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Yungui, Xu

Welcome to my homepage of University of Edinburgh (^_^)

I am a 1st year PhD student at the Earth Sciences Institute of the University of Edinburgh from China and my subject is Geophysics.

Here is a link to the Edinburgh Anisotropy Project (EAP) , where I spend most of my time these days. The EAP is a link between the British Geological Survey (BGS) and the University of Edinburgh. The information below is about my project and if you are interested in what I am doing and want to share some ideas with me, I will be very luck and just contact me

Things I love to do

·        Sports, especially Basketball, if you love too, don’t forget get me as your member of your team

·        Computer programming, such as Fortran, C, C++, Python, Qt, Linux, Unix, Seismic Unix, SEPLib

·        Music

·        Of course, my subject Physics

·        Chinese Food

Picture

EAP Team(Edinburgh Anisotropy Project, taken at BGS gate)
Me: up the girl, (^_^)

Some work I have done

Anisotropy system is a geophysical software on anisotropy assessment and aims to analyses the anisotropy phenomena underground and to find something about cracks of fractures

Seismic Superset picking and ellipse analysis

Seismic section from the superset point

The plan view of the fracture-density-and-azimuth distribution



PHD Project Name:  Modelling 3D seismic response in fractured media  

There are two approaches to modelling the propagation of seismic wave fields in fracture populations in the Earth.  The first is to use mean field or equivalent medium theory that neglects the size distribution or the spatial correlations in fracture pattern.   This is appropriate at low fracture density, but completely fails in the more general case of relatively dense, fractally-distributed populations commonly observed at outcrop and in boreholes.  Recently, the use of finite difference or finite element methods makes it possible to relax the low-density restrictions by incorporating the effects of discrete fractures.  The finite difference method is advantageous when modelling the scattering effect of discrete fractures because of its stability over a wide range of material property contrasts and its ability to model all wave types with minimal numerical dispersion and anisotropy (Nihei et al., 2002, Nakagawa et al. 2002, Vlastos et al. 2003, amongst others). 

Modelling seismic wave propagation is often computationally intensive, so computation speed is often a primarily concern for practical applications. Therefore, innovative solutions are still required to make modelling sufficiently fast but without compromising accuracy. This is particularly important for modelling 3D wave propagation in a realistic fractured media. For this, Nihei et al. (2002) and Nakagawa et al. (2002) adopted a hybrid approach that combines finite difference with the equivalent medium approach, following the idea of an equivalent medium anisotropic cell for finite difference modelling of discrete fractures proposed by Coates and Schoenberg (1995).  This approach allows rapid computation of the elastic properties of fracture networks with sufficient accuracy.  Vlastos et al. (2003) extended this approach for modelling seismic response in fracture networks with a realistic distribution.  However, this approach is limited to a 2D medium. There is still a lack of practical tools to modelling the seismic response in 3D media with complex fracture systems.  Here we propose a three-year PhD research to extend Vlastos et al. (2003) to 3D media.                

The proposed PhD project will begin by using one or more of the available theories, along with synthetic packages (e.g. finite difference, ray-based and wave-approximation codes developed by BGS) to study the 2D seismic response of fracture networks. It will then be extended into 3D layered media with complex fracture systems, e.g. fractured networks. The aim of the study will be to build a modelling facility that accounts for 3D wave propagation in a realistic fractured media, and to understand and test the sensitivity of various seismic attributes such as AVO, attenuation and anisotropy to changes in fracture spacing, length scale and density of the fractured media. The initial 3D fracture model will be constructed based on the work Li et al (2003) on the Yellow River Delta, and refined through seismic modelling, and validated using outcrop and borehole data.

The student will be given training in modern techniques in seismology, including computational modelling, use of parallel computer technology, database management, and data processing and interpretation. The following three areas of expertise can be identified: (1) seismic modeling and imaging, (2) seismic detection of naturally fractured reservoirs, and (3) multi-resolution uncertainty analysis.

References

Coates, R. T., and Schoenberg, M., 1995, Finite-difference modeling of faults and fractures, Geophysics, 60, n5, 1995.

Nihei, K., Nakagawa, S., Myer, L. and Majer, E., 2002, Finite difference modeling of seismic wave interactions with discrete, finite length fractures, 72nd Ann. Internat. Mtg: Soc. of Expl. Geophys., 1963-1966.
Li, X.-Y., Liu, Y.-J., Liu, E., Sheng, F., Li, Q., Qu, S.,  2003. Fracture detection using land 3D seismic data from the Yellow River Delta, ChinaThe Leading Edge, 22, No. 7, 680-683.
Nakagawa, S., Nihei, K. and Myer, L., 2002, Numerical simulation of 3D elastic wave scattering off a layer containing parallel periodic fractures, 72nd Ann. Internat. Mtg: Soc. of Expl. Geophys., 1967-1970.
Vlastos, S., Liu, E., Main, I.M. and Li, X.-Y., 2003. Numerical simulation of wave propagation in media with discrete distributions of fractures: effects of fracture sizes and spatial distributions. Geophysical Journal International, 152, 649-668.

Email
yunabc@ed.ac.uk, yunguixu@gmail.com

Address
British Geological Survey
Murchison House Room 5-1
West Mains Road

EH9 3LA
Edinburgh
UK


phone
+44 (131) 6671000 ext. 468 (no direct line)