Palaeomagnetic core re-orientation

Directional data from cores must be referred to geographic North before they can be used in reservoir models. Few cores are oriented during drilling, but fortunately most can be re-oriented subsequently by the palaeomagnetic method. This uses the remanent magnetism of the rock to define North.

The horizontal component, JH, of the mean palaeomagnetic vector, JT, in a run of core defines the direction of North within that run. Directional properties of the core (such as Fracture plane orientations ) are returned to their in situ orientations by effectively turning the core about its axis until JH points to geographic North.