ARK CLS

Seismic Inversion

 

ARK CLS offers a suite of seismic inversion products including:

  • Coloured Inversion
  • Seismic Broadband
  • Seismic Spectral Blueing
  • Seismic Feature Enhancement
  • Seismic Net Pay
  • Stochastic Seismic Inversion

Seismic Inversion is simply the transformation of seismic data into impedance data.   The impedance is a function of density and velocity.  The result is then used to predict reservoir properties such as lithology and porosity to better characterize reservoirs.  Interpreting in the impedance domain is frequently easier than in the seismic domain so a faster, more robust interpretation can be made.

 

By inverting seismic data, a geoscientist can gain a number of advantages over using reflectivity data:

1.       More geoscientists understand the concept of impedance and geology so working in the impedance domain is a way of integrating all the members of a subsurface team.

2.      The effects of the wavelet are removed from the seismic data

3.       Correct well ties need to be made and understood.

4.       Reservoir properties can be separated from the overburden.

5.       The seismic data may provide quantitative predictions of reservoir properties.

6.       The stratigraphic interpretation may be improved.

All of these assist in making better overall interpretations of a data volume and therefore improve the quality of the geological model of the area and reduce the risk of dry holes and poor reservoir performance.

There are a number of seismic inversion processes that can be applied to data that can improve the overall quality of an interpretation.

Coloured Inversion

Inversion of seismic data to Acoustic Impedance (AI) is usually seen as a specialist activity. In spite of the publicised benefits, inverted data are only used in a minority of cases. To help overcome this obstacle, this algorithm which is quick and easy to use, can increase the use of inversion technology. Seismic Coloured Inversion (SCI) performs significantly better than traditional fast-track methods such as recursive inversion, and benchmarks well against unconstrained sparse-spike inversion and gives broadly equivalent results. Sophisticated inversion methods are time consuming, expensive, require specialists and not performed routinely by the Interpretation Geophysicist, whereas SCI is rapid, easy to use, inexpensive, robust and does not require expert users.

With the inclusion of de-trend and normalisation functionality within SCI, geophysical meaning can now be assigned to the observed amplitude changes in the derived impedance volumes. This can be very powerful, particularly with 4D projects.

Once the SCI operator has been derived, it can be simply applied using the convolution function within the software. In this way, inversion can be achieved within hours since the data do not have to be exported to another package.

Traditional fast-track methods for band-limited inversion to relative AI are prone to error because no account is taken of the seismic wavelet or calibration to the Earth. Although more sophisticated techniques such as sparse-spike inversion take account of these factors, specialist skills are required.

SCI takes into account the seismic wavelet and is consistent with log data. With this technique, it is now possible to routinely invert any dataset within hours and establish a base case against which more sophisticated techniques must be judged.

SCI enable the rapid inversion of 3D and 4D data. A single convolution inversion operator is derived that optimally inverts the data and honours available well data in a global sense. In this way, the process is intrinsically stable and broadly consistent with known AI behaviour in the area. Construction of the operator is a simple process and implementation can be readily performed within the processing module. As an explicit wavelet is not required, other than testing for a residual constant phase rotation as the last step, this removes an inherently weak link that more sophisticated processes rely on.

Please contact us if you would like to know more about any of the products listed here.