TABLE 3-1 Examples of Collectors of Geoscience Data and Collections, and Their Purpose

Volume of Physical Samplesa

Public Sector

Private Sector

Entity

Purpose

Entity

Purpose

Largerb

Smithsonian Institution

Research, education

Large Petroleum Co.

Resource extraction, research

 

U.S. Geological Survey

Research, education, resource evaluation

 

 

Large State Geol. Survey

Research, regulatory

 

 

Department of Energy

Research, site characterization

Large Mining Co.

Resource extraction

 

U.S. Army Corps of Engineers

Site characterization

 

 

Ocean Drilling Program

Research, education

 

 

Continental Drilling Program

Research, education

Independent Oil Co.

Resource extraction

 

U.S. Nuclear Regulatory Commission

Site characterization

Small Mining Co.

Private Museums

Resource extraction

Education, research

 

National Ice Core Lab

Research, education

 

 

University

Education, research

 

 

Public Museum

Education, research

 

 

Water Management District

Regulatory, management

Consulting Firm

Various

 

Minerals Management Service

Regulatory

 

 

Small State Geol. Survey

Research, regulatory

 

 

Bureau of Land Management

Regulatory

 

Smaller

 

Individuals

Hobby, investment

aVolume is estimated only from physical data retained by each group (predominantly cores, cuttings, samples) (see Table 2-1).

bThese examples are ranked in approximate order of volume of physical geoscience collections held by each entity.

examining cores, or indirectly from examining other subsurface data. However, permeability, which is a measure of the connectivity of the pore spaces (i.e., how easily a fluid can move through the rock or sediment), can only be measured directly from examination of actual rock samples, which are recovered only in cores and cuttings from the deep subsurface. To derive particular kinds of information, cores and cuttings are subjected to a wide variety of analytical techniques, including simple visual inspection, X-raying, CT scans, thin sections, and permeability tests.

Ice cores and sediment cores are collected primarily because they preserve a record of past environmental change. For example, sediment cores from the ocean floor can reveal changes in ocean chemistry and, indirectly, temperature through time. Ice cores preserve ancient air bubbles, among many other useful records, allowing the determination of former levels of atmospheric carbon dioxide (CO2) against which modern levels can be compared (see Sidebar 1-7). Our understanding of global change is grounded in the discoveries made from collecting ice and sediment cores and the historical record unlocked by those discoveries.

After cores are taken at the drill site, they usually are stored in cardboard or wooden boxes. Volume commonly is expressed as the number of boxes, or, in the case of ice and sediment cores, the number of tubes. Boxes vary considerably in size, as does the amount of core each contains. A widely used box size is approximately 3 feet long and holds three to five 3-foot lengths of rock core (9 to 15 linear feet, total) side by side within the box. Segments of ice and sediment cores are stored singly in 3-foot-long tubes. Depending on the density of the rock, sediment, or ice, each container can weigh 35 to 50 pounds. While rock cores require limited special treatment, the containers for ice and sediment must be airtight and sufficiently cold throughout transport and storage.

Not all drill holes produce core, but almost all produce cuttings. Cuttings are the chips of rock that come up the outside of the drill pipe when using any type of rotating drill bit. Cuttings are samples of the rock through which the drill bit has cut, hence their name (see Figures 3-2 and 3-3). Huge amounts of cuttings have been produced and collected from various wells drilled over the decades (see Table 2-1). Holes that produce only cuttings are cheaper and quicker to produce and collect than holes that produce cores and cuttings. This is because not all cuttings are sampled and because cuttings flow to the surface during continuous drilling, as op-



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement