* Wells are not straight; even nominally vertical holes commonly show substantial horizontal displacement even if the deviation is too small to produce a large change in true vertical depth ([[:file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig1.png|Figure 1]]). | * Wells are not straight; even nominally vertical holes commonly show substantial horizontal displacement even if the deviation is too small to produce a large change in true vertical depth ([[:file:conversion-of-well-log-data-to-subsurface-stratigraphic-and-structural-information_fig1.png|Figure 1]]). |