Forams

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Forams in the Petroleum Industry

Offshore drilling rig
Offshore drilling rig.
(Credit: Minerals Management Service, US Department of the Interior)

Foram paleontologists who work in the petroleum industry use the same techniques to correlate drilling samples to age as described in the previous page Forams in the Integrated Ocean Drilling Program. Drilling samples are collected, forams are washed and examined under the microscope, and an age is assigned. Foram specialists correlate age within an individual well, and petroleum geologists use these data to correlate age between wells.

However there is a second important piece of information that forams reveal to the paleontologist - environment of deposition. Some foram species lived only in shallow water, some lived in middle depths and some preferred only very deep water. So when foram paleontologists provide the age of a sample, they can often provide the environment of deposition, sometimes called paleo water depth. Geologists use this information to make maps that help them decide where to drill for oil. Let's look at an example.

Locations where foram data have been collected
Locations where foram data have been collected (NW Gulf of Mexico).
(Image used with permission Paleo-Data, Inc.)

Here is a map showing the northwestern Gulf of Mexico. Southeast Texas and southern Louisiana are colored in green, and the offshore Gulf of Mexico is in white. Boxes in the offshore delineate major geographic areas in the Gulf. Notice the tiny red dots. These are more than 8000 individual well spots showing locations where foram data have been collected.

In order to make a map showing water depths at a particular time period, the geologist first needs to sort the foram data by age. Let's say he is interested in the Discoaster C biozone (age approximately 6.4 million years before present). Only those wells with Discoaster C data are selected. Now, rather than 8000 wells, he may only have 3000 wells to work with. At those well spots, he posts the environment of deposition interpreted from the forams - very shallow water, shallow, moderate, deep, and very deep. Next, areas of the map with the same environment are colored in.

Discoaster C foram paleoenvironmental map
Discoaster C foram paleoenvironmental map.
(Image used with permission Paleo-Data, Inc.)

That was the method used to make this Discoaster C paleoenvironment map. Just like the previous map, southeast Texas and southern Louisiana are colored green. The other colors indicate water depths for sediments deposited approximately 6.4 million years ago, light blue for shallow water, blue-green for moderately deep, pink for deep and purple for very deep. Since different types of oil deposits are found in deep water versus shallow water, this map is an important step in deciding where to drill new wells.

Go to Forams Highlight Pollution to see other foram applications.

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Revised on: January 15, 2005

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