Changes

[[File:GeoWikiWriteOff2021-Muamamr-Figure1.png|framed|center|{{Figure number|1}}Well log section showing the difference of rock physics properties between clean sandstone (Sand A), clayey sandstone (Sand B), and claystone.]]

[[File:GeoWikiWriteOff2021-Muamamr-Figure1.png|framed|center|{{Figure number|1}}Well log section showing the difference of rock physics properties between clean sandstone (Sand A), clayey sandstone (Sand B), and claystone.]]

As the available dataset is composed of gas saturated sands, one can model the expected elastic properties under wet condition by utilizing Gassmann’s Fluid Substitution.<ref name=2Gassman>Gassmann, F., 1951, Elastic Waves Through a Packing of Spheres: Geophysics, v. 16, no. 4, p. 673-685.</ref><ref name=2Dvorkinetal>Dvorkin, J., G. Mavko, and B. Gurevich, B., 2007, Fluid substitution in shaley sediment using effective porosity: Geophysics, v. 72, no. 3, p. O1-O8.</ref> The result of fluid substitution on Sand A and Sand B are shown on [[:File:GeoWikiWriteOff2021-Muamamr-Figure2.png|Figure 2]]. It can be observed that wet sands are acoustically harder (higher Vp and Rho, but with minor change in Vs) compared to gas sands, some of these wet sands are acoustically harder than the claystones.  

As the available dataset is composed of gas saturated sands, one can model the expected elastic properties under wet condition by utilizing Gassmann’s Fluid Substitution.<ref name=2Gassman>Gassmann, F., 1951, Elastic Waves Through a Packing of Spheres: Geophysics, v. 16, no. 4, p. 673-685.</ref><ref name=3Dvorkinetal>Dvorkin, J., G. Mavko, and B. Gurevich, B., 2007, Fluid substitution in shaley sediment using effective porosity: Geophysics, v. 72, no. 3, p. O1-O8.</ref> The result of fluid substitution on Sand A and Sand B are shown on [[:File:GeoWikiWriteOff2021-Muamamr-Figure2.png|Figure 2]]. It can be observed that wet sands are acoustically harder (higher Vp and Rho, but with minor change in Vs) compared to gas sands, some of these wet sands are acoustically harder than the claystones.  

[[File:GeoWikiWriteOff2021-Muamamr-Figure2.png|framed|center|{{Figure number|2}}Fluid substitution result of Sand A and Sand B.]]

[[File:GeoWikiWriteOff2021-Muamamr-Figure2.png|framed|center|{{Figure number|2}}Fluid substitution result of Sand A and Sand B.]]

[[File:GeoWikiWriteOff2021-Muamamr-Figure3.png|framed|center|{{Figure number|3}}AI-Vp/Vs crossplot of the utilized dataset.]]  

[[File:GeoWikiWriteOff2021-Muamamr-Figure3.png|framed|center|{{Figure number|3}}AI-Vp/Vs crossplot of the utilized dataset.]]  

On LR-MR crossplot (Figure 4), it can be observed that claystones have the higher LR but lower MR compared to Sand A and Sand B, whereas Sand A has the lowest LR (attributed to the presence of gas that is easily compressible) but similar MR compared to Sand B as this property is more sensitive towards the change in lithology rather than fluid content. In the case of wet sands, the LR is similar to that of the claystones but with higher MR, similar to the gas sands.  

On LR-MR crossplot ([[:File:GeoWikiWriteOff2021-Muamamr-Figure4.png|Figure 4]]), it can be observed that claystones have the higher LR but lower MR compared to Sand A and Sand B, whereas Sand A has the lowest LR (attributed to the presence of gas that is easily compressible) but similar MR compared to Sand B as this property is more sensitive towards the change in lithology rather than fluid content. In the case of wet sands, the LR is similar to that of the claystones but with higher MR, similar to the gas sands.  

These results suggest the validity of rock physics analysis to identify the presence of reservoir, where it successfully discriminate between Sand A, Sand B, wet sands and claystones. It should be noted that each property has their own functions and limitations. These crossplots can be utilized to determine the rock physics cut-off parameter for each lithology and later applied as a quality control for more advance geophysical methods such as seismic inversion.<ref name="1Goodwayetal" /><ref name=4Avsethetal>Avseth, P., A. Janke, and F. Horn, 2016, AVO Inversion in Exploration – Key Learnings from a Norwegian Sea Prospect: The Leading Edge, v. 35, no. 5, p. 405-414.</ref><ref name=5Samsetal>Sams, M., P. Begg, and T. Manapov, 2017, Seismic Inversion of a Carbonate Buildup: A Case Study: Interpretation, v. 5, no. 4, p. T641-T652.</ref>

These results suggest the validity of rock physics analysis to identify the presence of reservoir, where it successfully discriminate between Sand A, Sand B, wet sands and claystones. It should be noted that each property has their own functions and limitations. These crossplots can be utilized to determine the rock physics cut-off parameter for each lithology and later applied as a quality control for more advance geophysical methods such as seismic inversion.<ref name="1Goodwayetal" />[4], [5].

==Predicting Reservoir’s Seismic Response==

==Predicting Reservoir’s Seismic Response==

==References==

==References==

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6 Aki, K. and Richards, P. G., 1980, Quantitative Seismology: Theory and Methods, W. H. Freeman and Co.  

6 Aki, K. and Richards, P. G., 1980, Quantitative Seismology: Theory and Methods, W. H. Freeman and Co.