Development planning using integrated 3-D visualization and geocellular models from petrophysical and seismic data

A geocellular model is a 3-D facsimile of the distribution of rock properties such as those derived from log analysis. The advantage of the geocellular model is that rock properties derived from logs are represented at a much higher vertical resolution than achieved through conventional mapping and 3-D visualization methods provide the means to interact with the rock properties to discern how they affect reservoir performance. 3-D visualization provides a means to view, interact, and interpret data in a visually intuitive environment.  All of the data including geophysical, petrophysical and wellbore data can be displayed together facilitating interpretation. Visualization and data interrogation tools provide the means to interact with the geocellular model to investigate the interplay of lithology, porosity, structure, contacts and cutoffs, and in the case of an effective porosity model, yield volumetrics.

A new workflow was developed along with gained experience in geocellular model preparation and use. This workflow takes advantage of the geocellular model to resolve key reservoir architectural elements. It is a mistake to impose a complex stratigraphic interpretation on the model based on interpretations from 2-D sections.  It is best to start with one or two principal correlation horizons and a simple indicator of geology, such as shale volume. Through the use of shale geobodies and phase segregation (contacts), key correlation (flooding surface) and compartment-creating shale horizons can be identified.

In addition to geocellular models built from log data, geophysical data such as normalized interval velocity, impedance and AVO, have been used that, when interrogated for geometry relative to stratigraphy and fluid contacts, have both identified reservoir volumes that reconcile with produced volumes and those that are prospective. Such studies have been used in the definition of both conventional and unconventional prospects.

Geocellular model methods are not a new and different way of mapping; they are essentially the same as conventional mapping but in 3-D. They provide the advantage of incorporating a much greater degree of variability in the vertical dimension that is lost to 2-D mapping. The interactive 3-D visualization workspace aids in the preparation and validation of the geological model and, very importantly, reconciliation with the development history. Ultimately these models are well suited for dynamic simulation with the final up-scaled model design based on the geological character learned from the geocellular model. As opposed to pattern drilling, development plans based on a properly prepared geocellular model and its simulation tend to better incorporate the geological character of the reservoir.