The present study describes approaches for geological modeling applied on complex reservoir rocks formed by metamorphic processes on example of field located in Serbia, Pannonian basin. Key objectives are identification of productive intervals in contact zone of crystalline basement rocks and sedimentary deposits, reliable reserves estimation and new targets proposition. At the first stage of data analysis, the quality of logging and core availability was graded, which allowed to develop a strategy for working with data of varying degrees of representativeness. The algorithm of typing and correlation basement rocks is described taking into consideration different well log quality, volume and core recovery in the target interval. On wells with sufficient set of data, the concept of the reservoir formation mechanism and its structure was elaborated, and secondary data was used to confirm the model.
As a result of detailed material-genetic analysis of core the core-typing matrix has been developed. This matrix allowed us to determine vertical heterogeneity of rocks. Five main objects with different rock properties have been defined: crystalline schists - basement rocks, breccias are divided into three types based on formation mechanism and cap rocks - marls. Maps that describe lateral heterogeneity were used as a basis for block field’s structure. Lateral heterogeneity of rocks composition and seismic interpretation results has been juxtaposed. The proposed mechanism of deposition formation has been confirmed. These results formed the basis of 3D geological model. Previously, reserves estimation of the reservoirs related to basement rocks was carried out assuming average parameters of all layers. After a comprehensive analysis was done the detail geological model with block structure become the main tool for decision making process.
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