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Line 91: − − [[file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig7.png|thumb|{{figure number|7}}Conditions under which true stratigraphic thickness calculated according to its equation will be in error. (a) Variation in stratigraphic thickness is large in relation to the downdip deviation of the well path. (b) Change in dip produces an error in estimation of the true stratigraphic thickness.]] Line 113:
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Depth and thickness conversion (view source)
Revision as of 22:22, 6 March 2014
, 22:22, 6 March 2014→True stratigraphic thickness
[[file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig6.png|thumb|{{figure number|6}}Relationship between true dip of a planar surface and apparent dip of that surface in a plane at an angle of ε to the dip direction.]]
[[file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig6.png|thumb|{{figure number|6}}Relationship between true dip of a planar surface and apparent dip of that surface in a plane at an angle of ε to the dip direction.]]
''True stratigraphic thickness'' (TST) is the thickness of a stratigraphic unit measured in the direction perpendicular to the bedding planes of the unit ([[:file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig2.png|Figure 2]]). It is a critical measure for understanding both the structural and stratigraphic development of a field. The true stratigraphic thickness is derived from the true vertical depths by the following equation:
''True stratigraphic thickness'' (TST) is the thickness of a stratigraphic unit measured in the direction perpendicular to the bedding planes of the unit ([[:file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig2.png|Figure 2]]). It is a critical measure for understanding both the structural and stratigraphic development of a field. The true stratigraphic thickness is derived from the true vertical depths by the following equation:
where MD = measured depth.
where MD = measured depth.
[[file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig7.png|thumb|{{figure number|7}}Conditions under which true stratigraphic thickness calculated according to its equation will be in error. (a) Variation in stratigraphic thickness is large in relation to the downdip deviation of the well path. (b) Change in dip produces an error in estimation of the true stratigraphic thickness.]]
It is important to note the sign convention for the two angles α and δ′. The deviation is measured from the vertical and is positive, whereas the dip is measured from the horizontal and is positive if it is in the same direction as the deviation and negative if the dip is opposite to the deviation.
It is important to note the sign convention for the two angles α and δ′. The deviation is measured from the vertical and is positive, whereas the dip is measured from the horizontal and is positive if it is in the same direction as the deviation and negative if the dip is opposite to the deviation.