API Well Number - History

History

API well numbers grew out of an internal numbering scheme developed by Petroleum Information for its WHCS (Well History Control System) product. WHCS was first offered to the oil and gas industry at the 1956 annual meeting of the AAPG in Los Angeles. Several companies agreed to underwrite the WHCS project, and the first files were delivered in 1962.

The API Subcommittee on Well Data Retrieval Systems was formed in 1962 to standardize well identification numbers. The first recommendations of the subcommittee were published in 1966 as Appendix A of API Bulletin D12 (Well Data Glossary). In April 1968, API published Bulletin D12A, which dealt solely with well numbering systems. This publication was modified slightly in December 1970 and January 1979, and the 1979 edition (reissued in 1982 and 1985) is the most current version. In 1995, the Subcommittee drafted some modifications to the API numbering scheme, but the group was disbanded before the recommendations were published. The 1979 standards are still in effect, but the publication is no longer available from API . In early 2013, the PPDM Association issued a draft version of an updated standard for the API Number which includes a requirement to identify all wellbores within each well. The 1979 standard and the 2013 standard, along with supporting materials, are available at PPDM Association's website for well identification.

One of the Subcommittee's original recommendations was that the unique numbers should be assigned by regulatory agencies as part of the oil and gas well permitting process. In general, Petroleum Information assigned API well numbers before January 1, 1967. After that date, most of the numbers were assigned by the appropriate regulatory bodies.