Shaly sand rock physics analysis and seismic inversion implication
Adi Widyantoro A and Matthew Saul BA IkonScience.
B IkonScience/UWA.
The APPEA Journal 54(2) 503-503 https://doi.org/10.1071/AJ13076
Published: 2014
Abstract
The analysis of well data from the Enfield field of the Exmouth Sub-basin, WA, indicates that both cementation and pore-filling clay appear to have a stiffening effect on the reservoir sands. The elastic contrast between brine sand and the overlying shale is often small and the large amplitudes observed from seismic data are associated with hydrocarbon content. More detailed rock physics and depth trend analysis of elastic and petrophysical properties, however, indicate significant spatial variability in the cap rock shales across the field with different sand shale mixtures, causing changes in the elastic response of the rock. Areas where shales are softer produce weak seismic amplitude contrasts even with high hydrocarbon saturation; the amplitude response being similar to areas with stiffer shales and brine-filled sands. The variations in reservoir quality are, therefore, masked by the distribution of the brine, oil and gas, as well as the variations in the cap rock. The Enfield rock physics analysis provides an example of reducing amplitude ambiguity over lithology-fluid variation and improves the chance of successful interpretation of the results of seismic inversion.
Adi Widyantoro received his BSc in Geophysical Engineering and MSc in Petroleum Geoscience from the Institut Teknologi Bandung (ITB), Indonesia. He has worked over 16 years with Chevron, mainly involved in 4D seismic operations. He led Gorgon CO2 storage project monitoring and verification (M&V), using rock physics and geomechanical models to manage numerous feasibility studies and field designs for continuous passive 4D, surface and borehole microseismic, crosswell seismic tomography, surface and borehole electromagnetic, microgravity, and Interferometric Synthetic Aperture Radar (InSAR) methods for CO2 injection monitoring. He recently joined Ikonscience and his current projects include QI services for Australian and Southeast Asian companies. |
Matthew Saul recently completed his PhD in Geophysics at the University of Western Australia, focused on the 4D seismic method. He worked part-time for Ikon Science during his PhD, developing efficient workflows for quantitative interpretation projects. He was the recipient of the Best Student Paper presented at the Society of Exploration Geophysicists (SEG) annual conference in Las Vegas, 2012. He is currently working for Chevron Australia. |
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