API Well Numbers in Indiana (Draft 1)

Charles W. Zuppann
Indiana Geological Survey
July, 2011


The Indiana Geological Survey (IGS) is often asked for a list of API (American Petroleum Institute) numbers associated with petroleum wells drilled in the state. The question is usually posed by companies who tell us they use specialized mapping programs that require API numbers to uniquely identify wells. Although API well identification numbers are by far the most popular unique well identifiers used in U.S. states, and despite the fact that original API numbers were issued by the Indiana Division of Oil and Gas (DOG) from 1967 through July 1990, circumstances have inhibited their acceptance in Indiana and today (July 2011) API numbers are not used as unique identifiers either by DOG or IGS. The history of API number usage in Indiana is summarized in the timeline below.

Timeline of API Number Usage

1962  The API well number scheme was formalized by the API Subcommittee on Well Data Retrieval Systems, from an internal well numbering system developed by Petroleum Information Corporation (now IHS, Inc.) for use in computerized well data systems (IHS, Inc., 2010). The number is multi-part and the digits translate to certain information about the well. For instance, the first two digits are the state code (always 13 in Indiana), a number that designates the state were the well is located, and the third through fifth digits represent the county code. A detailed description of API Numbering Guidelines is presented at the Society of Petrophysicists and Well Log Analysts website: http://www.spwla.org/technical/api-technical (2009).

1966  The Indiana Division of Oil and Gas (DOG) was designated the primary organization responsible for assigning API numbers for new wells drilled in the state.

1967  The first API well number issued for new permits in Indiana was 13-103-20001, issued January 3 for the well identified as permit number (PN) 30856.

1967  The API plan envisioned two separate well numbering endeavors: 1) the ongoing assignment of API numbers to newly permitted wells, in Indiana to be issued by DOG, and 2) the assignment of API numbers to historical wells that had been drilled prior to 1967. The responsible party for assigning API numbers to historical wells varied from state to state, either by a state agency such as DOG or by an "industry group." (American Petroleum Institute, 1979). The IGS has no record of any actual attempts to assign API numbers to Indiana's historical wells, and it may be that no systematic attempt was ever made. An estimated 54,118 (+/-100s ?) known historical wells had already been permitted or drilled at the time when the first API numbers were assigned to newly permitted wells in 1967.

1990  On July 30, DOG made its final API number assignment for a newly permitted well (PN 49549). The reason DOG stopped issuing API numbers is not known to the author. Although a record of issued API numbers from 1967 through July 1990 is available in the form of typed entries on the permits issued from DOG during this time, the IGS does not have a database or cross reference of the API numbers assigned to permitted wells. A rough estimate of the number of newly permitted wells to which API numbers were assigned by DOG may be obtained by subtracting the permit number of the first well assigned an API number (PN 30856) from the permit number of the last well permitted on July 30, 1990 (PN 49549): 49549 minus 30856 = 18,693 (+/-???). This estimate is rough in part because workover wells were sometimes issued API numbers and sometimes not.

1994  Beginning in August, Petroleum Information Corporation (now IHS, Inc.), in its capacity as a secondary source for API numbers, evidently took over the task of assigning API numbers to newly permitted wells in Indiana. They continue to assign API numbers today in their weekly Drilling Wire report, Illinois Basin Edition.

1994  The IGS began planning for its online petroleum database, the PDMS, and immediately recognized the need for a unique identification number for every well. The API number was ruled out because of known inconsistencies, the lack of a convenient source for verifying numbers that had been earlier assigned, and difficulties that would be involved if the IGS attempted to add new numbers to the existing set of API numbers for which no cross reference was available. Using DOG-issued permit numbers as unique well identifiers was also rejected because permit numbering procedures had been revised over time in such a way that they are not unique. Also, permit numbers were not issued for wells prior to 1937. Owing to these difficulties, the IGS decided to assign a new identification number to each individual well in the state, the IGS Petroleum Well Identification Number (IGS ID). This 6-digit number is unique to a specific location on the ground surface. No other meaning is attached by the IGS ID. A unique IGS ID has been assigned to every known well drilled or permitted in the state.

Possible Future Use of API Numbers in Indiana

Restructuring the PDMS to accommodate API numbers would require completion of several tasks.

  1. API numbers would need to be assigned to an estimated 54,118 historical wells drilled before 1967, except for some workover wells. At some point, this could be done semi-automatically by serially adding API Numbers to wells that do not already have an API number; but, to avoid possible overwriting of existing numbers, this task would need to be done only after all the wells with existing API numbers were brought up to date.

  2. API numbers were assigned to the 18,693 well permits, roughly estimated, from 1967 through July 1990. There exists no publicly available cross reference linking IGS ID numbers or DOG permit numbers to their assigned API numbers. As things currently stand, numbers would need to be entered into the PDMS from the permit certificates, prohibitively costly in today's challenging economic climate. We understand that IHS, Inc. has such records, but they are currently available only to their clientele. The IGS could only participate in such a project if all API number data were to be made available to the public.

  3. About 4,569 "secondary source" API numbers have been assigned by IHS, Inc. or its ancestors beginning in August 1990 and continuing to today (July 2011).

Unfortunately, the current API numbering system with regard to Indiana is not in keeping with the original purpose envisioned for their use: "The API Well Number is a means whereby any company, governmental agency, or other group may interrelate or exchange well data from all logical geographic, geological, or arbitrary areas." (American Petroleum Institute, 1979, p. 6). Today, the organization that assigns the numbers (IHS, Inc.) reports them only in their own commercial publications, and holds the cross referenced list of assigned numbers proprietary. Under such circumstances, the API number is not available as a unique well identifier to the public, government, and to non-IHS-client operators.

At present, we are unaware of any specific plans by any organization to begin issuing and openly publishing API numbers in Indiana. Should a comprehensive, efficient, and openly shared system for handling API well numbers in Indiana be developed by an industry committee, nonprofit organization, company, or government body, the IGS would certainly entertain participating, and would attempt to work with parties to link API numbers to the well records in the PDMS. In the meantime, the IGS considers the IGS ID number to be the only unique and comprehensive identifier of petroleum wells in Indiana that is freely available to all potential users.

Cited References

American Petroleum Institute, 1979, The API well number and standard state and county numeric codes including offshore waters: API Bulletin D12A, January, 1979, 136 p.

Drilling Wire., 2011, Northeastern U.S., Illinois Basin Edition: IHS, Inc., Volume 50, Number 23, June 8, 2011, no page numbers.

IHS, Inc., 2010, API numbering guidelines; general overview & statistics: IHS, Inc. Web site, <http://www.ihs.com/products/oil-gas-information/training/reference-materials.aspx?tid=t5>, date accessed, July 1, 2011.

Society of Petrophysicists and Well Log Analysts, 2009, API Numbering Guidelines: Society of Petrophysicists and Well Log Analysts website: http://www.spwla.org/technical/api-technical, date accessed, July 1, 2011.