Increased hydrocarbon recovery and CO2 storage in Neogene sandstones, a Croatian example: part II

During 2003-2006, a pilot project of alternating water and CO2 injection was performed on a limited part of the Upper Miocene sandstone oil reservoir of the IvaniA double dagger Field. During the test period oil and gas recovery was significantly increased. Additionally 4,440 m(3) of oil and 2.26 x 10(6) m(3) of gas were produced. It has initiated further modelling of sandstone reservoirs in the IvaniA double dagger Field in order to calculate volumes available for CO2 injection for the purpose of increasing hydrocarbon production from depleted sandstone reservoirs in the entire Croatian part of the Pannonian Basin System. In the first phase, modelling was based on results of laboratory testing on the core samples. It considered applying analogies with world-known projects of CO2 subsurface storage and its usage to enhance hydrocarbon production. In the second phase, reservoir variables were analysed by variograms and subsequently mapped in order to reach lithological heterogeneities and to determine reliable average values of reservoir volumes. Data on porosity, depth and reservoir thickness for the "Gamma 3" and the "Gamma 4" reservoirs, are mapped by the ordinary kriging technique. Calculated volume of CO2 expressed at standard condition which can be injected in the main reservoirs of the IvaniA double dagger Field at near miscible conditions is above 15.5 billion m(3).