The basic prerequisites and factors leading to changes in petrophysical models of reservoirs of the fields at the late stage of development are considered on the example of oil fields at the platform part of the Republic of Bashkortostan. These oil fields are characterized by a limited complex of well log data, low and uneven removal of the core, lack of complex of the laboratory research, lack of accurate reference of the core to the depth. These disadvantages contributed to a significant difference in the approved parameters by the neighboring fields which are located in the same lithofacies zones. A prerequisite for reviewing of the reservoir model of the carbonate layer of Tournaisian Stage of some fields is a mismatch of the dynamics of watering in the oil deposits with equal effective thicknesses. Different rate of watering attests the heterogeneity of the reservoir. Analysis of production availability revealed deposits with low reserve multiplicity, while the decline in production in these deposits is not observed. The logical explanation is the underestimation of the pore volume. Significant factors which need to be taken into account for changing the traditional view of reservoir properties are noted during the revising of the petrophysical models. They include the problem of selection of analogues in conditions of low core removal, the typification of reservoirs by lithological and structural features, and the influence of the properties of modern research (methods and techniques) of the core. Also the analysis of the influence of changes in the petrophysical model on the volumetric parameters which are obtained from the interpretation of geophysical well data is shown in this proposed article. In most cases, a decrease in the leads of reservoir boundary values to an increase in the effective thickness and a decrease in the weighted average porosity. The application of modern methodological approaches to the creation of petrophysical models leads to a differentiated assessment of the quality of the reservoir and should be accompanied by changes of dynamic parameters.
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