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→MID crossplot
===MID crossplot===
===MID crossplot===
[[file:difficult-lithologies_fig2.png|thumb|{{figure number|2}}UMAA determination chart. © Schlumberger Educational Services, 1989.]]
[[file:difficult-lithologies_fig2.png|thumb|300px|{{figure number|2}}UMAA determination chart. © Schlumberger Educational Services, 1989.]]
The MID or ''m''atrix ''id''entification crossplot uses the apparent volumetric cross section (UMAA) and the apparent matrix grain density (RHOMAA) to identify minerals. UMAA represents the projection of the volumetric photoelectric absorption index, U (the product of Pe and electronic density), to the value at zero porosity. RHOMAA results from a mathematical projection of the bulk density of an interval to its value at zero porosity. These projections to zero porosity effectively eliminate variance due to porosity, resulting in a variance mainly due to lithology.
The MID or ''m''atrix ''id''entification crossplot uses the apparent volumetric cross section (UMAA) and the apparent matrix grain density (RHOMAA) to identify minerals. UMAA represents the projection of the volumetric photoelectric absorption index, U (the product of Pe and electronic density), to the value at zero porosity. RHOMAA results from a mathematical projection of the bulk density of an interval to its value at zero porosity. These projections to zero porosity effectively eliminate variance due to porosity, resulting in a variance mainly due to lithology.