Griffin Coal – Geological Modeling and Resource Estimation

Since Griffin Coal commenced operations in the Collie Coalfields of Western Australia in 1927, it has evolved into a major open cut mining operation, producing 4 million tonnes a year of predominantly low ash, high volatile thermal coal, from its Muja and Ewington mining operations.

SRK has been involved with Griffin Coal since 2005, and most recently was commissioned to:

• Conduct a full and comprehensive review of the existing geological models
• Develop new audited and robust geological models in Minex
• Provide JORC Coal Resource estimates for two of the Collie Basin deposits

The Collie Basin is a bilobate Permian fault-bounded sedimentary basin, its two lobes trending northwest-southeast, lying over Archaean basement rocks of the Yilgarn Craton. Griffin’s coal resources are located in two separate areas of the basin: Ewington in the north and Muja/Buckingham in the south. Resources are contained in the Permian-aged Collie Group, consisting of five formations, three of which are coal-bearing. The oldest of these coal-bearing sequences is the Ewington Coal Measures, followed by the Premier Coal Measures, with the younger Muja Coal Measures sitting on top of the Collie Group. The deposits are complex, with multiple seams of varying quality and thickness (1m – 13m), complex seam splitting, large faults (50m – 250m), rapid changes in dip, and thick barren zones (>50m) between coal measure sequences.

Dr. Gerry McCaughan, SRK Maitland, Pat Hanna, SRK Brisbane and other team members took on the project of reviewing and estimating the coal resources for the Buckingham and Ewington deposits. The first step in the work program involved a full and thorough data validation check of all of the borehole data from the existing Minescape (Mincom) database. The team cross-checked the original data, such as the coal seam intervals, downhole geophysical logs and the laboratory reports, with the data stored in Minescape from which the existing geological models were derived.

When the validation phase was completed, they built new databases in Minex for the Buckingham and Ewington resource
areas. The structure was checked and modified, consistent with borehole data. They then redeveloped five previously independent Minescape geological models into a single integrated Minex geological model for each of the Buckingham and Ewington Resource areas.

SRK provided an independent JORC Resources statement for the integrated Buckingham Resource in April 2007. A JORC Resource statement for the Ewington Coal Deposit was completed in July 2007.

Pat Hanna: phanna@srk.com.au
Gerry McCaughan: gmccaughan@srk.com.au


 

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