Minerals Report - International Seabed Authority

Where the ITIPRHHc is in Mmtoe (1 t oil = 1,000 m 3 gas); V, in thousands
km3; and Kec, is a fraction.
The volume-statistical method enables us to give a firstapproximation
estimate of hydrocarbon resources in frontier sedimentary
basins or their larger parts, for which the theoretical possibility of
petroleum generation and accumulation have been established and the
sedimentary cover, volume and qualitative characteristics of petroleum
potential can be estimated from the available geologic and geophysical
data. In this case, the first version of the method is applied (figure 4).
Not all reservoir rocks are interpreted as natural reservoirs. For
example, permeable seams without component seals above them or thick
reservoir units lacking intraformational seals and that are therefore easily
drained by formation water are not considered as “effective porosities”.
The proportion of natural reservoirs in a sequence or in the basin fill as a
whole is characterized by an effective porosity coefficient and depends on
the lithology of sedimentary sequences and units. This coefficient ranges
in value from 0.001 to 0.3-0.45. The lowest values are usually characteristic
of coarse-grained deposits of orogenic complexes; the highest are usually
characteristic of biogenic and bioclastic limestones (reefs in particular).
The objects of estimation in the volume-balance method of
hydrocarbon resource evaluation are large self-regulated equilibrium
petroleum–hydrodynamic systems, laterally extending through entire
basins or the constituent regions, sags, petroleum accumulation zones, and
vertically confined to certain lithostratigraphic units. The petroleumhydrodynamic
system (PHDS) volume encompasses the total volume of
natural reservoirs present in the object under consideration, and is filled
with three interrelated components, oil, gas, and formation water. The
ratio between the volume of oil and gas saturated reservoirs (pools) in
place and the total PHDS volume is the concentration coefficient (oil, gas,
or total hydrocarbon concentration, respectively).
Based on a simplified version of the volume-balance method, in the
absence of data on temperature, pressure, porosity, and other in-place
conditions of pay zones, the initial total-in-place hydrocarbon resources
are calculated using the following equation:
INTERNATIONAL SEABED AUTHORITY 493