API Well Number Explanation


The API (American Petroleum Institute) number is a unique number assigned to every oil and gas well. It is used by agencies to identify and track oil and gas wells. Every oil and gas well permitted in West Virginia since 1929 has been issued an API number. The API number is required to be posted on every oil and gas well. If you have a question about a particular well, it is very helpful if you know the API number of that well.

The API number has the following format:​


47 = State code. 47 is the state code for West Virginia. All API’s in WV will begin with 47.

001 = The next three digits are the County Code. County codes are odd numbers, beginning with 001 (Barbour) continuing, alphabetically, to 109 (Wyoming). The list of county codes is below.

00001 = Well number. Each well will have a unique well number. Well numbers are ordered sequentially by the order they are issued. The smaller the number, the older the well.


4700100001 – The first API number issued in Barbour County.

4709502000 – The 2,000th API number issued in Tyler County.

Exceptions and Practices

Over the years, different practices have developed concerning API numbers. Within West Virginia, historically the 47 state code was often dropped. Also, some computer systems and databases dropped the leading “0” county codes. The hyphens have sometimes been used in various systems. The examples below show these uses. All represent the same well.

47-085-01250 = A Ritchie county well with full API number.
4708501250 = The same well, no hyphens.
085-01250 = The same well, state code has been dropped.
85-01250 = The same well, leading “0” dropped.
8501250 = The same well, leading “0” and hyphen dropped.

The WV DEP has standardized the API number and will use the full 10-digit API for correspondence concerning wells.

West Virginia County Codes

County Code / County

001 Barbour
003 Berkeley
005 Boone
007 Braxton
009 Brooke
011 Cabell
013 Calhoun
015 Clay
017 Doddridge
019 Fayette
021 Gilmer
023 Grant
025 Greenbrier
027 Hampshire
029 Hancock
031 Hardy
033 Harrison
035 Jackson
037 Jefferson
039 Kanawha
041 Lewis
043 Lincoln
045 Logan
047 McDowell
049 Marion
051 Marshall
053 Mason
055 Mercer
057 Mineral
059 Mingo
061 Monongalia
063 Monroe
065 Morgan
067 Nicholas
069 Ohio
071 Pendleton
073 Pleasants
075 Pocahontas
077 Preston
079 Putnam
081 Raleigh
083 Randolph
085 Ritchie
087 Roane
089 Summers
091 Taylor
093 Tucker
095 Tyler
097 Upshur
099 Wayne
101 Webster
103 Wetzel
105 Wirt
107 Wood
109 Wyoming