DISCUSSION AND COMPARISON OF RESULTS WITH THE PREVIOUS

                    
USGS/MMS ASSESSMENT

                               
Oil
 

     On the basis of existing technology and geologic concepts, there
are, in total, approximately 110 billion barrels of technically recoverable
oil, largely in existing and undiscovered conventional accumulations
onshore and in State waters of the United States_this includes measured
reserves and inferred reserves in existing fields as well as
undiscovered accumulations. This number is significantly larger than
the comparable number of about 78 billion barrels of technically
recoverable oil recognized at the time of the previous assessment (Mast
and others, 1989). In 1993, the United States produced about 2.4 BBO,
approximately 50 percent of national consumption. At the time of the
last National Assessment (1989), yearly production stood at
approximately 2.5 BBO. The significant increase in technically
recoverable oil reported in this assessment largely reflects
anticipated increases in reserves of known fields.

     Estimated mean amounts of undiscovered conventional oil resources
onshore and in State waters of the United States are about 10 percent
lower than those reported in the 1989 National Assessment of oil and
gas resources (Mast and others, 1989) (30.3 BBO vs. 33.3 BBO,
respectively). Since the last assessment, more than 2 BBO has been
discovered in new fields, thereby reducing previous undiscovered
quantities by that amount. The change in estimated conventional oil
resources is also due to a reduction in our estimates of the
undiscovered oil resources in part of northern Alaska.

     Our understanding of the thermal history and geochemical makeup of 
the rocks of northern Alaska leads us to expect more natural gas and less
oil in the foothills region, an area that includes most of the Arctic
National Wildlife Refuge (ANWR) as well as the southern part of the
National Petroleum Reserve in Alaska. This information comes from
results of drilling the Tenneco Aurora well, located just offshore from
the ANWR; results of a major USGS study that summarized all thermal
data in Alaska; and USGS studies in the foothills region (which combine
thermal-history information with that of the time of origin of rock
structure and reveal an unfavorable relationship for the development of
hydrocarbon traps). This unfavorable relation has resulted in the
downgrading of oil resource potential in the foothills region but not
in the coastal plain to the north.

     The reduction in Alaska is, in part, offset in the national total 
by small increases in a number of other regions of the United States
(table 2). Estimates of undiscovered conventional oil resources in most
other regions of the United States are, in general, similar to those
published in the past, although they differ somewhat in detail. For
further information, refer to play-level documentation in the
supporting CD-ROM (Gautier and others, 1995). It should be emphasized
that substantial overlap exists in the resource-range values estimated
in the two studies.

     Estimates of anticipated inferred reserves are significantly greater
than those reported in 1989 (60 BBO vs. 21 BBO). This increase reflects
our employment of an entirely different and newer set of field-level
reserves data in this assessment. The last National Assessment (Mast
and others, 1989) relied on the American Petroleum Institute-American
Gas Association data collected during the 10-year period 1969-79,
whereas, in this assessment, we had access to the last 15 years of data
collected by the Energy Information Administration (EIA) in its Oil and
Gas Integrated Field File (OGIFF). The OGIFF file was collected during
a period of extraordinary variations of activity in the U.S. oil and
gas industry, including significant changes in oil and gas prices,
drilling activity, and development efficiency.
     
     For the first time, the USGS has assessed technically recoverable
resources in continuous-type (unconventional) accumulations. Included
are about 2 BBO in continuous-type deposits, mostly in fractured shale
reservoirs of the Bakken, Niobrara, Austin, and similar formations.
These resources in unconventional reservoirs may have been partially
accounted for as undiscovered resources in the previous National
Assessment (Mast and others, 1989).

     Proved reserves of the United States onshore and in State waters, 
at the time of this assessment, amounted to approximately 20 BBO,
according to EIA. These values are significantly lower than those
reported in 1989, when they stood at 24 BBO.

Note: Table 2 was subdivided into various Regions:


Table2a contains Regions 1 & 2

Table2b contains Regions 3 & 4

Table2c contains Regions 5, 6 & 7

Table2d contains Region 8