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Log analysis: lithology (view source)
Revision as of 19:36, 11 January 2016
, 19:36, 11 January 2016no edit summary
* Shaly sandstones
* Shaly sandstones
* Evaporites
* [[Evaporites]]
* Carbonates
* Carbonates
* Metamorphic and igneous rocks
* Metamorphic and igneous rocks
===Carbonates and evaporites===
===Carbonates and evaporites===
Carbonates and evaporites can complicate the interpretation process through the occurrence of fractures and vugs. The three primary porosity devices—the density, compensated neutron, and sonic—respond differently to the presence of fractures and vugs. The density investigates one side of the borehole, while the compensated neutron averages the formation properties around the borehole. The sonic generally does not respond to the secondary porosity associated with either fractures or vugs. This unequal response to these properties can lead to significant problems in determining lithology from any of the methods, as they generally presume that all the porosity devices see a common porosity and lithology.
Carbonates and [[evaporite]]s can complicate the interpretation process through the occurrence of fractures and vugs. The three primary porosity devices—the density, compensated neutron, and sonic—respond differently to the presence of fractures and vugs. The density investigates one side of the borehole, while the compensated neutron averages the formation properties around the borehole. The sonic generally does not respond to the secondary porosity associated with either fractures or vugs. This unequal response to these properties can lead to significant problems in determining lithology from any of the methods, as they generally presume that all the porosity devices see a common porosity and lithology.
Binary mixtures of carbonates or evaporites can be evaluated using graphical crossplot approaches. The density-neutron is generally the most used approach. This method will solve for sandstone-limestone, limestone-dolomite, or dolomite-anhydrite mixtures.
Binary mixtures of carbonates or evaporites can be evaluated using graphical crossplot approaches. The density-neutron is generally the most used approach. This method will solve for sandstone-limestone, limestone-dolomite, or dolomite-anhydrite mixtures.
| 14.12
| 14.12
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|-
| colspan = 13 | ''' EVAPORITES '''
| colspan = 13 | ''' [[EVAPORITE]]S '''
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|-
| Halite
| Halite