The systems approach to geology is both a sophisticated ideology and a scientific method for investigation of very complicated geological systems. As applied to petroleum geology, it includes the methodological base and technology of mathematical simulation used for modeling geological systems: the systems that have been previously investigated and estimated by experimental data and/or field studies. Because geological systems develop in lime, it is very important to simulate them as dynamic systems. The main tasks in the systems approach to petroleum geology are the numerical simulation of physical and reservoir properties of rocks, pore (geof-luid) pressure in reservoir beds, and hydrocarbon resources. The results of numerical simulation are used for prediction of geological system structure and behavior in both studied and noninvestigated areas.