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Introduction

During the past few years, promising case studies have indicated that better subsurface images can be acquired by integrated processing of borehole and surface seismic data than by processing either type of data alone Chopra et al. (2002); Kostov et al. (1999). A major advantage of this integration is that it helps determine an improved subsurface velocity model. Among different tomography methods, surface reflection tomography has gained popularity in modern 3D seismic projects for use in large-scale projects Clapp (2001); Stork and Clayton (1991); Stork (1992, 1994). However, surface reflection tomography suffers from inversion ambiguity because it perturbs both reflector position and velocity together to extract the unknown velocity field. Such velocity-depth ambiguity can be substantially reduced if transmission and reflection seismic data are used together for velocity inversion Mao and Stuart (1997).

Researches have been conducted to do integration tomography using VSP and surface seismic data simultaneouslyCao et al. (2000); Chiu and Stewart (1987). Claims have been made that the integration tomography can resolve the subsurface velocity field better than either tomography technique. However, the frequency bandwidth difference, the correlated errors between the two data types Brown and Clapp (2001), the difficulty to balance different tomography operations and the challenge of software design make integration tomography remain a topic of considerable academic and practical interest.

In this paper, a model-based joint tomography scheme is realized and analyzed. Surface reflection data and VSP traveltime are used simultaneously to invert the velocity in this integrated inversion scheme. Using the identity operator as integration operator, this integration tomography scheme is applied to a synthetic anticline model. The inversion result from integration tomography is compared to that from surface reflection and VSP tomography, respectively. Compared to surface reflection tomography, the integrated inversion result is better in areas where the VSP ray coverage is good and conversely, the integrated inversion result is poorer in the areas where VSP ray coverage is sparse or inexistent. The results suggest that we can obtain improved velocity field by this integration tomography scheme if using a well-designed integration operator.


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Next: Methodology Up: Chen: Joint tomography Previous: Chen: Joint tomography
Stanford Exploration Project
7/8/2003