Building velocity models for steepdip prestack depth migration through first arrival traveltime tomography brooke j. The corresponding 2d elliptic coordinate extrapolation wavenumber is demonstrated to introduce only a slowness model stretch to. Each shot record in a physical model data set is inverted separately with a common shot, prestack inversion routine with a laterally and depth variable velocity function. Interference of these ellipses will produce the prestack migrated section. It is intended for those who are unfamiliar with seismic imaging or are not knowledgeable of seismic. Introduction to the traveltime tomography and prestack migration for boreholedata within reflexw in the following the use of the traveltime tomography and the prestack migration for different types of borehole data is described. Prestack waveequation depth migration in elliptic coordinates je. If a good prestack depth migration is to be obtained, it is. In areas of rapid lateral and vertical velocity changes, energy is dispersed in such a way that conventional stacking with hyperbolic moveout dimin.
Prestack depth migration for easy unconventional plays. Pdf on sep 9, 2016, maya grigorova and others published comparison between prestack depth migration and direct. The massively parallel nature of graphics processing units has made them an attractive platform for some computationally tintensive algorithms. Follow this link for information on the equation and graph of an ellipse. As expected, due to the large velocity contrast at the steep top salt interface, the time migration is incapable of producing a meaningful image. Stanford exploration project, geophysics department, stanford university, stanford, ca.
This article presents a method to run 3d kirchhoff prestack depth migration on. The goals of this large scale project were accurate event placement and improved imaging of steep dips, salt boundaries, and subsalt events. Nevertheless, the real bottleneck in 3d prestack processes is the sheer amount of input and output data. Case history imaging complex structure in shallow seismicre. Kirchhoff least squares prestack migration lspsm attenuates acquisition artifacts resulting from irregularities or sparseness in the wavefield sampling and improves image resolution.
Reverse time migration is an ultrahighend prestack twoway waveequation migration for accurate imaging in and below areas with both great structural and velocity complexities, such as sedimentary areas with steep salt inclusions. Applications of leastsquares prestack depth migration in. Pdf prestack depth migration by 3d tomographic inversion. Can someone explain to me why migration is often times prestack and often times poststack, and if even both are ever done. Among all other methods for seismic prestack depth migration, grt is unique by. Integrated prestack depth migration of vsp and surface. Prestack depth migration methods for isotropic and polar. Most current trueamplitude migrations correct only for geometric spreading.
Carney thesis submitted to the faculty of the virginia polytechnic institute and state university in partial fulfillment of the requirements for the degree of master of science in geophysics dr. Pdf prestack depth migration in elliptic coordinates jeffrey shragge academia. Prestack kirchho time migration for complex media tariq alkhalifah1 keywords. The advantage and significance of prestack migration cseg. Use of prestack depth migration for improving the accuracy of horizontal drilling in unconventional reservoirs abstract depth imaging has long been a staple in offshore processing sequences. Prestack waveequation depth migration in elliptic coordinates. In this paper, 3d parallel shotgather prestack depth migration with hybrid is developed and implemented. A method of prestack time migration based on the principles of prestack kirchhoff time migration that can be applied to both 2d and 3d data. Prestack time migration is done by spreading the amplitude at every point in the prestack gathers over an ellipse. Kirchhoff prestack depth and time migration schlumberger. Prestack depth migration is a useful tool for understanding complex structures in the north sea and elsewhere around the world. It can be divided ray and wave equationbased method.
Use of prestack depth migration for improving the accuracy. Summary over the last decade, it is predominantly perceived that there have been significant evolutions in prestack depth imaging. Implementation of kirchhoff prestack depth migration on gpu. Davide teixeira, alex yeh and sampath gajawada, tgs. To solve this problem and improve the quality of imaging in complicated media, we propose a prestack depth migration operator with coefficient optimized paraxial wave equation on. Management david kessler, president, seismiccity, inc dr. Given that seismic data is bandlimited, the ideal response. Only full prestack time migration is considered in this paper. Prestack time and depth migration panorama technologies. Pdf prestack depth migration of ultrashallow seismic data.
The last 20 years have seen extensions of these methods to three dimensions and to prestack migration, and evergreater re. Studies for acceptance, a thesis entitled prestack depth migration methods for isotropic and polar anisotropic media submitted by xiang du in partial fulfilment. Kessler serves as the president of seismiccity since its incorporation in early 2000. Prestack depth migration an ultimate aspiration for subsurface imaging in geologically complex area. Prestack gaussianbeam depth migration in anisotropic media tianfei zhu, sam gray and daoliu wang, veritas dgc inc summary gaussianbeam depth migration hill, 1990, 2001 is a useful alternative to kirchhoff and waveequation migrations. Yu zhang, james sun, carl notfors, sam gray, leon chernis and jerry young, veritas dgc inc.
Model velocities were assigned from sonic logs from the vsp well. Seismic prestackdepth migration grt fraunhofer itwm. Introduction to the traveltime tomography and prestack. Note that the terms depth and time migration do not relate to whether the migrated results are presented as a function of time or depth. Integrated prestack depth migration of vsp and surface seismic data in order to test the new, integrated prestack depth migration algorithm, a numerical model was developed based on the interpretation of the field data. Prestack depth migration by 3d tomographic inversion of reflected and refracted arrivals. First off, all reflection seismic data is recorded in time whether onshore or offshore. Advances in prestack depth migration sciencedirect. Depth migration, tomography, velocity model, depth conversion introduction depth conversion, ideally, is an.
These tools involve a degree of interpretation not normally seen in conventional seismic processing. Many competing algorithms have been proposed by various authors. Prestack depth migration presdm is a robust method for obtaining proper image of complex subsurface. Seismic migration is the process by which seismic events are geometrically relocated in either space or time to the location the event occurred in the subsurface rather than the location that it was recorded at the surface, thereby creating a more accurate image of the subsurface. Prestack depth migration an ultimate aspiration for.
Details of the model at the target level are shown in figure 3a. Prestack gaussianbeam depth migration in anisotropic. That is, an energy source is used to generate a pulse of acoustic energy and direct it into the ground. Prestack time migration and post stack depth migration. Note that prestack depth migration produces an image that is free of the distortions observed on the image produced by poststack depth migration. Its effectiveness can become limited, however, when complex velocity structure causes multipathing of seismic energy. Pdf psdm is increasingly becoming rule rather than exception in near surface seismic imaging when the goal is to get detailed subsurface. Kirchhoff migration is the most popular method of threedimensional prestack depth migration because of its flexibility and efficiency. We present a new prestack depth migration method that uses the framework of reversetime migration to compensate for. To accomplish these goals, all available well information was used to calibrate the seismic velocity model from prior.
Kirchhoff prestack time migration pstm can accurately image steep or overturned events, provided that turning rays and anisotropy are taken into account. Seismic migration is a process to turn the reflectors on the stack image into true geological interface. Enhanced anisotropic model building methodology and. It gives an overview on the goals and techniques utilized in imaging of seismic data. I understand the idea of migration and how there are different algorithms that either solve it in time or depth. Riemannian wavefield extrapolation is extended to prestack migration through the use of 2d elliptic coordinate systems. Common scatter point csp gathers are created as an intermediate step for each output migrated trace. Introduction prestack depth migration presdm is a robust method for obtaining proper image of complex subsurface. Normal moveout nmo and stacking of csp gathers is performed to complete the prestack migration process. Trueamplitude prestack depth migration request pdf. He started his industrial career as a research geophysicist developing algorithms for velocity estimation, model building and prestack depth migration and held a senior research scientist position for landmarkita 19911994 and a senior research. Image in and below areas with structural and velocity complexities. Prestack depth migration generates more accurate images left reducing exploration risk and improving reservoir definition.
It overcomes the inability of kirchhoff migration in imaging multiple arrivals while retaining its. This process is necessary to overcome the limitations of geophysical methods imposed by areas of complex geology. Seismic migration based on ray methods such as kirchhoff gray and may,1994. Kinematic time migration and demigration of reflections in. Overview on the fundamentals of imaging cseg recorder. Generalized radon transform grt depth migration excellently demonstrates how the unified competence in the fields of geophysics, mathematics, and informatics of the department hpc could be used for the successful development of a tailormade product according to clients particular needs. Kirchhoff depth migration in the sense that the amplitude of the imaged reflections is proportional to the reflection coefficient. Panorama technologies chapter 6 prestacktimeanddepth migration prestackmigrationalgorithmsarerelativelysimplevariantsofthepoststack methodologies. Building velocity models for steepdip prestack depth. In areas of rapid lateral and vertical velocity changes, energy is dispersed in such a way that conventional stacking with hyperbolic moveout dimin ishes both noise and signal. Using synthetic examples, a few applications of lspsm including improvement in image resolution, the ability for data. Pdf prestack depth migration by 3d tomographic inversion of reflected and refracted arrivals giuliana rossi academia. Data preparation for prestack depth migration crewes.
Case history imaging complex structure in shallow seismic. Dai and others published an adaptive phase shift and ssfpi method for prestack depth migration find, read and cite all the research you need on researchgate. Calgary, alberta, canada t2p 5e9 introduction in western canada there is only a small percentage of seismic data processed with prestack migration. The goal of prestack depth migration is to reconstruct an image of the subsurface with the highest possible resolution.
Kirchhoff prestack depth migration ion geophysical. Prestack gaussianbeam depth migration geoscienceworld. The traveltime tomography allows to build a velocity model from the first arrival traveltimes. Geiger summary the goal of prestack depth migration is to reconstruct an image of the subsurface with the highest possible resolution. Prestack crewes research report volume 2001 555 cos rms stk v v.