Technical Paper
Technical Paper

Joint Impedance and Facies Inversion – Seismic Inversion Redefined

Michael Kemper of Ikon Science and James Gunning of CSIRO present a new seismic inversion system, which aims to overcome shortcomings in present-day simultaneous inversion tools by using joint impedance and facies inversion technology.

In this paper, we will first review the industry-standard simultaneous inversion method (which derives continuous impedances) and subsequently identify some pitfalls. We will then introduce our new Joint Impedance and Facies Inversion technology (which we call Ji-Fi for short in this paper), which overcomes these pitfalls by recasting the seismic inverse problem as mixed discrete/continuous. Having so captured the correct physics, we apply this first on a wedge model, followed by a case study, before drawing some conclusions.

Note that in this paper, it is assumed that the seismic to be inverted is an ensemble of true amplitude partial angle stacks with corresponding wavelets derived from well ties.

In-depth analysis of the present industry standard continuous simultaneous inversion method highlighted some shortcomings, which require the following remedies:

1. We need to invert to facies and impedances per facies (to capture the physics correctly)
2. We need to use per facies LFBMs

In this paper we have introduced a new joint discrete/continuous simultaneous inversion method which implements these two remedies, and which does not show unsightly artefacts of standard methods such as impedances tending to a non-geological value away from seismic energy, frequency deficiencies, or interpolation halos.

A particularly pleasing aspect of Ji-Fi is that well data is used in a ‘soft’ way only, making QC at the wells blind well QC by design.

Comparisons to a wedge model and to case studies (of which only one is shown in this paper; more will be presented in a future companion paper) indicates that Ji-Fi gives an improved inversion result compared to simultaneous inversion.

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