## Matrix identification using matrix math

Matrix identification Matrix identification (MID) refers to a lithology solution in petrophysics where the bulk density and photoelectric factor are used to estimate the lithologies of the rocks being logged. When a standard triple combo log is run in a well, the tool is utterly naive to the true identity of the rocks it encounters. The bulk density for example really measures electron density, and the neutron log (grossly simplified) measures hydrogen, and neither has any clue about what lithology it is looking at.