Visualization of subsurface geology is mainly considered as the framework of the required structure to provide distribution of petrophysical properties. The geological model helps to understand the behavior of the fluid flow in the porous media that is affected by heterogeneity of the reservoir and helps in calculating the initial oil in place as well as selecting accurate new well location. In this study, a geological model is built for Qaiyarah field, tertiary reservoir, relying on well data from 48 wells, including the location of wells, formation tops and contour map. The structural model is constructed for the tertiary reservoir, which is an asymmetrical anticline consisting of two domes separated by a saddle. It is found that the three formations in the tertiary reservoir is composed of limestone and dolomitic limestone with very thin shale rims introduced only in the Dhiban Formation, which have the minimum thickness compared to the main other two formations those considered the main reservoir units. Upscaling from the software has been used to distribute and correlate between the logs and core data, which came very acceptable results to be used for distribution to the entire field. Both log analysis and core data have showed that the reservoir is clean formation, no volume of shale has considered in the STIIOP calculations with average water saturation calculated to be 31.5% and average porosity of approximately 22% with temperature gradient of 1.2 °F/100 ft. This comes up with Stock Tank Initial Oil in Place calculated to be 6.519*109.
