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October 2, 2017

Earth cores provide a glimpse of what lies beneath the surface.

When core is drilled with a coring bit, it is captured inside the drill pipe which is pulled out of the ground. Then the core is emptied into a trough where it is marked to be put into boxes. This is a USGS Energy Resources Program coring operation for assessment of natural gas in the Mancos shale formation.(Public domain.)

For more than forty years, the USGS has been operating a rock core and cuttings repository which preserves these scientifically valuable geologic resources and makes them available for study by all interested parties. The USGS Core Research Center (CRC), located in  Denver, Colorado has amassed a collection of rock cores from more than 9,000 wells, and cuttings from more than 52,000 wells.

Cores and Cuttings

Rock cores are cylindrical sections of rock that are brought to the surface for study, providing a near-contiguous record of rock that can be examined for many physical and chemical features.  Cuttings are sand-like particles that are produced by a rotary bit as a hole is drilled. They can also be studied to learn about the composition of the underlying geological formations.

Thirty-three states are represented in the CRC collection by either cores or cuttings, with the majority of the materials having originated in the Rocky Mountain region and adjacent states.  Annually, up to 1,800 researchers from industry, academia, the USGS and other government agencies use the climate-controlled examination rooms at the CRC to further their understanding of geologic processes and resources.

Digging Deep

To discover geologic resources, it is necessary to see what is hidden deep beneath the earth’s surface. The USGS, along with petroleum and mining industries, produce cores and cuttings while conducting scientific research or searching for energy or mineral deposits.

Private companies normally keep their cores and cuttings for their proprietary use while they are developing a prospect, but eventually storage becomes a burden, and they often donate the materials to the CRC where they become available to everyone, including USGS scientists and other exploration geologists. Cores that were drilled by the USGS for scientific studies, including energy and mineral assessments, are also stored at the CRC and made available to the public. The USGS CRC represents a successful example of public-private collaboration that significantly benefits society in numerous ways.

Societal Benefits

Understanding the composition of the earth is essential to meet key societal needs such as:

Cores marked, cataloged and put in shipping boxes(Public domain.)
  • Energy and mineral resources
  • Water resources
  • Infrastructure development
Cuttings are sand-like particles that are produced by a rotary bit as a hole is drilled into the earth. They are stored in envelopes with the depth recorded on each packet. The CRC collection includes more than 125,000 boxes of cuttings.(Public domain.)

Discovering Energy and Mineral Resources.

The USGS Energy Resources Program uses the materials at the CRC to establish a geologic framework and complete energy assessments.  Recently completed assessments include the following formations and basins:

  • Mancos Shale Formation (Piceance Basin, Colorado and Utah),
  • Green River Formation (Uinta Basin, Colorado, Utah, Wyoming),
  • Niobrara Formation (Big Horn, Wind River Basins, Wyoming),
  • Heath Formation (Central Montana Trough),
  • and the Bakken Formation (Williston Basin, Montana, North Dakota, South Dakota).

These assessments are mandated by Congress with the goal of determining the oil and gas potential in priority areas of the United States. 


Decades-old cores and cuttings housed in the collection have provided opportunities for re-analysis that have led private industry geologists to new discoveries of highly valuable natural resource reserves. These insights have contributed to increased domestic production of oil and gas which reduces prices and advances energy independence. 

The value of the large and accessible CRC collection can be illustrated by the contribution of a CRC core to a recent, major oil discovery in Colorado’s Niobrara formation in the Denver Julesburg basin. The core came from a well that was drilled in 1991, but the technology of that time was not capable of bringing it to production, so the core was donated to the CRC. In 2009 the core was used as part of an industry study to determine the viability of using horizontal drilling techniques, which had been used successfully in the Bakken formation in North Dakota, in the area near where the core was drilled. Findings from the core and 3-D seismic data, justified the considerable expense of drilling three test holes in the area. The test holes were productive which led to drilling 71 horizontal wells in the immediate vicinity and the development of more than 4.400 horizontal wells in the DJ basin Niobrara area. Weld County, Colorado, where the operations are located, saw oil production increase nearly ten-fold from 11,686,550 barrels in 2005 to 112,853,527 barrels in 2015. This is just one of many examples of new resource discoveries based on re-analysis of old cores.

Distribution of more than 9,000 Wells with Cores in the CRC Collection.(Public domain.)

Further Energy Implications

Improved extraction technology has led to increased energy production from low permeability formations such as the Niobrara and Bakken. The CRC collection contains many examples from these formations and they have been studied extensively as recent technological advancements resulting in successful discoveries have increased the need to understand the nature of these hydrocarbon deposits.

Mineral Assessments

The USGS Minerals Program uses the CRC collection to assist with congressionally mandated minerals assessments. Projects include research to determine potential domestic sources of critical minerals that are used extensively in high-tech manufacturing. USGS researchers are seeking these minerals from traditional mineral-bearing formations as well as the oil-rich black shales, because they also contain these critical elements. CRC cores from these formations are being studied for both energy and mineral purposes.

Researchers at the CRC can study cores from one area or compare cores from many different areas. This cross section is from the Bakken Formation, Williams, County, North Dakota. Since 2008 approximately 450 million barrels of oil have been produced from the Bakken and the underlying Three Forks Formation. In the 2013 assessment, the USGS estimated mean undiscovered volumes of 7.4 billion barrels of oil in the Bakken and Three Forks Formations in North Dakota, Montana, and South Dakota.(Public domain.)

Discovering and Evaluating Water Resources

Groundwater supplies about 25% of the freshwater used in the United States. Aquifers provide a reliable source of groundwater for drinking water, expanding urban areas, agriculture, industry, and many other uses. When shallow aquifers are depleted, deeper ones must be discovered and developed.

Researchers from the USGS, state water resources departments, water conservation boards, water districts, and water consulting businesses all use cores and cuttings to obtain detailed geologic and hydrologic data on aquifers. Studies assess the conditions for aquifer recharge and estimate the vulnerability to water contamination from geologic materials and human activities. The porosity and permeability of the rock formations in the aquifer, which measures the ability of liquids to flow, will impact the movement of the water it contains. Naturally-occurring trace elements in the rocks and sediments can be a source of harmful contaminants that could impact water quality and be a concern for human health. By storing rock materials obtained from the sub-surface aquifers, the CRC provides important resources to determine water quality and quantity.

Similar to a library, the boxes of core and cuttings have a “catalog number” and an address in the warehouse.(Public domain.)

Discovering Materials and Constraints for Infrastructure

Infrastructure, including roads, bridges and buildings, is built from large quantities of concrete, steel, energy and water. The sand, gravel, iron and other minerals must be obtained from suitable deposits of these natural resources from within the earth. It is imperative to consider the underlying geology and earthquake probability when designing and building major infrastructure. Tall buildings must rest on solid bedrock. If roads or other structures are built on unstable swelling clays, they will rapidly suffer expensive damage. Surficial knowledge is not enough - seeing deep within the earth is required for all aspects of modern civilization. Cores and cuttings provide a component of the necessary in-depth vision.

Research and Educational Opportunities

The CRC provides a variety of research and educational opportunities:

  • University professors bring earth science classes to the CRC to see and compare different rock types from various geographic areas and depositional environments and to learn core description and research techniques. 
  • Geoscience and Industry organizations hold workshops at the CRC that combine classroom lecture with hands-on experience with actual cores.  Both seasoned professionals and students attend to expand their skillsets and exchange ideas.
  • Research done at the CRC has led to many useful publications including journal articles, theses and dissertations.  Such studies reveal new insights into the earth and can change the scientific understanding of depositional systems, tectonic controls on facies variations, and the nature of hydrocarbon reservoir systems.

Cost Savings

Drilling and coring operations are costly endeavors but the materials derived yield useful scientific information worth preserving for future use. These stored legacy materials can be studied with miniscule expense compared with the massive costs of planning, permitting, drilling and coring a new well. At today’s prices, re-drilling the entire collection would cost more than 80 billion dollars. For industry, this substantially reduces the economic risk inherent in discovering new prospects. Researchers from non-profit entities such as universities, government agencies and museums gain access to materials that would be too expensive for them to obtain through new drilling.

An Irreplaceable Collection

Over centuries, the easily-accessible supply of natural resources has been depleted, meaning that it is more difficult and expensive to find and gather the remaining viable resources from less accessible deposits. The preserved cores and cuttings are an actual representation of the substrata, providing vital information needed to locate new sources for water, energy, and mineral resources. The USGS CRC preserves this irreplaceable collection, in order to insure that these records of the earth’s past will be used in the future for yet-to-be-imagined discoveries advanced by a deeper knowledge of our planet.

Core workshops held at the CRC combine classroom lecture with hands-on experience with actual cores. Both seasoned professionals and students attend to expand their skillsets and exchange ideas.(Public domain.)