Date: Wednesday, 2nd September 2020
Time: 3.30pm to 4.45pm
Location: Online webinar
Cost: FESQ Members and Student Members free
Igneous intrusions in or adjacent to coal seams impact the coal quality directly and cause hazards for both coal mining and coal seam gas extraction. Specifically, sills can be identified at borehole level by wireline logs, e.g. natural gamma-ray, density, and resistivity tools because of their unique petrophysical characteristics. The literature describes also the use of surface seismic surveys as a tool to mapping thick sills distribution. However, there is no precise and efficient way to delineate its horizontal distribution where sills are thin in thickness, e.g. less than 5m. This paper presents an integrated method to predict igneous sill distribution in the Rangal Coal Measures, which are the Late Permian seams from the Blackwater Group in the Bowen Basin, based on petrophysical logs and seismic attributes. In this study, the mean amplitude, half-energy time, and root mean square amplitude from a post-stack 3D seismic survey have been used and compared. Results show that the sill thickness ranges from 0.5m to 6.4m with an average of 2.1m from 12 wells; The prediction results of the sill are depending on the time-depth windows for calculating and mapping the half-energy time and their cut-offs; The half-energy time calculated with a time-depth window of about 40ms with a cut-off of 13.5% yields the highest prediction accuracy of 83%. Compared to the mean amplitude and root mean square, half-energy time is the best surface seismic attribute in predicting horizontal sill distribution. At last, the sequential Gaussian simulation is used in mapping the sill distribution for the whole study area.
Fengde Zhou is a senior geologist at Arrow Energy Pty Ltd. Before joining Arrow, he was a research fellow at the University of Queensland and University of New South Wales and an associate professor at the China University of Geosciences. Fengde received his Ph.D. in Petroleum Engineering. He is an editorial board member of the Journal of Petroleum Science and Engineering. He is interested in reservoir characterisation for conventional and unconventional oil and gas reservoirs.
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