Analysis and Mapping of Geochemical and Geological Variables in the Area of Bjelovar Subdepression by Inverse Distance Weighting Method (IDW)

In the area of ​​Bjelovar subdepression, geochemical variables, vitrinite reflections (R_o) and Time-Temperature Indeks of Maturity (TTI) for wells Čep (field), Pav-1, Gr (field), Ha-7, Le-4, Rov- 1, NG-1, VC-1, Vis-1 and Ulj-1 which, together with their Gauss-Krüger coordinates (X, Y), represent the input data for the newly created digital maps. Based on the knowledge of the lack of several data on the values ​​of TTI and R_o, the thermal maturity of the rocks was determined by the EASY%R_o method by a simple conversion using a nomogram. The software package Surfer 8.0^TM was used for mapping by the Inverse Distance Weighting method (IDW), which was applied due to its simplicity in preparation and speed in the calculation, but also the obtained output that can be easily and meaningfully interpreted geologically. The Inverse Distance Weighting method (IDW), is a common method of interpolating maps for small samples (less than twenty pieces of data) in the Croatian Pannonian Basin System (HPBS). The newly created digital maps were used to refine the existing map of hydrocarbon migration routes.