Pennsylvanian | | |
Kansas |Pennsylvanian |Par.-Asph.| 45,451,017| 148,450,298
Kentucky, |Mississippian |Paraffin | 4,376,342| 18,213,188
Tennessee | | | |
Louisiana |Cretaceous-Quat. |Paraffin | 16,042,600| 150,769,911
| Cretaceous- | | |
| Eocene | | |
Michigan, |Carboniferous |Paraffin | (a) | (a)
Missouri | | | |
Montana | -- | -- | 69,323| 213,639
New Mexico |Carboniferous- | -- | (a) | (a)
| Cretaceous | | |
New York, |Devonian- |Paraffin | 8,216,655| 788,202,717
Pennsylvania| Carboniferous | | |
Ohio, East |Ordovician- |Paraffin | 7,285,005| 463,367,386
and West | Carboniferous | | |
Oklahoma |Pennsylvanian |Paraffin |103,347,070| 851,320,457
Texas |Pennsylvanian, |Asph.-Par.| 38,750,031| 327,550,005
| Cretaceous-Quat.| | |
Utah | -- | -- | (b) | (b)
West |Devonian- | -- | 7,866,628| 294,474,710
Virginia | Carboniferous | | |
Wyoming |Carboniferous- |Asph.-Par.| 12,596,287| 40,019,573
| Cretaceous | | |
Other | -- | -- | 7,943| 112,925
| | |-----------| -------------
| | |355,927,716| 4,608,571,719
-------------+-----------------+----------+-----------+---------------
(a) Included in "Other."
(b) Included in Wyoming.

[Illustration: FIG. 7. Chart showing the present tendency of
the United States in respect to its unmined reserve of petroleum. Data
from U.S. Geological Survey. After Gilbert and Pogue.]

=Methods of estimating reserves.= It may be of interest to inquire into
the basis on which predictions are made of the life of an oil pool. The
process is essentially a matter of platting curves of production, and of
projecting them into the future with the approximate slopes exhibited in
districts which are already approaching exhaustion.[21] While no two
wells or two districts act