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==Identifying the occurrence of difficult lithologies==

==Identifying the occurrence of difficult lithologies==

[[file:difficult-lithologies_fig1.png|thumb|{{figure number|1}}M-N crossplot for mineral identification. Copyright: Schlumberger Well Services, 1979.]]

[[file:difficult-lithologies_fig1.png|thumb|{{figure number|1}}M-N crossplot for mineral identification. © Schlumberger Well Services, 1979.]]

The occurrence of difficult lithologies can be identified from the following sources:

The occurrence of difficult lithologies can be identified from the following sources:

* Analysis of log responses

* Analysis of log responses

The methods to determine the occurrence of difficult lithologies from the first six sources just listed are not covered in this article. (For information on these sources, see “[[Mudlogging: Drill cuttings analysis]]” and “[[Mudlogging: The mudlog]]”; also see “[[Core description]]”.)

The methods to determine the occurrence of difficult lithologies from the first six sources just listed are not covered in this article. (For information on these sources, see “[[Mudlogging: drill cuttings analysis]]” and “[[Mudlogging: the mudlog]]”; also see “[[Core description]]”.)

Identifying the occurrence of difficult lithologies from logs can be formidable. Two crossplot techniques are commonly used to identify the occurrence of mineralogies: (1) the M-N crossplot and (2) the MID crossplot.

Identifying the occurrence of difficult lithologies from logs can be formidable. Two crossplot techniques are commonly used to identify the occurrence of mineralogies: (1) the M-N crossplot and (2) the MID crossplot.