Changes

# Friable Sand<ref name=9DvorkNur /> = this rock physics model (unconsolidated line) shows the change in velocity-porosity relations as the sorting deteriorates. Well sorted sands are interpreted to have higher porosity and therefore, lower velocity. Grain deterioration decreases the porosity but only slightly stiffening the rock.  

# Friable Sand<ref name=9DvorkNur /> = this rock physics model (unconsolidated line) shows the change in velocity-porosity relations as the sorting deteriorates. Well sorted sands are interpreted to have higher porosity and therefore, lower velocity. Grain deterioration decreases the porosity but only slightly stiffening the rock.  

# Friable Shale<ref name=9DvorkNur /> = similar rock physics model as above but the grain is modeled to be shale instead of sand.  

# Friable Shale<ref name=9DvorkNur /> = similar rock physics model as above but the grain is modeled to be shale instead of sand.  

# Contact Cement[11]= this rock physics model describes the change in velocity-porosity relations due to the cementation at grain contacts, effectively “gluing” the grains together. The cement at grain contacts significantly reinforcing the rock (large increase in velocity) but with small decrease of porosity.  

# Contact Cement<ref>Dvorkin, J., A. Nur, and H. Yin, 1994, Effective properties of cemented granular material: Mechanics of Materials, v. 18, no. 4, p. 351-366. </ref> = this rock physics model describes the change in velocity-porosity relations due to the cementation at grain contacts, effectively “gluing” the grains together. The cement at grain contacts significantly reinforcing the rock (large increase in velocity) but with small decrease of porosity.  

# Constant Cement[12]= explains a sand body with varying sorting and porosity but with similar amount of cement in which the decrease of porosity is attributed to sorting deterioration. This model is an expansion of Friable Sand model that takes into account the impact of cement to the velocity-porosity relations.<ref name=10Avsethetal />   

# Constant Cement<ref>Avseth, P., J. Dvorkin, G. Mavko, and J. Rykkje, 2000, Rock physics diagnostic of North Sea sands: Link between microstructure and seismic properties: Geophysical Research Letters, v. 27, p. 2761-2764.</ref> = explains a sand body with varying sorting and porosity but with similar amount of cement in which the decrease of porosity is attributed to sorting deterioration. This model is an expansion of Friable Sand model that takes into account the impact of cement to the velocity-porosity relations.<ref name=10Avsethetal />   

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.  

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11 Dvorkin, J., Nur, A. and Yin, H., 1994, Effective Properties of Cemented Granular Material, Mechanics of Materials, 18, pp. 351-366.

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12 Avseth, P., Dvorkin, J., Mavko, G. and Rykkje, J., 2000, Rock Physics Diagnostic of North Sea Sands: Link Between Microstructure and Seismic Properties, Geophysical Research Letters, 27, pp. 2761-2764.

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13 Avseth, P., 2000, Combining Rock Physics and Sedimentology for Seismic Reservoir Characterization of North Sea Turbidite Systems, Ph.D Dissertation, Stanford University.  

13 Avseth, P., 2000, Combining Rock Physics and Sedimentology for Seismic Reservoir Characterization of North Sea Turbidite Systems, Ph.D Dissertation, Stanford University.