John van der Laan¹, John Pendrel²

(1) Gulf Canada Ltd, Calgary, AB
(2) Jason Geosystems Canada, Calgary, AB

ABSTRACT: Geostatistical Simulation of Porosity in a Devonian Reef

We have done geostatistical simulation of impedance and porosity in a Devonian reef. The simulations are done consistent with well logs and also with the measured first and second order statistics. We use the technique of Stochastic Inversion to reduce variance. Simulations are restricted to those for which the corresponding synthetics agree with the seismic data. The collection of simulations and their variance can then be used to establish a range of possible outcomes. Alternately, the probability of occurrence of a particular property range can be computed from the simulations and viewed and interpreted in a 3-D perspective format.

The region of interest in the Goose River 3D programme is a Swan Hills reef at approximately 2800 m. Maximum porosity thickness is 45 m and there are 65 wells within the survey. At Goose River, impedance is directly related to porosity and yields information about the connectivity of different compartments. Therefore, it was decided to first do simulations of impedance. The stochastic inversion should control the transition from the fine scale of the input impedance logs to the lower resolution of the simulations. Given the good relation between impedance and porosity in the logs, we simply transformed the impedance simulations to porosity.

Twenty simulation sets of impedance and porosity were computed. The results show that. some regions of the Swan Hills facies exhibit more detail in the geostatistical simulations than previously observed from seismic data.. Different conclusions about connectivity between different parts of the reef complex can be inferred.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado