--> Abstract: A New Subsurface Mapping Technique as Applied to Extensional and Salt Structures, by R. Bischke; #91004 (1991)

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A New Subsurface Mapping Technique as Applied to Extensional and Salt Structures

BISCHKE, RICHARD, Subsurface Consultants, Lafayette, LA

A new mapping technique is presented that readily defines expansion rates along normal faults, and relative growth sedimentation rates associated with salt deformation or rollovers. It can be applied to E-log correlations to rapidly check for miss-correlations or the presence of faulting, and requires no calculations in its application to structures. After the sedimentary sequences have been correlated between two wells, the vertical distances that the sequences have been displaced (delta d) by the growth deformation are plotted against the corresponding correlative depths (d) in the structurally higher well. If the ages of the units are known, then the data can be plotted on a (delta d/t)/t diagram (which is acceleration), or if the ages are unknown on a delta d/d diagram. Rapid grow h results in large accelerations in the sedimentation rate or in steep slopes on the (delta d/t)/t or delta d/d diagrams. This condition often results in good reservoir units as was shown by Thorsen. The delta d/d diagrams can be integrated (summed) to show that they map the growth history of the deformation, and thus large growth faults or salt ridges are likely to exhibit similar growth history maps along trend that can be utilized in regional correlation studies. As the method is very sensitive to changes in rate, it can be used to determine when structures start and cease to grow; thereby defining the depths (times) at which hydrocarbons enter structures.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)