ABSTRACT: Porosity and fluid mapping from 3D seismic attributes in glauconitic m.australis sands (Wandoo field, NW Australia)

Reymond, Satyavan B.¹, Ashley Duckett², Christian Steiner³, and Alan Strudley¹
(1) Schlumberger, Perth WA, Australia 
(2) Mobil, Perth, Australia 
(3) University of Lausanne, Lausanne, Switzerland

Generalised inversion for reservoir parameters such as porosity and fluid content is obtained from multi-dimensional grid-based and 3D seismic attribute classification.

Petrophysical analysis of the Barremian M.australis glauconitic sands involving new logging (NMR) and log interpretation techniques did reveal that glauconitic sands can contain movable hydrocarbons.

On the Wandoo field (NW shelf, Australia) 6 wells have been used to calibrate seismic attributes for sand presence (porosity) and to predict lateral extent of hydrocarbons within sandy reservoir interval.

New grid-guided volume attributes based on orthonormal polynomial trace reconstruction were able to capture subtle lateral differences in seismic facies that were not represented on the observed wiggle trace. Multi-dimensional geostatistical (Fisher, Bayesian) and Neural Network classification algorithms were used to produce a set of class and probability maps from all volume attributes generated on the reservoir interval. Quantitative calibration of the derived seismic classes corresponding to changes in lithofacies and fluids was performed using log measured reservoir parameters.

Integrated databases allow direct cross-plotting and regression analysis of well measurments against single seismic attribute. Similarly, seismic inversion for lithofacies and fluids can be drastically improved by establishing relationships between probability maps (indicating the lateral geostatistical distribution of a given seismic facies) and given reservoir parameters.

Seismic classification results were validated by additional exploration wells not included in the initial study. The entire procedure has been captured and is presented as an optimum workflow leading to well data calibration of seismic attributes classification results.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia