Definition - What does Isopachous Line mean?
An Isopachous Line is a line that forms a contour by connecting points of equal depth or thickness. These lines connect points that have equal thickness and are in a stratigraphic unit. A series of isopachous lines form an isopach map which shows the true stratigraphic thickness of a rock layer. These lines help in estimating the in-place volumes of hydrocarbons that are present in a reservoir.
Petropedia explains Isopachous Line
Isopachous lines form the basis of Isopach maps. These maps are helpful in displaying the true stratigraphic thickness of sediments deposited either onshore or offshore. This is the reason why Isopachous maps are at times also called TST (True Stratigraphic Thickness) maps.
An isopach map consists of isopachous lines which connect points of equal depth or thickness and display the stratigraphic thickness of a formation as opposed to the true vertical thickness. Isopachous lines and isopach maps help in well positioning, well engineering and in understanding the gradient of the strata from the crestel level to contact level of stored liquid, i.e., at the levels crude oil comes in contact with water in the reservoir.