250 PETROLEUM TECHNOLOGY, ECONOMICS, AND POLITICS
geological and geophysical staffs. The minimum six-year period
needed to discover the five largest fields in any basin had passed
without making enough discoveries to whet top management's
enthusiasm, so the money dried up for all but prime prospects. This
is unfortunate because the huge remaining postulated resources
will never be converted to actual reserves unless discoveries are
made.
In addition, there is a great deal of disagreement on the issue of
future oil supply; one reason is that there is confusion among the
terms used, such as active and inactive reserves as well as known
and unknown resources. In addition, there is no means by which
foreign reserves can be accurately checked, leaving the numbers
open to serious doubt (Campbell and Laherrère, J.H. 1998). Some of
the reserve numbers may only be gross approximations.
Thus, it is essential to recognize that estimates of undiscovered
oil and gas resources are just that — estimates and the reality of
such estimates will, or should, always, be questioned. They are an
attempt to quantify something that cannot be accurately known
until the resource has been essentially depleted. For that reason,
resource estimates should be viewed as assessed at a point in
time based on whatever data, information and methodology were
available at that time. Resource estimates therefore are subject to
continuing revision as undiscovered resources are converted to
reserves and as improvements in data and assessment methods
occur (Attanasi, 1999).
Historically, estimates of the quantities of undiscovered oil and
gas resources expected to exist within a region or the nation have
been prepared for a variety of purposes using several different
methods. To make effective use of such estimates, or to compare
them with others, one must develop an understanding of how and
why they were prepared; the extent and reliability of the data upon
which they are based; the expertise of the assessors; the implications and limitations of the methodology used; and the nature of
any geographic, economic, technologic, or time limitations and
assumptions that may apply. It is equally important that those who
prepare estimates provide documentation adequate to allow the
users to evaluate the issues just described.
The purpose of this chapter is to examine, in general terms, some
of these issues and how they may impact on the credibility and usefulness of resource estimates. In general, uncertainties in estimates
of undiscovered oil and natural gas are greatest for areas that have
geological and geophysical staffs. The minimum six-year period
needed to discover the five largest fields in any basin had passed
without making enough discoveries to whet top management's
enthusiasm, so the money dried up for all but prime prospects. This
is unfortunate because the huge remaining postulated resources
will never be converted to actual reserves unless discoveries are
made.
In addition, there is a great deal of disagreement on the issue of
future oil supply; one reason is that there is confusion among the
terms used, such as active and inactive reserves as well as known
and unknown resources. In addition, there is no means by which
foreign reserves can be accurately checked, leaving the numbers
open to serious doubt (Campbell and Laherrère, J.H. 1998). Some of
the reserve numbers may only be gross approximations.
Thus, it is essential to recognize that estimates of undiscovered
oil and gas resources are just that — estimates and the reality of
such estimates will, or should, always, be questioned. They are an
attempt to quantify something that cannot be accurately known
until the resource has been essentially depleted. For that reason,
resource estimates should be viewed as assessed at a point in
time based on whatever data, information and methodology were
available at that time. Resource estimates therefore are subject to
continuing revision as undiscovered resources are converted to
reserves and as improvements in data and assessment methods
occur (Attanasi, 1999).
Historically, estimates of the quantities of undiscovered oil and
gas resources expected to exist within a region or the nation have
been prepared for a variety of purposes using several different
methods. To make effective use of such estimates, or to compare
them with others, one must develop an understanding of how and
why they were prepared; the extent and reliability of the data upon
which they are based; the expertise of the assessors; the implications and limitations of the methodology used; and the nature of
any geographic, economic, technologic, or time limitations and
assumptions that may apply. It is equally important that those who
prepare estimates provide documentation adequate to allow the
users to evaluate the issues just described.
The purpose of this chapter is to examine, in general terms, some
of these issues and how they may impact on the credibility and usefulness of resource estimates. In general, uncertainties in estimates
of undiscovered oil and natural gas are greatest for areas that have