Changes

===Mechanical core orientation===

===Mechanical core orientation===

Mechanical core orientation relies on a premeasured relationship being maintained between the compass lug at the top of the core barrel and the reference scribe at the bottom of the core barrel. Depending on barrel length, there are one or more makeup joints between the two components subject to torquing during coring rotation. Furthermore, the grooves in the core tend to precess along the length of the core. Hence, orientation accuracy in part depends on the ability to recognize and quantify these effects. Nelson et al.<ref name=pt03r37 /> and Bleakly et al.b<ref name=pt03r11>Bleakly, D. C., Van Alstine, D. R., Packer, D. R., 1985b, How to evaluate orientation data, quality control in technology: Oil and Gas Journal, v. 83, n. 49, p. 46–54.</ref> describe graphic and overlay techniques as well as wellsite procedures that can be used to recognize and partially correct for such problems.

Mechanical core orientation relies on a premeasured relationship being maintained between the compass lug at the top of the core barrel and the reference scribe at the bottom of the core barrel. Depending on barrel length, there are one or more makeup joints between the two components subject to torquing during coring rotation. Furthermore, the grooves in the core tend to precess along the length of the core. Hence, orientation accuracy in part depends on the ability to recognize and quantify these effects. Nelson et al.<ref name=pt03r37 /> and Bleakly et al.b<ref name=pt03r11>Bleakly, D. C., D. R. Van Alstine, and D. R. Packer, 1985b, How to evaluate orientation data, quality control in technology: Oil and Gas Journal, v. 83, n. 49, p. 46–54.</ref> describe graphic and overlay techniques as well as wellsite procedures that can be used to recognize and partially correct for such problems.

===Paleomagnetic core orientation===

===Paleomagnetic core orientation===