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→Example density-neutron log
==Example density-neutron log==
==Example density-neutron log==
[[file:predicting-reservoir-system-quality-and-performance_fig9-30.png|300px|thumb|{{figure number|1}}Example log recorded in sandstone units. From Alberty, 1994; courtesy AAPG.]]
[[file:predicting-reservoir-system-quality-and-performance_fig9-30.png|300px|thumb|{{figure number|1}}Example log recorded in sandstone units. From Alberty;<ref name=Alberty>Alberty, M. W., 1994, Standard interpretation; part 4—wireline methods, in D. Morton- Thompson and A. M. Woods, eds., Development Geology Reference Manual: AAPG Methods in Exploration Series 10, p. 180–185.</ref> courtesy AAPG.]]
The example log in [[:file:predicting-reservoir-system-quality-and-performance_fig9-30.png|Figure 1]] was recorded in sandstone units. Where the density and neutron logs nearly track together, the formation lithology normally is assumed to be sandstone (in the figure below). The slight separations may be due to changes in lithology as in more shale/clay. Where the density and neutron logs separate, either the lithology is different (neutron porosity > density porosity) from the recorded lithologic units (points 1 and 5) or gas is present (points 2, 3, and 4). A density–neutron crossplot resolves the separation problem (see [[:file:predicting-reservoir-system-quality-and-performance_fig9-31.png|Figure 2]]).
The example log in [[:file:predicting-reservoir-system-quality-and-performance_fig9-30.png|Figure 1]] was recorded in sandstone units. Where the density and neutron logs nearly track together, the formation lithology normally is assumed to be sandstone (in the figure below). The slight separations may be due to changes in lithology as in more shale/clay. Where the density and neutron logs separate, either the lithology is different (neutron porosity > density porosity) from the recorded lithologic units (points 1 and 5) or gas is present (points 2, 3, and 4). A density–neutron crossplot resolves the separation problem (see [[:file:predicting-reservoir-system-quality-and-performance_fig9-31.png|Figure 2]]).