5.5 Layer Modeling

Pseudo-wells are stratigraphic columns with attached well logs, but without geographical location. Any pseudo-well can be seen as a possible realization of a newly drilled well in the area. The pseudo-wells generation is achieved following a model that has to be defined. To achieve Layer Modeling, preliminary an extended well data analysis has to be carried out. The stratigraphy must be defined and then the well logs behavior have to be known in order to be used in the modeling.During the modeling process, the stratigraphy description is fixed and cannot be edited.

The Layer Modeling is accessible from the Analysis menu but also from the Manage Stratigraphy window.

Basic modeling can be achieved in OpendTect. More advanced modeling are available in SynthRock plugin.

The Layer modeling workflow is divided into three main steps:

1. Model definition: using the stratigraphy description, properties are assigned to the different lithologies within each units. These properties are fixed or can vary. The model definition is used to generate the pseudo-wells.
2. Synthetic and Log generation: the pseudo-wells are generated and their associated properties can be displayed. With a wavelet extracted from the real seismic, zero-offset synthetics are generated. Using a ray tracer synthetics can be computed for different offsets and restricted angle stacks can be created. Thus their behavior with varying offset can be analyzed.
3. Pseudo-well data analysis: the properties from modeled logs and synthetic seismic can be compared and analyzed layer by layer, lithology by lithology.

Example of a basic block model