Expert: Keith Patton - 10/28/2009

Question
please giv me every bit of details about what and how microfossils help in petroleum exploration,please giv d ans.as soon as possible

Answer
Maria:

Microfossils are abundant in marine sediments and marine sediments are the prevalent sediments in which petroleum is generated and occurs.

Micro fossils allow the following:

1) Paleoenvironmental analysis in which facies to be determined.  These fossils occur in ocean waters of certain type and temperature and their occurence in sediments indicate the type of depositional enviroment that existed when and where they were deposited.  Their presence in sediments of different compositon, can tell us that both sediments were deposited in the same depositional environment.

2) Biostratigraphy, where rock units are differenciated based on the types of fossils they contain.  They allow dating of sediments.  The different faunal assemblages can indicate a specific time range which allows us to accurately date a sedimentary layer relative to others.  Using a number of overlapping faunal ranges can let us date a layer or depth of sediments without need to refer to the make up of the sediments themselves and create "zones" independent of the changing lithology.  This information is critical to building accurate geologc models of a petroleum province to accertain where source rocks, and potential reservoir rocks may occur and their relationship to tectonic activity that may have resulted in faulting and structure formation.

Other uses include paleoclimatology which helps in determining what climate type prevailed in a depositional basin at the time of deposition.  Biogeography which can yeild information on the geography that prevailed.  They can also yield information on thermal maturation which tells us something of the history of the basin in which the sediments were deposited and whether the petroleum source rocks were buried long enough and deep enough to generate petroleum