[OpendTect_Users] MPSI_Plugin

[Renaud Meunier]

Dear E. Falebita,

One thing I forgot to mention is that when the wavelet scalar has been
properly estimated you can use the same value everywhere (using different
well constraints, using a filtered initial model, doing a stochastic
inversion
). Basically you only have to do the job once for a given
seismic and wavelet.

I hope it clarifies things.

Best regards,

Renaud.

-- 
Renaud Meunier
Geoscientist
Earthworks Environment and Resources Ltd Prestex House, Edison Road
Salisbury, Wiltshire. SP2 7NU

Direct Line: 01722 343999
Fax: 01722 343991
www.sorviodvnvm.co.uk

> Dear E. Falebita,
>
>> I tried to compute the deterministic Inversion from my 3D Impedance
>> Model
>> without success. The Screen showed something like this, "On
>> Deterministic
>> Inversion: Problem with the inversion, reflectivity 1.16676 out of
>> range."
>>
>> My question is: what is responsible for this? What are the many options
>> that would make reflectivity to be out of range.
>
> The reason is the wavelet scalar that is not accurate (i.e. the scaling
> between the seismic amplitudes and the wavelet’s ones). If you haven’t set
> it in your inversion settings, MPSI computes a default value at the well
> location. This default value is reported in the OD log file. Now it is
> only a first guess, so might not be always the best scalar to use. In
> order to find the good one you will have to do some scalar tests (at a
> given set of in-lines or cross-lines). The way to do that is by setting
> the well constraints to a very low value (i.e. <= 0.1) as you want as
> minimal model contribution as possible and manually edit the scalar
> starting from the default and progressively increasing or decreasing it. A
> last thing you need to be aware of is that the default scaling computation
> is not done using the well logs but the initial model values at the well
> location (something we need to change in the future) so you will need to
> use a broadband model (or as high as the max seismic frequency) to do the
> default scalar computation (the synthetic used in the computation to
> compare with the seismic trace is done from the model reflectivity
> convolved with the wavelet, so a too hash model filtering will give too
> low reflectivity response).
>
>> Also, what is the minimum number of wells that can be used for
>> inversion.
>
> You can use any number however they need to be within your survey range.
>
> Best regards,
>
> Renaud.
>
> --
> Renaud Meunier
> Geoscientist
> Earthworks Environment and Resources Ltd Prestex House, Edison Road
> Salisbury, Wiltshire. SP2 7NU
>
> Direct Line: 01722 343999
> Fax: 01722 343991
> www.sorviodvnvm.co.uk
>
>
>> Please
>> I tried to compute the deterministic Inversion from my 3D Impedance
>> Model
>> without success. The Screen showed something like this, "On
>> Deterministic
>> Inversion: Problem with the inversion, reflectivity 1.16676 out of
>> range."
>>
>> My question is: what is responsible for this? What are the many options
>> that would make reflectivity to be out of range.
>>
>> Also, what is the minimum number of wells that can be used for
>> inversion.
>>
>> Thanks
>>
>> --
>> D. E. Falebita
>> Department of Geology,
>> Obafemi Awolowo University, Ile-Ife,
>> NIGERIA
>>
>>
>>
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>