Abstract

The interpretation of reflection seismic data often does not allow the recognition of individual lithological units as a result of their limited thickness compared to the vertical resolving power of the seismic signal. However, such thin seismic units do modify the frequency and phase content of the seismic, often resulting in subtle variations in the character of reflections. In favourable cases, the re-reservoir parameters of thin units can be predicted laterally from the scrupulous analysis of the seismic response.

In this paper, a case of forward seismis modelling is presented based on seismic and well data from the Jambi Shell area. An HP 9845 Desk Top Computer has been used to calculate the seismic response of a given geological model by convolving it with a seismic signal defined by the user. The results of the calculations can be plotted in the usual seismic fashion and then compared with the real seismic data. The geological model can be adapted for iterative simulation runs, until a satisfactory similarity with the real seismic data is obtained. In the present case, the geological model was built up from well data and included various aspects such as changes in thickness, porosity and fluid content.

By visual comparison between the modelled seismic response and real seismic data from the Jambi area, regions of potentially higher porosity in a limestone interval and greater thickness of reservoir sand have tentatively been postulated.