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Well Cores 
 
Example of a cylindrical whole rock core        Detailed visual analysis of slabbed cores can provide valuable insight regarding the subsurface geology

Pictured left:  Example of a cylindrical whole rock core.  Pictured right:  Detailed visual analysis of slabbed cores can provide valuable insight regarding the subsurface geology. 

Well cores are cylinderical rock samples collected as part of the drilling process.  Cores provide valuable insight into the porosity and permeability, among other characteristics, of the rocks that are being drilled.

Several types of cores can be recovered from the well, including full-diameter cores, oriented cores, native state cores and sidewall cores.  For more information on types of well core, how they are collected and analyzed, go here.

Where can I find well cores from Colorado wells?

While there is not a state maintained repository for CO well cores, there are several options for finding core.

First, a visit to the Petroleum Technology Transfer Council's (PTTC) core locator website is very helpful.  This service includes CO cores that have been put in many of the largest repositories. 

Perhaps, most important locally is the US Geological Survey's Core Research Facility located at the Denver Federal Center.  This facility is one of the largest core repositories in the US, and contains many cores from CO, as well as throughout the Rocky Mountain region and beyond.  

Another option is the Core Research Facilities managed by the Texas Bureau of Economic Geology.  The collection located at three separated facilities in Austin, Midland, and Houston, includes well samples from Colorado and across the US.

A comprehensive list of the major core repositiories in the US is available here.

Wireline Logs 
 
Logs provide critical information for evaluating oil and gas reservoir potential, as well as giving engineers and geologists a better understanding of what to expect during production operations.

From the Schlumberger Oilfield Glossary, a wireline log can be defined as:

A continuous measurement of formation properties with electrically powered instruments to infer properties and make decisions about drilling and production operations. The record of the measurements, typically a long strip of paper, is also called a log. Measurements include electrical properties (resistivity and conductivity at various frequencies), sonic properties, active and passive nuclear measurements, dimensional measurements of the wellbore, formation fluid sampling, formation pressure measurement, wireline-conveyed sidewall coring tools, and others.

Wireline logs rely on physical measurements to be made by instruments lowered into the borehole on a cable (wire).  Once the zone of interest is reached, the actual measurements are  traditionally recorded as the instrument is pulled up towards the surface.  There are many types of sophisticated wireline logging tools, including newer tools that allow for logging to occur while drilling (LWD). For a good overview of the various tool classes go here

Where can I find wireline logs for Colorado wells?

Publically available wireline logs (both raster and LAS format) are available through the Colorado Oil and Gas Conservation Commission website.  Both a direct database query or map search utility are available.  Additionally, there are commercial vendors that maintain raster and digital log databases for purchase.
 
 
Wireline logs from three wells in northwest Colorado

Wireline logs from three wells in northwest Colorado.
Last Updated: 2/2/2012 2:06 PM 
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