RockPhysics & Quatitative Seismic Interpretation

[ashok]

Ashok, HI
This would be a subject for a paper...

Reconstruction of Vs is possible but you have to have a good set of logs: GR-RHOB, Ne (near and far counts), Pe and Vp; and an offset well with shear data; It all depends on data available and formation complexity.

QC logs: you need to check Caliper (or Caliper-Bit size) and look for wash-outs on density; Bad RHOB vakues should be replaced with reconstructed ones. Always correct your GR and Neutron for a given hole diameter (temperature/type and weight of mud);

If you are dealing with carbonates some normalization might be applied. My assumption here is that in limestone formation there is a tite section (not washed) with a low porosity (2-3%), with RHOB-Pe-Ne-DT values close to a clean calcite.

In soft/unconsolidated sediments (Malaysia, China offshore and Gulf-of-Mexico) often corrected Neutron and corrected/reconstructed density will provide better Vs reconstruction. But I always have 1-2 offset wells with dipole recorded data (i.e. Poisson ratio is a known value)

In certain ‘exotic” formations i.e. volcanics, mixed carbonates calcite+dolomite+shale, Black shales, etc. without offset data I would use possible analogues from Rock Catalogue (Corelab);

In clean sand-shale sequences you might build a trend lines RHOB/Vp/Vs vs. TVD for clean shale and clean wet sand; These trends are natural “boundaries” to cross-check and control reconstructed Vs;

If there is a pay beds in the well where shear should be reconstructed, you should calculate Total/Effective porosities and Sw first and remove Hc effects on RHOB and DTco (Vp) logs before reconstructing Vs.

Final QC for reconstructed Vs would be a) normalization to similar logs in the offset wells and b) calculating Poisson and Vp/Vs ratios to verify that we are still within physical bounds.

PS
I would NEVER use Castagna mudline equation…..

Hi ShadowRaven,
Many people in industry use Xu-White method for Shear wave prediction! Can you pls let me know the steps , especially data conditioning and QC part.

Thanks in advance

[olubij]

it seems we dont have many geophysicist around here.... anyway if you are one let me know especially if you are in to inversion theory....

lets share ideas books etc

[ShadowRaven]

Data conditioning;
In my world consists of two steps: a) "garbage - out", and b) "fill-the -gaps".

I would cross-plot Ne-Rhob and Rhob-DTco and verify that they are lying on a reasonable trends (i.e. sandstone-limestone matrix lines);

Then take out bad data: pick-up tails; wash-outs and cycle-skipping events; double-check casing points.

Reconstruct missing parts using fuzzy logic or trend analysis

Calculate total/effective porosity

[ShadowRaven]

I'm a petrophysicist and whenever can supporting inversion projects. But working in pair with AVO-processing geo.

Unfortunately most of offshore projects require elastic (not simple acoustic) inversion; So even for reservoir quality prediction (not pay-non pay) we are facing challenges.

The problem w/ Xu-White is that they put a "=" sign between shaly sand (10% clay + 90% quartz) and silty shale w/ 10% qrtz and 90% clay;

1; Shales are typically 40-60% clay and the rest - qurtz, hevay min etc.;
2;even 40% of silt/sand-sized particles will not add any silt/sand-sized pores; On contrary 10-20% clay added to 90-80% sand model will introduce a corresponding amount of clay-sized microporosity

[9skumar]

What about utilizing varying pore aspect ratio corresponding to the effective mineral fractions in the actual Xu-White.

[bratek]

Yes you are correct, but for an elobarate rock physics study and Quantitative Interpretation, I think the softwares available are Rokdoc, RockSolidImages software etc?
Does anyone know about anyother s/w, please share.

share the rocksolid software,
thank you

[landmark]

please share rockDoc software, thanks in advance

[Toba]

Hi Great members,

Pls i am in urgent need of R*/o*/k*/D*o/*c. Does any one have the software with ********?

bokey@cheerful.com

[braindrain]

please find few papers on rockphysics on the link below.....

[link Point to another website Only the registered members can access]

link is pas........ protected plz share pas.......!

[olevin]

Hi guy
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Also I need some Geoghysical softwares and ready to exchange. Anybody here could help me?
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