Abstract

The contribution that seismic data can make to the structural and stratigraphic model of a reservoir is well known, as is its ability to delineate fluid contacts in favourable cases. However, lithological controls in reservoir simulation models frequently are limited to information gathered at wells. Any advance in interwell correlation will strengthen the validity of the models. The concept in this work is to demonstrate a practical technique by which a seismic survey can be used to improve the estimates of lithological parameters and porosity in undrilled areas of a reservoir and between wells, on a scale appropriate for reservoir simulation modelling.

This technique is an extension of that of Cornish and King 1988, who produced wide-band synthetic acoustic logs throughout a field area by combining borehole logs with seismic and geological data. We have added a second inversion stage, using interpreted borehole data.

The basis of the method is to project conventionally interpreted borehole estimates of lithology and porosity throughout a field, guided by the existing seismic-geologic interpretation of the field's structure and stratigraphy. Then, selected petrophysical relationships and constraints are invoked in a two stage iterative inverse procedure, to perturb the lithological model at every point throughout the survey area, by the least amount necessary to explain the observed seismic data.

The final result is a highly detailed lithologic and porosity model of the field consistent with all available borehole, geologic, and seismic data, suitable for use in field evaluation and for building reservoir simulation models.

Example results are shown from a traverse through a complex field.