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Seismic Inversion

The RMS™ seismic inversion solution allows geoscientists to use seismic data to quickly create a rock property model. Moreover, it provides an accurate result with the implementation of highly efficient geostatistical algorithms: fine scale information from well logs is combined with band-limited information from the seismic data to provide an inversion where the output elastic parameters have realistic behavior.

Seismic Inversion Benefits

  • Puts the power of seismic inversion in the hands of the geomodeler.
  • Provides elastic parameters to help constrain petrophysical properties of the reservoir.
  • Facies probability cubes provide risk management support for estimating reservoir quality.

Seismic Inversion Features

Fast and Highly Automated Seismic Inversion

Optional automatic wavelet estimation and automatic time-to-depth conversion provide an efficient inversion tool to the geologist. The computed elastic parameters can be used to condition facies and petrophysical models, or for visual inspection and data analysis. The facies probability parameter directly provides information equivalent to many stochastic inversions. This tool is excellent for QC, and can assist the geomodeler in guiding facies simulations in the rich RMS facies modeling toolbox.

Incorporation of Seismic Data

Seismic inversion is a sophisticated process of inverting seismic data into the elastic properties of the reservoir. In RMS, it produces the output parameters through fast computation. Seismic data with various reflection angles can be used to improve the inversion result, based on the fact that the reflection strength from a subsurface interface depends on the material properties of the geologic event.

Maximum Output from Minimum Input

In RMS, a minimum amount of input data and parameters is needed to do inversion. RMS requires a grid volume of the region where the inversion will be computed. The optimal input data is AVA stacks, that is, stacks with common angle gathers. Facies logs are not necessary unless inversion is done for facies probabilities. Minimum well data requirement is a single vertical well with Vp, Vs, ρ and two-way travel time.

The output parameters include Vp, Vs, Density, P-Impedance (AI), S-Impedance (SI), Vp/Vs, Poisson Ratio, Lamé Lambda, Lamé Mu, Original Seismic, Synthetic Seismic and Residuals. If a facies log exists in the blocked wells, then a facies probability parameter can be created. It is also possible to output the estimated wavelets and inversion time grid. The output can be quality checked by comparing the original seismic data with the synthetic seismic or by checking the residual generated using them both.

Using Checkshot Surveys

The ability to tie wells to seismic data via Checkshot surveys plays an important role in improving the accuracy of the interpretation, in addition to facilitating velocity analysis. RMS has a provision for importing this data easily by way of time-depth tables. These tables reside in the individual wells folders; however, one table can be used (linked) to any number of wells, which is useful if there are limited checkshot data. Finally, it is fast and simple to create TWT logs from the time-depth data which is then required for input to seismic inversion. RMS checks the consistency between the TWT logs and the applied velocity model, to validate results.

1) Grid parameter Vp output from Seismic Inversion job in RMS. 2) Grid parameter Density output from Seismic Inversion Job in RMS. 3) Grid parameter Facies probability output from Seismic Inversion job in RMS. 4) Grid parameter Channel facies output from facies modeling job with conditioning to Seismic Inversion – result is Facies probability.