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[2], [3]). The result of fluid substitution on Sand A and Sand B are shown on 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[2], [3]). 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|thumbnail|Figure 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.]]

These property differences can be easily highlighted on AI-Vp/Vs and LR-MR crossplots. On AI-Vp/Vs crossplot (Figure 3), it can be observed that claystones have higher AI and Vp/Vs compared with Sand A and Sand B (Sand A has the lowest AI and Vp/Vs). Some parts of Sand B have overlapping AI with claystone and therefore may exhibit uncertainties in discriminating the reservoir and non-reservoir lithology by utilizing this property. Vp/Vs on other hand, successfully separated the reservoir and non-reservoir lithology. In the case of wet sands, it can be observed that these sands have higher AI but smaller Vp/Vs. It can be concluded that AI may have some uncertainties to discriminate the reservoir and non-reservoir lithology (with the exception of clean gas sand), whereas Vp/Vs has a better performance result in separating them.  

These property differences can be easily highlighted on AI-Vp/Vs and LR-MR crossplots. On AI-Vp/Vs crossplot ([[:File:GeoWikiWriteOff2021-Muamamr-Figure3.png|Figure 3]]), it can be observed that claystones have higher AI and Vp/Vs compared with Sand A and Sand B (Sand A has the lowest AI and Vp/Vs). Some parts of Sand B have overlapping AI with claystone and therefore may exhibit uncertainties in discriminating the reservoir and non-reservoir lithology by utilizing this property. Vp/Vs on other hand, successfully separated the reservoir and non-reservoir lithology. In the case of wet sands, it can be observed that these sands have higher AI but smaller Vp/Vs. It can be concluded that AI may have some uncertainties to discriminate the reservoir and non-reservoir lithology (with the exception of clean gas sand), whereas Vp/Vs has a better performance result in separating them.  

[[File:GeoWikiWriteOff2021-Muamamr-Figure3.png|thumbnail|Figure 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 (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.