Region
Utah
22
Texas
21
United States
18
Wyoming
18
Illinois
16
California
15
Colorado
15
Kansas
15
Oklahoma
13
New Mexico
11
Louisiana
10
Montana
7
Pennsylvania
5
Uintah County
5
Alaska
4
Arkansas
4
Kentucky
4
Kern County
4
Osage County
4
Powder River Basin (Wyo. and Mont.)
4
West Virginia
4
Duchesne County
3
Mississippi
3
North America
3
North Dakota
3
Ohio
3
Washington County
3
Africa
2
Alabama
2
Bakken Formation
2
Carbon County
2
Carter County
2
Coalinga
2
Columbia County
2
Grand County
2
Idaho
2
Indonesia
2
Iran
2
Mexico, Gulf of
2
Osage County (Okla.)
2
Russia (Federation)
2
San Juan County
2
Virginia
2
Washington (State)
2
Williston Basin
2
Acadia Parish
1
Anderson County
1
Appalachian Basin
1
Arizona
1
Austin County
1
more ...