Approximate traveltime inversion in downhole microseismic monitoring

Research output: Contribution to journalArticle

Abstract

In downhole microseismic monitoring, accurate event location relies on the accuracy of the velocity model. The model can be estimated along with event locations. Anisotropic models are important to get accurate event locations. Taking anisotropy into account makes it possible to use additional data – two S-wave arrivals generated due to shear-wave splitting. However, anisotropic ray tracing requires iterative procedures for computing group velocities, which may become unstable around caustics. As a result, anisotropic kinematic inversion may become time consuming. In this paper, we explore the idea of using simplified ray tracing to locate events and estimate medium parameters. In the simplified ray-tracing algorithm, the group velocity is assumed to be equal to phase velocity in both magnitude and direction. This assumption makes the ray-tracing algorithm five times faster compared to ray tracing based on exact equations. We present a set of tests showing that given perforation-shot data, one can use inversion based on simplified ray-tracing even for moderate-to-strong anisotropic models. When there are no perforation shots, event-location errors may become too large for moderately anisotropic media.

Original languageEnglish
Pages (from-to)918-925
Number of pages8
JournalGeophysical Prospecting
Volume68
Issue number3
DOIs
Publication statusPublished - 1 Mar 2020

Keywords

  • Microseismic monitoring
  • multicomponent data
  • passive seismic inversion
  • seismic anisotropy
  • transverse isotropy
  • SEISMIC ANISOTROPY
  • VELOCITY
  • FIELD

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