Repository of state drilling records moves to Natural Resources Building

corner of paper record jutting out of file folder

The Illinois State Geological Survey is the State of Illinois’ repository for records of drilling, including oil and gas wells, water wells, engineering borings, and miscellaneous test holes. The Geological Records Unit (GRU) is the gateway to Illinois geology. Because many Illinois regions lack abundant outcrops and road and stream cuts, drill-hole records provide the most abundant data available for geologic interpretation. These data are useful for environmental assessment, mineral resource evaluation, and groundwater resource evaluation and protection.

After being housed for several year at the Forbes Natural History Building, the GRU has moved back to the Natural Resources Building on the campus of the University of Illinois (615 E. Peabody Dr., Champaign).  Public access can be obtained through Room 239. 

Hours: Monday - Friday, 8 a.m. to noon and 1-4:30 p.m.     
Phone: 217-333-5109
Fax: 217-244-4544

The Geological Records Unit houses over 500,000 drilling records including:

  • Oil, gas, and Class II injection well records
  • Water well records
  • Coal test permits, plugging affidavits and records
  • Out of state records used in ISGS projects
  • Engineering reports
  • Highway and bridge borings
  • Sample studies
  • Structure and stratigraphic tests
  • Historical well records of many types, including skeleton logs

Online Access

Online access to the records unit data can be obtained through the ILOIL and ILWATER web applications.  Well information, oil fields, aquifers, log data, basemap data and more can be browsed and downloaded through these applications.

Additional Resources

  • Pipeline production books
  • Historical and current collections of scout tickets
  • Historical and current plat books
  • Oil and gas development maps
  • Office of Mines and Minerals well files


The Geological Records Unit maintains paper copies of individual well files. All documents for each drill hole are filed together in a folder and organized by location, including items such as

  • geophysical logs
  • drillers log
  • drilling time log
  • drill stem test report
  • core analysis report
  • commercial scout tickets
  • index numbers for samples and cores housed in the Samples Library
  • permit
  • casing report
  • well drilling report
  • well completion report
  • plugging affidavit
  • summary sheet - generated when all the documents for the well have been received

Water Wells

Most water wells have relatively few documents and rarely have individual folders. Water well construction and permit information is included in the water well summary sheets in our log books. The water well source documents (the applications, permits, and construction reports generated through September 1997) are maintained by GRU. The Illinois State Water Survey maintains the later source documents.

Well Log Books

The well log books contain summary sheets for all types of drill holes. The books are the sole source of many records and also serve as an index to ISGS file folders. Currently the collection contains 1,356 log books with approximately 680,000 pages on over 500,000 drill holes. These are arranged by county, then by township, range, and section. The books include

  • oil well summary sheet
  • report of gas flow measurement
  • water well summary sheet
  • index to cores in the Samples Library
  • bridge boring report
  • engineering report index
  • skeleton logs - pre-1920 oil well records, mainly in Crawford, Lawence, Clark and Cumberland Counties.

Wells Database

The well records database includes most of the basic identification information from our log books and files. It also includes much of the geologic formation and well construction/completion information. The database provides very versatile search capabilities. We are working toward making the database our most complete access tool. However, to be assured of a comprehensive search of our collections now, use all three access points: folders, well log books, and database.