*Article* **Potential for the Geological Storage of CO2 in the Croatian Part of the Adriatic O**ff**shore**

**Bruno Safti´c, Iva Kolenkovi´c Moˇcilac, Marko Cvetkovi´c \*, Domagoj Vulin, Josipa Veli´c and Bruno Tomljenovi´c**

Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, HR-10000 Zagreb, Croatia; bruno.saftic@rgn.hr (B.S.); ikolenko@rgn.hr (I.K.M.); domagoj.vulin@rgn.hr (D.V.); josipa.velic@rgn.hr (J.V.); bruno.tomljenovic@rgn.hr (B.T.)

**\*** Correspondence: marko.cvetkovic@rgn.hr

Received: 31 July 2019; Accepted: 20 September 2019; Published: 23 September 2019

**Abstract:** Every country with a history of petroleum exploration has acquired geological knowledge of its sedimentary basins and might therefore make use of a newly emerging resource—as there is the potential to decarbonise energy and industry sectors by geological storage of CO2. To reduce its greenhouse gas emissions and contribute to meeting the Paris agreement targets, Croatia should map this potential. The most prospective region is the SW corner of the Pannonian basin, but there are also offshore opportunities in the Northern and Central Adriatic. Three "geological storage plays" are suggested for detailed exploration in this province. Firstly, there are three small gas fields (Ida, Ika and Marica) with Pliocene and Pleistocene reservoirs suitable for storage and they can be considered as the first option, but only upon expected end of production. Secondly, there are Miocene sediments in the Dugi otok basin whose potential is assessed herein as a regional deep saline aquifer. The third option would be to direct future exploration to anticlines composed of carbonate rocks with primary and secondary porosity, covered with impermeable Miocene to Holocene clastic sediments. Five closed structures of this type were contoured with a large total potential, but data on their reservoir properties allow only theoretical storage capacity estimates at this stage.

**Keywords:** CO2 geological storage; depleted gas fields; deep saline aquifers; Adriatic offshore; Croatia
