Changes

  | part    = Predicting the occurrence of oil and gas traps

  | part    = Predicting the occurrence of oil and gas traps

  | chapter = Applied paleontology

  | chapter = Applied paleontology

  | frompg  = 17-1

  | frompg  = 17-5

  | topg    = 17-65

  | topg    = 17-5

  | author  = Robert L. Fleisher, H. Richard Lane

  | author  = Robert L. Fleisher, H. Richard Lane

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch17/ch17.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch17/ch17.htm

  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

}}

}}

Durable microscopic fossils have a wide distribution in time and space, and their rapid and irreversible evolution and morphologically distinctive evolutionary stages make them excellent tools for measuring relative geologic time. They are particularly useful in hydrocarbon exploration because they can be recovered from both cuttings and cores. Microfossil groups that are too rare in most sedimentary rocks, too limited in overall stratigraphic or paleoenvironmental range, or too poorly understood to be broadly useful in industrial application are not considered in this section.

Durable microscopic fossils have a wide distribution in time and space, and their rapid and irreversible evolution and morphologically distinctive evolutionary stages make them excellent tools for measuring relative geologic time. They are particularly useful in hydrocarbon exploration because they can be recovered from both [[Mudlogging: drill cuttings analysis|cuttings]] and [[Core description|cores]]. Microfossil groups that are too rare in most sedimentary rocks, too limited in overall [[Stratigraphic and geographic distribution of fossils|stratigraphic]] or [[Paleoenvironmental analysis|paleoenvironmental]] range, or too poorly understood to be broadly useful in industrial application are not considered in this section.

==Utility of microfossils in exploration==

==Utility of microfossils in exploration==

In an operational environment, microfossils can be examined shortly after being brought to the surface in ditch samples. Well-site analysis permits immediate identification of stratigraphic levels and drilling objectives, minimizing drilling time. Microfossils can also be used to accurately predict overpressured zones in advance of the drill bit.

In an operational environment, microfossils can be examined shortly after being brought to the surface in [[Mudlogging: drill cuttings analysis|cuttings]]. Well-site analysis permits immediate identification of stratigraphic levels and drilling objectives, minimizing drilling time. Microfossils can also be used to accurately predict [[Overpressure causes|overpressured]] zones in advance of the drill bit.

In the office, microfossil studies allow precise local, regional, and global time-stratigraphic correlations that help in hydrocarbon prospect and trend delineation, regional stratigraphic and geologic studies, and exploitation evaluations. Analysis of microfossils helps scientists recognize paleoenvironmental distributions, which in turn helps us interpret sequence stratigraphy and reconstruct the paleogeography and paleoclimate. Some microfossils function as “paleothermometers” by undergoing irreversible color changes with postburial heating. As such, they indicate hydrocarbon maturity levels.

In the office, microfossil studies allow precise local, regional, and global [[Biostratigraphic correlation and age determination|time-stratigraphic correlations]] that help in hydrocarbon prospect and trend delineation, regional stratigraphic and geologic studies, and exploitation evaluations. Analysis of microfossils helps scientists recognize [[Paleoenvironmental analysis|paleoenvironmental]] distributions, which in turn helps us interpret [[sequence stratigraphy]] and reconstruct the [[paleogeography]] and [[Paleoclimatology|paleoclimate]]. Some microfossils function as “[[Thermal maturation|paleothermometers]]” by undergoing irreversible color changes with postburial heating. As such, they indicate hydrocarbon maturity levels.

==Principal microfossils==

==Principal microfossils==

|-

|-

| Calcareous

| Calcareous

| Foraminifera, Ostracodes, Calcareous Nannofossils

| [[Calcareous_microfossils#Calcareous_foraminifera|Foraminifera]], [[Calcareous_microfossils#Ostracods|ostracods]], [[Calcareous_microfossils#Calcareous_nannofossils|calcareous nannofossils]]

|-

|-

| Agglutinated

| Agglutinated

| Foraminifera

| [[Agglutinated_microfossils#Agglutinated_foraminifera|Foraminifera]]

|-

|-

| Siliceous

| Siliceous

| Radiolarians, Diatoms, Silicoflagellates

| [[Siliceous_microfossils#Radiolarians|radiolarians]], [[Siliceous_microfossils#Diatoms|diatoms]], [[Siliceous_microfossils#Silicoflagellates|silicoflagellates]]

|-

|-

| Phosphatic

| Phosphatic

| Conodonts

| [[Phosphatic_microfossils#Conodonts|conodonts]]

|-

|-

| Organic walled

| Organic walled

| Chitinozoans, Pollen, Spores, Acritarchs, Dinoflagellates (collectively, Palynomorphs)

| [[Organic-walled_microfossils#Chitinozoans|chitinozoans]], [[Organic-walled_microfossils#Spores_and_pollen|pollen and spores]], [[Organic-walled_microfossils#Acritarchs|acritarchs]], [[Organic-walled_microfossils#Dinoflagellates|dinoflagellates]] (collectively, palynomorphs)

|}

|}

==See also==

==See also==

* [[Calcareous microfossils]]

* [[Calcareous microfossils]]

* [[Agglutinated microfossils]]

* [[Agglutinated microfossils]]

* [[Siliceous microfossils]]

* [[Siliceous microfossils]]

* [[Phosphatic microfossils]]

* [[Phosphatic microfossils]]

* [[Organic-walled microfossils]]

* [[Palynomorphs (organic-walled microfossils)]]

* [[Palynofacies and kerogen analysis]]

==External links==

==External links==

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

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

[[Category:Applied paleontology]]

[[Category:Applied paleontology]]