One of petrophysics basic challenges is to proceed from empirical dependences studying to construction and studying of reservoir theoretical petrophysical models for their subsequent association with well log analysis and petrophysical models of well logs. However petrophysical analysis results are often used for empirical regression calculations and very rarely as a starting point for analytical description of reservoirs.

The described approach tends to move petrophysical interpretation from the empirical level to the level where petrophysical models describe common effects on the regular basis. First of all such models could be introduced for granular reservoirs. Petrophysical models that are analytically describing basic properties of a granular reservoir reduce the number of influencing parameters to only four synthetic characteristic parameters, namely: water- and oil-holding capacity of the framework, waterholding capacity of the cement and porosity of the framework. However, there is no information loss, and completeness of all specific reservoir properties variety description is kept as well. All used parameters could be directly measured or established in analysis of the total porosity - residual saturation dependence.

Established granular model could be considered as a background model. If fractures presented in core sample then petrophysical dependences behavior will be different from granular ones. It is possible to show theoretically that such difference could be used for the quantitative analysis of the fractured porosity. Several core collections from the Eastern Siberian reservoirs were analyzed and such possibility was proved.

The developed approach shows that deficit of the information in studying of complex reservoirs can be compensated by strictly proved petrophysical models instead of building empirical multidimensional petrophysical dependencies.

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