General Overview & Statistics

The American Petroleum Institute (API) Subcommittee on Well Data Retrieval Systems was formed in 1962 to develop a standard method for nationwide well identification for use in computerized well data systems. They created the API well number, a unique, permanent, numeric identifier assigned for identification of a well (i.e. hole in the ground) which is drilled for the purpose of finding or producing oil and/or gas or providing related services.

The subcommittee's recommendations were first published in 1966 as Appendix A, API Bulletin D12, Well Data Glossary. In 1968 it became the API Bulletin D12A, The API Well Number and Standard State and County Codes. Several revisions have been made, the latest being published in 1985. In 1995, the subcommittee drafted a new API numbering scheme that allowed for better identification of wells with sidetracks and recompletions. However, the Subcommittee on Well Data Retrieval was disbanded before these recommendations were officially published.

In the draft, the subcommittee proposed adding an Event Sequence Code (digits 13 and 14) which would apply to re-entries, recompletions, and hole deepenings. (These codes may vary between vendors and other industry groups according to well records obtained.) This would make it easy to identify a true hole change for each borehole in a well. The geoscientist could then more easily reconstruct the borehole geometry and sequence events that happened during recompletions, workovers, or sidetracking.

Digits 13 and 14 of the API number have long been part of the IHS's Active well and WHCS well completion database from the former Petroleum Information Corp. However, these digits were incremented differently than what the subcommittee proposed before its disbandonment. Recognizing that this new numbering scheme for digits 13 and 14 would offer greater benefits to our customers, the IHS is adopting this new structure.

In January 1999, this new numbering scheme was implemented in the WHCS well completion and the Active well database. All the API numbers have now been updated and replaced to reflect the new system. Only digits 13 and 14 will be affected. (NOTE: the Active and WHCS databases are from the former Petroleum Information Corp. Only products derived from these databases will be affected, such as the discontinued Magellan®, petroROM® Active, and petroROM® Well Data. API numbers in the former Dwight's Energydata well database and corresponding products will not be affected).

In the Production Data database from the former Petroleum Information Corp., API's in regions that contain the full 14-digit API numbers may also have changes. These changes are implemented a state by state basis, as monthly production updates are released. (NOTE: Once again, these changes only affect products from the former Petroleum Information Corp production database, such as the discontinued Magellan® and petroROM® Production Data. No Dwights production products will be affected.)

If you are maintaining or updating a well database from a product using former PI well data, the following information could be of importance to you:

Well data obtained from products using the Active and WHCS well databases in January 1999 and thereafter will contain the new API numbering structure. Well data obtained from products using data from December 1998 and prior will have the previous API numbering structure. For example, petroROM's Well Data 4th quarter 1998 release will have the old numbering structure. petroROM's Active Well Data's January issue will have the new structure. Any data accessed from on-line systems today (i.e. PetroNet21^SM Select: U.S.: Well and Production Data, formerly the Oil & Gas Data Channel) will have the new numbering system implemented for all wells.

In our Active Well database 2,058 wells will have API number changes to digits 13 and 14. In our WHCS well completion database, 34,889 wells will have changes.

Here are the actual statistics for both databases:

WHCS well completion data:

Active well data:

(More detailed statistics are available if needed)
A cross-reference file of the replaced API numbers is available to our customers. You may need to update your database with these API number changes or duplications of wells could result. If you need this file to update your database, please contact client support online. 

If you are maintaining or updating a production database that utilizes the API number and is from the former PI production data, the following information may be of importance to you:

Some regions in the production database from the former PI will have API changes. Most regions will not be affected, as they did not contain the full 14-digit API number. Here are the statistics for each state:

Production Data:

State by state cross-reference files of the impacted API numbers are available to our customers. If you need these files to update your database, please contact our client support online.