Favorite Geology Word: Isopach (Accretionary Wedge #35)

This my first post to  Accretionary Wedge Geoscience Blog Carnival. The current topic for AW#35 is “ What’s Your Favorite Geology Word? ” hosted by .

My Favorite Geology Word Is – Isopach

Definition: A contour that connects points of equal thickness. Commonly, the isopachs, or contours that make up an isopach map, display the stratigraphic thickness of a rock unit as opposed to the true vertical thickness. Isopachs are true stratigraphic thicknesses; i.e., perpendicular to bedding surfaces.(Source)

Pronunciation:  ‘ī-sə-ˌpak

Date:  approximately 1918

Structure map includes an isopach of the reservoir with contours shown in red dashes. Venezuela Well Evaluation Conference, 1997, page 2-26

Isopach is a Map of the thickness variation of a stratigraphic unit; used in geological exploration for oil and for underground structural analysis.  I always love to draw it due to it’s importance to evaluate a reservoir or aquifer in subsurface geology.

My favorite Example

Five wells were drilled (I-V), which well no. (I) at the middle with respect to the others as shown on the sketch. The vertical thickness in meters of sands formation in these wells are as follows:

Well no

I

II

III

IV

V

Sands

25

100

75

100

75

Sandstone in this example is oil-bearing bed we need to know which direction it’s thickness increased to produce the maximum oil production from it.

Isopach map for sands formation with contour interval 20 CM

The thickness of sands formation incease outer the center

thickness in NE-SW direction is the maximum  100 m

and in NW- SE direction is 75 m

Isopach map helped us in this example to determine the direction that the thickness of sands formation increased.

For a list of other geologists’ favorite words, check out the Accretionary Wedge #35.

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