston) | Hao, Hu (University of Houston) | Lau, August (University of Houston)
ABSTRACT Hypocenter determination is an ever-green research topic in earthquake seismology, and it has gained interest recently for monitoring microseismicity in unconventional petroleum exploration. In the microseismic monitoring, both the seismic event positions and the velocity model of production area are critical for understanding the changes in the subsurface caused by the hydraulic fracturing. However, there are uncertainties in all velocity models due to limited data quality and coverage, and such uncertainties would degrade the accuracy of the event position inversion. We address these issues by simultaneously inverting for the velocity model and microseismic event positions. We incorporate the master station earthquake location method with equal differential time (EDT) surface and the multi-scale deformable-layer tomography (DLT). In this abstract, we tested this joint inversion with several synthetic datasets which yielded satisfactory results. Both the average travel time residual and the average position distance misfit were dramatically decreased by iterations. These synthetic examples successfully showed that our joint inversion is capable of improving the accuracy of event locating and velocity building. Presentation Date: Monday, October 17, 2016 Start Time: 1:25:00 PM Location: 144/145 Presentation Type: ORAL
ABSTRACT Imaging using the reverse time migration of multiples generates inherent crosstalk artifacts due to the interference among different order multiples. Traditionally, least-square fitting has been used to address this issue by seeking the best objective function to measure the amplitude differences between the predicted and observed data. We have developed an alternative objective function by decomposing multiples into different orders to minimize the difference between Born modeling predicted multiples and specific-order multiples from observational data in order to attenuate the crosstalk. This method is denoted as the least-squares reverse time migration of controlled order multiples (LSRTM-CM). Our numerical examples demonstrated that the LSRTM-CM can significantly improve image quality compared with reverse time migration of multiples and least-square reverse time migration of multiples. Presentation Date: Tuesday, October 18, 2016 Start Time: 1:50:00 PM Location: 171/173 Presentation Type: ORAL
ABSTRACT We develop the method using exact localized waves to detect the spacing between fractures from the idea of the earlier Double focusing Gaussian beams. First, we investigate the localized wave propagation in complex acoustic media to show its directional property with limited diffraction and capability to retain its geometric shape. Second, we apply the Gaussian wave packet (GWP) to invert for the spacing of fractures in an acoustic medium. The GWP is an exact solution to the wave equation and should be distinguished from the traditional asymptotic Gaussian beam or Gaussian packet. A directional localized wave illuminates the fracture targets and the multiply scattered waves can be captured in a time-space window using the multiple-scattering theory of plane waves upon a local periodic structure. The scattered wave depends on the fracture orientation and spacing. We scan all possible fracture parameters such that the predicted scattered waves match our observation. Because this method is not a seismic migration/imaging method, its dependence on background velocity accuracy is not stringent. Finally, our numerical examples will illustrate these points. Presentation Date: Tuesday, October 18, 2016 Start Time: 4:10:00 PM Location: 155 Presentation Type: ORAL
ABSTRACT Magnetic and electric vector potentials are presented for scattering from a lossy infinite cylindrical inhomogeneity in an otherwise homogeneous lossy space. These potentials are in response to a magnetic dipole in a three-dimensional space, oriented horizontally and perpendicular to the axis of the cylinder. The electromagnetic wavefield induced by this source is found analytically based on modal expansion of the wavefield both inside and outside of the tunnel. A new recursive scheme is introduced to overcome the numerical instabilities particularly at high frequencies corresponding to large angular orders. Our analytical method was used to study tunnel detection for a dipole magnetic source and a receiver located in opposing vertical boreholes straddling an underground tunnel. Detectability is achieved at relatively high frequencies (but below the frequencies used by ground penetrating radar) for fresh water saturated sand and for weathered granite; for fresh water saturated clay, comparable detectability is achieved at quite low frequency. The over-riding factor for detectability is wavelength, due to the rapid attenuation of electromagnetic waves in Earth media caused by Joule heating. Presentation Date: Wednesday, October 19, 2016 Start Time: 8:25:00 AM Location: Lobby D/C Presentation Type: POSTER
- Geophysics > Magnetic Surveying (0.85)
- Geophysics > Electromagnetic Surveying (0.70)
- Geophysics > Seismic Surveying (0.69)
- Energy > Oil & Gas > Upstream (0.70)
- Government (0.69)