FOREWORD
This report was prepared as part of the World Energy
Project of the U.S. Geological Survey. In the project, the world was divided
into eight regions and 937 geologic provinces. The provinces have been
ranked according to the discovered oil and gas volumes within each (Klett
and others, 1997). Then, 76 "priority" provinces (exclusive of the U.S.
and chosen for their high ranking) and 26 "boutique" provinces (exclusive
of the U.S. and chosen for their anticipated petroleum richness or special
regional economic importance) were selected for appraisal of oil and gas
resources. The petroleum geology of these priority and boutique provinces
is described in this series of reports. Assessment
results will be available later. The Po Basin Province
ranks 68th in the world, exclusive of the U.S, with respect to ultimate
recoverable hydrocarbons.
The purpose of this effort is to aid in assessing the
quantities of oil, gas, and natural gas liquids that have the potential
to be added to reserves within the next 30 years. These volumes either
reside in undiscovered fields whose sizes exceed the stated minimum-field-size
cutoff value for the assessment unit (variable, but must be at least
1 million barrels of oil equivalent) or occur as reserve growth of fields
already discovered.
The total petroleum system
constitutes the basic geologic unit of the oil and gas assessment. The
total petroleum system includes all genetically related petroleum occurring
in shows and accumulations (discovered and undiscovered) that has been
generated by a pod or by closely related pods of mature source rock and
that exists within a limited mappable geologic space, together with the
essential mappable geologic elements (source, reservoir, seal, and overburden
rocks) that control the fundamental processes of generation, expulsion,
migration, entrapment, and preservation of petroleum. The total petroleum
system concept is modified from Magoon and Dow, 1994.
The minimum petroleum system is that part of a total petroleum
system encompassing discovered shows and accumulations, together with the
geologic space in which the various essential elements have been proved
by these discoveries.
An assessment unit is a mappable part of
a total petroleum system in which discovered and undiscovered fields constitute
a single relatively homogenous population such that the chosen methodology
of resource assessment – based on estimation of the number and sizes of
undiscovered fields – is applicable. A total petroleum system might equate
to a single assessment unit. If necessary, a total petroleum system may
be subdivided into two or more assessment units such that each assessment
unit is sufficiently homogeneous in terms of geology, exploration considerations,
and risk to assess individually. Assessment units are considered
established
if they contain more than 13 fields, frontier if they contain 1-13
fields, and hypothetical if they contain no fields.
A graphical depiction of the elements of the
total petroleum system is provided in the form of an events chart
that shows the time of deposition of essential rock units;the
time processes, such as trap formation, necessary for the accumulation
of hydrocarbons; the critical moment in the total petroleum system; and
the preservation time, if any.
A numeric code identifies each region, province, total
petroleum system, and assessment unit; these codes are uniform throughout
the project and will identify the same item in any of the publications.
The code is as follows:
|
Example
|
| Region, single digit
|
3
|
| Province, three digits to the
right of region code
|
3162
|
| Total Petroleum System, two digits
to the right of province code
|
316205
|
| Assessment unit, two digits to
the right of petroleum system code
|
31620504
|
The codes for the regions and provinces are listed in
Klett and others, 1997.
Oil and gas reserves quoted in this report are derived
from the Petroleum Exploration and Production database (Petroconsultants,
1996) and other reports from Petroconsultants, Inc., unless otherwise noted.
Figure(s) in this report that show boundaries of the total
petroleum system(s), assessment units, and pods of active source rocks
were compiled using geographic information system (GIS) software. Political
boundaries and cartographic representations were taken, with permission,
from Environmental Systems Research Institute's ArcWorld 1:3 million digital
coverage (1992), have no political significance, and are displayed for
general reference only. Oil and gas field centerpoints, shown on this(these)
figure(s), are reproduced, with permission, from Petroconsultants, 1996.
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