Changes

To conduct rock physics diagnostic, it is essential to eliminate as much variations as possible, such as saturation<ref name=9DvorkNur /> because velocity depends on saturation. It is suggested to utilize the velocity log under wet condition to eliminate such variation. Figure 8 shows the total porosity-Vp crossplot of Sand A and Sand B where it can be observed that both sands follow the Friable Sand rock physics model indicating that the change in velocity and porosity of the sands are attributed to the difference in sorting.<ref name=9DvorkNur /> Sand B has lower porosity but slightly higher velocity compared to Sand A due sorting deterioration caused by the clays.  

To conduct rock physics diagnostic, it is essential to eliminate as much variations as possible, such as saturation<ref name=9DvorkNur /> because velocity depends on saturation. It is suggested to utilize the velocity log under wet condition to eliminate such variation. Figure 8 shows the total porosity-Vp crossplot of Sand A and Sand B where it can be observed that both sands follow the Friable Sand rock physics model indicating that the change in velocity and porosity of the sands are attributed to the difference in sorting.<ref name=9DvorkNur /> Sand B has lower porosity but slightly higher velocity compared to Sand A due sorting deterioration caused by the clays.  

As this approach may help interpreting the cause of such change in velocity-porosity relations as a function of subsurface geology in an area, this workflow can be utilized to predict the elastic properties of the rocks away from well control (e.g. to expect what seismic amplitude that corresponds to sand reservoir). Other examples of the application of this method have been reported by several authors[13], [14], [15].  

As this approach may help interpreting the cause of such change in velocity-porosity relations as a function of subsurface geology in an area, this workflow can be utilized to predict the elastic properties of the rocks away from well control (e.g. to expect what seismic amplitude that corresponds to sand reservoir). Other examples of the application of this method have been reported by several authors.<ref>Avseth, P., 2000, Combining rock physics and sedimentology for seismic reservoir characterization of North Sea turbiditsystems, Ph.D dissertation, Stanford University, Palo Alto, California.</ref><ref>Hossain, Z. and L. MacGregor, 2014, Advanced rock-physics diagnostic analysis: A new method for cement quantification: The Leading Edge, v. 33, no. 3, p. 310-316.</ref><ref>Antariksa, G., R. Muammar, and J. Lee, 2021, Performance evaluation of machine learning-based classification with rock-physics analysis of geological lithofacies in Tarakan Basin, Indonesia: Journal of Petroleum Science and Engineering, v. 208, part A, article 109250.</ref>

[[File:GeoWikiWriteOff2021-Muamamr-Figure8.png|thumbnail|Figure 8. Rock physics diagnostic (velocity-porosity relation) of the utilized dataset.]]

[[File:GeoWikiWriteOff2021-Muamamr-Figure8.png|thumbnail|Figure 8. Rock physics diagnostic (velocity-porosity relation) of the utilized dataset.]]

==References==

==References==

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