Changes

{{publication  

{{publication  

  | image  = exploring-for-oil-and-gas-traps.png

  | image  = exploring-for-oil-and-gas-traps.png

  | part    = Predicting the occurrence of oil and gas traps

  | part    = Predicting the occurrence of oil and gas traps

  | chapter = Exploring for stratigraphic traps

  | chapter = Exploring for stratigraphic traps

  | frompg  = 21-1

  | frompg  = 21-23

  | topg    = 21-68

  | topg    = 21-24

  | author  = John C. Dolson, Mike S. Bahorich, Rick C. Tobin, Edward A. Beaumont, Louis J. Terlikoski, Michael L. Hendricks

  | author  = John C. Dolson, Mike S. Bahorich, Rick C. Tobin, Edward A. Beaumont, Louis J. Terlikoski, Michael L. Hendricks

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch21/ch21.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch21/ch21.htm

==Procedure==

==Procedure==

The table below lists steps for a geometrical analysis of the sedimentary section of a basin in seismic sections, outcrop sections, and well log sections.

The table below lists steps for a geometrical analysis of the sedimentary section of a basin in seismic sections, [http://www.merriam-webster.com/dictionary/outcrop outcrop] sections, and well log sections.

# Identify [[Unconformity|unconformities]] (third-order sequence boundaries) in seismic sections, outcrop sections, and regional well log sections.

# Identify [[Unconformity|unconformities]] (third-order sequence boundaries) in seismic sections, outcrop sections, and regional well log sections.

==Identifying unconformities==

==Identifying unconformities==

[[Unconformity|Unconformities]] are [[Hierarchy of sequences|third-order]] sequence boundaries. They are generally regional onlap surfaces. In ''basinal settings'', they are characterized by onlap of [[allochthon]]ous deposits (i.e., debris flows, slump deposits, turbidites), [[Well_log_sequence_analysis#Parasequence_stacking_patterns|prograding]] deltas, carbonate platform deposits, or evaporites. In ''shallow-water or nonmarine settings'', they are characterized by onlap of strata deposited in fluvial, deltaic, or nearshore marine or peritidal environments.<ref name=ch21r48>Weber, L., J., Sarg, J., F., Wright, F., M., 1995, Sequence stratigraphy and reservoir delineation of the middle Pennsylvanian (Desmoinesian), Paradox basin and Aneth field, southwestern U., S., A., in Read, J., F., Weber, L., J., Sarg, J., F., Wright, F., M., eds., Milankovitch Sea-Level Changes, Cycles, and Reservoirs on Carbonate Platforms in Greenhouse and Ice-House Worlds: SEPM Short Course No. 35, 79 p.</ref> We can identify unconformities using stratigraphic evidence and individual well evidence.

[[Unconformity|Unconformities]] are [[Hierarchy of sequences|third-order]] sequence boundaries. They are generally regional onlap surfaces. In ''basinal settings'', they are characterized by onlap of [[allochthon]]ous deposits (i.e., debris flows, slump deposits, turbidites), [[Well_log_sequence_analysis#Parasequence_stacking_patterns|prograding]] deltas, carbonate platform deposits, or evaporites. In ''shallow-water or nonmarine settings'', they are characterized by onlap of strata deposited in fluvial, deltaic, or nearshore marine or peritidal environments.<ref name=ch21r48>Weber, L. J., J. F. Sarg, and F. M. Wright, 1995, Sequence stratigraphy and reservoir delineation of the middle Pennsylvanian (Desmoinesian), Paradox basin and Aneth field, southwestern U.S.A., in J. F. Read, L. J. Weber, J. F. Sarg, and F. M. Wright, eds., Milankovitch Sea-Level Changes, Cycles, and Reservoirs on Carbonate Platforms in Greenhouse and Ice-House Worlds: SEPM Short Course No. 35, 79 p.</ref> We can identify unconformities using stratigraphic evidence and individual well evidence.

===Stratigraphic evidence===

===Stratigraphic evidence===

===Individual well evidence===

===Individual well evidence===

* Dipmeter changes

* [[Dipmeter]] changes

* [[Basic open hole tools#Gamma ray|Gamma-ray]] log changes in response to increased uranium concentration at exposure surfaces

* [[Basic open hole tools#Gamma ray|Gamma-ray]] log changes in response to increased uranium concentration at exposure surfaces

* Vertical breaks in thermal maturity profiles (i.e., abrupt vertical change in vitrinite reflection values)

* Vertical breaks in thermal maturity profiles (i.e., abrupt vertical change in [[vitrinite reflectance|vitrinite reflection]] values)

* Changes in lithology as seen in cores that indicate subaerial exposure or nondeposition, as evidenced by the following:

* Changes in lithology as seen in cores that indicate subaerial exposure or nondeposition, as evidenced by the following:

** Paleosols and weathered horizons

** Paleosols and weathered horizons

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Exploring for stratigraphic traps]]

[[Category:Exploring for stratigraphic traps]]