StatMod

Geostatistical Inversion

StatMod® combines classic geostatistics with innovative Jason® suite seismic inversion methods in a program that is valuable in both exploration and reservoir development. StatMod uses geostatistics to identify models that are consistent with well log information and simultaneously inverts the data to find the subset of those models that are also consistent with the seismic data. This results in models that match all the input data in a single algorithm.

The litho cube output developed in StatMod is a kind of automatic interpretation or body checking. Informational synergies allow substantially increased resolution, capturing details well beyond seismic bandwidth. By providing multiple, realistic scenarios, StatMod provides a tangible, intuitive handle on development risk.

StatMod goes beyond traditional seismic inversion to solve problems like:

Fine scale interpolation between closely-spaced wells
Estimation of uncertainty to assess risk
Improvement of the resolution of standard seismic inversions
Generation of lithotype (e.g. sandstone, shale) volumes
Estimation of porosity from impedance
Integration of high resolution well data with low resolution seismic
Creation of inputs for reservoir simulation

How it works

In StatMod, a rigorous probability distribution is defined linking the property and lithofacies cubes with the seismic, well logs, histograms and variograms. The histograms and variograms are obtained from log analysis and geological insight, the former giving the likelihood of different values at any given point, the latter giving essentially the "characteristic scale" and texture of the geological features in lateral and vertical directions.

The seismic is interpreted in terms of discrete bodies of lithologies with sharp edges, where appropriate. Fine details (heterogeneity) are included. Histograms and cross plots observed in the wells or inferred from rock physics are fully taken into account.

While details beyond seismic bandwidth cannot, by definition, be resolved precisely and unambiguously, it is often possible to get a good idea of the existence, multiplicity, thickness and connectivity of sub-seismic sand formations.

It is possible to develop an intuitive, tangible picture of the remaining uncertainty in the details by comparing the multiple output scenarios. Variability in the software's lithofacies "interpretation" (hypothesizing bodies of different rock types) can also play a useful role in showing the true development risk.