Geology Reference
In-Depth Information
These performed estimates are ideologically minimal. Testing of this
approach on a number of well-studied prospects and areas in the region
supports about 95% reliability of the technique.
Table 11.3 illustrates the range of variation for the parameters most rep-
resentative in the initial exploration and appraisal stage. The parameters
include tectono-structural, lithophysical, hydrodynamical, hydrochemi-
cal, geothermal, geobaric and permeability-porosity attributes. The range
covers the environments of the formation and positioning of multiphase
oil, gas and condensate aggregations and the conditions, under which the
hydrocarbon saturation does not occur at all.
The depth to the top and base, the amount of erosion of the Productive
Sequence/Red-Bed Sequence,
structure steepness and per-unit faulting are
easily determined from 2D and 3D seismic data. A number of parameters
are determined from petrophysical data in the first wells. These param-
eters are the clay content, formation and pore pressure abnormality factors,
their development zone tops, ratio of AHFP and AHPP zone thickness to
the Productive Sequence/Red-Bed Sequence thickness and pore pressure
gradient at the top of the Productive Sequence/Red-Bed Sequence.
Hydrodynamical, geothermal, hydrochemical and reservoir property
parameters of the reservoirs are determined from careful and complete
testing of wells and target intervals.
An evaluation was conducted of undrilled structures in the central
deep-water area of the South Caspian. The top of the Productive Sequence
is extremely deep there. The clay content is 90-95% of total
thickness.
Exceptionally high
AHFP
and
AHPP are omnipresent. These conditions
cast serious doubt on the oil and
gas potential of its major portion. On
the other hand, the data in Table 11.3 set the structures' parameter range
(geologic “window”, “fence”), within which the hydrocarbon saturation
is likely.
Consideration of the aforementioned enables the development of an
exploration/appraisal algorithm conceptually different from the existing
exploration/appraisal process in the region. It provides for higher forecast
reliability of the regional, zonal and local oil and gas occurrences, its effi-
ciency and minimizing geologic and economical risks.
The suggested approach is based on the paradigm of oil and gas accu-
mulation process being caused by the geo-fluid-dynamical processes. Its
implementation assumes a certain sequence of operations.
The first stage is the review and interpretation of all available informa-
tion on the tectono-structural state of the natural reservoirs in specific areas
and zones. It allows for the quantitative estimation of their parameters.
