Classifying Mud-Rich Facies Successions in Dryland Systems

Marianne L. Sandstrom¹, Carmen B. Krapf¹, Ric F. Daniel¹, Kathryn Amos¹, and Tobias H. Payenberg^2
1Australian School of Petroleum, University of Adelaide, Adelaide, SA, Australia
²Quantitative Stratigraphy Team, Chevron Energy Technology Company Pty Ltd, Perth, WA, Australia

Mud-rich facies successions are important source, baffle and seal rocks in many dryland reservoirs. In modern dryland systems, muds occur in a range of depositional sub-environments. A greater understanding of these fine-grained sediments will assist in their identification and the prediction of their spatial distributions in ancient rocks, crucial to the development of robust facies and reservoir models for dryland environments.

A preliminary classification scheme for mud-rich facies successions in dryland systems is presented for the Kalaweerina terminal splay complex (TSC) and surrounds, Lake Eyre, central Australia.

Surficial sediment samples were collected from mud-rich depositional sub-environments including the Kalaweerina ephemeral fluvial channel, TSC avulsion distributary channels and their associated scour pools, the playa, interdune clay pans and side splays. Grainsize analysis, sequential loss on ignition, x-ray diffraction, micropalaeontology and palynology were applied to obtain a comprehensive textural, statistical and compositional dataset.

Distributions of the individual variables are presented as contour maps. Multivariate statistical analysis integrated the data, significant groupings or ‘facies’ were identified and their spatial arrangements are plotted as point maps. These investigations enabled the identification of trends and provenance relationships and the establishment of a preliminary classification scheme for mud-rich facies successions in dryland systems.

Testing the validity of the preliminary classification scheme involves comparison with other modern Lake Eyre TSCs, extrapolation into the subsurface and application to ancient outcrop and core data. The geometries of the fine-grained architectural elements will be investigated and the implications for reservoir modelling pursued.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas