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as a basis for calculating the reserves and establishing the well
spacing patterns.
2. Sources of reservoir energy are established by
comparing the initial formation pressure with the saturation
pressure, and also by establishing the dimensions of the entire
water drive system, the existence of an encroachment zone and the
degree of its activity. On the basis of the study of the energy
characteristics of the reservoir, it is possible to establish the need
for pressure maintenance operations in order to create an artificial
driving mechanism. Different reservoir drives are characterised by
different recovery factors which are used in calculating the
available oil reserves and the producing life of a reservoir.
3. The initial reservoir pressure and the permissible
pressures in producing wells during the production period
determined by the saturation pressure, the minimum free-flow
pressure, and also by technical factors (a type of well, the stability
of the collector rock and others). The maximum permissible
withdrawal is usually determined by the stability of the collector
rock and the strength of the casing.
The minimum permissible bottom-hole pressure or the
maximum permissible rate of withdrawal are the limiting
conditions in reservoir development planning.
4. The physical characteristics of the rock: permeability,
porosity, elasticity and mechanical composition which are used in
various hydrodynamic calculations.
5. The physicochemical properties of the fluid and gas
at formation pressure and temperature are determined by
examining bottom-hole oil samples. This data is used both in
hydrodynamic calculations and in estimating the commercial grade
of the oil. The saturation pressure is often taken as the limiting
condition of well performance.
The solubility factor, the initial gas saturation of the oil,
and the oil-to-gas viscosity ratio are used in calculations employed

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