Adding Value to Impedance Models through Sequence Stratigraphy

Abstract

Abstract Impedance models should be more than just the inversion of seismic data, they should result from the integration of data from diverse sources. This integration adds value to the impedance model by increasing the information content and interpretability of the various data. The integration of geological, geophysical and other data measured in the different domains of time and depth is often not straightforward. One solution is to integrate the data within a common sequence stratigraphic framework. A case study from a maturing oil field shows how this approach can lead to the improved understanding of the distribution of fluids and reservoir properties. An initial sequence stratigraphic framework was derived from the best quality well log data and preliminary seismic inversion results. This framework was used to guide the conditioning and integration of the all the well log data. As more well log data were integrated, improvements in wavelet estimation and seismic inversion were achieved. The initial framework was refined as the data demanded. The final result was an impedance model in time and depth consistent with the seismic data, the well log data and the geological interpretation. The development of the most productive interval in the field had previously been based on the assumption that vertical connectivity existed between the different sands within it. Although recent drilling has disproved this assumption and indicated vertical barriers to fluid flow, these could not be imaged using conventional analysis of reflection seismic data. Using the sequence stratigraphic framework to extract impedance values, the separate sand layers could be imaged. These extractions also confirmed that hydrocarbons in an unperforated sand had not yet been depleted and allowed new development drilling locations to be selected.