Changes

An assumption made here is that the dip of the top and bottom surfaces is essentially the same. The more closely the wellbore direction approximates the dip direction, the more sensitive the thickness calculation will be to stratigraphic thickness changes (see [[:file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig7.png|Figure 7a]]). The assumption is also violated if the well traverses a zone of strong curvature in the rock such that dip changes rapidly ([[:file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig7.png|Figure 7b]]). Such changes can be corrected for if sufficient data are available, but are commonly too small to be of significance.

An assumption made here is that the dip of the top and bottom surfaces is essentially the same. The more closely the wellbore direction approximates the dip direction, the more sensitive the thickness calculation will be to stratigraphic thickness changes (see [[:file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig7.png|Figure 7a]]). The assumption is also violated if the well traverses a zone of strong curvature in the rock such that dip changes rapidly ([[:file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig7.png|Figure 7b]]). Such changes can be corrected for if sufficient data are available, but are commonly too small to be of significance.

To calculate a TST requires survey information as well as some measure of the dip of the beds. Dip can be derived from dipmeter logs (with some caution) (see “[[Dipmeters]]”) or from maps of geological structure. In some instances, TST maps reveal anomalies in well correlation, resulting in iterative refinement of structural and stratigraphic models. It must be recognized that, where folding occurs, stratigraphic thickness trends on maps of true stratigraphic thickness will be distorted by compression.

To calculate a TST requires survey information as well as some measure of the dip of the beds. Dip can be derived from dipmeter logs (with some caution) (see [[Dipmeters]]) or from maps of geological structure. In some instances, TST maps reveal anomalies in well correlation, resulting in iterative refinement of structural and stratigraphic models. It must be recognized that, where folding occurs, stratigraphic thickness trends on maps of true stratigraphic thickness will be distorted by compression.

==True vertical thickness==

==True vertical thickness==