Study On Crosswell Seismic Tomography Combining Velocity And Attenuation

To improve the resolution and interpretative precision of crosswellseismic tomography is an evergreen topic. Combining velocity andattenuation tomography is to rebuild crosswell medium velocity and Q valueimages using seismic first arrival travel time and first peak value amplitude'sattenuation. The motive of developing multi-parameters tomographycombining velocity and attenuation is to improve explorational resolution toexpect efficacious utilize of crosswell seismic data and fully exert thetechnological capability.According to status quo and developing orientation of seismictomography techniques at present, considering actual demand of geo-projectsincluding engineering prospecting, environmental protecting, culture relicinvestigating, defending disaster and so on, some methods concentrated oncrosswell seismic first arrival and rebuilding velocity and attenuation imagesis studied in this paper. The main researching contexts are as follows:â—‡Ray tracing methods study. Seismic ray tracing methods study is basis of travel time tomography. More practical ray tracing methods currently include the wavefront method, the shortest path method, the travel time epenthesis method, the eikonal equation finite difference method, etc. The ray tracing using Ordinal Wavefront Construction Method(OWCM) is put forward based on the current ray tracing methods via comparison and analysis in theory and numerical value, and import of parallel arithmetic improves tracing efficiency and ray tracing software package to calculate the first arrival in any complex medium.â—‡Tomographic inversion study. High precision inversion arithmetic is one of key techniques on improving crosswell seismic tomographic resolution. Therefore, relational methods and techniques with linearization of non linearity questiones, differential coefficient matrix of rebuilding velocity image, coefficient matrix of attenuation image and optimize arithmetic are restudied. A new method of seismic wave travel time tomography, The Interlaced Gridding Method(TGM) is put forward in this paper. It's to use both high density gridding to trace ray and sparser gridding suiting actual rays to image, and to adopt task parallel computation to improvevelocity. it's testified more precision by numerical experiment and engineering practice.â—‡Tomographic restricted question discussion. It's effective to improve tomographic resolution using both compulsive condition of importing known geo-information and nature condition of importing inequations to inversion to computing least square question. A new seismic restricted tomography, Pseudo 3D Concerned Well Tomography, is put forward and testified more precision than routine inversions by numerical experiment and engineering practice.â—‡Non homogeneous viscoelastic seismic wave modeling. It's studied via pseudo-spectral method. To deduce the computing formula of 2D viscoelastic wave equation from athletics differential equation, free boundary conditions and absorb boundary conditions, and realize seismic modeling using pseudo-spectral method in computer validate the result of tomography and provide dependence for crosswell seismic attenuation tomography and wave from inversion.â—‡Attenuation tomographic study. It could not only improve crosswell seismic tomography but also expend image information and boost up understand on geo-structure and physical characters distributing in studied area and improve image resolution and reliability. The tomography of rebuilding 2D attenuation character distributing image using seismic wave peak amplitude is discussed. The eliminated method of attenuation variety resulted from seismic wave transmission loss etc. and the effect on rebuilding Q value image from velocity distributing and numeric experiment and engineering practice are studied.â—‡Practical crosswell seismic wave tomographic sofrtware system study. Based on study on crosswell seismic tomography combining velocity and attenuation, A higher resolution software package is developed.