Seismic Inversion

Roxar’s seismic inversion solution allows geoscientists to use seismic data to create a rock property model quickly. Moreover, it provides an accurate result with the implementation of highly effi cient geostatistical algorithms: fi ne scale information from well logs is combined with the band-limited information from the seismic data to provide an inversion where the output elastic parameters have realistic behaviour.

Fast and Highly Automated Seismic Inversion

Optional automatic wavelet estimation and automatic time to depth conversion provides an inversion tool accessible to the geologist. The computed elastic parameters can be used to condition facies and petrophysical models, or for visual inspection and data analysis. The new facies probability parameter directly provides information equivalent to many stochastic inversions. The facies probability parameter provides an excellent QC tool, and can assist the geomodeller to guide facies simulations in RMS’ rich facies modelling toolbox.

RMS combines well data & seismic data to invert for elastic parameters.

Incorporation of Seismic Data

Seismic inversion is a sophisticated process of inverting the seismic data into elastic properties of the reservoir. This is made simple in RMS and can retrieve the output parameters through fast computation. Seismic data with various refl ection angles can be used to improve the inversion result as it utilises the fact that the refl ection strength from a subsurface interface depends on the material properties of the geologic event.

Facies probaility volumes delineate channel structures in the subsurface.

IN SUMMARY

• 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.

ROXAR AS, GAMLE FORUSVEI 17, PO BOX 112, 4065 STAVANGER, NORWAY TELEPHONE +47 51 81 8800 FAX +47 51 81 8801 WWW.ROXAR.COM

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Seismic Inversion

Maximum Output from Minimum Input

A minimum amount of input data and parameters are needed to do inversion in RMS. 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 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 check the residual generated using these two.

Using Checkshot Surveys

The ability to tie wells to your seismic data via Checkshot surveys plays an important role in improving the accuracy of your interpretation, in addition to facilitating velocity analysis. RMS has a provision for importing this data easily by way of time-depth tables consisting of a standard two column ASCII fi le. These tables reside in the individual wells folders, however one table can be used (linked) to any number of wells which is useful if you have 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 the Seismic Inversion.

Facies probability statistics help risk reservoir management decisions.

To learn more please visit www.roxarsoftware.com or emailus on rss.marketing@emerson.com.